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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Bay, Nova Scotia, and in Buzzards Bay on the 

 south coast of Massachusetts. But they appear 

 to be more plentiful in depths of 25 to 30 fathoms 

 or more; there are rocklings in the deep gully off 

 Halifax, and also in the deep trough of the Gulf 

 of St. Lawrence. 62 They have been taken on the 

 continental slope off southern New England to a 

 depth of 724 fathoms. 63 And there is no reason 

 to suppose that the adult fish ever rise far above 

 the bottom, unless by accident. 



The occasional appearance of adult rockling in 

 very shallow water in winter near Woods Hole 64 

 suggests that some may work inshore and into 

 shoal water in autumn, to work offshore again 

 and deeper in spring, for the summer. Beyond 

 this they seem to be year-round residents wherever 

 they are found. 



The name "rockling" is a misnomer for this fish 

 for it is found most often on soft bottom in the 

 Bay of Fundy, while those that we have trawled 

 in Massachusetts Bay and in Ipswich Bay from 

 the Grampus were on smooth muddy sand be- 

 tween the hard patches. And most of the rock- 

 ling living in the deep sinks and channels in the 

 western side of our Gulf, and on the continental 

 slope, are on soft smooth ground. 



Judging from the stomach contents of Scandi- 

 navian and British fish (their stomach contents 

 have not been examined on this side of the water 

 so far as we know) they feed chiefly on shrimps, 

 isopods, and other small crustaceans, less often 

 on fish fry. On the other hand, rockling have 

 been found in cod stomachs in Massachusetts 

 Bay, and no doubt all fish of prey devour them 

 on occasion. 



The eggs are buoyant, described (we have never 

 seen them) as 0.66 to 0.98 mm. in diameter. 

 When newly spawned the oil is in small droplets, 

 most of which soon coalesce into one globule of 

 0.14 to 0.25 mm., often with one or two smaller 

 ones close to it. The danger of confusing them 

 with squirrel-hake eggs is discussed in the account 

 of that fish (p. 226). And Battle has found that 



•' Huntsman (Trans. Roy. Soc. Canada, 3, vol. 12, Sect. 4, 1918, p. 63) 

 and further Information contributed by him. 



« Ooode and Bean, (Smithsonian Contrlb. Knowl., vol. 30, 1895, pp. 

 384-385) give a long list of locality records for the rockling on the shelf and slope 

 between the offings of eastern Nova Scotia and of North Carolina flat. 35°40' 

 N.). 



- Sumner, Osburn, and Cole, Bull. U. S. Bur. Fish., vol. 31, Pt. 2, 1913, 

 p. 771. 



they develop normally at temperatures ranging 

 from 55° to 66°. 66 



Newly hatched larvae are a little more than 2 

 mm. long. The yolk is absorbed at about 3.6 

 mm. and the later larval stages, up to about 10 

 mm. long, are characterized by the very large 

 black ventral fins shown in the illustrations (fig. 

 114); by the presence of only one post anal band 

 of black pigment; and by the short stocky body- 

 form. Young hake are more slender and have 

 scattered pigment; young cusk have two post anal 

 bands; and all other Gulf of Maine gadoids have 

 short ventral fins. After the rockling is 17 to 20 

 mm. long the structure of the first dorsal fin 

 serves to identify it. 



These larger fry are silvery, awaiting their 

 descent to bottom before assuming the dull colors 

 of the adult. In British waters they are some- 

 times called "mackerel midges" because they sug- 

 gest little mackerel remotely, in their general 

 appearance. In European waters, where there 

 are more plentiful populations of the silvery fry of 

 one or the other species of rockling they are often 

 cast ashore. And one such instance is described 

 for our Gulf by Storer 66 who writes that many 

 were picked up on Nahant Beach during one tide 

 in the summer of 1860; and others found in the 

 surf at West Beach, Beverly. 67 



Rockling fry, like those of other gadoids, drift 

 at the surface for their first few months. How 

 long they do so in our waters is not known, but 

 analogy with cod, haddock, and other species 

 suggests three months at most. And it may be 

 assumed they seek the bottom at a length of 

 about 2 inches for our largest pelagic fiy were 40 

 to 45 mm. long. During this pelagic stage they 

 drift with the current like any other fish fry, and 

 are at the mercy of mackerel and other fish. But 

 they are not plentiful enough in the Gulf of Maine 

 to be as important an article in the diet of the 

 mackerel as the fry of the far commoner European 



« Battle (Contrlb. Canadian Biol., N. Ser., vol. 5, No. 6, 1930) has made a 

 careful study of the effects of extreme temperatures and salinities on the 

 development of the eggs of the rockling. 



•■ Fishes of Massachusetts, 1867, p. 279. 



97 These fry, and one recorded at Nahant earlier by Gill (Proc. Acad. Nat. 

 Sci., Philadelphia, (1863)1864, p. 241) were reported as an Arctic 3-bearded 

 species (Qaidropaarus aTgentatut Reinhardt) which was described originally 

 from Greenland and which has been found widely distributed In Denmark 

 Strait; on the north coast of Iceland; and in the Norwegian Sea from the 

 Faroes north to Bear Island. But there is no reason to suppose that the 

 Nahant specimens were anything other than the fry of our common four 

 bearded rockling. For a recent account and discussion of the species argen- 

 lotut, with excellent illustrations, see Jensen, Spolia Zool. Mus. Hauniensis, 

 Copenhagen, vol. 9, 1948. pp. 167-173, pi. 4, fig. 4. 



