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Chapter 7 - Demersal FishNorthwest Atlantic Distribution andImportant AreasMethodsSee methods overview in Chapter 5.Data LimitationsRelative distribution, weighted persistence, and trendsanalyses for the demersal fish group were based upon datafrom the NMFS bottom trawl survey database. Ottertrawl systems like the one utilized to conduct surveysampling are specifically designed to capture a variety ofdemersal fish species, including many of the species analyzedin this assessment. It is important to note, however,that the catch rates for various species within the groupare variable. Catchability coefficients are generally higherfor demersal, round-bodied species including Atlantic cod,haddock, pollock and hake and lower for flat-bodied fishand pelagic species. In additional, catch rates at any givenlocation can be heavily influenced by day/night differencesin species distribution within in the water column, andby seasonal variations in species distribution within theirgeographic range. As such, it should be recognized thatwhile analyses derived from the bottom trawl survey databaseare indeed informative, results obtained from otherdata sources should also be considered.Maps, Analysis, and Areas of ImportanceGadidsAtlantic cod (Figure 7-1a, b), haddock (Figure 7-3a,b), and pollock (Figure 5a, b) were distributed acrossthe Gulf of Maine, Georges Bank and Southern NewEngland, occurring in high numbers along the northernedge and Northeast Peak of Georges Bank. High numbersof Atlantic cod and pollock were also found to occuralong the 50 fathom curve in the western Gulf of Maine.Statistical analyses indicated a declining trend for Atlanticcod (Figure 7-1c, d) and pollock (Figure 7-5c, d) acrossmuch of their range, though increasing trends were observedfor Atlantic cod in parts of the Jeffreys Ledge andStellwagen Bank area and in discrete areas around theperimeter of Georges Bank. Statistical analyses for haddockdid not reveal significant trends across much of theirrange, though increasing trends were observed on parts ofGeorges Bank, in the Great South Channel, and shelf watersoff the coast of New Jersey (Figure 7-3c, d). Haddockdeclined in the Gulf of Maine in small portions of theJeffreys Ledge and Stellwagen Bank area and along thecoastal shelf in eastern Maine off of Penobscot Bay.Weighted persistence analyses identified the NorthernEdge and Northeast Peak of Georges Bank, and theGreat South Channel as important areas for Atlantic cod(Figure 7-2), haddock (Figure 7-4), and pollock (Figure7-6). The southern flank of Georges Bank was also importantfor haddock. In the Gulf of Maine, nearshorewaters of Massachusetts Bay, Jeffreys Ledge, andStellwagen Bank were identified as important for thesethree species, as were the Cashes Ledge area, the coastalshelf off Penobscot Bay in eastern Maine, and the areabetween Grand Manan Banks and German Bank off ofNova Scotia.Cusk were widely dispersed throughout the Gulf ofMaine and along the northern perimeter of Georges Bank(Figure 7-7a, b). High numbers occurred in the deeperwaters of the central Gulf of Maine, including watersextending from Cashes Ledge through the Jordan Basinand onto the Scotian Shelf in Canadian waters. Statisticalanalyses for cusk generally found no significant trendacross much of their range, though declining trends wereobserved in portions of the Gulf of Maine, includingnear Franklin Swell, the northern tip of Jeffreys Ledge,off the southern coast of Nova Scotia near Grand MananBanks and German Bank, and along the Northeast Peakof Georges Bank (Figure 7c, d). Weighted persistenceanalyses for cusk identified Jeffreys Ledge, waters west ofCashes Ledge to Sewell Ridge, the Northeast Channel,and the Northern Edge/Northeast Peak of Georges Bankas important areas (Figure 7-8).High numbers of red hake were found on Jeffreys Ledgeand Stellwagen Bank in the Gulf of Maine, along theperimeter of Georges Bank, along the Continental Shelfand Slope break in Southern New England as far south asNorthwest Atlantic Marine Ecoregional Assessment • Phase 1 Report 7-