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The spatial and temporal distribution patterns of the Atlantic wolffish (Anarhichas lupus) from the Gulf of Maine-Georges Bank region were examined based on bottom trawl survey data from 1963 to 1989. Age composition, growth and food habits were also evaluated from 1983 to 1989. Catches of wolffish were distributed throughout the region, but highest concentrations occurred along the 100 m depth contour of the Gulf of Maine-Georges Bank. Statistical analyses of the depth occurrences revealed a seasonal shift in depth distribution from shallow water ( 50 cm) wolffish migrate to these shallow waters in spring and return to deeper waters in autumn. The oldest wolffish aged was 22 years. Mean length-at-age ranged from 4.7 cm total length for age 0 to 98.0 cm total length for age 22 in spring. Growth was modelled best by the Gompertz function. Bivalve molluscs (primarily Placopecten magellanicus) dominated the diet, followed by echinoderms, gastropods and decapods. Introduction The Atlantic wolffish (Anarhichas lupus) is a commercially important, cold water species found on both sides of the North Atlantic. In the Northwest Atlantic, its distribution extends from off Greenland to the Nantucket Shoals off the eastern United States (Jonsson, 1982). It is typically captured incidental to fishing operations directed toward other benthic species in this region. Commercial landings in USA territorial waters are from the Gulf of Maine and Georges Bank (NAFO Subarea 5), where the total USA nominal catch increased from 200 tons in 1970 to 1 200 tons in 1983 and have since declined to 500 tons (NMFS/NEFC, 1991). Additionally, National Marine Fisheries Service (NMFS), Northeast Fisheries Center, Woods Hole, Massachusetts, bottom trawl surveys indicate a long-term decline in relative abundance since the 1970s (NMFS/NEFC, 1991). Such information suggests that the Atlantic wolffish population of the Gulf of Maine-Georges Bank may be overexploited. However, currently there is no fishery management plan implemented to control fishing mortality on this species. Data on population biology and dynamics of exploited species are essential for proper management strategies. Past research concerning the biology of the Atlantic wolffish has included studies on food habits (Jonsson, 1982; Albikovskaya, 1983; Templeman, 1985; Hawkins and Angus, 1986), distribution and migratory patterns (Albikovskaya, 1982; Jonsson, 1982; Templeman, 1984), reproductive behaviour (Keats et al., 1985), age and growth (Jonsson, 1982) and sexual maturity and fecundity (Templeman, 1986) from Icelandic to Nova Scotian waters. Only descriptive data on depth distribution, food habits and breeding habits (Bigelow and Schroeder, 1953) are available for fishes in United States territorial waters. This study was undertaken to document trends in spatial and temporal distribution patterns based on bottom trawl survey data, and to evaluate quantitatively age, growth and food habits of Atlantic wolffish from the Gulf of MaineGeorges Bank region. Materials and Methods Data used for the spatial and temporal distribution analyses were collected from 1963 to 1989 in the Gulf of Maine-Georges Bank region by NMFS in a synoptic bottom trawl survey. The survey was based on a stratified-random sampling design for continental shelf waters >27 m in depth, partitioned into strata of unequal area based on depth and geographic location (Grosslein, 1969; Azarovitz, 1981). Prior to 1968, sampling was conducted only in autumn. A spring survey was added to the annual schedule in 1968. Sampling effort was expanded in 1972 to include the nearshore waters between 5 and 27 m depth. Sampling during spring and autumn J. Northw. Atl. Fish. Sci., Vol. 13: 53–61 54 J. Northw. Atl. Fish. Sci., Vol. 13, 1992 occurred generally in March to May and September to November, respectively. Sampling stations were randomly selected within each stratum and effort (number of stations) allocated in rough proportion to stratum area. At each station, a # 36 or # 41 Yankee otter trawl with a 1.25 cm stretched mesh codend liner was towed at approximately 3.5 knots for 30 min; bottom depth and near-bottom temperature data were also recorded (Azarovitz, 1981). Changes in spatial distribution between spring and autumn were examined for the 1963–89 survey period. Depth of occurrences, weighted by the number of wolffish captured in each tow, were compared between seasons using Kruskal-Wallis nonparametric ANOVA (Gibbons, 1976). Further, length frequencies were examined by depth ranges for evidence of a seasonal reproductive migration noted by Keats et al. (1986). Due to the low numbers of wolffish captured annually, data from all survey years were combined for these analyses. Age and growth Wolffish were collected opportunistically for the age, growth and food habits analyses from autumn 1983 to spring 1989. Individuals captured in the otter trawl were weighed collectively to the nearest 0.1 kg, measured individually (total length; TL) to the nearest cm, and sexed. The head and entire digestive tract from the esophagus to rectal sphincter were then removed, stored in plastic bags, and frozen. Occasionally, small wolffish (<30 cm) were frozen whole. In the laboratory, sagittal otoliths were excised from the heads, cleaned of extraneous tissue, and stored dry in coin envelopes. Age determination used similar techniques to those described by Jonsson (1982). One otolith (either left or right) was placed on black velvet to enhance hyaline zones, submerged in 50% ethyl alcohol, and viewed under a binocular dissecting scope to 30X using reflected light. As Jonsson (1982) reported, otoliths from large wolffish can be very thick at the nucleus, thus hindering interpretation of the first few annuli. In order to expose the nucleus and innermost growth rings, we ground the region over the nucleus on the convex surface of such otoliths with fine grit sand paper until the central rings became clearly visible when viewed as described above. An annulus was identified as a translucent hyaline ring that was preceded by a white opaque zone. Jonsson (1982) concluded the hyaline and opaque zones are formed in the winter and summer, respectively. In the age determination we independently counted the annuli from the nucleus out to the dorsal edge of the otolith, or from the nucleus to the distal edge of the subrostrum. If our first age estimates did not concur (28% did not agree; age differences between the two readers were generally 1–2 years), we independently aged the otoliths a second time, then jointly examined the disputed otoliths until agreement was reached. A January 1 birthdate was assigned for all. A total of 132 wolffish heads or whole fish were collected during the survey period from fish that ranged from 3.8 to 118 cm TL (X = 61.5 cm). Only 126 of those were used in age determination due to incomplete data records for the others. Due to the low numbers of age samples, growth was modelled by fitting mean lengths-at-age (years) for all years combined, weighted by the inverse variance, to the following functions: Von Bertalanffy Lt = L∞ (1-exp -k o)) Logistic Lt = L∞ / (1 + exp o) Gompertz Lt = L∞ exp -exp-k(Age-to) Parameters L∞ , k and to were estimated using SAS nonlinear regression (Proc NLIN) with the optional derivative-free (DUD) method (SAS Institute, 1988). The goodness of fit of the assorted models was evaluated by comparing the magnitude of each model’s weighted residual sum of squares. Age in years was designated with a 0 or 5 decimal extension that represented fish captured in spring and autumn, respectively. Food habits

Distribution, Growth and Food Habits of the Atlantic Wolffish (Anarhichus lupus) from the Gulf of Maine-Georges Bank Region