Fishes of the Gulf of Maine

Status of fishery resources off the Northeastern United States for 1998

The Im~jor responsibilities or the National Marine Fisheries Service (NMFS) are to monitor and assess the abundance and geographic distribution of fishery resources, to understand and predict fluctuations in the quantity and distribution of these resources, and to establish levels for their optimum use. NMFS is also charged with the development and implementation of policies for managing national fishing grounds, with the development and enforcement of domestic fisheries regulations, with the surveillance of foreign fishing off U.S. coastal waters, and with the development and enforcement of international fishery agreements and policies. NMFS also assists the fishing industry through marketing services and economic analysis programs and through mortgage insurance and vessel construction subsidies. It collects, analyzes, and publishes statistics on various phases of the industry.' The NOAA Technical Report NMFS series was established in 1983 to replace two subcategories of the Technical Report series: "Special Scientific Report-Fisheries" and "Circular." The series contains the following types of reports: scientific investigations that document long-term continuing programs of NMFS; intensive scientific reports on studies of restricted scope; papers on applied fishery problems; technical reports of general interest intended to aid conservation and management; reports that review, in considerable detail and at a high technical level, certain broad areas of research; and technical papers originating in economics studies and in management investigations. Since this is a formal series, all submitted papers receive peer review and all papers, once accepted, receive professional editing before publication. Copies of NOAA Technical Reports NMFS are available free in limited numbers to government agencies, both federal and state. They are also available in exchange for other scientific and technical publications in the marine sciences. Individual copies may be obtained from the A llhough the contents of these reports have not been copyrighted and may be reprinted entirely, reference to source is appreciated. The ational Marine Fisheries Service (NMFS) does not approve, recommend, or endorse any proprietary product or proprietary material mentioned in this publication. No reference shall be made to MFS, or to this publication furnished by NMFS, in any advertising or sales promotion which would indicate or imply that NMFS approves, recommends, or endorses any proprietary product or proprietary material mentioned herein, or which has as its purpose an intent to cause directly or indirectly the advertised product to be used or purchased because of this NMFS publication.

Maturation of nineteen species of finfish off the northeast coast of the United States, 1985-1990

We ~nvestigated patterns of distribution and foraging by young-of-the-year pollock Pollachius virens in the rocky intertidal zone. Pollock were sampled by beach seine in fucoid macroalgae and in open habitats at all stages of the tide, day and night throughout the summer. Their presence in shallow water at the high tidal stages indicated that at least part of the pollock population migrated across the full width of the intertidal zone (150 m) each tide. Densities in shallow water were much higher at low than at high tidal stages suggesting that a large influx of pollock moved in from the subtidal zone at low tidal stages and then dispersed into intertidal habitats at high tidal stages. There were few differences in pollock densit~es between algal and open habitats but abundances likely increased in the algal habitat at higher tidal stages when changes in habitat availability are taken Into account. Densities were higher at night and there was an order of magnitude decline in pollock densities from early to late summer. In another study we showed that piscivorous birds are a probable cause of pollock summer mortality. Pollock fed on invertebrates from intertidal algae relatively continuously. The tidal migrations of juvenile pollock observed in this study and their use of macroalgae as a foraging and possibly a refuging habitat strongly suggests that the rocky intertidal zone may be an important fish nursery area. K E Y WORDS: Marine fish nursery . Rocky intertidal zone . Habitat selection . Pollachius virens . Pollock . Macroalgae . Foraging . Gadidae . Beach seine

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Use of rocky intertidal habitats by juvenile pollock Pollachius virens

The Georges Bank ecosystem has undergone dramatic changes in biomass and species dominance under exploitation. Sharp declines in the biomass of both pelagic and demersal fish populations have occurred associated with rapid increases in fishing effort by distant water fleets. We corrected nominal effort series for changes in vessel size, gear type and country of origin in an attempt to provide a measure of the intensity of the perturbation resulting from large scale changes in exploitation patterns on Georges Bank. A fourfold increase was noted in standardized effort over the period 1960–72. Declines in catch-perstandard day fished, and relative biomass indices derived from research vessel surveys indicated marked decreases in all components of the system during the period 1960–76. Decreases in fishing effort were effected with the implementation of extended jurisdiction to 200 miles in 1977; however, several major stocks had collapsed by that time. Fundamental changes were noted in the production levels on Georges Bank during the period 1960–76. Declines in overall production can be attributed largely to the collapse of the herring population by 1976–77 under heavy exploitation. Recent increases in biomass of elasmobranchs and principal pelagic species (herring and mackerel) have resulted in further shifts in system structure. The biomass of piscivores is currently high and this shift may act synergistically with increasing exploitation rates to cause further declines in biomass of commercially desirable species.

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Aggregate Fish Biomass and Yield on Georges Bank, 1960-87

Commercial exploitation of pollock in NAFO Divisions 4VWX and Subareas 5 and 6 has increased considerably over the past two decades as abundance of traditional groundfish species has declined. Total pollock landings from this area increased from less than 30,000 (metric) tons per year during the late-1960s to over 60,000 tons since 1985; USA recreational catches have contributed between 1,000 and 2,000 tons to the annual totals. Since 1977, when both the USA and Canada extended uni-Iateral jurisdiction over their fishery resources to 200 miles, domestic management programs for pollock have been either non-existent or ineffective in restricting total landings. Assessment and management advice for pollock has traditionally been predicated on the assumption of a single unit stock within the region. Tagging studies and morphometric and meristic measurements, however, suggest a possible separation of Gulf of Maine pollock from those on Browns Bank and Emerald Basin on the Scotian Shelf. The distribution of pollock eggs and larvae also indicates the presence of several spawning sites on the Scotian Shelf in addition to previously documented locations in the western Gulf of Maine. Sexual maturation and growth rates for pollock are similar throughout the region. Growth rates of males and females do not differ significantly, although the median size at maturity is slightly larger for males. The majority of pollock of both sexes become sexually mature during their third year. Recruitment has been consistent since the late-1960s with one or more relatively strong year-classes appearing throughout the region every 3-4 years. Pollock become fully recruited to the fishery between ages 6 and 7, although partial recruitment declines again after age 7. Estimates of total stock size (age 2+), derived from virtual population analysis (VPA), increased from 102 million fish in 1974 to 145 million in 1977, but declined to 97 million in 1980. Following recruitment of the 1979 year-class at age 2 in 1981, stock size increased to 168 million before declining to 113 million in 1988. Instantaneous fishing mortality (F) has exceeded Fo.i (0.29) but remained at or below Fm a, (0.57) throughout the 1970s. Fishing mortality has been close to Fm a" however, in 4 of the 6 years since 1982. Analyses of research vessel survey data generally agree with results obtained from the VPA, indicating a recent decline in stock abundance and biomass, and an increase in instantaneous total mortality. Equilibrium calculations suggest that fishing at Fa' would provide a long-term yield of 53,600 tons from a stock biomass of 317,700 tons, while fishing at Fm a, would provide a yield of 58,100 tons from a stock biomass of 204,600 tons. Corresponding spawning stock biomass levels at Fa' and Fm a, are 260,400 and 149,800 tons respectively. Although long-term yields are approximately 8% greater at the Fm a, level, fishing at Fa' provides for a 55% increase in total stock and 74% increase in spawning stock biomass over those allowed under Fma, . 'Present address: Max Planck Institute, 1A Marconi Strasse, Julich D-5170, Federal Republic of Germany. 14 J. Northw. Atl. Fish. Sci., Vol. 9,1989

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S H Clark

Papers

Patterns of Exploitation and Biological Status of Pollock (Pollachius virensL.) in the Scotian Shelf, Georges Bank and Gulf of Maine Area