Text

Soft-Shell Clam,Mya Arenaria Study
	ML20033A191
Person / Time
Site:	Seabrook
Issue date:	01/31/1981
From:	; NORMANDEAU ASSOCIATES, INC.
To:	;
Shared Package
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i SOFT-SHELL CLAM, MyA AREl/ ARIA STUDY TECHNICAL REPORT XI-i i

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Prepared for PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE l

tianchester, New Hampshire II

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NORMANDEAU ASSOCIATES, INC.

l 25 Nashua Road, Bedford, New Hampshire i

January 1981 j

8111240000 Ogggg jg g"DR ADOCK 050004k3 lg PDR

TABLE OF CONTENTS PAGE

1.0 INTRODUCTION

1 2.0 METHODS AND MATERIALS.................. 3 2.1 LARVAE TOWS.

3 2.2 SPAT SURVEYS....................... 6 2.3 ADULT SURVEYS...................... 6 2.4 GREEN CRAB (CARCINUS MAENAS) TPAPPING.........

12 2.5 HISTOLOGICAL STUDY OF GONADAL CONDITI0li........

12 3.0 RESULTS........................

14 3.1 PLAN KT0flIC LARVAE...................

14 3.1.1 Spatial Distribution........

.........14 3.1.2 Temporal Distribution.................

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3.1.1 Species Composition.........

.........19 3.2 AREAWIDE SPAT AtlD JUVENILE CLAf1 SURVEYS........

19 3.3 HAMPTON HARBOR SOFTSHELL CLAM SURVEYS.........

19 3.3.1 Survivorship and Growth................

19 3.3.2 Population Density Trends by Shell Size Category....

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3.3.3 Biomass and Standing Crop..

. 26 3.4 GREEN CRAB, CARCINUS PAESAS, TRAP CATCHES.....

32 3.5 TEMPORAL PATTERtl 0F G0NAD DEVELOPMENT.........

37 4.0 DISCUSSION.......................

39 4.1 PLANKTONIC LARVAE SPATIAL DISTRIBUTION.........

39 4.2 TEMPORAL RELATI0flSHIPS:

LARVAL SWARMING AND G0NAD DEVELOPMENT...................

39 lI 4.3 LARVAL ABUNDANCE AND SPAT FALL.............

40 4.4 BIVALVE M0LLUSC LARVAE SPECIES COMPOSITION....

41 4.5 PREDATION IN HAMPTON HARBOR BY CARCINUS PAENAS.....

42 5.0 SUf?ARY

....................45 l

6.0 LITEPATURE CITED....................

47 AP P EilD IC ES.......................

49 11

I LIST OF FIGURES I

PAGE 1.

Soft-shell clam, ^? a arenaria, ana green crab, Carcinus d

maenus sampl i ng s ta ti ons...................

4 2.

Location of seat study sites.................

8 3.

Temporal distribution of umboned Sega arenaria veligers at the intake site (14) off Hampton Beach, New Hampshire...

16 4.

1 m class length-frequency distribution of Mya arenaria collected in November 1979.................. 20 5.

5 mm class length-frequency distribution of Nya arenaria juveniles and adults in Hampton Harbor comparing November 1978 and 1979 surveys.................... 27 6.

Estimates of M. arer. aria biomass,1971 through 1979, on five tidal flats in Hampton Harbor, witn approximate 95% confidence intervals.........

28 7.

Scattergram of Flat 2 survey results illustrating harvest-ing impact on harvestable biomass (each dot represents I

a sample plot dug).

Hampton Harbor flats were closed to clam digging from the first week in June to the first week in September 1979.................

33 8.

Size-frequency distribution of Carcinas maenas catch at Flat 2, Hampton Harbor..

35 9.

Percentages of male and female N. arenaria in each gonadal development phase 1978 and 1979...........

18 10.

Means of daily minimum winter (February and March) water temperature off Hampton Beach, New Hampshire...... 43 I

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LIST OF TABLES PAGE 1.

CLAM SPAT SAMPLING EFFORT...................

7 2.

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

10 3.

G0NADAL SAMPLE COLLECTIONS, 1979...............

12 3

4.

DENSITY DISTRIBUTION (INDIVIDUALS PER m ) 0F UMBONED I

MyA ARENARIA VELIGERS ALONG THE ONSHORE-OFF-SHORE INTAKE (I) TRANSECT, AND AT SELECTED TIDAL STAGES, IN THE INLET TO HAMPTON HARBOR (HH)..............

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3 5.

DENSITIES (PER n ) 0F UMB0NED N. ARENARIA UMB0NED VELIGERS COLLECTED AT I4 (INTAKE SITE)............

17 6.

PERCEflT COMPOSITION OF BIVALVE UMBONED VELIGERS IN OBLIQUE NET TOWS AT I4 (INTAKE SITE)............ 21 I

YOUNG-0F-THE-YEAR (1-12 m) AND JgVENILE (13 TO 43 m) 7.

SOFT-SHELL CLAM DENSITIES (PER FT ) IN POTENTIALLY PRODUCTIVE AREAS OF SIX NORTHERN NEW ENGLAND ESTUARIES....

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8.

SUMMARY

OF MyA ARENARIA POPULATION DEN.ITIES, ANNUAL NOVEMBER SURVEY.....................

24 9.

RESULTS OF SUFT-SHELL CLAM STANDING STOCK ESTIMATES, I

HAMPTON-SEABROOK ESTUARY................... 29 10.

ESTIMATES OF " HARVESTABLE"I STANDING CR0P...........

30 11.

ESTIMATES OF CLAM FLAT PRODUCTIVE AREAI (%) IN HAMPTON-SEABROOK ESTUARY............

31 12.

SELECTED C. MAENAS CATCH STATISTICS 1977-1979.........

34 13.

COMPARIS0N OF M. ARENARIA UMBONED LARVAL ABUNDANCE

'I 0FF HAMPTON BEACH WITH YOUNG-OF-THE-YEAR SPAT DENSITIES IN HAMPTON HARBOR............

36 14.

RECENT HISTORY OF THE STANDING CP0P 0F HARVESTABLE SIZE ADULTa MyA AREllARIA IN HAMPTON HARBOR.

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1.0 INTRODUCTION

I In New Hampshire, recreational harvesting of soft-shell clams, Nya arenaria, focuses on Hampton-Seabrook estuary (Hampton Harbor). To put potential impact of Seabrook Station's cooling water system on this resource in perspective, some understanding of ecological problems currently facing the species it, essential. For Gis purpose, Normandeau I

Associates, Inc. has investigated the population dynamics of the soft-shell clam in the vicinity of Hampton-Seabrook estuary for the past eleven years. Data collected have contributed to knowledge of:

1) larval spatial and temporal distribution, 2) temporal fluctuations in abundance of spat, juveniles and adults, 3) growth and mortality rates,

4) predation and harvesting pressures and 5) reproductive activity j

cycles.

I The immediately preceding report (NAI, 1979) documented partial recovery of standing stock, to an estimated 7000 bushels by November 1978, af ter several years of c2 a m scarcity. Faither increases in standing stock were projected as the highly successful 1976 and 1977 clam sets attain harvestable size.

Most of the products of spawning in Hampton-Seabrook estuary are probably carried out along the open coast, there to congregate with larvae from nearby estuaries. Such larval aggregations, or swarms, appear influenced by hydrographic cor.ditions (the coastal boundary layer); during swarms, larval densities typically range from (200 to 3000 larvae per m within a mile of shore, and may occur in densities of 3

several hundred larvae per m even two miles offshore.

I Over the years, planktonic larval densities have proved to be poorly correlated with spatfall (clam settling) success. The highest I

larval densities on record preceded the heaviest spat fall by a year, and the poorest year for larval density, 1977, recorded the second heaviest spat fall since 1972.

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I Continuing along previously established investigatory lines, this report contains 1979 results, and interpretations thereof, for: 1) oblique plankton tows off Hampton Beach and in the inlet to Hampton Harbor, monitoring seasonal and offshore-onshora clam larvae distributions,

2) population surveys of young clams, up to 47 mm shell length, on flats W

in six estuaries, from Ipswich, Massachusetts, to Ogunquit Beach, Maine,

3) surveys of juvenile and adult clams, over 24 r:n shell length, in 6

Hampton-Seabrook estuary, 4) histological examination of tid gonadal development cycle in Hampton Harbor clams, and 5) a green crab, Carcinus maenas, trapping program, monitoring the relative pressure of these major predators on the Hampton Harber clam population.

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2.0 METHODS AND MATERIALS I

2.1 LARVAE TOWS I

To monitor temporal distribution of Mya arenaria larvae in the vicinity of the Seabrook Station cooling water intake (Figure 1),

I duplicate, two minute, oblique net tows were made approximately twice weekly, from 11 June to 22 O.

-eekly tows were taken from 16 April through 4 June and during the la w week of October when larvae were found to be scarce or absent A 0.5 m diameter No. 20 (73 pm) 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 Oceanics flow meter was used to record the volume of water passing through the net; in practice, this I

volume ranged from 4 to 11 m per tow, typically averaging 7 m per tow.

Upon recovery, net contents were thoroughly rinsed into a 1/2-gallon glass jar. The live material was transported immediately to the Piscataqua Marine Laboratory, Portsmouth for analysis.

I To separate the live bivalve larvae from the bulk of the plankton, the sample was transferred to 1000 ml dispensing burettes and I

the contents allowed to settle for 5-12 minutes. The relatively high density of the shells allowed the bivalves to rapi,ly accumulate at the bottom of the burette column, and to be withdrawn for identification and enumeration. The entire sample concentrate containing the bivalves was enumerated for umboned (length 145-320 pm) Mya arenaria larvae except when this species was particularly abundant.

In this event, the bivalve larvae were concentrated by a swirling motion, into the center of a I

round, 100 mm diameter, plastic culture dish. The resulting concentration of larvae was carefully df.vided into visually equal quadrants using a camel's hair probe, viewing the operation through a dissecting microscope at approximately 30x; two diagonally opposed quadrants were then enumerated.

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A Larvae tow stations 1

O Clam flats x Green crab trap stations Figure 1.

Soft-shell clam,.vya arcncria, and green crab, Carcinus caenas sampling stations. Seabrook /tsa arenaria Study, 1979.

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The same splitting technique was also used to reduce the amount of larvae, representing other bivalve succies, to sample fractions containing a total of 200 to 600 individuals. Depending on original (i.e.,

field) population densities, this required from one to four

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successive operations consisting of concentrating t'le lar'ne into the center of the dish and then separating and extracting a quadrant.

In all cases, two sample fractions were enumerated from each sample, each

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fraction having originated as one of two diagon111y opposite quadrants

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in the initial (whole sample) larvae concentrat.on.

i Principal references used as aids in ident fying larvae to

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species were: Sullivan (1948), de Schwenitz and Lv.tz (1976) and Savage and Goldberg (1976). With few exceptions, onif umboned veligers were identified and enumerated. Abundances of M. arenaria straight hinge veligers were noted only when their identity was reasonably obvious because of the large numbers involved and the paucity of straight hinge veligers of other species.

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: 1) define the onshore / offshore distribution of M.

arenaria larvae in the intake vicinity and 2) compare open coastal and Hampton Harbor larval population densities. Oblique tows were made at P

1/2-nautical mile intervals along a transect running east to west through the intake site; in Hampton Harbor inlet, oblique tows were made nn both high and low slack tides (Figure 1).

Sample analysis procedures were made as described above.

Inshore / offshore transect, and Hampton Harbor inlet high/ low slack tide, sample data were submitted to a 2-way fixed effect analysis of variance (Sokal and Rohlf, 1969) with two observations per cell. A I

square root transformation was used to make umple varidtion more homogeneous. Tukey's procedure for pairwise comparisons (Gue 1ther, 1964) was used to determine the significance of station differences within and across sample dates.

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I 2.2 SPAT SURVEYS I

To compare population densities of spat and seed clams, periodic surveys were conducted on Hampton Harbor Flats (Figure 1 and Table 1) and on flats in five adjacent estuaries, in New Hampshire, nortnern Massachusetts and southern Maine (Figure 2 and Table 1).

With t'.e exception of the November survey, the stations were fixed; once established W

(on the basis of preliminary evidence of high productivity), the same general locality was resampled with each survey. Using a section of PVC plastic pipe, three sediment cores four inches in diameter, and four inches deep, were extracted at each fixed collection site.

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 enumnated and measured to the nearest 1 mm.

I Spat samples were also obtained, as described above, during the annual Hampton-Seabrook clam flat survey in November; however, the stations (Table 1) were chosen at random from a larger set of stations designated for sampling adult clam populations. While the fixed station program, with emphasis on high yield locations, gave re itive estimates of temporal and geographical distribution, the random sampling program 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 As in past years, the five largest harbor flats were each surveyed in November for adult clams; additional surveys were conoucted 5

on Flat #2 in April and August (Figure 1 and Table 2).

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l TABLE 1.

CLAM SPAT SAMPLING EFFORT. SEABROOK MYA ARENARIA STUDY,1979.

a.

FIXED STATIONS I

NO. OF l

LOCATION STATIONS DATES Plum Island Sound, MA Middle Ground 5

3 Apr, 17 Jul, 12 Oct

!I Lufkin's Flat 3

l Nut Shoal 2

i ll Merrimack River, MA l5 Salisbury Flat 3 5

2 Apr, 12 Jul, 13 Oct l

Ball's Flat 1 5

Hampton Harbor, NH Flat 2 5

5 Apr, 11 Jul, 9 Oct l

Flat 4 5

!;5 Little Harbor Channel, m l

Cima Pit Island 5

6 Apr, 13 Jul, 8 Oct

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!3 Southern Maine York River @ Rt. 103 bridge 5

4 Apr, 18 Jul, 11 Oct Ogunquit Beach 6

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RANDOM STATIONS I

N0. OF LOCATION 3TATIONS DATES I

Hampton Harbor,Im Flat 1 20 1, 8, 21 Nov Flat 2 9

8 Nov Flat 3 4

8 Nov l

Flat 4 17 9, 21 Nov Flat 5 8

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Locatiori of spat study sites.

Seabrook 'fya arenaria Study,1979.

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Aerial photograrSs, taken on 11 August 1978 at mean low water, were used to construct sampling charts as in previous (1977, 1978) surveys. Acreage measurements were provided by the aerial survey con-tractor, employing the "stereotemplate lal own" procedure which is l

standard for the preparation of tax base maps.

The maximum error in computed flat acreage has been estimated by the contractor to be approxi-I mately 2-3%.

Sampling procedures were employed which minimized unproductive digging in extremely depopulated areas of the flats. Evidence of breath-ing or siphon holes was used as an indicator of the presence, and conversely the absence, of clans.

If, after determining the position of a sampling

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s tation, the investigator observed what was thought to be clam siphon holes, a two-square-foot area was dug thoroughly for clams. On the other hand, if ne 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 to estimate clar abundance and standing crop for those areas exhibiting no visible evidence of clams.

Previous experience (NAI 1977, 1978, 1979) has shown that large, deeply burrowed clams are occasionally present in such areas and :an substantially influence overall estimates of standing crop.

9 To establish the location of sampling stations, rectangular (x,y) coordinates were plotted on charts of each flat and nodes, or inter-secting points, chosen at random (using a table of random numbers) until the final quota of stations (Table 2) was attained. In the field, stativns were located by corpass bearing and distance from a predetermined central reference point. 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 sedinent outlined by the frame was dug to a depth of about 16 inches.

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TABLE 2.

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

MYA ARENARIA STUDY,1979.

I N0. OF P0TENTIALLY TOTAL NO. BARREN STATIONS NO. OF SURFACE SAf1PLE (NUMBER POTENTIALLY AREA STATIONS SUBSAftPLED PRODUCTIVE LOCATION DATE (ACRES)

OBSERVED IN PARENTHESIS)

STATIONS DUG Flat 1 1,8,21 Nov 54.91 72 44 (11) 28 Flat 2 8 Nov 24.96 33 14 (5) 19 25 Apr 35 18 (6) 17 23

'g 56 23 (6) 33 Flat 3 8 Nov 10.54 24 19 (2) 5 Flat 4 9,21 Nov 51.05 51 12 (7) 39 Flat 5 1,21 Nov 23.69 38 18 (4) 20 All flats 1-21 Nov 165.15 218 107 (29) 111 I'

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Juvenile and adult soft-shell clams (shell length > 25 mm) found during excavation, or in the spoil, were picked out and placed in a plastic bag along with a tag identifying the station and flat number.

In the labora-tory, clams were tallied and measured for shell length to the nearest 1 mm.

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Ind idual sample counts and shell measurements were converted l

to biomass estimates (bushels per acre) using a table of c1sm volumes provided in Belding (1930). The overall biomass estimate for each flat was obtained using the following formula:

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-X=

X1+

X "1

"2 n

n 2

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n = total nu:rber of sampling stations observed n = number of stations where ' siphon holes were observed j

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

observed I

X = average biomass (bushels per acre) estimate for the j

entire flat X = average biumass from n samples y

X' = average biomass from a subset of samples (n') repre-I senting stations where no siphon holes were observed I

To express results in tertas of standing crop (bushels of harvestable clams on the entir e. flat), the biomass estimate wos multiplied *y flat surface area (acres). Variance and standard error of biomass estimatec were calculated approximately, using formulae given in Hanson et al.,

I 1953. To obtain a rough approximation of 95 percent confidence intervals, standard errors were cultiplied by two, as suggested by Hanson et al.,

1953.

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2.4 GREEN CRAB (CARcINUS MAINAS) TRAPPING I

l Carcinus maenas were trapped twice a month at four stations around the perimeter of Plat #2 (Figure 1).

Two 13 mm mesh, baited traps were set at each station so that they were awash at MLW.

After fishing for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months they were pulled in and the catch enumerated, sized and sexed. Total weight of Carcinus maenas from each trap was also

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recorded.

2.5 HISTOLOGICAL STUDY OF G0NADAL CONDITION Cn the dates shown in Table 3 at least 20 N. arenarla w_th a minimum shell length of 51 mm were collected by clam fork from Hampton Harbor flats. The visceral mass (gonad, liver, gastrointestinal tract, e tc. ) was taken out and fixed in 10% buffered formalin. Blocks of gonadal tissue were dissected from each specimen and sent to the Uni-versity of f;ew Hampshire Department of Animal Sciences Veterinary Diagnostic Laboratory where the blocks were:

1) dehydrated in alcohol and infiltrated (Armed Forces Institute of Pathology, 1949), 2) embedded in paraplast, 3) sectioned at 7 pm and 4) stained in hematoxylin and eosin.

TABLE 3.

GONADAL SAMPLE COLLECTIONS, 1979.

SEABROOK MYA AREJARIA STUDY,1979.

i Il 21 March 5 July 2 April 20 July 18 April 31 July g

l 2 May 15 August E

16 May 30 August 29 May 10 September 4 June 25 Septerber 19 June Slide preparations were then returned to IIormandeau Associates for evaluation of reproductive development.

Recognition of the phases I

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of gonadal condition:

indifferent, developing, ripe, spawning and spent, was based on the same characteristics as those used by other r

investigators (Ropes and Stickney, 1965; Porter, 1974; Brousseau, 1978a).

l Sections analyzed were from the dorsal, posterior quadrant below the t

i heart, where Coe and Turner (1938) have claimed that maturation begins.

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3.0 RESULTS 3.1 PLANKTONIC LARVAE 3.1.1 Spatial Distribution Three factorial analyses of variance (Appen w 7.1) were run on M. arenaria larval density data (Table 4); all indicated significant station variation (a =.05). Date of collection was also significant, but station-date interaction was not (a =.05).

Tukef s procedure for pairwise comparisons (Appendix 7.1) determined that, in general, inshore stations, I and I4, had significantly greater abundances of larvae than 2

Station I farthest o" shore; these procedures also showed that M.

8 arenaria larvae were significantly more abundant during high slack tide 5

than at low slack in Hampton Harbor inlet, or at any of the open coastal

("I") stations.

3.1.2 Temporal Distribution In 1979, a sparse population of Mya arenaria urboned veligers was first recorded off hampton Beach on 21 May; then, three weeks passed until the species reoccurred in plankton samples taken on 11 June (Table 5).

With the next three sample collections, M. arenaria larval population densities progressively increased, peaking at approximately 480 larvae per m on 2 July (Figure 3 and Table 5).

A gradual decline followed the early July peak, with mid-su:mer population levels generally fluctuating between 2 and 20 larvae per m.

as The end of August marked the commencement of the late summer larval peak (Figure 3).

Larval swarming was particularly intense, from 1000 to 3000 larvae per m, during the second week of September (Table

5). After mid October, larvae populations declined below nidsummer levels (Figure 3).

Evidence from current-meter records (Appendix 7.2) suggest that the most prominent M.

arenaria swarms follow a period of northerly drifting surface water.

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3 TABLE 4.

DENSITY DISTRIBUTION (INDIVIDUALS PER m ) 0F UMBONED MYA ARENARTA VELIGERS ALONG Th5 ONSl10RE-0FF-Sil0RE INTAKE (I) TRANSECT, AND AT SELECTED TIDAL STAGES, IN Tile INLET TO HAMPTON HARBOR (HH).

SEABROOK NYA ARENARIA STUDY,1979.

STATION 12 STATION I4 STATION 16 STATION 18 (1/2 NAUT. MILE (1 NAUT. MILE (1-1/2 NAUT.

(2 NAUT. MILES HH @ OTHER OFFSHORE)b 0FFS110RE)b MILES OFFSHORE) 0FFSHORE)

HH @ HIGH SLACK TIDAL STAGE DATE TOW #1 TOW #2 TOW #1 TOW #2 TOW #1 TOW #2 TOW #1 TOW #2 TOW #1 TOW #2 TOW #1 TOW #2 1-1/2 HRS AFTER HIGH SLACK 2 Jul 362 393 316 194 26 52 10 10 552 361 792 626

@ LOW SLACK 7 Sep 268 332 197 202 177 174 130 283 5"

14

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<1" 11 Sep 764 1954 830 1451 346 765 322 543 746 398 72 88 5

17 Sep 918 437 546 580 398 248 145 249 616 551 52 92 25 Sep 108 64 222 154 132 144 128 78 9

10 4

9

" Sample heavily contaminated with suspended solid matter In July, larvae significantly more abundant at I and I than at I

" I 8 "bN

" """ 8 9" 4

6 8

more abundant at I and I than at I ey's test, a=.05).

2 4

8

Significantly less abundant than at any "I" station or during high slack (Tukey's test, a=.05)

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OCTOBER 1979 l

Figure 3.

Temporal distribution of umboned Aasa arenaria veligers at the intake site (I4) off Hampton Beach, flew Hampshire. Seabrook A*da Study,1979.

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3 TABLE 5.

DENSITIES (PER m ) 0F UMB0NED M. ARE?iARIA VELICERS COLLECTED AT I4 (INTAKE SITE). SEABROOK NYA ARENARIA SrdDY,1979.

I REPLICATE REPLICATE DATE 1

2 MEAN*

REMARKS

'I 16 Apr 0

0 0

24 Apr 0

0 0

30 Apr 0

0 0

7 May 0

0 0

'I 14 May 0

0 0

21 Mav 0

0.6 0.3 29 May 0

0 0

I 4 Jun 0

0 0

11 Jun 0.4 0

0.2 14 Jun 0.7 2.0 1.4

'g 18 Jun 0.6 7.7 4.2 5

21 Jun 13 20 17 25 Jun 100 30 67 28 Jun 44 23 33 l

2 Jul 423 534 481 See also Intensive Survey t

'E 5 Jul' 85 105 95 9 Jul 20 39 29 12 Jul 7.4 14 10 17 Jul 1.7 5.6 3.7 19 Jul 15 6.7 11 23 Jul 2.5 0.6 1.7 26 Jul 1.2 1.4 1.3 30 Jul 13 15 14 2 Aug 5.3 7.1 6.2

.E 6 Aus 4o 66 53

' g 9 Aug 15 14 14 14 Aug 3.0 5.5 4.4 16 Aug 24 33 28 20 Aug 0.3 1.4 0.8 23 Aug 24 20 22 Straight hinge larvae swarming 3

27 Aug 3.0 3.6 3.3 Late straight hinge larvae =45per m i.g 30 Aug 61 60 61

-3

,3 4 Sep 51 16 33 Straight hinge larvae 2122 m 7 Sep 368 618 500 See also Intensive Survey 10 Sep 425 446 428 I

11 Sep 831 1450 1160 Intensive Survey 14 Sep 2950 1850 2290 17 Sep 120 124 122 Sea also Intensive Survey ll 20 Sep 76 96 86 3

24 Sep 235 260 247 25 Sep 223 154 185 Intensive Survey I

27 Sep 4.0 7.0 5.5 l

(Continued)

,I

18 TABLE 5.

(CONTINUED)

REPLICATE REPLICATE DATE 1

2 MEAN REMARKS 2 Oct 57 73 64

=

5 Oct 27 38 33 8 Oct 19

no second replicate 12 Oct 48 28 43 g

15 Oct 4.4 4.5 4.5 g

18 Oct 1.6 0.5 1.1 22 Oct 2.4 1.1 1.7 29 Oct 2.2 1.5 1.9 I

I-S I

i g

I' I

i l

l l

i Average density:

21 May to 29 Oct:

136 larvae per m

" Adjusted for differences in replicate volumes filtered.

II I1 I

19 I

3.1.3 Species Composition I

Mya arenaria umbone veligers de-inated the bivalve veliger assemblage only on 24 September (Tabls In general, mussels were the dominant species, with Mytilus edulis predominating in early summer and in the f all, and Modiolus rodiolus predominating in mid to late summer.

Hiatella sp. overwhelmingly dominated the bivalve assemblage in spring.

Other bivalve mollusc species which exhibited seasonal prominence in-I c1uded: Mya truncata (?) (late May), Anomia sp. and "nisula solidissima (mid September) and Maccma balthica (October). Varying quantities of Ensis directus and Placopecten magellanicus larvae were also recorded (Ta. ale 6).

I 3.2 AREAWIDE SPAT AND JUVENILE CLAM SURVEYS I

Compared to previous years, clam sets in 1979 were generally modest in the six estuaries investigated (Appendix 7.3).

In the April survey, Hampton Harbor flats contained the largest concentration of small clams. By October, however, Plum Island Sound flats had overtaken the Hampton Harbor flats in terms of settling of small clams (Table 7).

Plats in both the Merrimack and Ogunquit Rivers retained modest spat and juvenile clam resources throughout 1979; flats in the York River and Little Harbor Channel, on the other hand, were relatively unsuccessful I

in sustaining young soft-shell clams (Table 7).

I 3.3 HAMPTON HARBOR SOFTSHELL CLAM SURVEYS I

3.3.1 Survivorship and Growth A prominent gap in the 1-mm class length-frequency distribution (Figure 4) for 1979, clearly segregates clams less than 8-mm from those ou r 10-mm.

Assuming this gap to represent the separation between young-of-the-year spat and older clams, the average number of clams one I

year and older is approximately 79 per ft In November 1978 the average I

J 6-YOUNG Of j

THE YEAR 5'

i 4-

i.

44 fr E' 3 -

U 3

8 2-1-

I, I i, 1 1 1 a.

0 2

4 6 8 10 12 14 16.

18 20 22 24 26 28 30 32 34 36 33 40 42 44 46 48 50 52 SIZE CLASS (nin)

Figure 4.

1 nm class length-frequency distribution of Arda arenaria collected in November 1979, Seabrook tha arenaria study,1979.

M M

M TABLE 6.

PERCENT COMPOSITION OF BIVALVE UMBONED VELIGERS IN OBLIQUE NET TOWS AT I4 (INTAKE SITE).

SEABROOK NYA ARENARIA STUDY,1979.

')

b h

A AVERAGE f$

4

[

4 ALL I LV S N

4e

+-

S Y

4/

T W

4' ci Y

(N0. PER M )

16 April 0.0 2.8 76.0 21.1 0.0 0.0 0.0 f 3 0.0 0.0 0.0 4

24 April 0.0 0.2 97.0 2.5 0.0 0.0 0.2 0 '. 0 0.0 0.0 0.0 21 30 April 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 42 7 Ma; 0.0 0.1 99.8 0.1

<0.1 0.0 0.0 0.0 0.0 0.0 0.0 2,720 14 May 0.0 0.0 96.2 0.0 3.8 0.0 0.0 0.0 0.0 0.0

<0.1 230 21 May 0.1 2.6 93.0 0.0 1.6

<0.1 0.9 0.6 0.0 0.0 1.1 594 28 May 0.0 10.7 58.9 0.0 0.1 0.0 0.1 27.6 0.1 0.0 2.6 671 4 June 0.0 46.7 42.4 0.0 0.8 0.0

<0.1 8.1

<0.1 0.0 1.9 3,000 11 June 1.7 88.4 7.4 0.1 0.1

<0.1

<0.1 1.4

<0.1 0.0 0.8 38,700 18 June 31.9 54.2 11.4 0.3 0.6

<0.1

<0.1 0.1

<0.1 0.0 1.4 89,800 25 June 21.8 62.2 14.6 0.4

<0.1

<0.1 0.0 0.1 0.0 0.0 0.9 523,000 y

2 July 30.5 54.5 11.1 2.2 0.1 0.2 0.0 0.1 0.0 0.0 1.4 235,000 9 July 18.9 64.3 11.7 2.4 0.9 0.1

<0.1 0.1 0.0

<0.1 1.6 26,600 17 July 74.8 15.5 2.5 4.9 0.1 0.1 0.0 0.1

0. 0 0.0 2.2 17,100 t

23 July 42.1 32.5 5.6 15.6

<0.1

<0.1 0.0 0.0 3.3 45,700 30 July 45.1 28.1 11.7 11.1 0.2

<0.1 0.1

<0.1 0.1 0.6 2.8 19,400 6 August 32.2 40.8 1.7 16.0 1.0

<0.1

<0.1 0.9 0.9 6.4 10,200 14 August 60.7 23.5 6.8 5.3

<0.1

<0.1 0.9

<0.1 0.6 0.3 1.8 20,100 20 August 71.7 10.0 3.1 12.5 0.0

<0.1 0.3

<0.1 1.2 0.2 0.9 1,760 27 August 30.9 34.8 13.8 12.8 0.1 0.3 0.4

<0.1 4.4 0.1 3.3 1,020 4 September 53.0 11.4 1.8 10.2 3.9 2.2

<0.1 0.0 2.6 13.5 1.3 1,520 10 September 6.7 L2.0 1.8 26.7 9.9 16.5

<0.1

<0.1 6.7 16.7 2.9 2,600 17 September 5.1 27.9 2.1 37.1 6.4 3.5

<0.1

<0.1 2.2 14.8 0.8 3,470 24 September 2.6 14.4 0.3 2.8 11.0 36.8 0.2 0.0 2.7 27.0 2.1 672 2 October 10.4 13.3 3.5 11.4 6.5 7.5 0.1 0.0 31.8 13.1 2.4 860 8 October 30.9 34.3 2.5 19.0 2.3 5.0

<0.1 0.0 2.4 2.3 1.2 380 15 October 3.0 28.4 1.0 6.1 7.5 0.3 2.3

<0.1 38.4 11.0 1.9 1,310 22 October 2.6 26.8 4.2 11.7 5.4 0.1 2.3

<0.1 37.3 6.1 3.4 1,520 29 October 1.0 50.1 2.0 6.9 5.2

<0.1 1.1 0.0 25.7 5.4 2.5 4,450

2 TABLE 7.

YOUNG-OF-THE-YEAR (1-12 mm) Ah JUVENILE (13 TO 43 nm) '.20FT-SHELL CLAM DENSITIES (PER FT )

i IN POTENTIALLY PRODUCTIVE AREAS OF SIX NORTHERN NEW ENGLAND ESTUARIES. SEABROOK MYA ARENARIA STUDY, 1979.

APRIL JULY OCTOBER YOUNG-0F-YOUNG-0F-YOUNG-0F ESTUARY THE YEAR JUVENILES THE-YEAR JUVLNILES THE-YEAR JUVENILES Plum Island Sound (Ipswich, MA) 96 84 79 75 152 72 Merrimack River (Newburyport & Salisbury, MA) 16 23 11 33 27 34 Ilampton liarbor (llampton & Seabrook, Nil) 220 198 139 154 148 107 Little llarbor Channel (Portsmouth, NII) 13 1.3 26 1.3 14 0.0 u

1 u

York River (York, ME) 31 S.'

33 2.2 18 0.0 Ogunquit niccI

' k unquit Beach, ME) 26 13 27 29

'33 10 J

.s

23 density for clams of all ages was 213 per f t indicating an apparent survivorship of 37%. Actual survivorship is almost certainly somewhat lower as spat settling late in the fall of 1978 would have been less than 1 mm wide (the screen mesh size), and, therefore, would not have been counted.

The median shell size of clams one year and older was 20 mm, compared to 15 mm in 1978.

In 1978, fewer than 0.2 clams per ft had a I

shell size greater than 42 mm (a category dasignated as " harvestable";

see Section 3.3.3). By 1979, however, an average of 1.8 clams per ft had attained a length of at least /.3 mm, representing an order of magnitude increase in number of harvestable clams. Because of the variety of physical arid biological variables at work, individual clam growth is difficult to infer from size-frequency distribution comparisons and impossible to verify. The leading edge of the length-frequency slope, however, appears to have moved

(" grown cut") approximately 16 mm from an inflection point in the vicinity of 39-40 mm in 1978 to a comparable slope break in the vicinity of 55-56 mm in 1979 (Appendix Tables 7.3 and 7.4).

3.3.2 Population Density Trends by Shell Size Category Size categories delineated in Table 8 are retained for continuity with earlier surveys. The 50 mm limit refers to the former minimum legally harvestable size (51 mm = 2 inches) abolished in 1976.

The 25 mm limit may have been a convenient partitioning of previously sublegal I

shell sizes, but also relates to the size at which clams generally establish their first permanent burrows (Dow and Wallace, 1957).

On three of the five Hampton Harbor flats surveyed, population densities of young clams, 26 to 50 mm, increased for the second year in a row; population gains on Flats 1 and 4 broke all previous survey records (Table 8).

Clams over 50 mm exhibited modest increases in density on all flats except Flat 5; while, a' decline in clams less than 26 mm, continued in 1979 on all flats except Plat 2 (Table 8). Similar I

L

24 TABLE 8

SUMMARY

OF MYA ARENARIA POPULATION DENSITIES, ANNUAL NOVEMBER SURVEY. SEABROOK NYA ARENARIA STUDY,1979.

I NUMBER OF SAMPLES POPULATION DENSITY (#/SQ. FT.)

COLLECTED SPAT JUVENILES ADULTS l

LOCATION YEAR ADULTS SPAT

(>l TO 25 m) (26 TO 50 m) (>50 m) i l

Flat 1 1971 18 18 48 6.8 2.1 1972 18 18 I!O 8.1 3.3 E

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 l

1976 63 18 1084 0.12 0.53 1

1977 66 14 819 0.04 0.15 l

1978 66 14 372 0.62 0.15 1979 72 20 72 31.0 0.24 Flat 2 1971 9

9 91 4.8

?.8

{

1972 9

9 152 2.2

.4 1973 9

9 136 3.8 1.1 1974 21 9

0.0 2.1 1.9 l

1975 21 9

9.1 0.0 0.5 1976 24 9

351 0.0 0.21 W

1977 33 7

86 0.0 0.08 1978 33 7

15 2.1 0.16 1979 33 9

57 3.6 0.29 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 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 1977 24 6

75 0.12 0.04 1978 24 6

50 1.2 0.14 1979 14 4

10 1.0 0.15 Flat 4 1971 12 12 106 17.6 2.8 1972 12 12 138 10.6 2.3 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 1978 51 11 309 12.4 0.05 l-1979 C7 17 175 39.0 0.52 l

(Continued) l

l j

25

'I TABLE 8.

(Continued) 4

,;I l

NUMBER OF ig StMPLES POPULATION DENSITY (#/SQ. FT.)

g COLLECTED

_PA-JUVENILES ADULTS LOCATION YEAR ADULTS SPAT

(>l TO 25 m) (26 TO 50 m) (>50 m)

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 1974 17 11 2.4 0.0 0.1 f

1975 9

11 7.5 0.0 0.01 1976 24 12 549 0.0 0.14 1977 38 9

114 0.08 0.03 1978 38 7

56 4.1 0.07 1979 32 8

14 1.8 0.03 All Flats 1971 54 54 92 7.7 2.7 1972 54 54 130 6.2 2.2 1973 111 56 47 2.8 1.0

{

1974 119 56 2.1 2.1 2.0 1975 106 56 37 0.2 0.8 1976 216 62 762 0.06 0.2 I

1977 212 47 388 0.05 0.07 1978 212 45 208 4.4 0.09

}

1979 218 58 86 24.0 0.3 I

ll I

I

~

I I

26 I

population trends were evident from 5 mm size class comparisons of present and past survey data (Appendix 7.6).

i 3.3.3 Biomass and Standing Crop Substantial growth in the population of mid-sized clams, j

between November 1978 and November 1979 (Figure 5), produced comparable increases in estimates of biomass and standing crop (Figure 6 and Table 3

b i

9).

In NAI (1979), the term " marketable" (here replaced by the term

" harvestable") was chosen to distinguish clams larger than 42 mm from smaller clams. In November 1978 only 940 bushels (5.7 bushels per acre) was estimated to be " harvestable"; by November 1979, harvestable biomass had increased by a factor of six (Figure 6).

Similarly, biomass of soft-shell clams of all sizes had quadrupled over the 12-month period.

Virtually all of the substantial 1979 gains in biomass and standing crop occurred on Flats 1 and 4 (Tables 9 and 10).

Only these two flats held small aggregations of clams exceeding the equivalent of 250 bushels per acre (Table 10).

Such high yields (equivalent to more than ten 2-inch clams per f t ) are typical of commercially valuable clannting areas in Maine and Massachusetts (based on examination of Maine Department of Marine Resources and Massachusetts Division of Marine Fisheries shellfish survey records). Sample yields equivalent to 40 bushels per acre (the equivalent of slightly less than two 2-inch clams per f t ) may be regarded as the threshold between a marginal fishery and one with healthy potential for recreational digging. According to this criterion, approximately 24% of the clam flat area in Hampton-Seabrook estuary could readily suppcrt recreational digging as of November 1979.

I An additional 38% of the flat area possessed marginal capacity to sustain recreational' digging (cf. Tables 10 and 11).

Only 38% of the total flat area in Hampton Harbor was devoid of clams larger than 24 mm, an improvement over the years 1975 through 1978 (Table 11).

I I

~

i 27

!I I

9-l 1978 g

8-

), 1979 I

j 7-6-

I i

5-I 4-3-

'l 2-I t-I l

_d

_c 0

I I

I 30 35 40 45 50 55 60 65 70 SIZE CLASS (mm)

I Figure 5.

I 5 mm class length-frequency distribution of t@a arenaria juveniles and adults in Hampton Harbor comparing November 1978 and 1979 surveys.

Seabrook /@a arenaria Study,1979.

I

28 I

220 -

T T

Harvestable e J uvenile I

l h,. and Adult

'. Clams

(

A 1

g etoms i

E, 200 -

la 43 mm)

I I

iso -

l

?

I l

I 160 -

l I

140 -

1 I

N c: 120-d

$w g 100-o=

80 -

60 -

T I

1 h,

l 40 -

l 4.I i

o 1

m zo -

r.

i 6

[

1.

y 10 i

i i

71 72 73 74 75 76 77 78 79 YEARS Figure 6.

Estimates of M. crer. aria biomass,1971 through 1979, on five tidal flats in Hampton Warbor, with approximate 95% confidence intervals. Seabrook Mya crer. aria Study, 1979.

I I

TABLE 9.

RESULTS OF SOF1-SHELL CLAM STANDING STOCK ESTIMATES, HAMPTON-SEABROOK ESTUARY. SEABROOK MYA ARENARL4 STUDY, 1979.

1 TOTAL NUMBER NUMBER MEAN BIOMASS STANDING CR0P NUMBER OF UNITS BURROWLESS (BUSHELS PER ACRE)

(BUSHELS)

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

(n)

(n )

(nj)

(i )

i STD.EV.

i STD DEV y

j 2

Plat 1 1,8,21 Nov 54.91 72 28 11 462.9 92.7 236.6140.9 13,00012240 Flat 2 8 Nov 24.96 33 19 5

54.8 9.5 35.61 8.9 888i 222 25 Apr 35 17 6

23.0 19.6 22.21 6.6 5301 164 23 Aug 56 33 6

177.4 0.0 104.6131.0 2,6101 774 Flat 3 8 Nov 10.54 14 5

2 48.9 0.0 17.Si 7.0 184 74 Flat 4 9&21 Nov 51.05 67 39 7

496.3 8.3 292.4129.6 14,90011510 Flat 5 1&21 Nov 23.69 32 20 4

25.6 1.2 16.4i 9.7 3901 230 All Plats 1-21 Nov 165.15 218 111 29 307.3 40.3 175.7119.2 29,00013180 Harvestable clams

(>43 mm) 58.4 8.9 34.3 4.4 5,670t 736

TABLE 10.

ESTIMATES OF "IIARVESTABLE"I STANDING CROP. SEABROOK MYA ARENARIA STUDY,1979.

TOTAL ESTIMATED

% OF SAMPLES

% OF SAMPLES HARVESTABLE CR0P

% OF SAMPLES YlELDING EQUIVALENT YIELDING EQUIVALENT (BUSHELS)

YIELDING HARVESTABLE OF > 40 BUSilELS OF >250 BUSHELS FLAT NOV 1978 NOV 1979 CLAMS, NOV 1979 PER ACRE, NOV 1979 PER ACRE, NOV 1979 1

383 1890 44 21 1.4 i

2 185 350 44 18 0.0 3

113 126 29 11 0.0 4

126 3160 52 40 3.0 5

74 143 22 6

0.0 All 940 5670 43 24 1.4 y

t Defined as clams with shells > 43 mm long M

M M

M m

M M

m M

m m

m

31 1

!I l

TABLE 11.

ESTIMATES OF CLAM FLAT PRODUCTIVE AREAI (%) IN HAMPTON-SEABROOK ESTUARY. SEABROOK NYA ARENARIA STUDY,1979.

1

!I Y M R OF SURVEY

.I j

LOCATION 1979 1978 1977 1976 1975 1974 Flat 1 72 60 17 35 53 80 l

Flat 2 62 36 15 17 44 63 Flat 3 29 42 32 48 39 67 4

Flat 4 76 62 20 19 57 88 Flat 5 22 43 22 27 4

20 s

All Flats 62 52 19 26 45 66 l

\\

1 J

lI i

!I 1 Includes all clams > 25 mm il i

1 lI

32 I

The rapidity with which harvesting pressure can alter conditions, however, is illustrated in Figure 7 Flat 2 is a relatively small flat 5

(25 acres) essentially accessible only by boat, but close to docking facilities in the town of Hampton.

In recent years this flat has apparently received a dicproportionate share of clam digger attention.

I:

3.4 GREEN CRAB, CARCItcs 3'AF.vAS, TRAP CATCHES I,

For comparison, data from surveys in 1977 and 1978 have Leen presented in Tatle 12 along with 1979 catch data; also, size frequency distribution data frem both the 1978 and 1979 catch data are presented in Figure 8.

After having generally declined to a range of 6 to 9 crabs per I

trap per day (excluding the mid winter lull), green crab catch per unit effort returned abruptly, to summer 1977 levels, in October through Decerter 1979. The cause of this high value was a record catch of 468 crabs (58.5 crabs per trap) on 10 October 1979 (Appendix 7.5). Sex ratios, on the other hand, have remained about the same since July through Septerter 1978, with slightly more females in the catch than males (Table 12).

Few gravid females were caught in 1979, but, as in 1978, the main period of fecundity was April through June.

It The smallest crab taken in 1979 was 2.9 cm at the widest part of the carapace; the largest was 7.5 cm wide.

Approximately 98.5% of the crabs caught had carapaces between 3.0 and 7.0 cm at the widest point. Crabs which were 6.5 cm in carapace width tended to be males (Appendix 7.7).

I' I,

I:

I'

M M

h Marginal Recreational Potential C ommercial Potential Potential

g-->

i l

I I

l I

1 l

1 i

l I

I 25 April 1979 (~5 weeks prior to closing) 3:

l g

i i

I i

l I

I I

I i

l l

23 August 1979 (*2 weeks prior to opening) e I

i i

I i

I l

l i

I i

l i

I l

8 November 1979 h9 weeks off er opening)

I i*

-~

1 I

I l

1 0

50 10O 15 0 200 250 30'O Equivalent bushels per acre. clams s 43 na figure 7.

Scattergram of Flat 2 survey results illustrating harvesting impact on harvestable biomass (each dot represents a sample plot dug). Hampton Harbor flats were closed to clam digging from the first week in June to the first week in September 1979. Seabrook Mja arenaria Study,1979.

34 TABLE 12.

SELECTED C. MAENAS CATCH STATISTICS 1977-1979. SEABROOK NYA ARENARIA STUDY,1979.

I FECUNDITY CATCH PER SEX RATIO

(% GRAVID a

SAMPLE PERIOD UNIT EFFORT (M:F)

FEMALES)

Summer 1977 July 24.6 1:4.9 6.2 August 10.3 1:3.5 9.4 September 21.6 1:2.2

'). 9 Oct-Dec 1977 17.5 1:0.9 0.3 Jan-Mar 1978 0.1 Fenales only 0.0 Apr-Jun 1978 7.5 1:3.3 7.0 Jul-Sep 1978 8.6 1:1.5 3.2 Oct-Dec 1978 7.2 1:1.3 0.5 l

Jan-Mar 1979 2.7 1:1.7 0.0 Apr-Jun 1979 6.4 1:1.0 6.0 Jul-Sep 1979 6.0 1:1.5 0.6 j

Oct-Dec 1979 22.1 1:1.5 0.0 l

l I

t I

I a

l Nu.tber of C. maenas per trap per day Two " prism" traps, 'ishing for 2 to 5 days at a time c From Oct 1977 to Dec 1979, eight " box" traps, fishing for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months twice per month.

E I

-w---

l l

3 1979 l

E 1978 30 -

l

~

$ a 3

O 20 -

l t;

5 O

g5 _

E u.

10 -

5 -

II I

11 i,

<3 I

3-3 '/ 2 I 3'/ -4 I

4 -4 '/

I ' '2 - 5 I 5 - 5 '/2 I Sh-6 I

6 - 6'/

I 6-7 I

>7 I

k 2

2 2

2 MAXIMUM CARAPACE WIDTH (CM)

Figure 8.

Size-frequency distribution of Carcinus macnas catch at Flat 2, llampton Harbor.

Seabrook Mpa arenaria Study,1979.

TABLE 13.

COMPARISON OF M. ARENARIA UMB0NED LARVAL ABUNDANCE OFF liAMPTON BEACil WITil YIflG-0F-THE-YEAR SPAT DENSITIES IN llAMPTON HARBOR. SEABROOK MYA ARENARIA STUDY,1979.

LARVAL DENSITY DAILY MEAN x DENSITY OF PERIOD OVER WHICil MEAN SEASON LENGTH YOUNG-0F-TiiE-YEAR 3

3 2

YEAR LARVAE WERE COLLECTED (per m / day)

(per m )

(Spat per ft }

1974 16 Jul to 5 Sep (51 days) 69 3,520 7

l 1975 16 Aug to 14 Oct (59 days) 532 31,400 37 1976 28 Jan to 17 Oct (113 days) 158 17,800 762 1977 27 Jun to 6 Oct (102 days) 7 714 179 1978 22 May to 31 Oct (163 days) 83 13,600 56 1979 21 May to 29 Oct (162 days) 136 22,000 30

)

37 I

3.5 TEMPORAL PATTERh 0F GONAD DEVELOPMENT I

Histological determinations in 1979 indicated a single annual spawring cycle in Hampton Harbor sof t-shell clam populations (FigIre 9).

In what appears to be the typical pattern, gametogenesis had already begun in the majority of females by mid March; while, all or most males remained indifferent until late May.

Throughout the late spring, however, gonad development proceeded rapidly in both sexes, with the first evidence of active spawning coming in mid to late June. The peak of spawning activity appeared to be in July through early August, at a time when M.

I arenaria larvae were not very abundant off the coast of Hampton Beach (cf. Figures 3 and 9). A few spawning females were found in late September suggesting that small quantities of eggs may have continued to be released after that date. No spawning males were found in late September, however, a surprisingly large proportion of the sample appeared to be in the early stages of gametogenesis, reminiscent of mid-spring conditions.

I I

-I I

38 I

i N=

12 S

10 12 Il 11 15

of Adults 80 0 -

gg r:t gg :gg Phases:

y y g

f M

t hDIFFE R ENT b

DEVELOPING I

RIPE y

hs N

SPAWNING g

28' il 26' 9

22' 18 31' 11 12 e

O SPENT APRIL M AY JUNE JULY AUG SEPT M ALES g

N*

19 13 20 14 13 14 16 14 10

ef Adults g

l. -

I

=

-- g.

5 5

5 N

U E

5 e 50 -

=

b U

b

.i 5

5 b

y.Mn 0

4 i

i i

i 28 il 26 9 22 IS 31 11 12 APRIL MAY JUN E JULY AUG SEPT FEMALES No 13 il 11 15 21 14 15 13 23 18 10 11 10

## Advi's t

i=-

l g=yE A3,

g

=

s

.g 9-5 2

55

$ 50-g E

E O

16.2 i 4 19 S

20,3 f 45 30 15 25 8

4 21 2

18 2

l MARCH APRIL M AY JUNE JULY AUG SEPT M ALES No il 14 14 10 18 il 20 12 27 7

15 14 15

ef Adults

' " ~

i

!! ! !'8

'i HREE E

E=:

E E

=l E

W 5

W

.=,

E

=

=-

=

-E

'5.

5 5ii 5

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hbM

=

0 2i 6 2 is 3 2 16,2 93 4 19 I 5 20,5 a l 15 30 3 to 2S VARCH APRIL M AY J ue4 E JULY AUG SEPT FE M AL ES Figure 9.

Percentages of rale and female M. arenaria in each E

gonadal development phase 1978 and 1979.

Seabrook 3

sa arenaria Study, 1979.

I

L 39 4.0 DISCUSSION

(

4.1 PLANKTONIC LARVAE SPATIAL DISTRIBUTION

~

As in previous years, M. arenaria larvae were present in substantial quantities up to two nautical miles from shore, when swarms occurred along the New Hampshire coast. Previous findings of a statisti-cally sign:'iicant onshore-offshore gradient received further support I

from the 1979 data. Apparently, however, the " neritic band" may be more than two nautical miles wide during periods of intense swarming, such as occurred on 11 September 1979.

For the first time the relationship between M. arenaria larval swarms along the open coast and inside Hampton IIarbor was examined.

Generally, 1979 results were consistent with the favored hypothesis that I

the bulk of the larvae enter Hampton Harbor on the flood tide and empty out o. the Harbor on the subsequent ebbing tide.

In two ineances, 7 September and 25 September, however, there appears to have oeen little exchange between larvae-poor Harbor waters and larvae-rich coastal waters. Possibly, coastal water masses subducted into Hampton Harbor can occasionally be faunistically distinct from water masses in the vicinity of the Seabrook Station cooling water intake (Station I ).

4 4.2 TEMPORAL RELATIONSHIPS:

LARVAL SWARMING AND G0NAD DEVELOPMENT As in 1978, plankton tow coll-ctions clearly demonstrated bimodal temporal distribution of M. arenaria larvae.

In 1978, peak densities in early to mid June characterized the spring-early summer node; however, in 1979, the early summer peak occurred later in June and into early July.

The late su=mer-early fall peak was similar for both years, except that c'ensities in excess of 100 larvae per m were sustained for a longer time in September 1979.

l

40 I

3 Prior to 1978, densities in exces.= of 100 larvae per m had not been recorded in July. Onset of larval swarming appears subject to year-to-year shif ts, although environmental influences are not completely understood. Biologically, these shifts are probably related to the timing of spring spawning in northern Massachusetts sof t-shell clam populations which may be a source of the majority of M. arenaria larvae present off Hampton Beach (NAI, 1979).

In contrast to the recent tendency for larvae to swarm later in summer, Hampton Harbor soft-shell clams appear to have spawned slightly earlier in 1979 than in 1978. Timing of spawning in Hampton Harbor and larval swarming off Hampton Beach was such that, in 1979, Hampton Harbor reproductive activity could have contributed to both early summer and late summer-early fall peaks. This was not the case in 1978, when spawning did not begin until the latter half of July in Hampton Harbor (NAI, 1979).

m Evidence to support speculation, that the apparent increase in midsummer " background" larval abundance, from 1978 to 1979, could be due partly to larger Hampton Harbor breeding populations, comes from gonad samples indicating spawning in Hampton Harbor throughout the interval between swarms, both in 1978 (NAI, 1979) and in 1979 (Section 3.5).

In the interval between major swarms, from mid-July until the end of August 1978, larval densities at Station I averaged approximately 1.1 per m ;

4 whereas densities during a comparable period in 1979 averaged 8.9 larvae g

3 per m. Coincidentally, in 1979, there was a marked increase in the abundance of clams with shell sizes larger than 40 mm, which Brousseau (1978a, 1978b) determined to be the threshold of sexual maturity.

I 4.3 LARVAL ABUNDANCE AND SPAT FALL I

In general, M.

arenaria larvae were relatively abundant during the 1979 season; however, the ensizing spat fall in Hampton Harbor was relatively light (Table 13).

Thus, further support is given to the argument that year-to-year trends in larval abundance have little direct I

I 41 I

I influence on the success of clam sets.

Apparently crucial are the little understood physical and biological forces occurring during the period between larval swarming and spat settlement.

4.4 BIVALVE MOLLUSC LARVAE SPECIES COMPOSITION General trends in species composition, described in previous reports (NAI, 1978, 1979) cont aued to prevail during 1979. A difference perhaps worth mentioning was that larvae of the sea sca. lop, Placopecten I_

magellanicus, was scarce throughout 1978, but fairly common in the latter half of October 1979.

I Beginning in 1979, a bivalve mollusc veliger, identical in size, shape and general appearance to M. arenaria at comparable stages of development, has been identified and enumerated separately as M.

trunca ta. Despite a close resemblance with M. arenaria, experienced I

planktologists at Normandeau Associates readily distinguished M.

truncata using fre.h or very recently preserved plankton samples and illuminating the microscope stage by diffused light. Living or carefully preserved specimens of M. arenaria are easily recognizable by distinctive pigment characteristics described by several workers (Sullivan,1948; Loosanoff and Davis, 1963; Savage and Goldberg, 1976).

In M.

truncata, the only strongly pigmented area is the visceral mass under the peak of the I

umbone, which, as in M.

arenaria, ranges in color from burnt orange to Frown-black. The rest of M.

truncata appears chalky-gray at lower magnifications (25 to 30x); at slightly high magnification (40 to 60x) the chalky effect is seen to be due to a network of fine gray-black line:

This animal was designated as M.

truncata in recognition of the physical resemblance with M. arenaria and because specimens of adult M.

truncata have been collected by Nomandeau Associates divers, in close proximity to bivalve larvae sampling stations off Hampton Beach.

These M.

truncata colonies had nestled, along with Hiatella sp., under clusters of Modiolus modiolus.

I I

42 I

Except for one or two weeks in late spring, M. truncata larvae g

comprise a very small proportion of the total bivalve larvae assemblage.

5 Conseqently, any effect on previous quantitative Mya data can be considered negligible, especially since, prior to 1978, collections typically began in late June, following the principal swarming period of M.

truncata.

I 4.5 PREDATION IN HAMPTON HARBOR BY CARCINUS MAE7/AS The previous report (NAI, 1979) considered the probability of declining abundance of the chief non-human clam predator, Carcinus maenas, based on trends in trap catches and winter water temperatures.

Winter temperatures appear to correlate well with relative abundance of certain marine and estuarine species such as soft-snell clams and green crabs (Welsh, 1969; Dow, 1977). Until 1979, winter water temperatures had been declining (Figure 10), consistent with the assumption of declining green crab abundance. The 1979 trap data, however, showed a return, in October, to green crab catches reminiscent of summer 1977 levels.

Correspondingly, water temperature minima during the previous winter showed the beginnings of an upward trend (Fit;ure 10). Such signs, combined with expected renewed public interest in clam digging, suggest that intermediate sized soft-shell clams (lengths: 10-40mm) may become increasingly scarce, eventually affecting the standing crop of harvestable W

class (Table 14).

I 1

I I

38 -

p 37 -

LJ T

D F-

<t

@ 36 -

c.

2 tij I-35 -

U 34 -

l l

E 3

I I

l 1973 1974 19 75 1976 1977 1978 1979 YEAR OF RECORD Figure 10.

Means of daily mininum winter (February and March) water temperature off Hampton Beach, New Hampshire.

Seabrook

/ta arenaria study, 1979.

d

B

~

lI TABLE 14.

RECENT HISTORY'0F THE STAi1 DING CR0P OF HARVESTABLE SIZE ADULTa l#A AREl/ ARIA IN HAMPTON HARBOR. SEABROOK MIA AREllARIA STUDY,1979.

I ESTIMATED BUSHEL TOTAL ESTIMATED NUMBER DATE PER ACRE OF BilSHELS November 1967 152.0 23,400 July 1969 103.0 15,840 Noverber 1971 84.0 13,020 November 1972 58.0 8,920 November 1973 41.0 6,310 g5' November 1974 56.0 8,690 November 1975 29.0 4,945 November 1976 11.0 1,350 November 1977 6.4 1,060 November 1978 5.7 940 November 1979 34.3 5,670 I

I I

I

1967-1975, shell length = 50 mm and up; 1976-1978, shell length =

43 en and up from Ayer (1968)

I I

I

45 5.0

SUMMARY

For the second consecutive year, plankton tows produced evidence of bimodal temporal distribution of Mya arenaria larvae, with major abundance peaks occurring in early July and mid September. Several years of current-meter records have indicated northerly drif t immediately preceding or during these abundance peaks, suggesting an important I

contribution of larvae from clam breeding areas to the south of Hampton-Seabrook estuary.

As has often occurred in previous years, M. arenaria larvae were significantly more abundant (p >.05) within one nautical mile (1.85 kilometers) of the New Hampshire coastline than at two nautical miles. During periods of peak abundance, M. arenaria larvae were generally more abundant inside Hampton Harbor following flood tide than after ebb tide. On at least two occasions in Septerter, however, M. arenaria larvae were found in the Harbor in low nu:rbers on both tides, although I

abundance was at or near peak offshore.

Despite an approximately 60% increase in overall larval abundance over the previous year, the 1979 spat set was relatively light, down 30%

from that of the previous year. Further support was thus given to the argument that year-to-year trends in larval abundance have little direct impact on spat fall intensity.

I The second consecutive study of gonad development in M. arenaria corroborated the earlier study in showing a single annual spawning cycle for Hampton Harbor populations.

In 1979, spawning activity peaked from early July through early August, when 40 to 80% of clams, over 50 mm long, showed histological evidence of active spawning. This range represented a marked increase over the previous year and coincided with I

an approximately six-fold increase in biomass of sexually nature clams in Hampton Harbor, primarily recruited from a heavy spat set in 1976.

46 I

The total standing crop, in November 1979, was estimated at 29,000 bushels, of which 5670 bushels were of " harvestable" size (i.e.,

> 43 mm).

Natural predation and human clam digging have an impact on M. arenaria standing stocks in Hampton Harbor. From April 1978 through September 1979, green crab, Carcinus maenas, trap catches were reasonably stable, averaging 6 to 9 crabs per trap per day.

In October 1979, however, trap catches increased sharply to an average of 22 crabs per trap per day, thereby rivaling records established in the summer and g

fall of 1977. A virt2 ally parallel pattern of winter water temperature W

fluctuation was noted from temperature-recording buoys off Hampton Beach. Along with renewed public interest in clam digging, such trends suggest that M. arenaria standing crop may peak during 1980 and could decline unless existing seed stocks are replenished.

I I

r 1

l I

I I

(

47 6.0 LITERATURE CITED Armed Forces Institute of Pathology.

1949. Manual of histologic and special staining techniques. McGraw Hill. 2nd edition.

pp. 7-14, 25-30.

Ayer, W. C.

1968. Sof t-shell clam population study in Ham 1_ ton-Seabrook Harbor, New Hampshire. New Hampshire Fish and Game Dept.

39 pp.

1i Belding, D. L.

1930. The soft-shelled clam fishery of Massachusetts.

Commonw. Mass. Dep. Conserv. Div. Fish Game, Mar. Fish. Ser. 1,65 p.

Brousseau, D. J.

1978a. Spawning cycle, fecundity and recruitment in a population of soft-shell clam, Mya arenaria, from Cape Ann, Massachusetts. Fishery Bulletin. 76(1):155-166.

1978b. Population dynamics of the soft-shell clam Nya a renaria. Marine Biology.

50:63-71.

1979. Analysis of growth rate in Mya arenaria using the Von Bertalanffy equation. Marine Biology. 51:221-227.

I Coe, W. R. and H. J. Turner, Jr.

1938. Development of the gonads and gametes in the soft-shell clam (Mya arenaria).

J. Morphol. 62:91-111.

Dow, R. L.

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).

Maine Dept. of Sea and Shore Fish. Bul., Augusta, Maine.

35pp.

Guenther, W.

1964. Analysis of variance. Prentice-Hill, Inc., Engle-wood Cliffs, N. J.

199 pp.

I Hansen, M.

H.,

W. H.

Hurwitz and W. G. Madow.

1953.

Sample survey methods and theory.

Vol. II.

Wiley-Interscience.

pp. 257-260.

I Loosanoff, V. L. and H. C. Davis.

1963.

hearing of bivalve molluscs.

Advances in Marine Biology.

1:1-136.

Normandeau Associates, Inc.

1977.

Seabrook Ecological Studies 1975-I 1976.

Studies on the sof t-shelled clam, Mya arenaria, in the vicinity of Hampton-Seabrook estuary, New Hampshire. Technical Report VII-3.

73 pp.

1978.

Seabrook Ecological Studies 1976-1977.

Studies on the sof t-shelled clam, Mya arenaria, in the vicinity of Hampton-Seabrook estuary, New Hampshire. Technical Report VIII-2.

85 pp.

l 48 I

1979. Seabrook Ecological Studies 1978. Soft-shell clam, Mya arenaria, T"chnical Report X-3.

85 pp.

Porter, R. G.

1974. Reproductive cycle of the sof t-shell clam, Mya arenaria, at Skagit Bay, Washington. Fish. Bull.

72:648-656.

Savage, N. B. and R. Goldberg. 1977 Investigation of practical means of distinguishing Mya arenaria and H2atella sp. larvae in plankton samples.

Proc. Nat. Shellfish Assoc.

66:42-53.

deschweinits, E. H. and. A.

Lutz.

1976.

Larval development of the northern horse musse., Modiolus modiolus (L.), including a com-g, parisor. with the larvae of Mytilus edulis (L.) as an aid in plank-g tonic identification.

Biol. Bull.

150(3):348-360.

Sokal, R. F. and F. J. Rohlf.

1969.

Biometry.

W. H. Freeman Co.,

San Francisco. 776 pp.

Sullivan, Charlotte M.

1948. Bivalve larvae of Malpeque Bay, P.E.I.

Fish. Res. Bd. Can. Bull. 77.

36 pp.

Welch, W.

R.

1969. Changes in abundance of the green crab, Carcinus maenas (L.) in relation to recent temperature changes.

U.S. Fish Wildl. Serv. Fish. Bull. 67(337-345).

I I

l E

I I

E I

I

i l

i

!,I 1

.il I

4 I

!;I APPENDICES

I I

r lI i

lI I

!I t

'I I

I I

50 APPENDIX 7.1.

ANALYSIS OF VARIANCE TABLES. MYA ARE!/ ARIA LARVAE.

I I.

SEPTEMBER 1979:

"I" STATIONS ONL" "#ING SQUARE ROOT TRANSFORMATION D.F.

d.5.

M.S.

F Station 3

307.010 102.337 5.09*

Day 3

1335.974 445.324 22.15***

Sta x Day 9

249.266 27.696 1.38 Error 16 321.704 20.106 Total 31 2213.954 I

II.

SEPTEMBER 1979:

"I" AND "HH" STATIONS USING SQUARE ROOT (9/7/79 DELETED)

D.F.

S.S.

M.S..

F.

Station 5

1196.259 239.252 12.76***

Day 2

1558.406 779.202 41.56***

Sta x Day 10 411.143 41.114 2.19 N.S.

Error 18 337.484 18.749 Total 35 3503.291 i

III. JULY 1979:

"I" STATIONS ONLY USING SQUARE ROOT D.F.

S.S.

M.S.

F Station 3

349.284 116.428 46.047 ***

i Error 4

10.114 2.528 I

I = Intake II = Hampton Harbor Inlet I

I I

51 J

APPENDIX 7.1 (Continued)

RESULTS OF TUKEY'S PROCEDURES FOR PAIRWISE MULTIPLE COMPARIS0NS I

I.

SEPTEMBER DATA: STATIONS "I" 0NLY: ALL DATES i

(a) Station comparisons I2, I4 > I8 (b) Date comparisons 9-11-79 > 9-7-79, 9-17-79, 9-25-79 I.

9-17-79 > 9-25-79 II. SEPTEMBER DATA: STATIONS "I" AND "HH": 9/7/79 DELETED (a)

Station comparisons HH-Flood > I2, I4, I6, 18, HH-Ebb I2, I4 >'I8 (b) Dates not tested for this group - see above (I) i III. JULY DATA: STATIONS "I" ONLY (a) Station comparisons I2, I4 > I6, I8 I

I i

I I

l 52 I

I I

I 8m 1

s arm - avaoc a>+ue ernim van _v mur wruentmann mei

, 17. te i is i a a2 i m i a i e4 i a i m i o i m i m i m i at i i

l l

tuum

[L 4\\j g

l

_ ll

'1 l!

l i

6 I

1 I

I E

l l

Apper. dix 7.2.

E i

I E

53 I

EEAEMIK STATD4 - GHHJE (1HoeT erTORD0 POR Y AVE.RE VEITCNStDIETD4 OARD)

AL i 1S79 G%f5 ad.L 16 iS79 I i i2 1 3 6 4 1 5 i G i 7 8 9 I 9 4 10 1 11 1 12 I 13 1 141151 16 i hb M AE W<r's gvp p pr'o I

=i -

~

u eiH1K STATD4 - OT9-GE QJ+t.NT OIT3tDO PGR.Y AVERE VEITOe5iulh tad TOs APC)

AL 17 is'9 CAYS at.L 31 19/9 1 17 6 19 l 191201214 2 123124 3 25 i 5 6 & I 29 1 29 1 30 I 31 I i

'I i 17 I 9 4 19 1 20 4 21 i e i 23 1 24 4 25 1 2G i & I 29 1 29 8 30 1 31 I i

b% $sLJa\\f_'%

hI l

n,-

(*ETER 2)

A

[

9 sf{IK STAT D4 - OT904. C1ME.N' OTT34PG FGR.Y AvtRE vtITOGiufM.LTI:N TUa ACJ EP 1 19'9 DMS H P 1G 19/9 l 1 1 2 1 3 1 4 4 5 i G I 7 i B i 9 l 10 t 11 1 12 1 13 4 14 1 15 8 1G i I

'l 1G 1

/

i 1 i 2 1 3 1 4 i 5 E

I, / I 9 l 9 1 13 1 11 1 12 1 13

'1 P'OCRIE D3UP

\\/

_ ~

fi

[

N

~

3 TR )

/

9 e(IK STATD4 - GMOE ClR4.NT erT:RPG Mf AvtRE VEL ~"JE(CIMITRA D*M7 cEP 171979 CAf5 G P W 1979 4 17 1 19 i 19 1 20 1 21 22 23 24 i c5 1 2G I & I 29 4 29 6 30 l i

i PCCpl% ILt,P

[

/

(%TER 1) 7

/ '

\\

l 17 1 19 i 19 1 20 1 21 1 & I 23 i 24 t 25 i LE I & I 29 1 29 I TI

!I

=-

4-run n Appendix 7. 2 (Continued)

I

5 e4 I

d.N 1 iT9 OMS J N 1G 1979 I 1 1 2 1 3 1 4 1 5 i G I 7 iB I 9 1 10 1 11 I id i 13 I 14 t is i 16 I I

1... I... I.,

,,.... I 1.,

..1.,

ll' kh4 6 Yl-g:y y&

7 7-9 N STATI:N - G7304' C1RO4T h04ITIRIPG H1R_Y AW.R%I Wr.T3S tutRA.11Ltd 10am JN 17 1879 CMS 1N 3D L979 1 17 1 19 l 19 I 20 1 21 1 2E I 23 1 24 i ES I E I 27 1 28 8 23 i I I I

I I

ja_,

f 1

1,, 1.

19, _, 5 I 2, _

ppngap?,1Q I

idhk nu

=-

g

11. 1 1.T 9 GAW ll. 15 1979 4 1 1 2 6 3 1 4 i S I G I 7 i O 1 9 1 10 1 11 1 12 1 13 1 14 6151 1G 1 l

I 1 a2 1 3 1 4 i S I G I 7 i B l 9 l 10 1 11 I i 13 6 14 4 15 i 1G 1

/

U E

$I /'-

p tg\\Q Afci 6-c az.c 12

=

~

I r

i

e. - s,Tr:u - _ _ x

_ _ - =1_ m..

LI 17 LTS CWS J1. 31 1979 l 17 1 18 1 19 1 20 8 21 i a i 23 i 24 i 25 1 26 8 27 1 29 I a i 30 1 31 1 6

12 f-, !,,Y,l\\ // A,'bl %.._.

.)2,

__s I

Appendix 7.2 (Continued)

I

E l

55 I

l I

E6 5' ATD4 - N W.N* @T"NN2 Y *.4RaiE 4I.;

MWI.TDJ 'JmAh r 1 1979 CA(5 "I.' AG.9/9 4

15./ G.

ai3 i 4. 5

.G

./

3 9 ; O 11

. 1 i 1

. 1.

i

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MCOstING 10 9

'#,,fp[ - - "

j

/

d

k ER 1) l d

3 i4

.5 G

/

3 9. 13. 11 12 13. 14 1

A5. 15 1 g9 i

E *dEDt 5* ATDJ - N C.RTN' OI'34M2 MY Ad.RE kT.I".F5i3!ETDJ "Ja AC' r 17 1979 3A 6 QC' 31 17/9 I

1/ i '19 A i cD ct. 2 i 23 i 24 i d5 2G S. d9 i 29 33 i 31 i i

6 7

I

]O

$$$$fmAN&

w-x '

'W3

.,4

("ETER 1 }

df\\

-~N'

/ /

17 13 A

d3 di ee dd cM c5 c5 6 d3 c9 33 e 31 I

I cEN STATDJ - MGE CREN' OI'ORI U

'GH Y A4RE E"FSIC!%I'D4 "Je ARD?

W 1 LT9 3AYS

'C/ 1G 1979 6 1 1 2 1 3 4 4 i 5 G I 7 8 9 i 9 I 14 5 11 1 22 i J i 14 1 15 1 15 i i

'OCRIMG IIP q

f

'y J

/

kwkE

)

b N

i 1 I ai 3 i 4. 5 6

/

9 i 9 i lo i 11. 2, 23 14 i 15 i 16 i i

I T_*LM 5' ATD4 - 3 MOE C1H4.N' O!"FI'G MY A4RE W.I*.R3 COI9Er'. D4 "Js A.C?

c/ o twa Ac o m 1979 i 17 i 13 1 19 i dQ i di ieiae d4 i d5 I cT2 6 &. d9 i 29 i I

I l/

)

[

f 7

I

. re:.s : n s

iO8t >

j\\

b 1

i

" - ~ ~~- ~ -

Appendix 7.2 (Continued)

1 APPENDIX 7.3.

SHELL SIZE DISTRIBUTION (NUMBER PER FT ) 0F YOUNG MYA ARENARIA COLLECTED FROM FIXED STATIONS IN SELECTED NORTHERN NEW ENGLAND ESTUARIES, 1976 THROUGH 1979. SEABROOK MYA ARENARIA STUDY,1979.

i PLUd ISLAND SOUND MIDDLE GROUND SIZE 19 21 17 28 11 11 8

5 19 6

4 13 11 12 3

17 11 CLASS APR JUN AUG OCT

'"8 APR JUN AUG OCT JAN APR JUN AUG OCT APR JUL OCT (mm) 1976 1976 1976 1976 1 1977 1977 1977 1977 1978 1978 1978 1978 1978 1979 1979 1979 5

5 2

11 208 101 149 127 7 625 91 127 31 19 114 44 24 18 10 7

8 10 44 132 5

46 22 20 69 27 29 7

93 14 15 1

1 1

6 98 49 29 7

6 32 112 94 13 33 48 20 1

29 87 45 35 23 7

61 28 12 6

14 25 15 38 37 41 33 8

14 9

17 8

3 30 9

21 24 26 13 15 12 17 14 6

35 2

4 5

7 6

14 12 17 12 8

40 2

3 2

9 10 12 11 14 45 1

8 9

4 13 16 M

M M

M W

APPENDIX 7.3 (Continued)

PLUM ISLAND SOUND LUFKIN'S FLAT l

SIZE 11 8

5 19 6

4 13 11 12 3

17 11 CLASS APR JUN AUG OCT JAN APR JUN AUG OCT APR JUL OCT (m) 1977 1977 1977 1977 1978 1978 1978 1978 1978 1979 1979 1979 5

165 169 10 171 60 87 5

16 8

29 2

41 10 43 79 1

15 15 31 3

6 3

8 46 15 32 13 1

1 9

13 10 3

2 8

20 5

4 5

6 3

3 3

10 25 11 3

9 25 3

1 14.

8 3

1 19 17 15 1

5 30 4

8 23 3

11 13 5

8 2

8 35 3

15 4

9 1

3 5

13 5

9 U

40 1

1 4

5 1

4 8

3 2

45 1

1 1

1 2

2 l

APPENDIX 7.3.

(Continued) l l

l l

PLUM ISLAND SOUND EAGLE HILL RIVER AT NUT SH0AL SIZE 11 8

5 19 6

4 13 11 12 3

17 11 CLASS APR JUN AU6 0CT JAN APR JUN AUG OCT APR JUL OCT l

(mm) 1977 1977 1977 1977 1978 1978 1978 1978 1978 1979 1979 1979 l

5 142 23 68 912 199 182 50 97 80 292 13 534 10 28 58 12 36 27 143 13 10 59 10 15 11 110 28 4

2 38 55 74 10 61 4

20 2

26 66 8

6 6

15 59 63 25 17 8

25 49 30 19 23 4

32 38 32 19 8

j 30 10 27 27 15 4

6 4

6 11 10 35 8

25 19 8

8 4

11 11 13 40 8

6 11 10 11 15 23 13 17 45 2

4 4

8 8

23 8

6 l

M M

M W

W M

M M

W

M APPENDIX 7.3.

(Continued)

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

2 18 4

5 19 9

13 2

12 10 CLASS APR JUN AUG OCT JAN APR JUN AUG OCT JAN APR JUN AUG OCT APR JUL OCT (nin) 1976 1976 1976 1976 1977 1977 1977 1977 1977 1978 1978 1978 1978 1978 1979 1979 1979 5

44 6

22 353 244 368 265 15 81 364 131 116 10 5

29 10 2

7 2

1 1

84 3

9 4

12 15 3

1 3

24 3

4 5

7 20 1

37 27 14 16 4

25 5

36 18 21 7

30 2

5 5

19 10 l

1 2

2 16 35 1

14 40 1

8 45

t l

APPENDIX 7.3.

(Continued) l MERRIMACK RIVER ESTilARY SALISBURY FLAT #3 SIZE 23 17 18 26 28 13 6

2 18 5

6 19 9

13 2

12 10 CLASS APR JUN AUG OCT JAN APR JUN AUG OCT JAN APR J!Pt AUG OCT APR JUL OCT (nin) 1976 1976 1976 1976 1977 1977 1977 1977 1977 1978 1978 1978 1978 1978 1979 1979 1979 5

18 7

12 102 82 86 28 31 22 15 27 2

30 15 8

8 8

10 1

4 5

1 1

2 1

1 1

4 4

2 15 2

1 2

2 1

2 2

20 4

2 1

1 25 1

1 1

30 1

35 40 45 i

l l

i 4

l as sus e

m um m

m m

aus e

e m

m m

m W

W

M M

M APPENDIX 7.3.

(Continued)

HAMPTON HARBOR FLAT #2 SIZE 12 21 18 16 21 11 14 1

17 4

5 9

14 9

5 11 9

CLASS MAR APR JUN AUG OCT JAN APR JUN AUG OCT JAN APR JUN AUG OCT APR JUL OCT (m) 1976 1976 1976 1976 1976 1977 1977 1977 1977 1977 1978 1978 1978 1978 1978 1979 1979 1979 5

168 112 18 80 1284 612 691 593 219 118 78 157 42 24 106 97 93 103 10 1

2 1

10 104 119 58 29 38 43 5

9 40 10 3

15 39 89 87 69 8

77 29 10 17 3

20 2

4 15 21 3

64 61 39 12 9

25 2

46 51 29 17 20 30 18 20 22 21 10 35 2

5 8

12 11 40 2

1 4

12.

14 45 2

12 i

APPENDIX 7.3.

(Continued)

HAMPTON HARBOR FLAT #4 (MIDDLE GROUND)

SIZE 5

9 14 5

5 11 9

CLASS APR JUN AUG OCT APR JUL OCT j

(m) 1978 1978 1978 1978 1979 1979 1979 5

282 70 170 529 268 30 144 l

10 306 85 47 137 80 141 46 i

15 394 96 56 145 77 62 36 20 68 56 75 140 86 64 30 25 5

5 26 00 59 43 37 30 1

16 21 17 25 29 m

.I N

35 3

5 14 13 12 l

l 40 7

7 7

1 l

45 1

5 4

l i

i I

I l

APPENDIX 7.3.

' Continued) l l

LITTLE HARBOR CHANNEL l

FLATS l

l SIZE 24 22 23 19 25 12 15 13 10 10 13 10 16 8

6 6

13 8

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

(nm) 1976 1976 1976 1976 1976 1977 1977 1977 1977 1977 1978 1978 1978 1978 1978 1979 1979 1979 i

5 15 66 13 6 114 84 175 182 56 29 9

11 12 22 11 26 16 10 3

1 13 4

2 4

4 1

2 1

15 2

1 1

20 1

1 1

j 25 i

30 35 40 45 1

1 4

APPENDIX 7.3 (Continued)

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

9 21 17 3

14 10 11 4

18 12 CLASS APR JUN AUG OCT JAN APR JUN AUG OCT JAN APR JUN AUG OCT APR JUL OCT (m) 1976 1976 1976 1976 1977 1977 1977 1977 1977 1978 1978 1978 1978 1978 1979 1979 1979 5

180 267 91 103 119 90 395 89 70 76 29 31 9

28 29 24 18 10 9

1 2

2 20 16 5

12 19 15 12 2

2 2

1 15 2

2 4

2 5

5 2

1 20 3

2 2

2 25 1

1 1

2 1

30 2

2 1

35 1

m

]

I 40 1

1 j

45 M

M M

W W

M M

-~

(

1 APPENDIX 7.3 (Continued)

OGUNQUIT BEACH FLAT SIZE 20 22 20 29 14 12 9

9 21 17 3

14 10 11 4

18 CLASS APR JUN AUG OCT JAN APR JUN AUG OCT JAN APR JUN AUG OCT APR JUL OCT (nm) 1976 1976 1976 1976 1977 1977 1977 1977 1977 1978 1978 1978 1978 1978 1979 1979 1979 5

35 2

8 57 100 64 48 19 26 18 9

20 18 40 22 11 89 f

10 2

1 1

50 4

2 3

13 1

4 15 15 5

33 2

1 1

4 12 1

11 20 66 12 6

10 1

9 2

2 1

1 25 8

6 11 5

5 4

4 1

2 30 4

4 10 10 5

3 2

5 2

35 2

2 6

2

?.

6 2

40 1

1 8

3 4

3 2

45 4

4 4

5 4

I i

l APPENDIX 7.4.

I ttM SIZE CLASS LEHGTH-DENSITY DATA FROM THE NOVEMBER 1978 SURVEY.

1 1

1 i

LENGTH DENSITY

%-AGE

%-AGE LENGTH DEt' CITY

%-AGE

%-AGE LENGTil DENSITY

%-AGE

% AGE 2

2 j

[mm]

[#/ft2 CUM

[mm]

[# -t ]

CUM

[an]

[#/ft ]

COM l

l J

1 0.45 0.211 100.000 26 1.19 0.559 3.185 43 0.02 0.009 0.073 2

4.38 2.056 99.789 27 1.07 0.502 2.627 44 0.005 0.002 0.063 i

3 7.39 3.469 97.732 28 0.66 0.310 2.124 45 0.005 0.002 0.061 l

4 11.47 5.385 94.233 29 0.74 0.347 1.815 46 0.002 0.001 0.059 5

9.20 4.319 88.878 30 0.74 0.347 1.467 47 0.005 0.002 0.058 6

9.51 4.465 84.559 31 0.38 0.178 1.120 48 0.02 0.009 0.655 7

10.41 4.887 80.094 32 0.41 0.192 0.941 49 0.007 0.003 0.046 8

10.56 4.958 75.207 33 0.30 0.141 0.749 50 0.002 0.001 0.043 L

i 9

10.11 4.746 70.249 34 0.23 0.108 0.608 51 0.002 0.001 0.042 l

10 11.92 5.596 65.503 35 0.30 0.141 0.500 52 0.007 0.003 0.041 11 11.32 5.314 59.907 36 0.15 0.070 0.359 53 0.

0.0 0.038

(

l 12 10.26 4.817 54.593 37 0.15 0.070 0.289 54 0.

0.0 0.038 m

13 10.11 4.746 49.176 38 0.10 0.047 0.218 55 0.019 0.009 0.038 14 12.22 5.737 45.072 39 0.08 0.038 0.171 60 0.014 0.007 0.029 15 11.32 5.314 39.292 40 0.06 0.020 0.134 65 0.023 0.011 0.022 16 12.00 5.634 33.978 41 0.04 0.019 0.106 70 0.005 0.002 0.011 17 12.55 5.892 28.344 42 0.03 0.014 0.007 75 0.012 0.006 0.009 l

18 11.27 5.291 22.452 80 J.005 0.002 0.003

[

19 8.06 3.784 17.161 85 0.002 0.0009 0.0009 20 7.09 3.329

13.378 E

213.005 21 4.83 2.268 10.049 22 4.93 2.314 7.782 23 1.92 0.901 5.467 I

(

24 1.54 0.723 4.566 25 1.40 0.657 3.843 l

i L

M M

M We M

M M

W W

M W

WWW

'W W

W m7 n

M_

C APPENDIX 7.5.

1 W1 SIZE CLASS DATA FROM THE NOVEMBER LENGTH-DENSITY 1979 SURVEY.

LENGT:t DENSITY

%-AGE

%-AGE LENGTil DENSITY

%-AGE

%-AGL LENGTH DENSITY

%-AGE

%-AGE 2

2 2

[mm]

[#/ft ]

CUM

[mm]

[#/ft ]

CUM

[mm]

[#/ft ]

CUM 1

0.12 0.107 100.000 26 1.83 1.626 19.984 43 0.32 0.284 1.623 2

4.11 3.651 99.893 27 2.00 1.848 18.358 44 0.22 0.195 1.339 3

4.69 4.166 96.243 28 1.99 1.768 16.510 45 0.27 0.240 1.143 4

5.16 4.584 92.077 29 1.70 1.510 14.743 46 0.14 0.124 0.903 5

5.28 4.690 87.493 30 2.28 2.025 13.232 47 0.14 0.124 0.779 6

4.81 4.273 82.803 31 1.55 1.377 11.207 48 0.116 0.103.

0.655 7

4.56 4.051 78.530 32 1.41 1.252 9.831 49 0.107 0.095 0.552

)

l 8

2.31 2.052 74.480 33 1.19 1.057 8.578 50 0.192 0.171 0.457 9

2.52 2.238 72.428 34 1.03 0.915 7.521 51 0.061 0.054 0.286 l

10 2.81 2.496 70.189 35 1.22 1.083 6.606 52 0.041 0.036 0.232 11 3.75 3.331 67.693 36 0.81 0.720 5.522 53 0.034 0.030 0.195

'8 12 5.16 4.584 64.362 37 0.75 0.666 4.803 54 0.023 0.020 0.165 13 3. '.4 3.233 59.779 38 0.81 0.720 4.137 55 0.025 0.022 0.145 14

5. J 4 '

4.477 56.545 39 0.59 0.524 3.417 56 0.040 0.036 0.123 15 4.22 3.749 52.068 40 0.67 0.595 2.893 57 0.005 0.004 0.087 16 4.34 3.855 48.320 41 0.35 0.311 2.298 50 0.014 0.012 0.083 17 3.75' 3.331 44.465 42 0.41 0.364 1.987 59 0.013 0.012 0.070 18 2.58 2.292 41.134 60 0.007 0.006 0.059 19 3.05 2.709 38.842 61 0.002 0.002 0.052 20 3.40 3.020 36.133 62 0.002 0.002 0.051 21 2.93 2.6C' 33.112 63 0.

0.0 0.047 22 4.22 3.749 30.510 64 0.

0.0 0.049 23 2.70 2.398 26.761 65 0.009 0.008 0.049 24 2.58 2.292 24.363 70 0.013 0.012 0.041 25 2.35 2.087 22.071 75 0.008 0.007 0.029 80 0.000 0.007 0.022 85 0.017 0.015 0.015 90 E

112.577 I

1

APPENDIX 7.6.

TABLE A.

SHELL SIZE DISTRIBUTION OF SOFT-SHELL CLAMS ON FLAT 1 FOR THE NOVEMBER SURVEYS, 1971-1979.

SEABROOK MA ARENARIA STUDY,1979.

i SIZE l

CLASS (mn) 1971 1972 1973 1974 1975 1976 1977 1978 1979 1

1 5

19.00 74.00 30.00 2.50 55.00 1031.00 283.00 38.00 16.98 10 11.00 9.00 6.00 1.14 52.00 413.00 100.00 8.15 15 11.00 15.00 3.00 0.75 117.00 148.00 14.26 l

l 20 7.00 11.00 5.00 0.02 5.82 76.00 20.00 l

25 0.47 2.50 0.16 0.11 0.48 9.20 19.50 30 1.30 2.30 0.51 0.17 0.02 0.02 0.56 13.57 l

35 1.50 1.20 0.60 0.48 0.04 0.03 6.10 l

40 1.80 1.40 0.67 0.89 0.23 0.01 0.03 3.33 l

45 1.80 0.61 0.49 1.10 0.14 0.10 0.01 0.94 g

50 1.00 0.83 0.42 1.20 0.36 0.03 0.02 0.03 0.31 55 0.64 1.60 0.30 0.82 0.25 0.04 0.03 0.03 0.06 l

60 0.36 0.33 0.29 0.42 0.28 0.23 0.02 0.03 0.03 l

65 0.08 0.19 0.18 0.31 0.14 0.13 0.01 0.04 l

70 0.03 0.19 0.11 0.10 0.11 0.06 0.04 0.01 75 0.03 0.08 0.05 0.10 0.03 0.03 0.02 0.02 0.03 80 0.02 0.07 0.02 0.03 85 0.01 0.01 0.01 0.05 90 0.01 0.01 M

M M

APPENDIX 7.6 (Continued)

TABLE B.

SHELL SIZE DISTRIBUTION OF SOFT-SHELL CLAMS ON FLAT #2, NOVEMBER 1971-NOVEMBER 1979. SEABROCK MYA ARENARIA STUDY,1979.

SIZE j

CLASS NOV APR JUL NOV FEB MAY AUG NOV JAN MAY AUG NOV i

(mm) 1971 1972 1972 1972 1973 1973 1973 1973 1974 1974 1974 1974 l

5 37.00 1.60 2.90 116.00 138.00 199.00 15.00 314.00 4.20 7.60 5.90 10 35.00 9.70 8.70 26.00 34.00 110.00 20.00 8.00 2.00 2.50 15 11.00 0.91 5.50 2.40 2.40 13.00 28.00 2.60 0.36 20 9.00 1.50 4.40 0.91 1.00 1.00 42.00 10.00 2.00 25 0.89 0.11 4.70 0.11 0.38 0.42 0.56 0.67 0.91 0.97 0.11 0.50 30 0.44 0.14 4.20 0.44 0.44 0.63 0.27 0.80 0.58 1.40 0.27 0.22 35 0.67 0.19 2.80 0.50 0.38 0.80 0.08 0.66 0.44 1.40 0.61 0.30 40 1.20 0.33 1.60 0.83 0.38 0.97 0.08 0.61 0.38 0.91 0.75 0.40 45 1.60 0.61 0.80 0.27 0.27 0.72 0.08 0.39 0.55 0.83 0.38 0.65 g

50 1.10 0.33 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 0.00 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 0.30 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 0.05 0.11 0.06 0.07 90 0.04 0.06 0.11 0.r 2 95 0.01 0.06 100 0.03 105 110 (Continued)

i i

i APPENDIX 7.6 (Continued) l TABLE B.

(Continued) 1 SIZE i

CLASS FEB MAY AUG NOV FEB MAY AUG NOV FEB MAY AUG NOV APR NOV APR AUG NOV l

(mm) 1975 1975 1975 1975 1976 1976 1976 1976 1977 1977 1977 1977 1978 1978 1979 1979 1979 j

5 5.90 9.80 3.40 9.10

--- 351.00 ---

--- 83.00

--- 11.00

--- 32.44 l

10 2.90

--- 10.56 i

15

--- 10.56 1

20 1.94 2.26 l

25 0.04 2.61 2.03 2.50 1.04 30 1.58 4.13 o.82 1.03 35 0.13 0.06 0.02 0.29 1.03 8.30 0.88 40 0.32 0.18 0.02 0.11 0.02 0.15 0.70 5.25 0.90 45 0.37 0.28 0.13 0.02 0.02 0.04 0.06 1.73 0.35 50 0.67 0.32 0.06 0.02 0.02 0.02 0.04 0.08 0.06 0.06 0.>3 0.21 55 0.72 0.52 0.09 0.02 0.02 0.02 0.02 0.09 0.10 i

60 0.24 0.44 0.02 0.07 0.04 0.02 0.02 0.03 0.04 0.05 65 0.18 0.18 0.06 0.02 0.02 0.11 0.06 0.03 0.05 70 0.20 0.11 0.02 0.09 0.02 0.02 0.03 75 0.04 0.02 0.07 0.04 0.11 0.02 0.02 0.04 0.02 0.02 i

80 0.06 0.04 0.02 0.07 0.02 0.04 0.02 0.09 0.02 0.02 l

85 0.06 0.02 0.02 0.04 0.04 0.03 0.03 90 0.02 0.02 0.02 0.04 0.09 0.06 0.02 0.02 95 0.02 0.02 0.06 0.09 100 0.04 0.04 0.02 0.02 0.02 0.02 105 110 0.02 0.02

--- = Not randomly sampled; see Appendix 7.2 for fixed station results e

e m

m W

W W

m W

W W

m m

W

i 71 I

lI j

APPENDIX 7.6 (Continued)

TABLE C.

SHELL SIZE DISTRIBUTION OF SOFT-SHELL CLAMS ON FLAT 3 FOR NOVEMBER SURVEYS, 1971-1979. SEABROOK MYA ARENARIA STUDY, 1979.

SIZE i

CLASS 1

(mm) 1971 1972 1973 1974 1975 1976 1977 1978 1979 1

I 5

35.00 28.00 6.00 0.63 1.14 556.00 67.00 38.00 10.18 10 29.00 4.70 1.00 4.10 3.40 1.10 15 5.20 4.00 3.40 3.00 i

20 4.80 2.00 1.13 3.71 l

25 0.17 0.42 1.00 0.05 3.74 0.18

{

30 0.92 0.25 1.00 0.14 0.85 0.14 35 0.67 0.17 0.38 0.12 0.02 0.10 0.27 0.14 l

40 1.50 0.33 0.62 0.11 0.02 0.29 i

45 1.40 0.42 0.50 0.30 0.02 0.04 0.14 l

50 1.30 0.17 0.29 0.11 0.03 0.02 0.02 0.07 55 1.10 0.17 0.79 0.08 0.03 0.02 0.04 0.04 l

60 0.83 0.08 0.54 0.18 0.08 0.02 i

65 0.58 0.46 0.38 0.08 0.04 0.02 0.07

{

70 0.33 0.08 0.42 0.14 0.02 0.04 i=

75 0.25 0.08 0.22 0.03 0.06 0.02 0.02 80 0.08 0.08 0.14 0.03 0.06 lg 85 0.04 0.03 0.08

!g 90 0.08 0.06 0.08 0.04 l

?

lI l

lI

\\I I

I I

I

72 APPENDIX 7.6.

(Continued) l TABLE D.

SHELL SIZE DISTRIBUTION OF SOFT-SHELL CLAMS ON FLAT 4 FOR NOVEMBER SURVEYS, 1971-!979.

SEABROOK MYA ARENARIA STUDY, 1979.

l SIZE CLASS (mm) 1971 1972 1973 1974 1975 1976 1977 1978 1979 l

5

'" 20 116.00 12.00 2.50 66.00 830.00 117.00 113.00 49.13 10 11.00 31.00 1.00 1.80 13.20 183.00 91.00 38.34 m

15 7.00 20.00 3.00 115.00 48.00 49.13 20 4.00 10,00 2.00 0.64 20.40 45.10 30.75 25 2.80 1.10 0.52 0.05 0.01 0.62 12.38 16.77 30 3.50 3.00 1.40 0.26 0.01 0.02 8.29 13.46 35 4.60 2.80 0.62 0.58 0.01 0.01 3.19 8.98 40 4.00 1.70 0.46 0.96 0.16 0.85 4.98 45 2.60 2.00 0.35 0.92 0.16 0.09 0.02 2.21 50 1.30 1.00 0.38 0.80 0.18 0.03 3.85 55 1.10 0.79 0.14 0.50 0.21 0.13 0.01 0.27 60 0.25 0.21 0.08 0.29 0.12 0.07 65 0.17 0.04 0.14 0.21 0.14 0.01 0.01 0.02 70 0.12 0.08 0.06 0.03 0.04 0.01 75 0.02 0.01 0.01 80 0.04 0.01 0.01 85 0.01 0.01 0.01 I

I I

I' t

I I.

I

73 I

E l

APPENDIX 7.6 (Continued)

TABLE E.

SHELL SIZE DISTRIBUTION OF SOFT-SHELL CLAMS ON FLAT 5 FOR NOVEMBER SURVEYS, 1971-1979. SEABROOK MYA AREVARIA STUDY, 1979.

SIZE CLASS (mm) 1971 1972 1973 1974 1975 1976 1977 1978 1979 I

5 67.00 136.00 22.00 2.40 7.50 546.00 92.00 44.00 11.03 10 38.00 94.00 1.00 2.80 8.30 4.80 2.55 15 12.00 16.00 7.50 20 3.00 6.00 5.30 4.80 25 0.06 0.55 0.10 0.75 2.28 0.05 30 0.11 0.89 0.31 2.17 0.31 I

35 0.33 0.61 0.14 0.01 0.01 1.41 0.73 40 0.44 1.00 0.28 0.07 0.41 0.33 45 0.44 0.77 0.12 0.10 0.22 I

50 0.94 0.94 0.10 0.02 0.04 0.12 55 0.39 0.61 0.12 0.01 0.03 60 0.28 0.50 0.12 65 0.11 0.65 0.08 0.01 I

70 0.11 0.05 0.04 75 0.05 0.01 0.01 0.01 80 0.06 0.01 85 90

1 J

APPENDIX 7.7 CARCINUS MAENAS CATCil RECORD JANUARY TilROUGil DECEMBER 1979, EIGitT TRAPS. SEABROOK MyA ARENARIA STUDY,1979.

)

l 1

MAXIMUM CARAPACE WIDTilS (cm)

TOTAL TRAPP1NG CANCER CARCINUS DATES

<3 3-3 1/2 3 1/2-4 4-4 1/2 4 1/2-5 5-5 1/2 5 1/2-6 6-6 1/2 6 1/2-7

>7 SPP.

NAENAS J

8-9 Jan 4M 2M 6M 9t1 9M 5M 6M IM 2M 207 126 2F 3F 16F 19F 28F 10F 4F 18-19 Jan 1M 1

1 31 Jan-1 Feb IM 1

1 27-28 Feb No catch 0

0 15-16 Mar No catch 3

0 27-28 Mar 1M 5

1 y

4 9-10 Mar 1M 1F 1M 75 4

j 1F 25-26 Apr 1M 2M 7M 21M 35M 32M 12M 3M 185 149 2F 4F 9F (lg) 3F 6F 4F 8F 5-10 May 1M 3M SM IM 7M 8tt 3M 2M 81 46 2F

. 3F 3F (lg) 6F ( ?g) 1F 1F 23-24 May No catch 54 0

5-6 Jun 1F 8F SF(lg) 13F 1M 176 32 4F 20-21 Jun IF 1M 20F 3M 3M 3M 195 78 13F(2 )

24F(2 )

9F 1F 9

9 i

(Continued)

M M

W M

M

APPENDIX 7.7 (Continued)

)

MAXIMUM CARAPACE WIDTliS (tm)

TOTAL j

TRAPPING CANCER CARCINUS j

DATES

>3 3-3 1/2 3 1/2-4 4-4 1/2 4 1/2-5 5-5 1/2 5 1/2-6 6-6 1/2 6 1/2-7

>7 SPP.

MAENAS 5-6 Jul 3F 3M 4M

,M 8M 15M 6M 133 93 9F 17F 20F SF j

18-19 Jul 1M 1F 2F 1M 122 5

I I

l-2 Aug 1F SF 2M 6M lOM IM 6M 4M 2M IM 60 61 j

6F 2F 7F 3F 4F 1F l

j 15-16 Aug 4M 2M SM 3M 3M 1F 145 39 2F 3F llF(lg) 2F 3F l

6-7 Sep 1F 1F 3M 3M 3M SM 2M 30+

69 I

ISP llF 15F 9F 1F a

w l

19-20 Sep 1M IM 1F 1M 2M IM 180 10 1F IF 1F 9-10 Oct 1M 3F 3M 9M 18M 28M 34M 20M SM 3M 57 468 f

1F 9F 39F 102F 108F 65F 17F 3F 4

j 27-28 Oct 2M IM 2M 13M 15M 15M 4M 2M 133 89 1F 3F 7F 11P 7F 6F i

7-8 Nov 1M 2F 3ri 3M 3M 8:1 SM 7M 6M 34 68 4F SF 7F 3F SP 5F 1F I

i 24-25 Nov lti 3M 2M SM 7M 17M 12M 1M 2M 46 131 l

1F 7F 12F 21F 23F 14F 1F 2F i

l 11-12 Dec 1F 2M IM 12M 12M 26M 20M 14M 3M 103 126 3F 2F lOF 13F 6F 2F i

I One trap missing i

ML20033A191

Contents

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ML20033A191

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1.0 INTRODUCTION

SUMMARY

1.0 INTRODUCTION

SUMMARY

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