ML072070383

Atlantic Surfclam by James Weinberg (January 2000)

ML072070383
Person / Time
Site:	Oyster Creek
Issue date:	01/31/2000
From:	Weinberg J - No Known Affiliation
To:	Office of Nuclear Reactor Regulation
Davis J NRR/DLR/REBB, 415-3835
References
Download: ML072070383 (4)

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Last Revised: January 2000 Summary Status Landings and Abundance Trends Landings Data Atlantic Surfclam by James Weinberg Atlantic surfclams, Spisula solidissima, are distributed in the western North Atlantic from the southern Gulf of St. Lawrence to Cape Hatteras. Commercial concentrations are found primarily off New Jersey, the Delmarva Peninsula, and on Georges Bank. In the Mid-Atlantic region, surfclams are found from the beach zone to a depth of about 60 m. Beyond 40 m, however, abundance is low.

Surfclams reach harvestable size in about six years. Maximum size is about 22.5 cm (8.9 in.), but clams larger than 20 cm (7.9 in.) are rare. Surfclams are capable of reproduction in their first year of life, although full maturity may not be reached until the second year. Eggs and sperm are shed directly into the water column; recruitment to the bottom occurs after a planktonic larval period of about three weeks.

The fishery for surfclams in the Exclusive Economic Zone (EEZ) is managed under the Surfclam-Ocean Quahog Fishery Management Plan (FMP) of the Mid-Atlantic Fishery Management Council. Management measures include a total allowable annual catch (TAC) and an individual transferable quota (ITQ) system which was adopted under Amendment 8 to the FMP in 1990. Landings from the EEZ were 18,600 mt (meats) in 1997 and 18,200 mt in 1998 under a TAC of 19,800 mt per year. Fisheries taking place closer to shore are managed by state authorities.

The principal fishing gear for surfclams is the hydraulic clam dredge. Recreational and foreign fishing are insignificant. Total annual landings of surfclams averaged about 20,000 mt in the early 1960s, increased to over 40,000 mt in 1974, and then decreased to about 16,000 mt in 1979.

Since 1983, total annual landings have ranged between 24,000-35,000 mt. Landings from state waters, primarily from New York and New Jersey, increased from 8,100 mt in 1989 to over 11,000 mt during 1992-1993 and have since averaged about 8,000 mt. Total combined landings from EEZ and state waters were 26,300 and 24,500 mt for 1997 and 1998, respectively.

In 1990, 128 vessels participated in the Mid-Atlantic EEZ fishery for surfclams. With the adoption of Amendment 8 to the FMP, the number of vessels in the fishery declined to 75in k.- SC4-- X C

1991, and to 31 by 1998. Two management areas, New England and the Mid-Atlantic, were formerly identified, but were combined in Amendment 8. A single annual TAC now applies to the entire US EEZ. The Georges Bank region has been closed to the harvesting of surfclams since 1990, due to the risk of paralytic shellfish poison (PSP).

Biomass indices from research vessel surveys employing hydraulic dredge gear have loosely paralleled trends in regional landings. Some of the variability over time in the survey indices has been due to changes in dredge efficiency, rather than changes in clam biomass. Stock biomass (as indicated by the survey) and landings were low in the late 1970s following mass mortality of surfclams, due to a hypoxic event off the New Jersey coast. Surveys from 1978 onward indicated substantial recruitment in the area subjected to the clam kill, notably from the 1976 year class.

The proportion of total Mid-Atlantic landings from off northern New Jersey increased with surfclam recruitment and biomass. From 1982-1999 the Mid-Atlantic survey index has been variable, and without a distinct trend.

Concentration of the offshore fishery in Delmarva waters between 1976 and 1980 resulted in a decline in harvestable biomass. There is currently little fishing effort off Delmarva and recent surveys indicate that abundance of clams is now relatively high. Clams in the Delmarva region have grown at substantially slower rates and have lower yields than those off New Jersey, due to high density and perhaps other factors.

Discarding of small surfclams was common in the early 1980s when a size limit of 12 cm (5.4 inches) was enforced. The size limit was suspended for the 1991 fishing season due to the relatively low abundance of prerecruit-sized clams and the likely incentive under Amendment 8 to target beds of larger surfclams. Recruitment occurred continuously during the 1980s and 1990s, although no year class has dominated the population in the manner that the 1976 year class did following the hypoxic event. Populations off New Jersey and the Delmarva peninsula are now composed of 15-20 year classes.

The most recent stock assessment indicates that the surfclam resource is at a high level of biomass and is under-exploited. In the EEZ, the annual quota is relatively small compared with the entire stock biomass of 1.3 million mt, and recent F levels (0.02) were substantially lower than the overfishing (FTHRESHOLD) level of 0.15. In the last decade, fishing has been concentrated off New Jersey. Catch per unit effort (bushels per hour fished) for the New Jersey area has declined slowly throughout the 1990s with a small increase in 1999.

For further information Chintala, M. M., and J. P. Grassle. 1995. Early gametogenesis and spawning in "juvenile" Atlantic surfclams, Spisula solidissima (Dillwyn, 1819). J. Shellf. Res. 14(2): 301-306.

Murawski, S. A., and J. S. Idoine. 1990. Yield sustainability under constant catch policy and stochastic recruitment. Trans. Amer. Fish. Soc. 118(4):349-367.

NEFSC [Northeast Fisheries Science Center]. 1998. [Report of the] 26th Northeast Regional Stock Assessment Workshop (26th SAW), Stock Assessment Review Committee (SARC) consensus summary of assessments. Northeast Fish. Sci. Cent. Ref. Doc. 98-03. 283 p.

Weinberg, J.R., and T.E. Helser. 1996. Growth of the Atlantic surfclam, Spisula solidissima, from Georges Bank to the Delmarva peninsula, USA. Mar. Biol. 126: 663-674.

Weinberg, J. R. 1998. Density-dependent growth in the Atlantic surfclam, Spisula solidissima, off the coast of the Delmarva Peninsula, USA. Mar. Biol. 130:621-630.

Weinberg, J. R. 1999. Age-structure, recruitment, and adult mortality in populations of the Atlantic surfclam, Spisula solidissima, from 1978 to 1997. Mar. Biol. 134:113-125.

NEFSC [Northeast Fisheries Science Center]. In press. [Report of the] 30th Northeast Regional Stock Assessment Workshop (30th SAW), Stock Assessment Review Committee (SARC) consensus summary of assessments. Northeast Fish. Sci. Cent. Ref. Doc.

Summary Status Long-term potential catch (MSY) = 80,000 mt Biomass corresponding to MSY = BMSy = 630,000 mt Minimum biomass threshold = /2 BMSY = 315,000 mt Stock biomass in 1997-99 = 1,260,000 mt (Implies stock was not overfished)

FMsY1 SM =0.15 FTARGET = not specified Overfishing definition =FTHRESHOLD2 = 0.15 at 1997-99 biomass level F 1 9 97 . 99 = 0.02 (Implies overfishing was not occurring)

Age at 50% maturity = 1year Size at 50% maturity = <4 cm (1.6 in.) shell length Assessment level = Size structured (biomass model)

Management Surfclam and Ocean Quahog FMP M = 0.15 F0.I = 0.19 Fmax = 0.70 1M is currently used as a proxy.

2 FTHRESHOLD = FMSy = 0.15 when biomass >= '/ BMSy, declining linearly to zero at B=0.

3 As per recommendations from 26th SAW; incorporates efficiency-corrected swept-area biomass estimates.

Atlantic Surfclam Middle Atlantic 50 - 15 Commercial Landings 40.

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\ Mid-Atlantic Survey Index 0 I 1 I I 0 1960 1965 1970 '175 1960 195 1990 1 95 2000 Year Table 3 1.1 Recreational and commercial landings (thousand metric tons, meats)

Year 1979-88 Category Average 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 U.S. recreational - - - - - - - - -

Commercial United States EEZ 19.6 21.9 24.0 20.6 21.7 21.9 21.9 19.6 19.8 18.6 18.2 State waters 5.6 8.1 8.5 9.4 11.0 11.6 9.1 9.1 9.0 7.7 6.3 Canada - - - - - - - - - - -

Total nominal catch 25.2 30.0 32.5 30.0 32.7 33.5 31.0 28.7 28.8 26.3 24.5