FISHES OF THE GULF OF MAINE 



215 



larvae that are liberated in harbors from the 

 hatcheries are always in danger of being snapped 

 up by the young pollock that are plentiful in such 

 situations. When a pollock only 9 inches long is 

 capable of eating 77 herring up to 2% inches long 

 at one meal, 3 "ravenous" is only mildly descriptive. 

 However, pollock so seldom strand in pursuit of 

 prey that we have never seen one on the beach 

 though schools often come close in and are caught 

 in the traps. 



In the Gulf of Maine, pollock depend perhaps 

 as much on pelagic shrimps as on fish. At East- 

 port, for example, where these shrimps (genera 

 Meganycliphanes and Thysanoessa) are very abun- 

 dant all summer, Kendall * reports pollock of all 

 sizes not only fattening on them but so evidently 

 preferring them to young herring that he did not 

 find a single "sardine" in a pollock stomach, though 

 these were plentiful enough at the time. He adds 

 that "if at any time the crustaceans disappeared 

 from a place the large pollock disappeared also." 

 And pollock, breaking the surface in pursuit of 

 shrimp are familiar sights there, as we can bear 

 witness with many others. 



Similarly, Welsh found large pollock in schools 

 feeding on the surface dn shrimp (Thysanoessa 

 raschii) off the Isles of Shoals and off Boon Island 

 in April 1913, remarking in his field notes for the 

 25th that "in the last few days pollock have begun 

 to appear in small schools of 400 to 500 fish with 

 the appearance of large schools of feed (shrimp, 

 'all eyes'), the feed (shrimp) breaking water trying 

 to get away from the pollock which are after them." 

 He described the fish themselves as "rising and 

 sinking at intervals; when at the surface swimming 

 like porpoises, leaping up and over with open 

 mouths, the feed being in dense streaks 6 inches 

 to 1 foot down." These feeding fish were "very 

 sluggish and tame on this feed and easily taken in 

 the purse seines." All were "stuffed to capacity" 

 with shrimps, and only a few contained herring. 



Large pollock take morsels as small as copepods. 

 Willey * for example, speaks of a fish caught near 

 Campobello Island which contained proportion- 

 ately as many of these as of euphausiid shrimps, 

 and it is probable that the little pollock depend 

 chiefly on copepods. Glass worms (Sagitta), too, 



• Smltt, Scandinavian Fishes, vol. 1, 1892, p. 503. 

 « Eept. U. S. Comm. Fish., (1896) 1898, p. 180. 



• Proc. Amer. Acad. Arts, Sci., vol. 66, 1921, p. 192. 



have been found in pollock stomachs. Sometimes 

 they consume considerable quantities of cteno- 

 phores; we found many pollock full of them on 

 Cashes Ledge and on Platts Bank in August 1928; 

 one had 105 of these watery organisms in its 

 stomach. They also feed to a small extent on 

 bottom-dwelling crustaceans on both sides of the 

 Atlantic, thus crabs, and bottom-dwelling shrimp 

 have been found in fish caught at Woods Hole 

 and in the Gulf of Maine. They have also been 

 reported as gorging themselves on herring spawn. 

 They never take shelled mollusks, so far as we 

 are aware. But they bite on clams as greedily 

 as on fish baits. And fishermen speak of them 

 as one of the few species that will bite, that is, 

 feed, during the spawning period. 



Experiments on fish kept in captivity at Woods 

 Hole 6 have shown that the pollock captures its 

 food more by its keen sight than by scent. 



The pollock is a cool-water fish. We have never 

 seen any large ones caught at the surface when 

 the temperature there was higher than about 52° 

 F., though there may be plenty of them a few 

 fathoms deeper down where the water was cooler. 

 Even the little "harbor pollock" of 8 inches or so 

 do not appear in any great numbers at times or 

 places where the water is warmer than perhaps 

 60° F. At the other extreme, pollock of all sizes 

 from the 1 year-old fish upward must experience 

 temperatures as low as 32° F. on the fishing 

 grounds in the southern side of the Gulf of St. 

 Lawrence, and on the more easterly of the Nova 

 Scotian banks during the late winter or early 

 spring, unless they descend then to considerably 

 greater depths, a possible shift of which we have 

 no direct evidence. But it is probable that the 

 pollock's need of water as warm as about 38° F. 

 for the incubation of its eggs (p. 216) and perhaps 

 of temperatures a little higher than that for the 

 maturation of its sex organs (p. 216) is the factor 

 that sets the northern boundary to the mainte- 

 nance of a permanent resident population (p. 218"). 



The pollock is a late autumn and early winter 

 spawner, and the shortness of the spawning 

 season (p. 220), with the fact that the vertical 

 temperature gradient covers a range no greater 

 than 3° to 5° F. down to 50 fathoms at that 

 season, makes it easy to establish the physical 

 conditions under which the eggs are produced 



« Herrick, Bull. V. 8. Comm. Fish., vol. 22, 1904, p. 268. 



