ML20033A214

Ecological Studies 1976-77,Studies on Soft-Shelled Clam,Mya Arenaria,In Vicinity of Hampton-Seabrook Estuary, Nh

ML20033A214
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Site:	Seabrook
Issue date:	08/31/1978
From:	NORMANDEAU ASSOCIATES, INC.
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VIII-2, NUDOCS 8111240921
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I SEABROOK ECOLOGICAL STUDIES 1976-1977 STUDIES ON THE SOFT-SHELLED CLAM, I

MYA ARENARIA, IN THE VICINITY OF HAMPTON-SEABROOK ESTUARY, I

NEW HAMPSHIRE l

TECHNICAL REPORT VIII-2 Prepared for PU3LIC SERVICE COMPANY OF NEW HAMPSHIRE Manchester, New Hampshire 1

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By i

NORMANDEAU ASSOCIATES, INC.

Bedford, New Hampshire i

August 1978 I

B111240921 011118 I

{DR ADOCK 05000

I TABLE OF CONTENTS I

PAGE

1.0 INTRODUCTION

1 2.0 METHODS AND MATERIALS................. 4 2.1 LARVAE TOWS...................... 4 2.2 SPAT SURVEYS...................... 6 2.3 ADULT SURVEYS.....................

7 2.4 SEDIMENT SURVEYS...................

14 l

3.0 RESU'.TS.......................

17 3.1 BIVALVE LARVAE: SPECIES COMPOSITION AND ABUNDANCE..

17 3.2 CLAM SPAT: ABUNDANCE, DISTRIBUTION AND GROWTH....

23 3.3 ADULT CLAMS: DISTRIBUTION AND ABUNDANCE.......

30 3.4 SEDIMENT GRAIN-SIZE DISTRIBUTION CHARACTERISTICS OF FLATS 2 AND 4....................

34 4.0 DISCUSSION......................

42 4.1 BIVALVE MOLLUSC LARVAE................

42 4.1.1

@a arenaria.....................42 4.1.2 Planktonic Larvae of Other Bivalve Mollusc Species..

43 l

4.2 SOFT-SHELL CLAM SPAT.................

43 4.3 STATUS OF ADULT SOFT-SHELL CLAM STOCKS IN HAMPTON HARBOR........................

46 4.4 RELATIONSHIP 0F SEDIMENT GRAIN-SIZE DISTRIBUTION TO SOFT-SHELL CLAM PROPAGATION P0TENTIAL.......

51 I

5.0

SUMMARY

53 6.0 LITERATURE CITED...................

55 i

PAGE APPENDIX 7.1:

RESULTS OF BIVALVE LARVAE TOWS OFF HAMPTON BEACH, NEW HAMPSHIRE......

58 2

i APPENDIX 7.2:

SHELL SIZE DISTRIBUTION (#/FT ) 0F SOFT-SHELL CLAM SPAT COLLECTED FROM FIXED STATIONS IN SIX NORTHERN NEW ENGLAND ESTUARIES 1976 THROUGH 1977..................

63 2

l APPENDIX 7.3:

SHELL SIZE DISTRIBUTION (#/FT ) 0F SOFT-SHELL CLAM SPAT AND ADULTS COLLECTED FROM RANDOM STATIONS AT FIVE HAMPTON HARBOR FLATS, 1971 THROUGH 1977..............

74 APPENDIX 7.4:

CONT 0URED CHARTS OF HAMPTON HARBOR i

FLATS INDICATING NOVEMBER 1977 SURVEY STATIONS............

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I LIST OF FIGURES PAGE 1.

Soft-shell clam,3tsa arenaria, sampling stations......

5 2.

Location of fixed station spat study sites.........

9 3.

Abundance of veligers of bivalve mollusc species I

associatad with Afga arenaria, collected in the vicinity of the intake site off Hampton Beach, New Hampshire....

20 I

4.

Species composition of tow samples from the intake transect stations, 22 August 1977.............

22 5.

Shell length medians and ranges for juvenile soft-shell clams collected from northern New England estuaries....

27 6.

Spat shell length medians and ranges in Hampton Harbor, I

November 1976 and 1977...................

28 7.

Spat size-frequency distributions for juvenile soft-shell clams from Hampton Harbor, November 1976 and 1977..

29 8.

Estimates of soft-shell clam, Afga arenaria, biomass for five tidal flats in Hampton Harbor; with approximate 95% confidence intervals. Adult clam populations esti-mated after 1974......................

32 9.

Length-density distribution of adult clams collected from five flats in Hampton Harbor in 1975, 1976 and 1977....

35 I

10.

Distribution of mean grain-size classifications on clam fl a t 2...........................

38 11.

Distribution of mean grain-size classifications on clam fl a t 4...........................

39 12.

Comparison of size ranges at " disturbed" and undisturbed areas, Flat #2, Hampton Harbor, N. H., August 1977.....

45 13.

dstimated shell growth rate of soft-shell' clam, Atja arenaria, with approximate 95% confidence intervals.

Seasonal dips in the curve suggest slowing of growth in the late fall and early winter (NAI,1977).......

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14.

Comparisons of size-density distrib tions at undisturbed, I

relatively well-settled areas of selected flats in Hampton Harbor, N. H., November 1977.

Clams are approx-imately 13-15 months old..................

48 I

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1.

I LIST OF TABl.ES I

PAGE 1.

CLAM SPAT SAMPLING EFFORT, HAMPTON-SEABROOK ESTUARY....

8 2.

FIXED STATION CLAM SPAT SAMPLING EFFORT, SELECTED ESTUARIES ADJACENT TO HAMPTON-SEABROOK ESTUARY......

10 3.

ADULT CLAM SAMPLING EFFORT, HAMPTON-SEABROOK ESTUARY...

12 4

SEDIMENT SURVEY SAMPLING EFFORT.

15 3

5.

DENSITIES (/M ) 0F UMB0NED MyA ARENARIA VELIGER L/RVAE COLLECTED BY OBLIQUE NET TOW...............

18 6.

PERCENTAGE COMPOSITION OF BIVALVE M0LLUSCS IN OBLIQUE NET TOWS IN THE VICINITY OF THE INTAKE SITE........

19 7.

DISTRIBUTION OF UMBONED M. ARENARIA VELIGERS ALONG THE EAST-TO-WEST INTAKE TRANSECT, 22 AUGUST 1977.......

17 I

8.

SEED CLAM DENSITIES (FT 2) FOR SIX NORTHERN NEW ENGLAND ESTUAPIES.

(VALUES DO NOT INCLUDE SPAT LESS THAN 1.5 MM MAXIMUM WIDTH).....................

24 9.

SUMMARY

OF MYA ARENARIA POPULATION DENSITIES, ANNUAL NOVEMBER SURVEY......................

25 10.

RESULTS OF SOFT-SHELL CLAM (MYA ARENAl?IA) ESTIMATES, HAMPTON-SEABROOK ESTUARY 31 I

11.

ESTIMATES OF NON-PRODUCTIVE CLAM FLAT, HAMPTON-SEABROOK ESTUARY.........................

33 12.

CRAPHIC MEANS (M,) AND STANDARD DEVIATION (o ) 0F GRAIN I

SIZE (4) VALUES FOR FLAT 2.........y 36 13.

GRAPHIC MEANS (M ) AND STANDARD DEVIATION (cy) 0F GRAIN I

SIZE (c) VALUES FOR FLAT 4................

41 z

14.

COMPARISON OF M7A ARENARIA UMB0NED VELIGER ABUNDANCES OF HAMPTON BEACH, NEW HAMPSHIRE, 1974-1977........

42 7

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l PAGE 15.

RECENT HISTORY OF THE STANDING CR0P 0F LEGAL SIZE MzA l

AREll4RIA IN HAMPTON HARBOR.................

49 t

16.

RECENT HISTORY OF THE STANDING CR0P 0F NYA AREl/ ARIA

(>50 mm LONG) ON FLAT *2.

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1.0 INTRODUCTION

I Soft-shell clam investigations at Hampton-Seabrook Estuary (Normandeau Associates, Inc., 1973, 1974a, 1975a, 1976a, 1977) have provided ample documentation of severe adult stock depletion.

By 1976, recreational clam diggers had removed approximately 87% of the harvest-abla clams that had existed in 1971, leaving only an estimated 11.7 bushels per acre remaining (NAI, 1977).

This loss might be expected to severely restrict reproductive potential, and, hence, the possibility of repopulating the flats.

However, since it has been observed that the planktonic larval stage has a life span of from 2 to 4 weeks (S tickney, 1964; Savage and Goldberg, 1977), it would appear that given favorable I

hydrographic conditions, it is probable that breeding stocks in estua-ries up to 25 miles away (cf. Ayers, 1956) can repopulate the Hampton-Seabrook clam flats.

The high flushing rate which characterizes the estuar'f also leads to the conclusion that Hampton-Seabrook depends heavily on the coastal drift of planktonic larvae for recruitmant (NAI, 1972, 1973).

Planktonic surveys (NAI, 1973, 1974b, 1975b, 1976b, 1977) have shcwn that, in some years, several hundred to a few thousand soft-shell clam larvae per cubic meter appear immediately offshore, in the vicinity of Hampton-seabrook Estuary for brief periods, ranging from several days to one or two weeks.

These short-lived occurrences have been primarily concentrated in late summer, from the end of July to mid-September, concurring with other reports of the period of peak spawning activity in this region of New England (Ropes and Stickney, 1965; NAI, 1971; Savage and Goldberg, 1977).

Occurrence of high planktonic larval population densities near the entrance to Hampton-Seabrook Estuary has, however, not always proved to be a totally reliable predictor of spatfall (i.e., primary settling of very young metamorphosed clams) within the estuary itself.

For example, high larval densities (avereging 532 per m ) were observed in late summer of 1975; however, spatfall densities (37 per ft ) were I

1

3 (1952) theorized that the species may have been introduced via the I

bilges of fishing vessels, during a period of expanding trade in lob-sters and sardines. Welch (1969, 1975) das demonstrated a positive correlation between green crab abundance in. caine waters and yearly fluctuations in ocean water temperature.

His data i..dicate that the present green crab population boom began about 1970 and had been pre-ceded by an earlier, similar, boom between 1948 and 1954.

Clam growth is enhanced by a prolonged growing season generally associated with a rise in sea temperature; however, survival declines drastically under such conditions. The observed inverse relationship between sea temp-erature and soft-shell clam harvests has been attributed to increased predation pressure from expanding green crab populations (Dow, 1977), as I

warmer winters also enhance the reproductive success of the green crabs.

The present report continues along the lines of investigation established in previous reports.

Notable methodological changes from the previous report (NAI, 1977) include:

1) exclusive use of oblique tows to monitor temporal (seasonal) and spatial (horizontal) larval distributions off Hampton Beach, (2) utilization of aerial photography to enhance precision with which estimates of standing stock can be made, and (3) sampling of intertidal flat sediments to establish grain-size I

distributions characteristic of clam propagation areas.

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4 2.0 METHODS AND MATERIALS 2.1 LARVAE TOWS To monitor temporal dist;

• of Mya arenaria larvae in the vicinity of the Se Q ook Station cool."'g water intake (Figure 1), dupli-cate, two minute, oblique net towe were made approximately twice weekly, from 27 June to 27 October. A 0.5 m f..ameter No. 20 (73 um) mesh net, with a 10 lb. depressor attached, was towed at approximately 1/2 knot.

The net was lowered to a depth of approximately 13 m (43 feet), in the first minute and returned to the surface after a second minute had I

elapsed ending the tow.

A General Dynamics flow meter was used to record the volume of water passing through the net; in practice, this volume ranged from 4 to 11 m per tow.

Upon recovery, net contents were I

thoroughly rinsed into a 1/2 gallon glass jar.

The live material was transported immediately to the piscataqua Marir.e Laboratory, Portsmouth, where it was temporarily stored in a refrigerator.

To separate the live bivalve larvae from the bulk of the plankton, the sample was transferred to 1000 ml dispensing burettes and the contents allowed to settle for 5-12 minutes.

The relatively high density of the shells allowed the bivalves to rapidly accumulate at the bottom of the burette column, and to be withdrawn for identification and I

enumeration. The entire sample concentrate containing the bivalves was enumerated for umboned (length 145-320 pm) M. arenaria larvae except when this species was particularly abundant; whereupon, the bivalve larvae were concentrated by a swirling motion, into the center of a round, 100 mm diameter, plastic culture dish.

The resulting concen-tration of larvae was carefully divided into visually equal quadrants using a camels hair probe, viewing the operation through a dissecting microscope at approximately 30x; two diagonally opposed quadrants were then enumerated.

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7Cf50' 48' 70'46' 42*56' -

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Figure 1.

Soft-shell clam,/?sa arenaria, sampling stations.

Seabrook ltga arenaria Study,1977.

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The same splitting technique was also used to reduce the amount of larvae, representing other bivalve species, to sample frac-tions containing a total of 200 to 600 individuals.

Depending on ori-ginal (i.e.,

field) populatien densities, this required from one to four successive operations consisting of concentrating the larvae into the I

center of the dish and then separating and extracting a quadrant.

In all cases, two sample fractions were enumerated from each sample, each fraction having originated as one of two diagonally coposite quadrants in the initial (whole sample) larvae concentration.

Principal refer-ences t ad as aids in identifying larvae to species were: Sullivan (1948), de Schvenitz and Lutz (1976) and Savage and Goldberg (1976).

With few exceptions, only umboned veligers were identified and enumer-ated.

Enumeration of M. arenaria straight hinge veligers was carried out only when their identity was reasonably obvious because of the large I

numbers involved and the paucity of straight hinge veligers cf other species.

From 27 June to 28 July, a second larvae monitoring station was maintained at a site which, prior to July 1975, had been designated as the intake site. Collection, identification, and enumeration proce-dures were as described above for the presently designated intake loca-tion.

On those dates when the M. arenaria umbone veliger population density was found to exceed 50 per m, a special towing program was carried out to define the onshore / offshore n. arenaria larval density elstribu-tion in the intake vicinity. Oblique tows were made at 1/2 nautical mile intervals along a transect running east to west through the intake site (Figure 1).

Data collection procedures were as described above.

I 2.2 SPAT SURVEYS To compare population densities of seed clams (shell length:

1.5 to 25 mm) periodic surveys were conducted on Hampton Harbor Flat No.

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l 2 (Figure 1 and Table 1) and on flats in five adjacent estuaries, in New Hampshire, northern Massachusetts and southern Maine (Figure 2 and Table 2).

With the exception of the November survey, the stations were fixed in that once established (on the basis of preliminary evidence of high productivity), the same general locality was resampled with each survey.

At each fixed collection site, sediment cores three or four inches in diameter, and four inches deep, were extracted in triplicate, using a section of PVC plastic pipe.

Sediments from these core samples were washed through a 1 mm mesh screen and the M. arenaria spat picked from the screen with forceps.

After transfer to small fingerbowls, the spat from each core sample were enumerated and measured to the nearest 1 cm.

I Spat samples were also obtained, as described above, during the annual Hampton-Seabrook clam flat survey in November; however, the November stations (Table 1) were chosen at random from a larger set of stations designated for sampling adult clam populations.

Whereas the fixed station program, with emphasis on high yield locations, facili-tated determination of temporal and relative geographical distribution, the utilization of randomly determined stations in November provided the best estimate of actual spat density over a particular flat, including portions less favorable for spat settlement.

I 2.3 ADULT SURVEYS I

As in past years, the five largest harbor flats (Figure 1) were each surveyed in November 1977 for adult clams. Additional surveys

. I were conducted on Flat #2 in May and August 1977.

In preparation for the actual collection of sa.ples, flats were mapped and contoured.

To determine the various dimensions, beach profiles were surveyed using a transit, dumpy level and stadia rod.

Transects were laid out in five directions from a central point on the flat.

Stadia rod readings were made with the level at one hundred foot intervals.

Observed water levels were refer enced to mean low water.

To

I TABLE 1 CLAM SPAT SAMPLING EFFORT, HAMPTON-SEABROOK ESTUARY.

SEABROOK MYA ARE:: ARIA STUDY,1977.

I LOCATION DATE NO. OF STATIONS FIXED STATIONS Flat 2 January 11 6

Flat 2 April 14 6

Flat 2 June 7 6

Flat 2 August 1 6

Flat 2 October 17 6

'i RANDCM STATIONS Flat 2 November 16 7

Flat 1 November 15 14 Flat 3 November 15 6

Flat 4 November 16 11 Flat 5 November 14 9

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OGUNQUIT l

BEACH I

J YORK RIVER l

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HAMPTON-SEABROOK ISLES OF 3,

ESTUARY SH0ALS

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w#:'.

l STUbv MERRIMACK

/

AREA RIVER

/

5

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PLUM SLAND NAUTICAL MILES

,,., i,,,,i Figure 2.

Location of fixed station spat study sites.

Seabrook Mya arenaria Study, 1977.

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TABLE 2.

FIXED STATION CLAM SPAT SAMPLING EFFORT, SELECTED ESTUARIES ADJACENT TO HAMPTON-SEABROOK ESTUARY.

SEABROOK MYA ARENARIA STUDY, 1977.

NO. OF LOCATION STATIONS DATES Plum Island Sound, MA Middle Ground 5

11 Feb 11 Apr 8 Jun 5 Aug 19 Oct Neck Cove 5

11 Feb Lufkins Flat 3

--- 11 Icpr 8 Jun 5 Aug 19 Oct 11 Apr 8 Jun 5 Aug 19 Oct Nut Shoal 2

I Merrimack River, MA I

Salisbury Flat 3 5

28 Jan 13 Apr 6 Jun 2 Aug 18 Oct Ball's Flat 1 5

27 Jan 13 Apr 6 Jun 2 Aug 18 Oct Little Harbor Channel, NH Clam Pit Island 5

12 Jan 15 Apr 13 Jun 10 Aug 10 Oct Flat, opposite side 1

12 Jan 15 Apr 13 Jun 10 Aug 10 Oct I

Southern Maine York River 5

14 Jan 12 Apr 9 Jun 9 Aug 21 Oct Ogunquit Beach 6

14 Jan 12 Apr 9 Jun 9 Aug 21 Oct a

11 aid in interpretation of horizontal dimensions given by the transect lengths, important topographic details of the flat were sketched in the field by the survey crew.

From these, charts were constructed of each flat surveyed.

Preparation of sampling charts for Flats 1, 2,

4 and 5 was greatly facilitated by the use of aerial photography, which was initiated with the November 1977 annual survey to more accurately measure flat acreage and to provide permanent records of existing flat configuration.

Photographic were made on 18 October 1977 at mean low water and at intervals of approx-imately 1.2 m water-depth increments on the flood tide, making projection of topographic contours possible (Appendix 7.4).

Acreage measurements were provided by the aerial survey contractor, employing the "stereotemplate laydown" procedure which is standard for the preparation of tax base maps.

The maximum error in computed flat acreage has been estimated by the con-tractor to be approximately 2-3%.

Flats 1, 2, 4 and 5 were done this way; due to difficulties encountered in the overflights; Flat 3 was not fully photographed. Areal estimates were done as in the past for this flat.

Random sampling procedures were employed which minimized unpro-ductive digging in extremely depopulated areas of the flats.

Evidence of breathing or siphon holes was used as an indicator of the presence, and I

conversely the absence, of clams.

If, after determining the location of a sampling station, the investigator observed what was thought to be clam I

siphon holes, a two-square-foot area was dug thoroughly for clams. On the other hand, if no sign of siphon holes was detected within the two square foot sampling area, the investigator in most cases simply noted this fact on a field card and proceeded to the next sampling station. Several stations on each flat which showed no sign of clam holes were randomly selected and dug thoroughly as a check on the effectiveness of establishing the absence of clams by the absence of siphon holes (Table 3).

Total number of samples to be observed for evidence of siphon holes was roughly determined by the surface area of the flat above mean low tide (Table 3).

To establish sampling stations, randomly generated rectangular (x, y) coordinates were plotted on charts of each flat.

12 TABLE 3 ADULT CLAM SAMPLING EFFORT, HAMPTON-SEABROOK ESTUARY. SEABROOK MYA ARENARIA STUDY,1977.

I I

TOTAL N0.

NO. OF NO. OF SURFACE SAMPLE P0TENTIALLY P0TENTIALLY E

AREA STATIONS BARREN STATIONS PRODUCTIVE E

LOCATION DATE (ACRES)

OBSERVED SUBSAMPLED STATIONS DUG Flat 2 May 25.5 27 4

7 Flat 2 August 25.5 27 4

8 Flat 2 November 25.5 33 8

1 Flat 1 November 55.0 66 13 13 Flat 3 November 11.6 24 4

5 Flat 4 November 50.6 51 6

2 Flat 5 November 23.9 38 5

11 All Flats November 166.6 212 36 32

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13 Random coordinates were generated until the full quota of stations was attained for the flat.

In the field, stations were located by compass bearing and distance from the central reference point established during the beach profile survey.

To delineate the sample area, a two-square foot frame was placed on the substrate, with the lef t hand corner of the frame at the investigator's right foot.

The substrate surface outlined by the inner edges of the frame was carefully inspected for evidence of siphon holes.

If a sample was to be taken because siphon holes were evident, or if a random subsample of a "no-hole," station was required, the sediment outlined by the frame was dug to a depth of about 16 inches.

Adult soft-shell clams found during excavation, or in the spoil, were picked out and placed in a plastic bag along with a tag identifying the I

station and flat number.

In the laboratory, clams were tallied and measured for shell length to the nearest 0.1 mm.

Individual sample counts and shell measurements were converted to biomass estimates (bushels per acre) using a table of clam volumes provided in Belding (1931). The overall biomass estimate for each flat was obtained using the following formula:

I n1 _

n2 X=

X X

1+

n 2

n where:

n = total number of sampling stations observed n = number of stations where siphon holes were observed y

2 " "'"1 = number of stations where no siphon holes were observed n

I 3i = average biomass (bushels per acre) estimate for the entire flat I

2 = average biomass from n samples

-X' = average biamass from a subset of samples (n,') representing stations where no siphon holes were observed.

To express results in terms of standing crop (bushels of harvestable clams on the entire flat), the biomass estimate was multiplied by flat surface area (acres). Variance and standard error of biomass estimates were calculated approximately, using formulae given in Hanson et al.,

I

14 1953. To obtain a rough approximation of 95 percent confidence inter-vals, standard errors were multiplied Ly two, as suggested by Hanson et al.,

1953.

I 2.4 SEDIMENT SURVESS I

Clam flats 2 and 4 were each surveyed five times, as shown in Table 4.

On Flat 2, sediment sampling stations were randomly distributed I

and, therefore, were in different positions for each of the five sur-veys. On Flat 4, fourteen fixed stations were established, and resur-veyed each subsequent time.

Either 63 mm or 34 mm, inside diameter, coring tubes were used to extract two approximately 10 cm long sediment cores at each station.

The two cores from each station were mixed together in a sealable plas-tic bag and transported to the Normandeau Associates' Analytical Lab-oratory for grain-size distribution analysis.

I Methods employed for sediment grain-size distribution analysis followed procedures described in Folk (1968) and Carver (1971) including the use of empirically established particle settling velocities (applying Stoke's Law) to determine the proportional representation of p, rticles l

finer than sand.

particle dispersion was first assured by vigorously shaking a subsample of each field sample with distilled water and sodium hexametaphosphate (dispersing agent). The silt and clay fraction was then separated from the coarser-grained particles by passing the sub-sample slurry through a 62.5 um mesh sieve.

j u

Upon separation, the silt-clay fraction was again thoroughly j

mixed with dispersant and put into a graduated cylinder.

At times and to depths determined oy formulae prescribed in Folk (1968) and Carver (1971), 20 ml volumes were withdrawn from the cylinder by pipette.

These sample aliquots were oven dried and weighed to an accuracy of 1 mg.

The coarse particle portion (principally sand) was washed, oven 1

15 TABLE 4.

SEDIMENT SURVEY SAMPLING EFFORT.

SEABROOK lHA AREllARIA STUDY, 1977.

LOCATION DATE NUMBER 0F STATIONS Random Stations Flat 2 November 1975 4

Flat 2 February 1976 9

Flat 2 August 1976 6

Flat 2 November 1976 10 Flat 2 December 1977 9

Fixed Stations Flat 4 August 1976 14 Fla't 4 November 1976 14 Flat 4 February 1977 14 Flat 4 August 1977 14 Flat 4 Ncvember 1977 14 I

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16 dried and sieved through a U.S. Standard Sieve Series, at intervals of 350, 177, 88 and 44 um.

Each of these sieve fractions was weighted to an accuracy of 10 mg.

~

Weights of the various sieve and pipetted fine-grain frac-tions, representing each sample, were submitted to a computer program (adapted from Kane and Hubert, 1963) which produced an extrapolated L

particle distribution curve for each sample.

For presentation, and to facilitate interpretation, the graphic mean and graphic standard devi-ation were calculated for each sample, according to the following formula:

Graphic Mean (Mz)

I

$16 + $50 + 684 M

=

z 3

I Inclusive Graphic Standard Deviation (c )

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684 - 616

?95 - c5 O I" 4

6.6 I

The value 4 is the base 2 logarithm of the reciprocal of grain size (in fractions of a mm), such that a 1 mm grain of sand has a $

value of 0.0, a 1/2 mm sand grain has a $ value of 1.0, and 1/4 mm sand grain has a $ value of 2.0, etc.

Numbers next to the symbol $, in the above formulae, specify the percentile, e.g., $16 means the value of 4 in the 16th percentile of the grain-size distribution curve.

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17 3.0 RESULTS 3.1 BIVALVE LARVAE:

SPECIES COMPOSITION AND ABUNDANCE Results of twice weekly net tows are presented in Tables 5 and 6 and in Figure 3.

Details pertaining to population density estimates for the more abundant bivalve mollusc species, other than M. arenaria, I

are tabulated in Appendix I.

Throughout the sampling period, N.

are-3 naria umboned veligers never appeared in densities greater than 15 per m,

with one exception. That exceptien was on 22 August, when the average M.

arenaria umboned veliger density, for the two replicatc tows, approached 100 per m (Table 5).

For the 102 day period from 27 June to 6 October, the M.

arenaria umbone veliger density averaged only 7.0 per m.

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Table 7, below, displays the results of the only horizontal distribution tow study conducted:

I TABLE 7.

DISTRIBUTION OF UMBONED N. AEmiRIA VELIGERS ALONG THE EAST-T0-WEST INTAKE TRANSECT, 22 AUGUST 1977.

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I STATION 2

4 6

8 REPLICATE 1

2 1

2 1

2 1

2 Sample volume 3

(m )

6.9 7.3 10.0 7.4 9.7 8.2 8.1 9.5 Total count 1506.0 1978.0 1092.0 964.0 2357.0 2065.0 347.0 146.0 Mya Veligers 3

(per m )

218.3 271.0 109.0 130.0 243.0 252.0 43.0 47.0 t

Since this study was not repeated, there being no other date at which M.

I arenaria umbone veligers were present in sufficient abundance, no basis for statistical treatment existed. Umbone veliger total abundance and species composition, on 22 August, is presented in composite for each of I

I

18 3

TABLE 5 DENSITIES ( /M ) 0F UMBONED n?A ARENARIA '!ELIGER LARVAE COLLECTED BY OBLIQUE NET TOW.

INTAKE SITE PROPOSED PRESENT INTAKE PRIOR T0 1975 REPLICATE REPLICATE REPLICATE REPLICATE DATE 1

2 Y

l 2

Y 27 Jun 0.8 0.7 0.8 4.9 2.4 3.6 30 Jun 1.4 0.7 1.0 5.1

<.1

<.1 5 Jul 0.3 0.6 0.4 11.6 3.9 7.8 8 Jul 14.1 12.1 13.1 8.2 10.5 9.4 I

11 Jul 1.2 0.7 1.0 1.4 3.2 2.3 14 Jul 0.4 2.2 1.3 0.7 0.6 0.6 18 Jul 0.7 0.2 0.4 0.6 0.6 0.6 21 Jul 0.5 0.7 0.6 0.5 0.7 0.6 5

28 Jul 0.1 0.1

<.1 0.0 0.1

<.1 l

1 Aug

<.l(53)

<.1(50)

<.1 4 Aug 13.0 15.0 14.0 I

8 Aug 1.0 0.4 0.7 11 Aug 2.1 1.9

, 2.0 15 Aug 4.4(5.4) 2.0(2.4) 3.2 18 Aug 4.7 8.1 6.4 22 Aug 129.0 67.0 98.0 25 Aug 11.1 13.8 12.4

.I 29 Aug 3.9 1.4 2.6 1 Sep 11.7 10.0 10.8 6 Sep 0.3 0.4 0.4 8 Sep 0.0 0.1

<.1 I

12 Sep 0.6 0.9 0.8 15 Sep 2.5 3.2 2.8 19 Sep 14.4 13.8 14.1 22 Sep 0.7 1.0 0.8 l

29 Sep 0.2 0.2 0.2 1

6 Oct 0.8 0.5 0.6

.l 10 Oct 0.0 0.0 0.0 m

13 Oct 0.0 0.0 0.0 20 Oct 0.0 0.0 0.0 27 Oct 0.0 0.0 0.0 avg. density:

27 June to 6 October (102 days) lI 3

7.0 larvae per m numbers in parentheses represent straight hinge larval densities I

19 TABLE 6.

PERCENTAGE COMPOSITION OF BIVALVE M0LLUSCS IN OBLIQUE NET TOWS IN THE VICINITY OF THE INTAKE SITE.

SEABROOK MYA ARE.VARIA STUDY, 1977.

/

/

n p,

r DATE 4-4-

27 Jun 60.6 29.1 8.6 0.4 1.2

<0.1 I

30 Jun 73.7 13.0 11.5 0.1 1.7

<0.1 5 Jul 75.3 7.0 12.0 4.3 1.4

<0.1 8 Jul 42.8 49.8 5.9 0.1 1.3 0.1 I

11 Jul 72.2 10.7 11.0 5.6 0.5

<0.1 14 Jul 55.1 12.7 18.8 12.5 0.8

<0.1 18 Jul 33.2 33.7 23.3 7.1 2.7

<0.1 I

21 Jul 15.8 34.1 24.5 22.9 2.7

<0.1 25 Jul 39.4 30.5 14.2 12.0 3.9

<0.1 28 Jul 43.4 27.3 13.9 13.1 3.2

<0.1 1 Aug 24.5 14.6 24.2 25.9 10.8

<0.1 I

4 Aug 19.1 15.4 31.2 24.2 9.1 1.0 8 Aug 10.0 50.2 14.7 18.7 6.2 0.2 11 Aug 7.9 50.6 18.0 14.6 6.7 2.2 I

15 Aug 7.0 16.1 24.4 45.2 6.9 0.4 18 Aug 6.2 19.1 12.7 46.8 14.0 1.2 22 Aug 2.7 13.7 18.2 32.7 15.9 16.8 I

25 Aug 10.3 7.2 14.3 54.3 13.3 0.5 29 Aug 34.5 8.5 8.4 42.4 6.1 0.1 1 Sep 32.0 23.4 10.0 27,5 6.9 0.2 6 Sep 26.4 28.4 11.7 24.2 2.3 6.9

<0.1 I

8 Sep 7.8 53.9 16.9 17.4 0.7 3.3

<0.1 12 Sep 27.1 33.7 15.9 11.9 2.2 9.1 0.1 15 Sep 14.0 33.5 23.9 20.6 1.6 6.3 0.1 19 Sep 8.0 25.5 11.5 31.8 19.6 3.4 0.2 22 Sep 7.7 28.8 5.6 50.7 0.7 6.4

<0.1 26 Sep 4.4 67.9 5.0 14.2 2.0 6.4

<0.1 I

29 Sep 5.1 35.0 11.9 40.7 1.4 5.9

<0.1 3 Oct 4.1 17.2 4.9 65.2 6.0 2.6 0.0 6 Oct 8.5 32.7 4.5 37.7 8.9 7.6

<0.1 10 Oct 33.7 17.9 6.3 34.2 4.2 3.7 0.0 I

13 Oct 20.8 3.8 7.0 55.4 9.0 4.0 0.0 20 Oct 22.4 20.4 1.8 46.1 2.2 7.0 0.0 27 Oct 47.0 14.0 4.1 29.4 2.7 2.7 0.0 I

Included with "others" category

t l

i i

10000u --

I j

10000 --

"r C

~

5 a

100(L 1

10 I

III I

50 i-JULY AUGUST SEPTEMBER OCTOBER Figure 3.

Abundance of veligers of bivalve mollusc species collected in the vicinity of the intake site off Hampton Beach, New flampshire.

Seabrook Nya arenaria Study, 1977.

t E

l

21 the four stations along the intake transect in Figure 4.

These data indicate that, on this date, Anomia sp. increasingly predominated the bivalve veliger assemblage in the offshore direction, at least as far out as 2 nautical miles.

Among the other kinds of bivalve mollusc veligers collected in the tous, four species: Modiolus modiolus, Mytilus edulis, Hiatella 3

sp.

and Anomia sp.

stood out as being consistently the most abundant throughout the collection period (Figure 3; Appendix I).

Total abun-dance (all species collectively) peaked very early in the collection period, primarily due to the very high density of Modiolus modiolus (horse mussel) larvae in the water.

On 30 June, estimates of N. modi-olus density at the previously proposed intake location ran as high as 137,000 per m, while estimates from the present site were about half that i

value (Appendix I).

I Several other species, notably, Cerastoderma pinnulatum (nor-thern dwarf cockle), Zirphaea crispara (piddock clam), Macoma balthica and Placopecten magellanicus (sea scallop) rarely comprised more than 15% of any of the tow collections, collectively.

In early summer col-lections, Ensis directus (razor clam) larvae were also lumped with the low density species; however, as E. directus larval populations became relatively more dense in later collections (often exceeding 100 per m )

these species were enumerated separately.

Highest E. directus densities (estimates ranged from 1250 to 2000 per m- ) were observed on 19 September I

(Appendix I).

A secondary peak in total bivalve veliger abundance was evi-dent from late August to late September.

Five species:

M. modiolus, M.

edulis, Hiatella sp., Anomia sp. and Cerastoderma pinnulatum predomi-nated (Figure 3; Appendix I).

1 I

Tentatively, mostly H. striata

(= gallicana) 2Tentatively, mostly A. squamula (= A. aculeata) (spiny jingJe shell)

._A

M M

M M

M M

M M

M M

M M

M M

M M

M M

M 1

TOTAL DENSITY I

TOTAL DENSITY 2

4 720 larvae /m-3 400 larvae /m-3 Others 2%

Others 2%

\\

\\

Cevaatodeuna Cevaatodeuna 13%

Mya Nya 34%

Anomia Anomia 22%

30%

niateila Mytilus 19%

Mytilus 14%

Modiolus__2%

y,ggo7u, gg niatella I

TOTAL DENSITY 1

TOTAL DMSITY 6

8 2000 1arvae/m~

ccrastodo ma tig carastoderm Mytilus 6%

1i.

I"

]

Mytilus 9%

6% niatella 10%

"*E5 I"" 4 Anomia 54%

13%

niatella Anomia

)

72%

Figure 4.

Species composition of tow samples from the intake transect stations, 22 August 1977.

O Seabrook Mya arenaria Study, 1977.

r I

23 l

3.2 CLAM SPAT:

ABUNDANCE, DISTRIBUTION AND GROWTH Spat densities recorded for fixed stations in six New England estuaries are presented in Table 8; further detail pertaining to the I

fixed station survey can be found in Appendix II.

Both the Plum Island Sound and Hampton Harbor flats exhibited reasonably good retention of the 1976 spat set, which, as shown in Table 9, represented the highest I

spatfall density in seven years of study at Hampton-Seabrook Estuary (=

Hampton Harbor;.

Retention was also reasonably high at Ogunquit Beach until October 1977 when densities fell to approximately one quarter of the maximum observed densities.

Attrition of the 1976 spat set was almost complete in the Merrimack River estuary, Little Harbor channel, and the York River estuary.

Spatfall was relatively modest in 1977 at all of the estuaries studied, except Plum Island Sound, where the 1977 spatfall was even higher than in the previous year.

I Shell length data, obtained from the fixed station program, are represented in Figure 5.

Shell growth was most rapid at the Plum Island flats.

Shell growth at Ogurquit Beach was initially compara-tively slow, but later accelerated, particularly between samplings in June and August.

By October, 1977, a wide gap was evident between the shell size ranges of the 1976 and 1977 year classes, at both Plum Island Sound and Ogunquit Beach, as Figure 5 clearly shows. To minimize clut-ter, size-frequency characteristics of the 1977 set were not included in Figure 5 for the October, 1977, Hampton Harbor collection, but were essentially the same as depicted for the same month in the Merrimack River.

In October 1977, 1976 year class spat were virtually non-exist-I ent in the Merrimack River (Table 8).

Results of the 1976 and 1977 annual spat collections at random l

stations, are summarized for the five principal flats, collectively, in Figures 6 and 7.

These data indicate that median shell size has increased only 6 mm, from 3 to 9 mm, in the 12 month period between surveys.

However, clams in the upper 97.5 percentile of shell size have grown approximately 11 mm, from 6 mm to 17 mm, between the two surveys (Figure

!I lI

M M

M M

M M

M M

M M

M M

M M

M TABLE 8.

SEED CLAM DENSITIES (FT 2) FOR SIX NORTHERN NEW ENGLAND ESTUARIES.

(VALUES DO NOT INCLUDE SPAT LESS THAN 1.5 mn FMXIMUM WIDTH).

SEABROOK MYA ARENARIA STUDY,1977.

JAN-APR JUN AUG OCT FEB APR JUN AUG OCTOBER SAMPLE PERIOD 1976 1976 1976 1976 1977 1977 1977 1977 1977 YEAR CLASSES LOCATION 1976 1977 Plum Island Sound, MA 63 2

17 178 112 212 336 156 101 572 Merrimack River Estuary, MA 33 14 23 228 164 227 149 25

<1 52 llampton liarbor, NII 113 15 96 1283 614 692 615 363 254 77 Little liarbor, Nil 69 19 6

105 85 176 200 60 2

31 York River, ME 181 277 92 105 119 92 416 108

<1 75 Ogungoit Beach, ME 37 2

8 57 101 63 102 108 24 25 E

t

ll 2e TABLE 9.

SUMMARY

OF NYA ARENARIA POPULATION DENSITIES, ANNUAL NOVEMBER SURVEY.

SEABROOK MYA ARENARIA STUDY,1977.

I POPULATION DENSITY (#/SQ. FT.)

NUMBER OF i

I SAMPLES COLLECTED SIAT ADULTS ADULTS LOCATION YEAR ADULTS SPAT

(>l TO 25 mm) (25 TO 50 mm)

(>50 mm)

Flat 1 1971 18 18 48 6.8 2.1 1972 18 18 110 8.1 3.3 1973 36 18 44 2.5 1.3 1974 40 18 2.6 2.8 3.0 1975 35 18 56 0.4 1.2 1976 63 18 1094 0.12 0.53 1977 66 14 819 0.04 0.15 Flat 2 1971 9

9 91 4.8 3.8

'972 9

9 152 2.2 1.4 I

1973 9

9 136 3.8 1.1 1974 21 9

0.0 2.1 1.9 1975 21 9

9.1 0.0 0.5

gg 1976 24 9

351 0.0 0.21 1977 33 7

86 0.0 0.08 Flat 3 1971 6

6 74 4.7 4.6 1972 6

6 39 1.6 0.4 1973 12 6

8 3.6 2.2 I

1974 12 6

0.6 0.7 1.7 1975 12 6

1.1 0.0 0.6 1976 24 5

560 0.07 0.23

,g 1977 24 6

75 0.12 0.04

.g Flat 4 1971 12 12 106 17.6 2.8 1972 12 12 138 10.6 2.3

.I 1973 24 12 18 3.8 0.6 1974 29 12 1.1 2.8 1.8 1975 29 12 68 0.3 0.7 1976 81 18 843 0.04 0.16 1977 51 11 436 0.09 0 01 Flat 5 1971 9

9 176 1.3 1.6 1972 9

9 196 3.8 2.3 1973 21 11 23 1.0 0.4 l

1974 17 11 2.4 0.0 0.1 i

1975 9

11 7.5 0.0 0.01 l"

1976 24 12 549 0.0 0.14 1977 114 0.08 0.03 l11 (Continued) lIl

26 TABLE 9.

(Continued)

POPULATION DENSITY (#/SQ. FT.)

NUMBER OF SAMPLES I

COLLECTED SPAT ADULTS ADULTS LOCATION YEAR ADULTS SPAT (>l TO 25 m) (25 TO 50 m)

(>50 m)

I All Flats 1971 54 54 92

'.7 2.7 1972 54 54 130 6.2 2.2 1973 111 56 47 2.8 1.0 I

1974 119 56 2.1 2.1 2.0 1975 106 56 37 0.2 0.8 1976 216 62 762 0.06 0.20 1977 212 47 388 0.05 0.07 I

I I

I I

27

[

y Plum Island Sound (Ipswich)

MA l

h Merrimack River Estuary l

I l

35 -

liampton Harbor l

o NH l

I Little Harbor g

fYorkRiver

~

b!

ME I

e 30 -

Ogunquit Beach l

5l, Nl-

'1 l

Rll v-l ei E!

1 I

3l-

}

25 -

I I

5 l

l 1 -l I

l E

I g

j i

a l

I I

d 20 -

I y

I I

I l

l m

i I

l i

j I

l I

l I

I i

l l

1 15 -

1 I

ll l

I l

l 1

j l

l j

{

10 -

0 lN I

l

$l ll 5 I

l l

]

I i

i i

li i.

[

li ll 1

l "l

i i

E Eli l

I i.

el i!

pl II I

I i }i.l ll U l l

5-ll

"[li t q

il I!

i li l my l

"I "1

eit i:

i 11oo((

,[no{l 11"ljj j

i ll i

0 1

OCT JAN-FEB APR JUN AUG OCT 1976 1977 Figure 5.

Shell length medians and ranges for juvenile soft-shell clams collected from selected northern New England estuaries.

Sea-brook lega arenaria Study, 1977.

28 IL

[

~

1977 16-I 14 -

I 12-T10-s POPULATION

' I E-DENSITY =

b-8 d

I 1976 6-4-

I g

POPULATION DENSITY =-2 2-762 ft Limit of discrimination = 1.5mm 0-I Figure 6.

Spat shell length medians and ranges in Hampton Harbor, November 1976 and 1977.

Seabrook 3%a arenaria Study,1977.

l 29 223 415 80 -

l ll 11 I

70 - ll l1976 ll l

ll,

1977 4

Ill 60 -

l l

'g l ll l ll 50 -

l l

l I

'"$ 4 -lll l

llI I

ll

!l!

30 - !ll l

l I

l lll l

l l

1. 3-l l I

l l 10 -

l l

I I

l j

l l

l l

I l

l l

l l

l l

lli,.

l l

l l

l 1

I i

i 0

2 3 4 5 sT 8 9 to 11 12 is 14 is is 1718 is 20 2122 23 24 25 SIZE CLASS (mm)

I Figure 7.

Spat size-freNency distributions for juvenile soft-shell clams from Hampton Harbor, November 1976 and 1977.

I Seabrook erga arenaria Study, 1977.

I 1

30 6).

As of November 1977, approximately 2.5% of all spat were between 17 and 25 mm long (Figures 6 and 7); whereas, there were no spat larger than 12 mm in November 1976 (Figure 7).

Data pertaining to spat density estimates for each of the five principal Hampton Harbor flats is summarized in Table 9.

Further details are presented in Appendix 7.3.

Flat 1 appears to have retained much of the spat observed a year earlier, in November 1976.

Between the 1976 and 1977 annual surveys, densities on Flat 4 have been reduced by approximately one half; while, attrition has been substantially greater on the other three flats.

3.3 ADULT CLAMS:

DISTRIBUTION AND ABUNDANCE Results of Hampton Harbor adult clam surveys conducted through-out 1977 are su=narized in Table 10.

Considering the entire five-flat area, totaling 167 acres, there has been a 45% reduction in biomass since November 1976 and an 88% reduction since November 1974 (Figure 8).

Large declines from the previous year are indicated by the biomass and standing crop values for the individual flats (Table 10), except for Flat 2 which appears to have maintained a fairly stable, albeit sparse, soft-shell clam population for the past two years.

As indicated by the relatively large number of stations on Flat 1 where burrows were evi-dent, and the high yield at these stations (see Column X ; Table 10),

Flat 1 remains an important soft-shell clam propagation area in Hampton Harbor.

Estimates of the percentage of flat area no longer bearing soft-shell clams continued to increase, from 1976 to 1977 (Table 11).

By November 1977, 81% of the 167 acres on the five largest flats had become non-productive.

The smallest proportion of non-productive area (68%) was found on Flat 3.

I L

TABLE 10.

RESULTS OF SOFT-SilELL CLAM (NYA ARENARIA) ESTIMATES, llAMPTON-SEABROOK ESTUARY.

MYA ARENARIA STUDY,1977.

TOTAL NUMBER NUMBER MEAN BIOMASS STANDING CROP NUMBER OF UNITS NUMBER BURROWLESS (BUSHELS / ACRE)

(BUSHELS)

SURFACE SAMPLING BURROWS UNITS WITH UNITS BURROWS NO BURROWS COMBINED AREA UNITS OBSERVED NO BURROWS SUBSAMPLED OBSERVED OBSERVED ESTIMATE ESTIMATED LOCATION DATE (ACRES)

(n)

(n )

(n )

I"EI I 1)

(j)

Y STD DEV X

STD DEV j

2 Flat 2 May 25.5 27 7

20 4

31.00 0.0 8.04 1 3.72 205 1 95 Flat 2 August 25.5 27 8

19 4

27.88 28.0 27.96 1 12.51 712 1 318 Flat 2 November 25.d 33 1

32 8

67.00 6.98 8.79 i 6.76 224 1 172 Flat 1 November 55.0 66 13 53 13 45.92 0.0 9.05 1 2.01 498 1 111 Flat 3 November 11.6 24 5

19 4

13.04 1.08 3.57 1 1.76 41 1 20 Flat 4%

November 50.6 51 2

49 6

16.15 1.15 1.73 1 1.15 88 1 58 Flat 5 November 23.9 38 11 27 5

5.77 1.10 2.45 1 2.94 59 1 70 TOTAL ALL FIATS November 166.6 212 32 180 36 25.78 2.92 6.37 1 1.64 1061 1 273 w

I

4 32 I

l 100-ESTIMATES INCLUDE:

1 LARGER THAN 50MM 90 _

i i

lI o

l 1 ALL ADULT CLAMS 80-i l

70-t E 60-M o

o i n e

' g E

cnd 50-5 om 1

40-l.-

O lo l

1 30-lo 1

,I 20-lI oo l

l T

1..

7 i

l 19'6 1d77 Id71 Id72 1973 19'74 l$75 7

YEAR OF SURVEY

(

Figure 8.

Estimates of soft-shell clam, Ata arenaria, biomass for five j

tidal flats in Hampton Harbor; with approximate 95% confi-dence intervals. Adult clam populations estimated after 1974.

l Seabrook /@a arenaria Study, 1977.

lI l

'I

33 I

TABLE 11 ESTIMATES OF NON-PRODUCTIVE CLAM FLAT, HAMPTON-SEABROOK ESTUARY.

SEABROOK MYA ARL7 ARIA STUDY,1977.

ESTIMATED % OF AREA WHICH WAS

% OF

% 0F UNPRODUCTIVE I

n1 STATIONS nf STATIONS LOCATION MONTH DEVOID OF CLAMS DEV0ID OF CLAMS 1977 1976 1975 1974 Flat 2 May 29 100 81 43 52 Flat 2 August 50 50 50 92 52 Flat 2 November 0

97 85 83 56 37 Flat 1 November 15 100 83 65 47 20 Flat 3 November 40 75 68 52 61 33 Flat 4 November 0

83 80 81 43 12 Flat 5 November 73 80 78 73 96 80 All Flats November 38 89 81 74 55 34 I

I

I I

I

34 Length-frequency distributions of clams, collected from the five major Hampton Harbor flats during the past three November surveys, are presented in Figure 9.

Compared to the previous year there was an increase in 35 mm size-class density, and a reappearance of clams in the 40 mm size-class. On the other hand, there were no longer any individ-uals in the 30 mm class, in 1977; a reasonable explanation is that clams in this group (probably representing the 1975 year class) were recruited to the next larger size classes of 35 and 40 mm.

From the 45 mm size class upwards, densities declined from 1976 values; this was most marked in the mid-range of harvestable adult clam sizes (size classes 55 to 65 mm).

Size frequency records, dating from November 1971, are presented for each of the five principal flats in Appendix 7.3.

I 3.4 SEDIMENT GRAIN-SIZE DISTRIBUTION CHARACTERISTICS OF FLAT 2 AND 4 Graphic means (M ) and standard deviations (c ) of & values y

are presented for Flat 2, in Table 12, and for Flat 4, in Table 13.

There was little evidence of substantial change in sediment character-istics with time, indicating that large portions of these flats are sedimentologically stable.

Approximately 79% of Flat 2 was composed of fine to very fine sand (M $ = 2.7 to 3.2).

Two localities which departed substantially z

from general Flat 2 characteristics are identified, in Figure 10, as I

regions of fine sand (M $ = 2.2 to 2.5) and medium sand (M $ = 1.4 to 1.9), respectively.

These two areas also tended to be less well sorted than the rest of Flat 2 (Table 12).

Flat 4 exhibited a somewhat more complex sedimentological structure than Flat 2 (Figure 11).

The northwestern corner of Flat 4, north of the mussel bed area, was characterized as a medium sand area (M $ = 1.1 to 2.0).

Medium sand also prevailed on landward portions of Flat 4 (M ? = 0. 9 to 2. 3).

Sediments associated with the mussel beds and the drainage away from the beds (Figure 11), tended to be the finest I

35

.20 -

F

.18 -

i i1975 1976

'n -

i i

1977

.14 -

.12 -

i i

i I

ca r

i u.

'm

.10 --

C I

a u

.08 -

I

.06 -

I

.l

.04 -

.l E

l

• l

I

l

l

l

l

l

.02 -

i i.

i; i

il i,

i I

I

I

I

l

l

l

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l

l

i

l

l

l

l

l

l

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.l

.l

l

l

l g :.

.I

.I I

II

.I I'

I I

?

O-30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 SIZE CLASS (mm)

Figure 9.

Length-density distribution of adult clams collec'.ed from five flats in Hampton Harbor in 1975, 1976 and 1977.

l Seabree? A@a arenaria Study,1977.

I m

a

TABLE 12.

GRAPHIC MEANS (M ) AND STANDARD DEVIATION (o ) 0F GRAIN SIZE (4) VALUES FOR FLAT 2.

y SFABROOK NYA AREhARIA STUDY,1977.

t NOVEMBER 1975 FEBRUARY 1976 AUGUST 1976 NOVEMBER 1976 DECEMBER 1977 GRID LOCATION (see Figure 10)

STA M,

g z

"I z

I z

"I STA M o

STA M STA M STA M z

"I Al M5 2.5 0.8 B1 11 8 2.9 154 2.7 0.7 M7 2.9 0.6 MS 2.5 0.8 B2 L3 2.7 5

2.2 1.0 8

3.0 0.5 Cl 11 6 3.1 0.6 C2 IIS 2.9 L1 3.1 0.8 til 2.9 L7 2.8 L8 2.9 D1 4

3.0 0.46 11 1 3.2 0.7 4

3.2 0.7 D2 3

3.0 0.4 6

2.9 0.4 E2 3

2.9 0.33 11 7 3.0 0.5 E3 2

3.0 0.5 F2 11 1 3.0 0.5 9

3.0 0.5 F3 2

3.8 0.48 M4 2.8 L5 1.9 1.1 M1 1.9 1.0 1

1.6 1.2 1

1.4 1.08 F4 L1 2.7 0.6 L5 1.6 1.1 G2 M9 2.9 M3 2.9 0.5 7

2.7 0.5 L6 2.9 L7 2.9 0.5 L3 2.8 0.5 (Continued)

TABLE 12.

(Continued) i KEY (INTERPRETATION):

GRAPillC MEAN (M ) 0F 4 PARTICLE DIAMETER (MM)

GRAPilIC STANDARD DEVIATION (og) 0F 4 7

1.0 0.500 Medium sand

.35 to.50 - well sorted 1.5 0.350

.51 to.70 - moderately well sorted 2.0 0.250

.71 to 1.00 - moderately sorted 2.5 0.177 Fine sand 1.01 to 2.00 - poorly sorted 3.0 0.125 3.5 0.088 Very fine sand 4.0 0.0625 U

ll W

W n

i N

b b

h m

D NAS W

E L

N E

I N

F N

A H

H S

C o

x R

A E

M G

f A

l l

A R

j D

4 o

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W,E iN T

V m

P EV O

T 3'

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/

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^

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4$9aa c% sp j

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11I

)l l

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39 1

I

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A1 8

DRAINAGE CHANNEL A2 A3 h+

I B1 4'

l

@4 B3 B2 I

ci C2 m

y C3 l

C

(

2 x

D12 z D2 l

D3 Y

8 E

I EI W

^ ' #*

I El E2 t

i

?

I 1

1 500 FT Figure 11.

Distribution of mean grain-size classifications on clam flat 4.

Seabrook Mya crenaria Study,1977.

40 grained (M $ = 2.7 to 3.1).

The remainder of Flat 4 bordered on fine to medium sand (M $ = 1.8 to 2.5).

In general, Flat 4 presented a slightly more poorly sorted situation than Flat 2; this was p.rticularly evident at Stations B3 and D3, in February 1977 and at Station E2, in December 1977 (Table 13).

I I

I I

I E

I

'I l

I I

I lI i

I l

r e

---ee-------

,e--*--v

,4-g,,

41 i

I TABLE 13. GRAPHIC MEANS (Mz) AND STANDARD DEVIATION (c ) 0F GRAIN-SIZE (4) VALUES FOR FLAT 4.

SEABROOK NYA AREVARId STUDY,1977.

l SUMMER AUTUMN WINTER SUMMER AUTUMN 1976 1976 1977 1977 1977 c4 M*

"I*

4 M4 o4 M4 c4 M4 STATION M*

z I

7 7

7 7

7 y

z I

4A1 1.6 0.9 1.4 0.9 1.5 0.8 1.1 0.9 1.4 0.9 4A2 3.0 0.5 3.0 0.5 3.1 0.5 3.0 0.5 3.1 0.5 4A3 3.1 0.5 2.8 0.5

.7 0.8 2.9 0.7 2.8 0.8 I

4B1 1.9 0.8 1.5 0.9 2.0 0.8 1.9 0.7 1.5 0.8 4B2 3.0 0.6 3.1 0.7 2.2 1.2 3.2 0.6 3.2 0.6 4B3 1.9 0.6 1.8 0.7 2.1 2.0 2.1 1.0 2.1 0.8 4Cl 2.8 1.0 2.7 1.0 2.7 0.7 2.0 0.7 2.7 0.7 I

4C2 2.4 1.1 2.5 1.4 2.0 0.9 1.9 1.0 1.9 1.2 4C3 1.9 1.2 2.6 1.0 2.0 1.2 1.7 1.2 2.1 0.9 4D1 1.8 1.0 2.6 0.6 2.3 0.8 2.0 1.0 2.2 1.2 B

4D2 1.5 0.9 1.7 0.9 1.7 0.9 1.7 0.9 2.1 0.9 4D3 1.4 1.0 1.7 1.0 2.2 1.6 2.0 1.0 1.4 1.1 4El 1.7 1.0 2.3 0.7 2.3 0.7 1.8 0.9 1.9 0.7 4E2 1.7 0.7 1.4 0.9 1.1 1.0 0.9 1.7 1.5 0.9 I

I B

E

42 1

4.0 DISCUSSION 1

4.1 BIVALVE MOLLUSC LARVAE I

4.1.1

!ba arenaria As the following table shows, M. arenaria umboned veliger densities attained a record low in 1977:

l TABLE 14.

COMPARIS0N OF MYA ARENARIA UMB0NED VELIGER ABUNDANCES OF HAMPTON BEACH, NEW HAMPSHIRE, 1974-1977.

I DAILY MEAN x I

PERIOD OVER WHICH MEAN DENSITY SEASON LENGTH YEAR LARVAE WERE COLLECTED (per m3/ day)

(per ra 3)

I 1974 16 Jul to 5 Sep (51 days) 69 3,520 1975 16 Aug to 14 Oct (59 days) 532 31,400 1976 28 Jun to 17 Oct (1 3 days) 158 17,800 1977 7 Jun to 6 Oct (102 days) 7 714 I

It should be noted that data presented for 1974 and 1975 were collected by low capacity submersible pumps; however, the previous report (NAI, 1977) demonstrated that, when enumerated under carefully controlled conditions, bivalve mollusc larvae density values obtained from pump collections are approximately equivalent to net tow results.

Horizontal distribution data given in Table 7 (Section 3.1) appears to take some exception to the hypothesis, suggested as early as 1973 (NAI, 1974b) and generally substantiated by subsequent data (NAI, I

1977) that M. arenaria larval densities decrease with distance from shore.

However, the fact that there was only one occurrence of this type in 1977 necessitates reserving any further judgement as to the overall expected spatial distribution of patches of M. arenaria pelagic larvae along the New Hampshire coast.

5

5 43 4.1.2 Planktonic Larvae of Other Bivalve Mollusc Species So far as is known, the present study of bivalve larval abun-I dance and species distribution is unique; no other studies have been identified with wnich the data presented here can be compared.

Bivalve mollusc larvae are usually among the most abundant forms in the mero-plankton, and have been enumerated as a generic group (e.g., McAlice, 1972; Lee, 1974); only qualitative species ccmposition information has been given, ho"ever.

Total densities reported by McAlice (1972) and Lee (1974) averaged one or two orders of magnitude lower than densities reported here.

I Species composition off Hampton Beach appears to reflect relative abundance and proximity of adult bivalve mollusc populations I

inhabiting the study area.

The two mussel species are dominants and principal habitat formers on nearby rocky outcroppings. The nestling clam, Riatella sp. is quite frequently found with the M. modiolus habi-tat.

Anomia squamula are frequently recovered from benthic dredge samples. Many bivalve mollusc species common to the study area were poorly represented in the planktan samples or not found at all.

This may be due to a larval demersal habit, or because larvae of certain species tend to remain in the brood chambers of the adults until they are almost ready to settle as spat; the clams Gemma gemma and Nucula spp. are primary examples of the latter habit.

I Data presented in Figure 4 tend to suggest that a density decrease with distance seaward, as hypothesized for M. arenaria, may not hold for larvae of other bivalve mollusc species, particularly Anomia sp.

As was the case with M. arenaria spatial distribution (Section 4.1.1), general inferences drawn from a single collection date cannot be evaluated as to reliability.

i 4.2 SOFT-SHELL CLAM SPAT 1

i i

The high density of the 1976 spatfall has provided an excel-l i

lent opportunity to compare soft-shell clam growth and survival in lI l

l 44 l

\\

several estuarine locations. As reported in Section 3.2, virtually complete failure of the 1976 set occurred in three of the estuaries studied. What appeared to distinguish these three estuaries, from those where the 1976 set had substantially survived, was the relative propor-tion of " disturbed" substrate.

In " undisturbed" areas, the substrate I

was relatively smooth; depressions made by natural and human predators, where present, were widely scattered.

" Disturbed" area could be classi-I fied as either:

1) ripple marked and coarse sandy areas, predominantly influenced by storm waves and/or strong tidal flow or 2) relatively calm areas of finer sediment, but which were heavily pocketed with predator pits.

I By October 1977, substantial acreage of relatively undisturbed substrate was limited almost exclusively to Plum Island Sound and Hamp-ton Harbor, the latter having been closed to digging since May.

The second (predator pit) type of disturbed substrate seemed to increase in i

extent in all six estuaries, throughout the su=mer.

Over the same time interval, the greatest spat loss was apparent (Table 8).

August 1977 sample results from " disturbed" and " undisturbed" areas on Flat #2 were compared in terms of both spat density and size frequency distribution (Figure 12).

This comparison indicated that not only were the disturbed areas relatively depleted, but that the sur-vivors were generally smaller in disturbed areas than in the undisturbed area. These observations are consistent with the expectation that those predators which are most active during the summer (namely, green crabs) would detect and devour the larger clams in preference to the smaller I

ones thereby leaving space for smaller clams to resettle in the areas depleted of larger clams.

At growth rates previously projected for soft-shell clam shell growth (Figure 13) it was anticipated that survivors of the 1976 spat set might attain harvestable size in approximately 3 years.

It now appears that this projection was overly optimistic.

Only on the Plum Island Sound flats did shell growth even approach projections shown in

I 45 I

16 -

I 14 -

I 12 -

I 10 -

.I 5

Apparently undisturbed area I

h8-

~18,000 clams /m 2

(~1700/ft )

Obvious I

d substrate

!E disturbance m

by water action I

and predators 6-

-(i.e. dug pits) i 2

~1300 clams /m )

(~120/ft )

4-j l

I 2-Limit of Discrimination = 1.5mm 0

l

-I l

Figure 12.

Comparison of size ranges at " disturbed" and undisturbed areas, Flat #2, Hampton Harbor, N.

H., August 1977.

l Seabrook rya crencria Study,1977.

I t

46 l

Figure 13.

One factor which was not anticipated by the Figure 13 pro-jections was the extremely crowded conditions existing on the relatively

" undisturbed" substrate areas, particularly in Hampton Harbor.

Data presented in Figure 14 indicate an inverse relationship between shell growth and population density.

Causes of the observed interval of several years between highly successful spatfalls at Hampton Harbor (Table 9) remain largely obscure.

It is apparent, however, that seasonal planktonic larval abundance was a relatively poor predictor of spatfall success during 1977 (Tables 9 and 14).

I 4.3 STtTUS OF ADULT SOFT-SHELL CLAM STOCKS IN HAMPTON HARBOR 8

In addition to considerably reducing the uncertainty of clam flat acreage estimates, delineation of natural flat boundaries using f

aerial photography resulted in the incorporation of about 25% more flat area than would have been practical using ground survey methods des-cribed in Section 2.3.

(which depend on line-of-sight and therefore cannot include " blind" area obscured behind salt marsh).

This increase of 30 to 40 acres to the study area as of November 1977, not included in previous surveys, should be kept in mind when referring to historical I

standing crop values presented in Tables 15 and 16.

Correcting for the acreage added in 1977, it has been esti-l mated that approximately 950 bushels of harvestable clams were taken from the five principal clam flats in the interval between November 1976

(

and November 1977; this amounted to approximately 46% of the standing crop as of November 1976.

In contrast, approximately 3600 bushels (73%

of the November 1975 standing crop) were harvested in the previous 12 month interval (NAI, 1977).

Some of the reduction in proportion of harvested to unharvested clams reflects an increasingly diminishing

=

return for digging effort; but much is also due to the fact that the I

Hampton Harbor flats were closed to clam digging throughout the summer I

l I

1

00-80 -

I 70-f,, j GO-f..

@ 50-g i

d 40-y m

30-20-10 -

0 4

5 6

AGE, YEARS Figure 13.

Estimated shell growth rate of soft-shell clam, Nya arenaria, with approximate 95% confidence intervals.

Seasonal dips in the curve suggest slowing of growth in the late fall and early winter (NAI, 1977).

Seabrook #sa arenaria Study, 1977.

U

25 as I

I 20 -

I FLAT

1. 5 15 -

h FLAT l

5

1. 4

~

d I

E:!

Di 10 -

FLAT il I

I I

5-'

I I

I O

s s

a s

s.

.s.

s 2

4 6

8 10 12 14 16 18 20 I

POPULATION DENSITY (FT-2X 100)

Figure 14.

Comparisons of size-density distributions at undisturbed, I

relatively well-settled areas of selected flats in Hampton Harbor, N. H., November 1977.

Clams are approximately 13-15 months old. Seabrook Nya arenaria Study, 1977.

I

I 49 TABLE 15.

RECENT HISTORY OF THE STANDING CR0P OF LEGAL SIZE MYA ARENARIA IN HAMPTON HARBOR.

SEABROOK MYA ARENARIA STUDY,1977.

I I

ESTIMATED BUSHEL TOTAL ESTIMATED NUMBER DATE PER ACRE OF BUSHELS November 1967 152 23,400 July 1969 103 15,840 November 1971 84 13,020 November 1972 58 8,920 November 1973 41 6,310 November 1974 56 8,690 l

November 1975 29 4,945

.I November 1976 11 1,350 November 1977 6

1,060 I

I I

I I

'I I

(from Ayer, 1968)

I I

50 l

TABLE 16. RECENT HISTORY OF THE STANDING CROP 0F MYA ARENARIA (>50 mm LONG)

ON FLAT #2.

SEABROOK MYA ARENARIA STUDY,1977.

I ESTIMATED BUSHELS TOTAL ESTIMATED NUMBER DATE PER ACRE OF B'JSHELS 1

November 1967 220 5,500 July 1969 119 2,970 Noverber 1971 139 3,480 I

April 1972 118 2,960 July 1972 61 1,530 November 1972 55 1,380 I

February 1973 39 980 May 1973 59 1,480 August 1973 52 1,310 November 1973 63 1,580 I

January 1974 48 1,200 May 1974 33 825 August 1974 29 730 I

November 1974 60 1,510 February 1975 71 1,300 May 1975 68 1,060 I

August 1975 20 355 November 1975 36 785 February 1976 23 385 May 1976 17 260 I

August 1976 3

50 November 1976 8

140 February 1977 I

May 1977 8

205 August 1977 28 712 November 1977 9

224 I

I I

I 1 (from Ayer, 1968)

I

51 of 1977.

Extrapolating the rate of standing stock depletion prior to 1977 (Figure 8), it appears that as much as 600 bushels might have been added to the 1977 harvest had the flats been open all summer.

Substantial replacunent of depleted adult stocks through the I

recruitment of juvenile clams appears to be a hopeful prospect but still at some distance in the future. At recently observed growth rates, very few of the juveniles now inhabiting the flats can be expected to attain harvestable size by November 1978.

A reasonable expectation, based on estimated mortality (NAI, 1977) and densities of 20 to 25 mm clams observed in November 1977 would be recruitment of 150 to 200 bushels by November 1978. This amounts to less than 1/3 of the most recent annual yield,... suggests an additional " deficit" withdrawal of 550-600 bush-I els in 1978, leaving perhaps 650-700 bushels remaining on the flats in November, assuming another closed summer season.

I 4.4 RELATIONSHIP 0F SEDIMENT GRAIN-SIZE DISTRIBUTION TO SOFT-SHELL CLAM PROPAGATION POTENTIAL Results of both the clam and sediment surveys can only be compared qualitatively since the sample sites were spatially and temp-orally separated. Nevertheless, there appears to be an affinity between areas characterized as containing fine sand sediments and the presence of Mya arenaria.

Such an association is supported by the observations I

of Stanley (1970).

Very few specimens of M. arenar'ia were found in areas characterized by medium sand; clams that were present were large (8 to 10 cm long) and deeply burrowed (approximately 20 to 25 cm).

Exclusion of small soft-shell clams from medium sand areas was probably due to prevalence of somewhat stronger currents (imposing a mechanical disadvantage at these locations) and not due to any aversion to coarser sediments.

In the vicinity of mussel (Mytilus edulis) beds, sediments tended to be characterized by very fine sand; here, larger M. arenaria I

lI

52 l

tended to be excluded, probably because of the difficulty soft-shell I

clams have in clearing their siphons of silt (Stanley, 1970), heavy siltation being a natural result of mussel encroachment.

l l

R 1

i I

i I

I 1

I l

l I

t

53 I

5.0

SUMMARY

As of November 1977, it was estimated that approximately 1060 I

bushels of adult clams remained on the five largest flats of Hampton Harbor totalling 167 acres.

It was also estimated that since the pre-vious survey (*ovember 1976), clam diggers removed approximately 950 bushels or 70% of the clams present in November 1976.

Re-uitment of newly harvestable stock from a very modest population of juvenile clams (mostly from the 1972 year class) plus a slight expansion of the study area (i.e., addition of 30-40 acres) accounted for the apparent decrease of only about 300 bushels.

I The 1976 year class of clam spat continued to survive in Plum Island Sound (approximately 100 per f t ), Hampton Harbor (approximately I

250 per ft ) and Ogunquit Beach (approximately 24 per ft ), but has been virtually eliminated f. rom the Merrimack River Estuary, the York River at Route 103 bridge, and Little Harbor Channel in Portsmouth, New Hamp-shire. The latest year class (1977) has a population density of 80 to 90 per ft in Hampton Harbor and is exceeded in abundance only in Plum Island Sound (570 per ft ).

Nya arenaria umboned larvae densities averaged only 7 per m during a 102-day period of observation.

This was by far the lowest level of abundance in four years of record. Only on one date (22 August 1977) did larval densities exceed 15 per m. On that date densities up to 250 per ft were recorded as far as 1.5 nautical miles offshore.

At 2 nautical miles from the New Hampshire coast the larval density dropped to approximately 45 per m. Other species of bivalve mollusc larvae associated with M. arenaria in the plankton included, in order of decreasing abundance, Modiolus modiolus (horse mussel), Mytilus edulis (edible mussel), Hiatella sp. (a small clam which nestles among the Modiolus), Cerastoderma pinnulatum (northern dwarf cockle) and Ensis directus (razor clam).

I I

54 Intertidal flats containing soft-shell clams were largely composed of sand grains ranging in size from.10 to.30 mm.

Larger clams (length greater than 10 mm) tended to be excluded from the very I

fine sandy areas (average particle size less than 0.12 mm); smaller clams (length less than 45 mm) tended to be excluded from areas of medium sand (average particle size greater than.25 cm).

It has been estimated that clams representing the 1976 lear class will attain harvestable size in 1981 and 1982.

Notwithstanding this projection, restoration of soft-shell clam stocks to pre-1971 levels will require several spatfalls as successful as the 1976 settle-I ment.

I I

I I

I I

I

55

'l 6.0 LITERATURE CITED Ayer, W.

C.

1968.

Soft-shell clam population study in Hampton-Seabrook Harbor, New Hampshire. New Hampshire Fish and Game Dept.

39 pp.

Ayers, J. C.

1956.

Population dynamics of the marine clam. Mya are-naria.

Limnol. and Oceanogr.

1(1):26-34.

Carver, Robert E.

(ed.).

1971.

Procedures in sedimentary petrology.

John Wiley and Sons.

New York, NY.

Dow, R.

L.

1972.

Fluctuations in Gulf of Maine sea temperature and specific molluscan abundance.

J. Cons. Int. Explor. Mer.

34:532-534.

1977.

Effects of climatic cycles on the relative abundance and availability of commercial marine and estuarine species.

J.

Cons. Int. Explor. Mer.

37(3):274-280.

and D.

E. Wallace.

1957.

The Maine clam (Mya arenaria).

e Maine Dept. of Sea and Shore Fish. Bull.

35 pp.

Folk, Robert L.

1968.

Petrology of sedimentary rocks.

Hemphills, Austin, TX.

Hansen, M.

H.,

W.

H. Hurwitz and W. G. Madow.

1953.

Sample survey I

methods and theory.

Vol. II.

Wiley-Interscience.

pp. 257-260.

Kane, W.

T. and J. F. Hubert.

1963.

"A Fortran Program for the Cal-culation of Grain-Size Textural Parameters on the IBM 1620 Com-puter".

Sedimentology.

2:89-92.

Lee, W.

Y.

1974.

Succession and some aspects of populativn dynamics of copepods in the Damariscotta River estuary, Maine.

Ph.D. Thesis, Univ. of Maine, Orono.

181 pp.

McAlice, B.

J.

1972. Plankton.

IN:

Survey of the hydrography, sedi-ments, plankton, benthos and the commercially important plants and animals including finfish in the Montsweag Bay-Back River area.

Third Annual Report.

Ira C. Darling Ref. No. 72-12.

Normandeau Associates, Inc.

1971.

Seabrook Ecoltgical Study:

Phase I 1969-1970, Hampton-Seabrook Estuary, New Hampshire.

Prepared for Public Service Company of New Hampshire.

313 pp.

1973.

Studies on the soft-shelled clam, Mya arenaria, in the Hampton-Seabrook Estuary, New Hampshire.

Technical Report IV-2.

1974a.

Studies on the soft-shelled clam, Mya arenaria, in the Hampton-Seabrook Estuary, New Hampshire.

Technical Report V-2.

56 I

1974b.

The impact of entrainment by the Seabrook Station.

Technical Report V-4.

I 1975a. Studies on the soft-shelled clam, Mya arenaria, in the Hampton-Seabrook Estuary, New Hampshire.

Technical Report VI-l 3.

1975b.

Spatial and temporal distribution of the larvae of the soft-shelled clam, Mya arenaria, in the Hampton-Seabrook Estu-ary and nearby offshore waters. Technical Report VI-1.

1975c. Mya arenaria confirmational study.

Report prepared for Public Service Company of New Hampshire.

1976a. Studies on the soft-shelled clam, Nya prenaria, in the Hampton-Seabrook Estuary, New Hampshire. Technical Report VII-1.

1976b. Spatial and temporal distribution of the larvae of the soft-shelled clam, Mya arenaria, in New Hampshire coastal waters, 1975. Technical Report VI-10.

1977. Seabrook Ecological Studies 1975-1976.

Studies on I

the soft-shelled clam, Mya arenaria, in the vicinity of Hampton-Seabrook estuary, New Hampshire.

Ropes, J. W.

1968.

The feeding habits of the green crab, Carcinus I

maenas (L.).

Fish. Bull.

67(2):183-203.

and A. P. Stickney.

1965.

Reproductive cycle of Mya are-naria in New England. Biol. Bull.

128:315-327.

Savage, N. B. and R. Goldberg.

1977.

Investigation of practical means I

of distinguishing Mya arenaria and Hiatella sp. larvae in plankton samples.

Proc. Nat. Shellfish. Assoc.

66:42-53.

I Scattergood, L. W.

1952. The distribution of the green crab, Carcinus maenas (L.) in the northwestern Atlantic.

Maine Dept. Sea and Shore Fisheries Fish. Circ.

8:2-10.

deSchweinitz, E.

H. and R. A. Lutz.

1976.

Larval development of the northern horse mussel, Modiolus modiolus (L.), including a compar-ison with the larvae of Mytilus edulis (L.) as an aid in planktonic identification.

Biol. Bull.

150(3):348-360.

Stickney, A. P.

1964.

Salinity, temperature and food requirements of soft-shell clam larvae in laboratory culture.

Ecology.

45(2):283-291.

l Sullivan, Charlotte M.

1948.

Bivalve larvae of Malpeque Bay, P.E.I.

Fish. Res. Bd. Canada Bull.

77.

36 pp.

57 Welch, W.

R.

1969.

Changes in abundance of the green crab, Carcinus maenas (L.) in relation to recent temperature changes U.S. Fish Wild 1. Serv. Fish. Bull. 67(337-345).

1975.

Report on the relative abundance of green crabs along the Maine coast, Fall 1975. Maine Dept. of Marine Resources.

I a

ss l

I I

lr L

I n

L_

E ww---n----emen,,m

-,w,--

--m--------w-m-w---ew--w--

m---

.--e~

~,

--w,-

,w- - - - - - - - - --

L E

E I

.I I

I APPENDIX 7.1 RESULTS OF BIVALVE LARVAE TOWS OFF HAMPTON BEACH, NEW HAMPSHIRE I

I I

N

m M

M M

M M

M M

Hampton NH isivalve larvae 1977 Station I Wets Wr m )

4 kplicate Species 27 June 30 June 5 July 8 July 11 July 14 July

!N iolus 5,518 5,319 54,248 55,832 47,594 53,219 9,490 10,902 14,178 18,905 22,101 21,416 ftytilus 3,157 3,470 5,851 9,143 4,038 1,875 4,149 5,870 11,422 2, b.o 4, l e.4 H,lo2 1

Hiatella 1,024 910 9,265 9,307 7,788 6,346 1,368 750 5,514 2,48 2 6,102 7,9a9 Anomia 170 P

P P

721 1,154 P

P 4,431 591 900 1,601 others 2u a5 1,340 1,340 1,298 H65 177 220 98 P

l let 194 lbad iol u s 4

3, 16, M 20, 0 1 11 859 11,106 flytilu s 13,885 17,356 9,017 2,445 9,504 9,446 3,34u H,763 4,533 2,240 2

Hiatella 1,902 866 12,149 10,414 H,712 7,642 1,000 441 3,249 2,462 5,913 0,lH1 Anomia P

P P

P 7,336 1,987 P

P 398 1,772 H,213 5,440 others 75 376 1,909 1,562 764 917 294 118 P

590 53

.52 0 sample j

Volumes (m ) :

1 9.0 H.4 7.1 5.8 10.4 9.1 2

6.H 5.9 6.7 8.7 10.4

9. e, 18 July 21 July 25 July 26 July 1 August 4 A.quqt Modiolus 2,488 2,943 1,551 1,812 1,665 2,3u6 1,560

'1,582 239 2H4 IN 141 ft tilus 3,491 1,890 3,624 3,682 1,255 1,342 827 920 530 38u 201 145

/

1 Hiatella 1,770 1,412 2,704 2,618 447 1,193 539 439 317 310 300 249 Anomia 407 359 3,480 1,093 211 1,441 396 JI3 601 517 11 7 209 Cera st o.ler ma 72 65 317 213 111 91 Others 1b7 167 288 316 112 149 36 14.4 26 19.4 22 16.H Modiolus 2,442 2,737 1,743 899 1,556 1,876 517 1,223 733 584 38u 2e,5 Mytilus 2,824 2,678 3,568 2,941 618 887 501 845 148 130 246 220 2

Hiatella 2,442 1,971 1,716 2,H05 480 436 246 336 668 475 5H2 498 Anomid 971 559 926 3,677 313 233 246 459 232 631 104 459 Cerastoderma 240 33 90 102 102 71 97 Zirphaea 37 9.3 Others 205 324 300 191 218 14.5 25 25 9.3 0.0 52 19.4 Sample Volumes (m'):

1 10.7 8.9 10.3 8.9 9.9 9.5 2

8.7 9.4 8.8 7.8 6.9 9.9 in P - present in small quantities v

i 1 - mostly Cerastoderma i

i 1

t

M M

M M

M M

M M

M 3

Itampton NH Bivalvo larvae 1977 Station 1 (courit s ger m )

4 Implicate species u August 11 August 15 Augun.t 18 August 22 August 25 Au.just ibliolum 43 31 4

5 30 70 27 la 13 13 121 399 Itytilus 211 217 13 75 177 207 143 77 90 90 1 15 101 Hiatella 45 53 16 18 262 174 82 62 198 109 j70 too 1

Anoman bu 7H 7

13 390 293 273 155 128 262 1,015 a19 Ce r a s t rale r ma 16 12 2

3 42 52 58 32 90 67 213 314 On.is others 2

6 7

7 30 9

10 5

19 to 11 28 ndiolus

's 4 27 4

3 27 59 20 15 9

9 26 21i 135 121 70 26 121 IH3 122 flytilus 126 130 44 38 l

Hiatella 69 32 21 14 160 237 96 66 61 65 345 125 i

2 Anumi.n 46 41 14 18 210 680 254 234 181 199 1,554 1,(25 Cosastuivama 30 9

2 1

29 29 46 26 52 121 345 173 2irphaea 2

9 Ensas 7

7 others 14 0

4 4

11 32 0

0 0

13 51 30 Sample volumes (m,)s 1

7.8 10.4 10.5 9.6 9.8 9.0 2

7.0 7.9 7.1 8.G 8.6 6.3 29 August 1 Sept.

6 Sept.

8 Sept.

12 Sept.

15 Sept.

Mxtiolu s 1,203 2,082 1,341 1,097 2,001 2,377 1,074 1,074 137 242 361 392 Mytilus 213 410 777 716 2,306 3,352 6,744 5,010 522 549 1,687 1,446 1

Hiatella 410 341 366 411 965 1,300 2,588 1,844 294 242 1,0e,9 1,024

~

Arxmia 819 2,594 1,630 1,250 1,524 2,458 1,211 1,266 170 144 1,129 648 Cerastexter na 136 239 168 152 518 447 275 413 85 52 45 90 Ensis 183 244 110 110 26 72 45 75 others 111 34 107 91 173 142 138 110 26 d5 120

!H1 5,512 6.060 Str. Hinge I

1 Mtx11olus 1,180 2,060 1,757 1,580 1,715 1,997 582 785 698 545 999 718 Mytilus 280 700 1,294 1,389 2,099 1,587 6,662 6,051 487 487 2,217 1,140 Hiatella 370 460 477 613 794 1,178 1,600 1,629 233 211 1,296 1,093 Anomia 2,590 1,960 1,226 803 2,176 1,408 2,473 3,004 182 225 1,296 843 Cerastoderma 290 200 286 354 410 307 204 175 58 51 172 109 Ensis 154 154 29 58 29 7

78 109 others 70 60 41 41 179 102 29 175 65 124 359 125 Str. Hinge

• 6,342 6,065 Sample Volumes (m }

1 7.5 4.2 6.3 9.3 9.8 8.5 l

2 6.4 4.7 5.0 8.8 H.8 8.2 C.

O a

Hampton NH Biyalve larvae 1977 Station I (counts ger n )

4 Replicate Species Modiolus 758 573 231 42 110 110 60 80 12 7

29 22 Mytilus 1,495 2,028 1,070 1,070 1,597 1,872 745 645 67 28 94 107 Hiatella 799 614 462 2 94 110 26 230 210 12 9

14 12 1

Anomia 2,191 2.970 2,665 2,350 358 440 720 740 229 114 76 101 Ensin 2,007 1,249 42 0

55 55 30 25 10 17 19 25 Cerastoderma 164 82 147 147 55 26 20 25 other 123 26f 189 42 110 165 80 70 14 3 1/2 19 18 Str. Hinje 21,251 23,783*

Modiolus 238 449 230 288 62 48 48 103 4 1/2 7 1/2 15 13 Mytilus 3,088 3,246 2,474 1,266 1,129 1,025 453 670 39 64 44 42 Hiatella 871 818 2B8 345 83 55 145 193 7

16 9

8 2

Anomia 2,138 3,141 3,%9 2,618 179 193 604 821 145 222 93 69 Ensis 1,399 1,636 56 56 28 21 30 12 7

16 21 13 Cerastoderm 106 259 230 14 7

18 30 17 13 Other 158 211 259 201 76 69 72 103 4 1/2 13 Str. Hinge i

6,'59 16,654*

Sample volumes (m ):

1 12.5 12.3 9.3 12.8 9.3 13.3 2

9.7 8.9 9.3 10.6 8.8 10.1 10 Oct.

13 Oct.

20 Oct.

27 Oct.

Modiolus 35 30 67 99 218 139 175 40 Mytilus 12 18 47 27 201 99 36 17 1

Hiatella 4 1/2 5 1/2 27 30 20 28 9 1/2 0

Anomia 32 37 308 295 419 292 79 34 Ensis 31/2 4

56 30 5 1/2 20 5 1/2 5 1/2 Placopecten 5 1/2 5 1/2 2

4 Cerastoderna 11 20 Other 3 1/2 4 1/2 13 24 23 51 5 1/2 5 1/2 Modiolus 35 28 105 93 332 187 51 156 Mytilus 23 15 50 30 274 224 15 46 2

Hiatella 9 1/2 5

47 48 54 50 11 13 Ar.omia 32 29 335 287 690 366 42 110 Ensis 3 1/2 2 1/2 40 25 17 4

0 9

Placopecten O

8 1/2 0

2 Cerastoderma 33 31 other 5 1/2 4 1/2 30 17 58 42 5 1/2 2

Sample 3

Volumes (m ):

1 9.7 9.5 11.3 8.'$

2 8.5 9.6 7.7 8.7 W

• 24-48 hr Mcxliolus modiolus

Itampton ten B1 valve larvae 1977 Station Mrq 5 (counts per m )

peplicate Species 27 June 30 June 5 July 8 July 11 July 14 July Modlotus 3,013 2,160 112,924 143,644 24,017 33,140 33,858 26,756 17,101 20,992 3,657 2,405 Mytilus 7,440 6,747 7,111 13,369 14,336 5,399 34,849 47,071 7,270 20,070 1,280 768 1

Hiatella 1,200 1,547 3,413 3,129 3,351 2,606 3,468 2,312 3,482 3,174 567 1,125 Anomia P

P 569 P

745 465 P

P 307 1,946 128 46 Others 453 107 569 372 279 49%

495 102 102 91 110 natiolus 121,791 137,042 22,499 31,874 43,174 28,783 21,333 11,70) 2,654 2,500 Mytilus 5,882 5,665 13,701 9,807 55,075 50,672 13,653 13,531 1,748 952 2

Hiatella 5,229 3,050 3,317 3,461 8,441 1,937 3,291 5,120 1,623 1,733 Ancela P

P

$77 P

.1,522 P

243 1,219 390 P

Others 1,0H9 654 433 289 969 415 243 P

109 156 Sample 3

Volumes (m ):

1 9.6 3.6 5.5 6.2 10.0 7.0 2

7,2 4.7 7.1 7.4 8.4 H.2 18 July 21 July 25 July nuliolus 1,039 1 965 2,608 2,198 1,045 1,003 Mytilus 3,636 2,894 4,903 4,709 2,741 1,664 1

Hiatella 1,169 723 1,352 966 320 480 Arva t a 2,319 1,299 604 1,352 245 139 Others 111 106 313 97 53 96 n=11olus 2,848 4,759 1,801 1,291 Mytilua 0,942 5,661 1,562 1,432 2

Hiatella 2,091 1,659 911 597 Anomia 1,803 649 103 163 Ottwr s 72 36 43 119 Sample 3

Volumes (m ) s 1

6.9 10.6 12.0 2

7.1 8.7 11.8 P - present in small quantitles hJ s

E l

I I

s I

APPENDIX 7.2 SHELL SIZE DISTRIBUTION (#/ft ) 0F SOFT-SHELL CLAM SPAT COLLECTED FROM FIXED STATIONS IN SIX NORTHERN NEW ENGLAND ESTUARIES I

1976 THROUGH 1977 I

I I

I I

I

~

64 i

PLUM ISLAND SOUND MIDDLE GROUND I

SIZE 19 21 17 28 11 11 8

5 19 I

CLASS APR JUN AUG OCT FEB APR JUN AUG OCT (mm) 1976 1976 1976 1976 1977 1977 1977 1977 1977 1

1.5 l

2 4.6 47.0 6.1 34.0 0.76 63.0

}

3 1.5 0.76 4.5 103.0 27.0 37.0 1.5 1.5 206.0 i

4 0.76 2.3 31.0 24.0 25.0 18.0 3.1 160.0 5

0.76 18.0 25.0 18.0 28.0 0.76 71.0 6

2.3 4.6 16.0 20.0 35.0 0.76 77.0 7

0.76 4.6 3.1 15.0 44.0 0.76 47.0 8

2.3 5.3 2.3 16.0 38.0 25.0 9

1.5 3.1 11.0 31.0 13.0 10 1.5 2.3 5.3 24.0 1.5 3.1 11 1.5 0.76 7.6 18.0 2.3 5.3 12 1.5 0.76 1.5 3.8 21.0 1.5 13 0.76 3.1 25.0 5.3 2.3 14 0.76 27.0 5.3 1.5 15 0.76 1.5 22.0 8.4 6.1 16 0.76 0.76 12.0 13.0 7.6 17 12.0 17.0 11.0

}I 18 0.76 8.4 15.0 11.0 19 6.1 20.0 8.4 4

20 6.9 22.0 8.4 g

4 21 4.6 15.0 11.0

'E i

22 3.1 15.0 6.1 23 6.1 9.1 8.4 24 3.1 11.0 9.1 25 3.1 8.4 8.4 26 1.5 6.1 6.9 27 1.5 3.8 4.6 I

28 3.1 7.6 29 3.1 5.3 30 2.3 4.6

'I 31 2.3 I

32 0.76 1.5 33 2.3 1.5 I

34 1.5 35 1.5 I

65 PLUM ISLAND SOUND LUFKIN'S FLAT E

SIZE 11 8

5 19 CLASSES APRIL JUNE AUGUST OCTOBER

{

(mm) 1977 1977 1977 1977 1

r-2 25.0 3.8 24.0 3

73.0 25.0 1.3 70.0 4

36.0 36.0 1.3 45.0 5

18.0 36.0 3.8 22.0 6

8.9 46.0 2.5 7.6 7

3.8 22.0 1.3 2.5 8

13.0 45.0 1.3 9

7.6 20.0 10 5.1 10.0 11 8.9 2.5 12 7.6 1.3 13 8.9 2.5 14 6.4 2.5 15 6.4 1.3 16 3.8 1.3 17 6.4 5.1 18 3.8 1.3 1.3 2.5 19 20 1.3 1.3 21 1.3 1.3 1.3 2.5 22 1.3 1.3 23 1.3 3.8 1.3 24 1.3 25 3.8 2.5 26 2.5 1.3 27 1.3 3.8 2.5 28 3.8 6.4 29 1.3 1.3 3.8 30 1.3 3.8 31 1.3 1.3 5.1 32 1.3 3.8 33 3.8 I

34 1.3 2.5 35 1.3 2.5 36 3.8 37 2.5 38 1.3 39 40 41 42 43 44 45 1.3 I

i 66 I

l l

PLUM ISLAND SOUND IPSWIC11 RIVER AT NECK C0VE ijg SIZE 19 21 17 28 11 JE CLASS APRIL JUNE AUGUST OCTOBER FEBRUARY l

(mm) 1976 1976 1976 1976 1977 1

2 0.76 6,9 79.0 79.0 3

9.9 47.0 66.0 i

4 4.6 0.76 0.76 11.0 12.0 l

5 0.76 2.3 1.5 6.1 6

3.8 2.3 0.76 l

7 1.5 0.76 l

8 2.3 0.76 9

10 11 l

12 0.76 1

13 l

14

{

15 l

16 0.76 17 18 19

(

20 l

21 0.76 l

22 l

23 24 25 I

I I

1 l

l l

i i

i, l

l l

67 I

4 ll PLUM ISLAND SOUND i a EAGLE HILL RIVER AT NUT SH0AL SIZE 11 8

5 19

!l CLASSES APRIL JUNE AUGUST OCTOBER (mm) 1977 1977 1977 1977 lI 1

2 13.0 7.6 158.0 d

3 44.0 5.7 36.0 382.0 4

40.0 5.7 17.0 185.0 5

17.0 3.8 3.8 105.0 6

11.0 1.9 1.9 67.0 7

17.0 5.7 1.9 15.0

{g 8

11.0 7.6 9.6 i

9 5.7 5.7 1.9 10 1.9 19.0 i

11 1.9 11.0

}

12 7.6 15.0 13 3.8 25.0 3.8 Ig 14 1.9 31.0 5.7 3

15 1.9 29.0 7.6 i

16 1.9 15.0 5.7 l

17 1.9 9.6 5.7 18 1.9 11.0 7.6 19 5.7 13.0 1.9 20 5.7 15.0 l

21 1.9 17.0 3.8 l

22 1.9 13.0 1.9

{l 23 19.0 11.0 lE 24 5.7 1.9 25 9.6 1.9 26 11.0 5.7 j

27 3.8 9.6 l

28 1.9 7.6 29 1.9 1.9 I

30 1.9 3,8 31 1.9 7.6 32 1.9 5.7 33 ll l

34 1.9 l5 35 36 5.7 37 38 3.8

{

39 3.8 40 l

41 j

42 43 1.9 44 i

I 68 i

MERRIMACK RIVER ESTUARY BALL'S FLAT #1 i,I SIZE 23 23 17 18 26 27 13 6

2 18 CLASS MAR APR JUN AUG OCT JAN APR

-JUN AUG OCT l

(mm) 1976 1976 1976 1976 1976 1976 1977 1977 1977 1977 1

2 6.9 1.5 164.0 115.0 47.0 21.0 0.76 27.0

!g 3

0.76 16.0 0.76 11.0 151.0 83.0 201.0 121.0 4.6 37.0 lg 4

1.5 9.9 2.3 3.8 27.0 37.0 89.0 72.0 6.1 13.0 2

5 5.3 1.5 5.3 6.1 7.6 23.0 25.0 3.1 1.5 6

4.6 0.76 3.8 0.76 4.6 18.0 2.3 7

1.5 0.76 0.76 1.5 0.76 3.1 7.6 0.76 j

8 1.5 0.76 2.3 0.76 0.76 9

3.1 3.1 I

10 2.3 11 0.76 12 13 14 2.3 15 16 0.76 I

17 18 19 20 0.76 21 22 23 I'

24 25 0.76 I

I

w 69 r

L MERRIMACK RIVER ESTUARY SALISBURY FLAT #3

{

E SIZE 23 23 17 18 26 28 13 6

2 18 CLASS MAR APR JUN AUG OCT JAN APR JUN AUG OCT (m) 1976 1976 1976 1976 1976 1977 1977 1977 1977 1977 p

1 2

3.8 56.0 15.0 11.0 1.5 5.3 6.9 3

2.3 5.3 0.76 39.0 29.0 43.0 7.6 20.0 6.9 4

2.3 5.3 1.5 3.1 4.6 26.0 21.0 8.4 5.3 3.8 5

1.5 2.3 1.5 2.3 1.5 9.2 7.6 6.9 3.1 6

1.5 1.5 1.5 3.1 2.3 3.1 2.3 1.5 7

2.3 3.1 0.76 0.76 8

0.76 1.5 3.1 0.76 9

0.76 0.76 0.76 10 0.76 0.76 I

11 1.5 0.76 0.76 0.76 12 13 0.76 14 0.76 15 16 0.76 0.76 0.76 17 18 1.5 19 20 0.76 21 22 0.76 23 0.76 I

24 25 0.76 I

I I

{

ll

>o HAMPTON HARBOR, FLAT #2 i

i l

SIZE 12 21 18 16 21 11 14 7

1 17 4

CLASS MAR APR JUN AUG OCT JAN APR JUN AUG OCT I

(mm) 1976 1976 1976 1976 1976 1977 1977 1977 1977 1977 1

2 119.0 37.0 2.7 57.0 589.0 327.0 167.0 71.0 7.6 3.8 3

44.0 46.0 5.5 18.0 605.0 230.0 361.0 180.0 55.0 18.0 4

4.6 17.0 3.8 3.8 73.0 46.0 124.0 170.0 48.0 23.0 i

5 9.8 2.2 1.3 14.0 8.3 31.0 99.0 41.0 19.0 6

1.1 2.2 1.9 0.64 5.7 46.0 43.0 26.0 7

0.55 1.6 0.64 1.9 27.0 24.0 2S a j

8 0.64 13.0 20.0 75.0 9

1.1 1.1 6.4 20.0 20.0 10 3.2 20.0 18.0 11 0.55 20.0 33.0 3

I f:

14 12.0 33.0 l

15 5.1 20.0 16 0.64 11.0 17 2.5 l

18 0.64 3.2 l

19 1.3 20 0.64 i

21 f

22 23 24 l

25 0.76 26 27 28 29 30 l

i i

1 l

l

4 t

71 i

i i

i LITTLE HARBOR CHANNEL FLATS j

SIZE 24 22 23 19 25 12 15 13 10 10 i

CLASS FEB APR JUN AUG OCT JAN APR JUN AUG OCT i

(mm) 1976 1976 1976 1976 1976 1977 1977 1977 1977 1977 I

1 1.9 2

11.0 20.0 2.2 73.0 34.0 40.0 20.0 4.5 2.5 3

0.96 22.0 4.3 2.2 39.0 35.0 82.0 74.0 19.0 11.0 l

4 15.0 3.3 1.1 4.5 13.0 34.0 40.0 16.0 5.1 i

5 0.96 5.1 1.9 0.64 1.9 13.0 22.0 10.0 7.0 3

6 2.5 1.9 0.64 4.5 17.0 5.1 1.9 7

1.3 1.4 1.3 9.6 1.3 1.3 8

1.9 8.9 9

0.55 0.96 1.3 0.64 0.64 10 0.64 1.3 0.64 11 0.55 0.48 0.64 1.3 0.64 12 1.9 0.64 13 1.3 1.3 14 0.64 15 16 0.64 17 18 19 20 0.64 21 j

22 23 I

o.e4 26 27 28 j

29 30 0.64 31 32 33 34 35 0.64 I

72 YORK RIVER FLAT AT ROUTE 103 BRIDGE SIZE 20 22 20 29 14 12 9

9 21 CLASS APR JUN AUG OCT JAN APR JUN AUG OCT (mm) 1976 1976 1976 1976 1977 1977 1977 1977 1977 1

l 2

53.0 30.0 40.0 48.0 49.0 18.0 25.0 1.5 1.5 j

3 65.0 88.0 34.0 40.0 51.0 41.0 94.0 30.0 17.0 4

30.0 74.0 15.0 11.0 14.0 24.0 126.0 24.0 31.0 5

15.0 38.0 1.5 3.8 2.3 83.0 16.0 14.0 6

12.0 27.0 2.3 2.3 1.5 2.3 33.0 9.9 5.3 7

4.6 9.9 2.3 34.0 7.6 1.5 8

3.1 0.76 11.0 1.5 0.76 9

2.3 4.6 4.6 1.5

l 10 1.5 0.76 1.5 3.8 6.1

!E 11 1.5 0.76 0.76 1.5 0.76 l

12 0.76 0.76 2.3 1.5

!E 13 0.76 1.5 3.1

!E 14 i

15 16 1.5 0.76 17 j

18 0.76 1

19 il 20 in 21 1

22 iE 23 0.76

!g 24 25 1

26 i

27 i

28 I

I E

73 OGUNQUIT BEACH SIZE 20 22 20 29 14 12 9

9 21 CLASS APR JUN AUG OCT JAN APR JUN AUG OCT I

(mm) 1976 1976 1976 1976 1977 1977 1977 1977 1977 f

1 2

6.4 2.5 28.0 48.0 8.9 13.0 I

3 13.0 5.1 23.0 26.0 24.0 2.5 5.1 3.8 l

4 7.0 1.1 0.64 5.7 18.0 16.0 4.5 6.4 l

5 4.5 0.55 0.64 6.4 9.6 8.9 0.64 5.7 4

6 1.3 1.3 5.1 17.0 8.3 7

2.5 0.55 0.64 15.0 1.3 j

8 1.9 0.55 15.0 2

9 13.0 10 0.64 7.6 0.64 i

11 5.1 1.3 12 9.6 1.9 l

13 0.64 6.4 l

14 3.8 3.8 l

15 3.2 4

16 0.64 8.9 17 11.0 1.9 18 19.0 1.3 19 13.0 1.9 l

20 19.0 2.5

! E 21 6.4 3.8 3

22 8.9 2.5 23 2.5 1.9 24 2.5 0.64 i

(

25 1.3 i

26 0.64 1.9 l

27 0.64 1.3 28 1.3 I

29 1.3 30 1.3 31 l

32 I

I

I i

!I s

I 1

sI iI g'

.=

APPENDIX 7.3

{

SHELL SIZE DISTRIBUTION (#/ft ) 0F SOFT-SHELL CLAM SPAT AND ADULTS COLLECTED FROM RAND 0M STATIONS AT FIVE HAMPTON HARBOR FLATS, 1971 THROUGH 1977 i

i l

1 i

I 4

1 i

1

I I

i

i i

I TABLE A.

SHELL SIZE DISTRIBUTION OF SOFT-SHELL CLAMS ON FLAT 1 FOR THE NOVEMBER SURVEYS, 1971-1977.

SEABROOK MYA MEllARIA ll STUDY, 1976.

I SIZE CLASS (mm) 1971 1972 1973 1974 1975 1976 1977 5

19 74 30 2.5 55 1031 283 10 11 9

6 1.14 52 413 15 11 15 3

0.75 117 20 7

11 5

0.02 5.82 25 0.47 2.5 0.16 0.11 0.48 30 1.3 2.3 0.51 0.17 0.02 0.02 35 1.5 1.2 0.60 0.48 0.04 40 1.8 1.4 0.67 0.89 0.23 0.01 45 1.8 0.61 0.49 1.1 0.14 0.10 0.01 50 1.0 0.83 0.42 1.2 0.36 0.03 0.02 55 0.64 1.6 0.30 0.82 0.25 0.04 0.03 I

60 0.36 0.33 0.29 0.42 0.28 0.23 0.02 65 0.08 0.19 0.18 0.31 0.14 0.13 0.01 70 0.03 0.19 0.11 0.10 0.11 0.06 0.04 75 0.03 0.08 0.05 0.10 0.03 0.03 0.02 I

80 0.02 0.07 0.02 85 0.01 0.01 99 0.01 I

I I

I I

I I

I

M M

M M

M M

M M

M M

M M

M M

TABLE B.

SHELL SIZE DISTRIBUTION OF SOFT-SHELL CLAMS ON FLAT #2, NOVEMBER 1971-NOVEMBER 1977. SEABROOK NYA ARENARIA STUDY,1976.

SIZE CLASS NOV APR JUL NOV FEB MAY AUG NOV JAN MAY AUG NOV (mm) 1971 1972 1972 1972 1973 1973 1973 1973 1974 1974 1974 1974 5

37 1.6 2.9 116 138 199 15 114 4.2 7.6 5.9 10 35 9.7 8.7 26 34 110 20 8

2.0 2.5 15 11 0.91 5.5 2.4 2.4 13 28 2.6 0.36 20 9.0 1.5 4.4 0.91 1.0 1.0 42 10 2.0 25 0.89 0.11 4.7 0.11 0.38 0.42 0.56 0.67 0.91 0.97 0.11 0.5C 30 0.44 0.14 4.2 0.44 0.44 0.63 0.27 0.80 0.58 1.4 0.27 0.22 35 0.67 0.19 2.8 0.50 0.38 0.80 0.08 0.66 0.44 1.4 0.61 0.30 40 1.2 0.33 1.6 0.83 0.38 0.97 0.08 0.61 0.38 0.91 0.75 0.40 45 1.6 0.61 0.80 0.27 0.27 0.72 0.08 0.39 0.55 0.83 0.38 0.65 50 1.1 0.53 0.69 0.22 0.22 0.55 0.14 0.36 0.50 0.58 0.56 0.75 55 0.89 0.67 0.56 0.33 0.17 0.32 0.19 0.33 0.19 0.17 0.33 0.32 60 0.94 0.68 0.28 0.27 0.22 0.18 0.08 0.08 0.17 0.25 0.17 0.34 65 0.44 0.36 0.22 0.22 0.08 0.16 0.19 0.14 0.14 0.08 0.06 0.15 70 0.33 6.30 0.19 0.11 0.17 0.12 0.03 0.11 0.14 0.08 0.06 0.19 75 0.08 0.06 0.11 0.06 0.09 0.08 0.14 0.03 0.03 0.06 80 0.06 0.17 0.03 0.06 0.06 0.08 0.06 0.06 0.03 0.06 85 0.06 0.03 0.06 0.03 0.04 0.11 0.06 0.02 90 0.04 0.06 0.11 0.02 95 0.01 0.06 100 0.03 105 110 (Continued)

M M

M M

M M

M M-TABLE B.

(Continued)

SIZE CLASS FEB MAY AUG NOV FEB MAY AUG NOV FEB MAY AUG NOV (mm) 1975 1975 1975 1975 1976 1976 1976 1976 1977 1977 1977 1977 5

5.9 9.8 3.4 9.1 351 83 10 2.9 15 20 25 30 35 0.13 0.06 0.02 40 0.32 0.18 0.02 0.11 0.02 45 0.37 0.28 0.13 0.02 0.02 50 0.67 0.32 0.06 0.02 0.02 0.02 0.04 1

55 0.72 0.52 0.09 0.02 0.02 l

60 0.24 0.44 0.02 0.07 0.04 0.02 0.02 l

65 0.18 0.18 0.06 0.02 0.02 0.11 0.06 70 0.20 0.11 0.02 0.09 0.02 0.02 75 0.04 0.02 0.07 0.04 0.11 0.02 0.02 0.04 80 0.06 0.04 0.02 0.07 0.02 0.04 0.02 0.09 l

85 0.06 0.02 0.02 0.04 0.04 90 0.02 0.02 0.02 0.04 0.09 0.06 95 0.02 0.02 0.06 0.09 100 0.04 0.04 0.02 0.02 0.02 105 110 0.02 0.02

--- = not randomly sampled; see Appendix II for fixed station results d

78 TABLE C.

SHELL SIZE DISTRIBUTION OF SOFT-SHELL CLAMS ON FLAT 3 FOR NOVEMBER SURVEYS, 1971-1977.

SEABROOK MYA ARENARIA STUDY, 1977.

F SIZE L

CLASS (mm) 1971 1972 1973 1974 1975 1976 1977 r

L-5 35 28 6

0.64 1.14 556 67 10 29 4.7 1.0 4.1 3.4 15 5.2 4.0 3.4 c_

{

20 4.8 2.0 1.13 25 0.17 0.42 1.0 0.05 30 0.92 0.25 1.0 0.14

[

35 0.67 0.17 0.38 0.12 0.02 0.10 40 1.5 0.33 0.62 0.11 45 1.4 0.42 0.50 0.30 0.02 50 1.3 0.17 0.29 0.11 0.03 0.02 L

55 1.1 0.17 0.79 0.08 0.03 0.02 60 0.83 0.08 0.54 0.18 0.08 0.02 65 0.58 0.46 0.38 0.08 0.04 r_

l 70 0.33 0.08 0.42 0.14 0.02 g

75 0.25 0.08 0.22 0.03 0.06 0.02 80 0.08 0.08 0.14 0.03 0.06 g

[

85 0.04 0.03 0.08 L

90 0.08 0.06 0.08 I

lI 1I lI 1I i

n I

79 TABLE D.

SHELL SIZE DISTRIBUTION OF SOFT-SHELL CLAMS ON FLAT 4 FOR NOVEMBER SURVEYS, 1971-1977.

SEABROOK MYA ARE.7 ARIA STUDY,

[

1977.

I SIZE CLASS (mm) 1971 1972 1973 1974 1975 1976 1977 5

38 116 12 2.5 66 830 117 l

10 11 31 1.0 1.8 13.2 183 B

13 7

20 3.0 115

'20 4

18 2.0 0.64 20.4 25 2.8 1.1 0.52 0.05 0.01 0.62 1

30 3.5 3.0 1.4 0.26 0.01 0.02 35 4.6 2.8 0.62 0.58 0.01 0.01 40 4.0 1.7 0.46 0.96 0.16 45 2.6 2.0 0.35 0.92 0.16 0.09 50 1.3 1.0 0.38 0.80 0.18 55 1.1 0.79 0.14 0.50 0.21 0.13 1

60 0.25 0.21 0.08 0.29 0.12 65 0.17 0.04 0.14 0.21 0.14 0.01 70 0.12 0.08 0.06 0.03 0.04 75 0.02 0.01 0.01 1

80 0.04 0.01 0.01 85 0.01 0.01 0.01 1

I I

I I

I I

P

80 I

TABLE E.

I SHELL SIZE DISTRIBUTION OF SOFT-SHELL CLAMS ON FLAT 5 FOR NOVEMBER SURVEYS, 1971-1977.

SEABROOK MA ARE.7 ARIA STUDY, 1977.

I I

SIZE CLASS (mm) 1971 1972 1973 1974 1975 1976 1977 5

67 136 22 2.4 7.' 5 546 92 I

10 38 94 1

2.8 8.3 15 12 16 7.5 1

20 3

6 5.3 25 0.06 0.55 0.10 0.75 30 0.11 0.89 0.31 4

35 0.33 0.61 0.14 0.01 0.01 I

40 0.44 1.0 0.28 0.07 I

45 0.44 0.77 0.12 50 0.94 0.94 0.10 0.02 55 0.39 0.61 0.12 0.01 I

60 0.28 0.50 0.12 65 0.11 0.05 0.08 0.01 i

70 0.11 0.05 0.04 75 0.05 0.01 0.01 I

80 0.06 l

85 90 0.11 i

!I lI lI lI I

I I

l

4

!I

!I lll i

II I

APPENDIX 7.4 I

CONTOURED CHARTS OF HAMPTON HARBOR FLATS INDICATING NOVEMBER 1977 SURVEY STATIONS (Refer to Figure 1 for orientation)

I I

I I

I I

I I

I

82

'N

'\\ n,\\

e

\\ 'N l

/ _"'N.' R '\\

's

/

.J

'x I

/

N

/

\\

gl

\\

( 'N

/

\\,

I

\\v s

g-4.y '\\,

k:

\\-

s/

e.

l

)

=.

=\\

s f

=

l

'\\

~

\\

~ N,

~

\\

l

'z, N.

4.,

g l

e..x 3

!\\

x I

\\)

,6 2

\\

i s.

%g -

d

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