454 



BULLETIN OF THE BUREAU OF FISHERIES 



about the same size with several oil globules (p. 461). The yolk of the North Sea rock- 

 ling is colorless, which fact, if it were the universal rule, would be a sufficient distinc- 

 tion between the two species; but it is sometimes pigmented in rockling eggs in the 

 Baltic, 21 and since rockling eggs have not yet been carried through to hatching in 

 the Gulf of Maine it remains to be seen whether the presence or absence of pigment 

 on the yolk can be depended on to separate its egg from that of the hake. There 

 is also a danger of confounding newly spawned eggs of the squirrel hake with those of 

 the butterfish (p. 24S), which are about the same diameter, but as a rule the number 

 and size of the oil globules is diagnostic. 



The larval stages of the squirrel hake still remain unknown, nor have its pelagic 

 fry been described under their own name; but fry figured by Alexander Agassiz 

 (1882, PI. VII, fig. 6; PI. VIII, figs. 1-3) as " Motella argentata" 22 were undoubtedly 

 one or the other of our hakes, for they showed the long ventrals, the two dorsal fins, 



Fig. 224. — Egg of the squirrel hake C Urophycis chuss), after 1 

 hour's incubation 



Fig. 225. — Egg of the squirrel hake ( Urophycis ckvss), after 74 

 hours' incubation 



and the single barbel of the latter and agreed perfectly with the hake fry we ourselves 

 have taken. The young of these little hakes, which are greenish blue on the back 

 with silvery sides, are separable from rockling by their more elongate form and by the 

 arrangement of the pigment, which is not in a band but scattered (this requires veri- 

 fication on larger series of specimens) . Older stages are identified by the presence 

 of two well-developed dorsal fins, and the silvery sides mark them at a glance from 

 the dull-colored fry of the cusk (p. 466) . 



Commercial importance. — Though sof t-meated, both the common hakes — " squir- 

 rel" and "white" — are excellent table fish and are readily absorbed by the market. 

 The greater parts of the catch is made on line trawls. 



21 Agassiz and Whitman (1885, p. 24), provisionally identified as "rockling" certain eggs with pigmented yolk taken in the 

 tow net at Newport, but they may have been hake. 



22 The single post-anal pigment band, short stocky form, and fanlike ventrals of the younger larval stages (PI. VII, figs. 1-4) 

 which he pictured under this name suggest identity with the four-bearded rockling. 



