FISHERY BULLETIN: VOL. 80. NO: 4 



lap or, at least, extremely low levels of overlap 

 with longhorn sculpin. 



Silver Hake — Scup 



Silver hake and scup both prey on crustaceans, 

 but they share few prey species in common so 

 that diet overlap values are quite low (Fig. 5D). 

 There is a trend for the overlap values to decrease 

 when comparing larger silver hake and scup 

 which mirrors the shift towards fish predation 

 by these larger silver hake. 



Silver Hake — Butterfish 



The diets of silver hake and butterfish overlap 

 at very low levels, the highest value being 17% 

 which was the result of predation on the squid 

 Loligo (Fig. 5E). Generally, the butterfish is more 

 planktonic in its predatory habits than the silver 

 hake which is reflected in the low overlap values. 



Silver Hake — Atlantic Cod 



Silver hake and Atlantic cod are generally 

 found to have low to intermediate levels of diet 

 overlap and very few values that are >60% (Fig. 

 6A). All of the high values are the result of un- 

 identified fish remains forcing up the computed 

 overlap values. Both of these predators become 

 more piscivorous as they grow larger, but this 

 size-specific dietary shift is not reflected in an 

 obvious change in the level of diet overlap. In 

 other words, the smaller fish share crustacean 

 prey species such as euphausiids while the larger 

 predators both prey on a number of different spe- 

 cies of fish. 



Silver Hake — White Hake 



There is a clear pattern of overlap when com- 

 paring the diets of silver and white hake (Fig. 

 6B). The diets of the larger fish of both species do 

 not overlap with the smaller fish of the opposite 

 species. In other words, the diet of small silver 

 hake has little in common with the larger white 

 hake and vice versa. The explanation for this is a 

 size dependent change in diet for both predators. 

 When small, they both rely on crustaceans, such 

 as euphausiids, and then gradually shift to fish as 

 the predator grows. For example, the high value, 

 74% between 16-20 cm (size class 4) silver hake 

 and 31-35 cm (size class 7) white hake results 

 from over 50% of either of these predators feed- 



ing on Meganyctiphanes norvegica. For compari- 

 son, the other high value, 75%, for 41-45 cm (size 

 class 9) silver hake and 66-70 cm (size class 14) 

 white hake, is the result of fish predation on such 

 fish as silver hake, clupeids, and other unidenti- 

 fiable fish remains. 



Silver Hake — Red Hake 



The diet overlap between silver and red hake 

 ranges from 0% to intermediate levels as high as 

 56%. The general pattern is increasing overlap 

 with increasing predator size up to 26-30 cm (size 

 class 6) and then leveling off or decreasing slight- 

 ly between the larger fish (Fig. 6C). The peak 

 value, occurring between 26-30 cm silver hake 

 and 41-45 cm (size class 9) red hake, can be ex- 

 plained by predation on fish, Die he lop and al us 

 leptoeerus, and other invertebrates. 



Silver Hake — Spotted Hake 



Silver and spotted hake show, for the most 

 part, intermediate to high levels of diet overlap 

 between similar size fish (Fig. 6D). Peak values 

 of 60% and 70% occur, for example, between 11- 

 20 cm (size classes 3-4) and 16-25 cm (size classes 

 4-5) silver and spotted hake, respectively. These 

 peaks are the result of a reliance by both preda- 

 tors on Meganyctiphanes norvegica, Dichelopan- 

 dalus leptoeerus, and Crangon septemspinosa. 

 The intermediate overlap values are also, how- 

 ever, a reflection of predation on fish, especially 

 for the larger silver and spotted hake. 



Silver Hake — Pollock 



High diet overlap values exist between silver 

 hake 16-20 cm (size class 4) and pollock 16-65 cm 

 (size classes 4-13). Two prey categories are re- 

 sponsible for these high levels, Meganyctiphanes 

 norvegica and unidentified fish remains. Medi- 

 um levels of overlap between these two predators 

 are common for most size classes except for silver 

 hake below 10 cm. Overlap between these small- 

 er silver hake and all sizes of pollock falls into the 

 lower overlap category. There are also extremely 

 low values between small pollock and large sil- 

 ver hake (Fig. 6E). 



Silver Hake — Haddock 



Silver hake and haddock show little similarity 

 in their diets and the resulting diet overlap val- 



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