Fishes of the Gulf of Maine

There is an ongoing controversy on whether ¢sh farming aiects the quality of wild ¢sh in fjords. In northern Norway, local people prefer not to eat saithe, Pollachius virens L., from areas in the vicinity of ¢sh farms because they say the taste is inferior to saithe from other areas. To address this issue, saithe were collected in the vicinity of a salmon ¢sh farm in a fjord in northern Norway and in two reference areas: one site 6 km away from the nearest ¢sh farm in the same fjord, and the other in a fjord nearby with no ¢sh farms. The objective of this study was to clarify whether the physiology or taste of saithe near ¢sh farms diiers from saithe in areas with no or limited in£uence from ¢sh farms. The ¢sh collected near farms were larger than those from control sites of the same age and had been eating pellets. Analysis of fatty acid composition of the ¢llet indicated that ¢sh collected near the farms had fatty acid pro¢les that resembled that of pellets more than ¢sh from reference sites. The results suggest that there were individual diierences in the time spent near cages for saithe collected near the farm, and that saithe collected at the reference area in the same fjord had also been eating pellets, i.e. had visited at least one of the ¢sh farms in the fjord. In a sensory test, the test panel found that saithe from the fjord without ¢sh farms tasted better than saithe collected near the cages. The test panel found no clear diierences in taste between saithe collected near the ¢sh farm and saithe from the same fjord, but 6 km from the nearest ¢sh farm.

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Salmon farming affects the fatty acid composition and taste of wild saithe Pollachius virens L.

The pelagic (i.e. fishes that spend most of their time swimming and feeding in the water column) fish assemblage was examined within a temperate estuary to determine the seasonal patterns of abundance, biomass, richness, and species composition. These measures were related to abiotic measures including temperature, salinity, water transparency, and depth. Pelagic fish (n 000) were sampled weekly from August 1995 through December 1996 in Great Bay in New Jersey, USA, with a pop net (5 m diameter, 5 m length, 3 mm cod end). The most frequently occurring and abundant species included Clupea harengus (frequency of occurrence, 27.4%; abundance, 80.5% of total catch), Menidia menidia (frequency of occurrence, 83.5%; abundance, 10.6% of total catch), Anchoa mitchilli (frequency of occurrence, 66.5%; abundance, 6.0% of total catch), and Anchoa hepsetus (frequency of occurrence, 23.1%; abundance, 1.9% of total catch). There were strong seasonal trends in species richness, total abundance, and total biomass with peaks in spring, summer, and autumn, and very low values for these parameters in winter. In addition, there were five seasonal groupings within this pelagic fish assemblage that were primarily, but not exclusively, represented by young-of-the-year (age 0+). Winter (December–March) was represented by adult Gasterosteus aculeatus and age 1+ by M. menidia . Spring (April–early June) was overwhelmingly dominated by age 0+ C. harengus . Early summer (late June–early July) was relatively species rich and characterized by age 0+ of Brevoortia tyrannus , Pomatomus saltatrix , Alosa pseudoharengus , and age 1+ of A. mitchilli . Late summer (late July–August) remained relatively species rich and included mostly age 0+ of A. mitchilli , A. hepsetus , and M. menidia . Autumn (September–November) continued to have high catches of age 0+ of M. menidia and A. mitchilli . As expected for temperate estuaries, the best of the measured abiotic predictors of these groupings included temperature, salinity, and degree of change in temperature. However, timing of life history characteristics, such as location, and timing of reproduction and migration also influenced the seasonal occurrence of these pelagic species. The large abundance and biomass of a relatively few species, as observed in this study, are typical of estuaries, although this is one of the few studies that have focused solely on the pelagic component of estuarine fish assemblages.

Seasonal changes of the pelagic fish assemblage in a temperate estuary

We studied the composition of harbour seal (Phoca vitulina) diets in two areas, the lower Bay of Fundy and along the northeastern coast of Nova Scotia, that differ in prey species diversity, bottom type, and physical oceanography. Prey remains were found in 250 of 470 harbour seal stomachs collected mainly from May to September between 1988 and 1992. Although 23 taxa were identified, four species, Atlantic herring (Clupea harengus), Atlantic cod (Gadus morhua), pollock (Pollachius virens), and short-finned squid (Illex illecebrosus), accounted for 84% of the estimated biomass of prey consumed in the two areas combined. Species, such as herring and squid, that dominated the diets in both habitats, also tended to be abundant in both habitats during the summer. Atlantic cod was the principal gadoid in the Bay of Fundy, whereas pollock was most important along the Atlantic coast. Differences in prey distribution and abundance appeared to account for differences in the contribution of the alewife (Alosa pseudo...

Comparison of harbour seal diets in two inshore habitats of Atlantic Canada

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

Data collected from tagging studies along the coast of Nova Scotia and offshore ichthyoplankton surveys were used to investigate growth and inshore-offshore migrations of juvenile pollock. Age zero pollock from 0.3 to 4.2 cm in length were found in the offshore plankton between November and June and small pollock at lengths of 7-11 cm were caught inshore in July. These small pollock appear to have moved inshore after leaving the offshore pelagic community at 3-6 months of age. They remain inshore until they reach approximately 30+ cm during their second year. Tagged inshore pollock were observed to grow 17-18 cm during their first year of life, an annual instantaneous growth rate (G) of4.1, and 27-30 cm by the end of their second year (G =1.8). Seasonal variability in growth was also observed in juvenile pollock. Mean absolute growth from May until August was 1.75 cm per month, from August until October 1.50 cm per month, and from November until April about 0.5 cm per month. A tagging related mortality experiment using winter tagged juveniles indicated a 11% mortality during the first 3 months after tagging.

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B Beck

Papers

Growth of Juvenile Pollock (Pollachius virensL.) Along the Atlantic Coast of Canada with Inferences of Inshore-offshore Movements