364 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 





liss^^^^' 



Figure 192. — Butterfish (Poronolus triacanthus) , New Jersey. From Goode. Drawing by H. L. Todd. 



of water. Though definite evidence is lacking, we 

 believe butterfish seldom descend deeper than 15 

 to 30 fathoms during the summer, and that most 

 of the fish caught by the otter trawlers on the 

 Nantucket grounds and on Georges Bank in sum- 

 mer are picked up by the trawl on its way up or 

 down, not while dragging on bottom. In fact, 

 mackerel fishermen often take a few butterfish on 

 Georges in their purse seines. But such evidence 

 as is at hand is to the effect that they spend the 

 winter and early spring near bottom, and in depths 

 down to 100-115 fathoms (p. 367). 



Food. — The butterfish feeds on small fish, squid, 

 Crustacea such as amphipods and shrimp, and 

 annelid worms. And ctenophores have been 

 found in butterfish stomachs at Woods Hole, 

 though these watery objects are not a regular item 

 in its diet. 



Breeding habits. — Butterfish begin spawning in 

 the Gulf of Maine in June, soon after their arrival. 

 The height of the reproductive season is in July 

 and their eggs have been taken throughout August. 

 Observations at Woods Hole suggest that butter- 

 fish spawn some few miles out at sea, returning to 

 the coastwise waters when they are spent. 10 We 

 have taken its eggs in our tow nets at several 

 stations in Massachusetts Bay, and it would not 

 be astonishing to find them anywhere off the New 

 England and western Nova Scotian coasts or on 

 the Scotian side of the Bay of Fundy, Huntsman 



having found large spawning individuals in St. 

 Mary Bay in July. But despite the considerable 

 number of butterfish eggs that are produced in the 

 Gulf of Maine, we doubt whether the latter is a 

 favorable nursery for this fish, for we have taken 

 its larvae only twice there (off Cape Cod on August 

 16 and on Georges Bank on July 23, 1916) a total 

 of only 3 specimens, 5 to 30 mm. long, although 

 we have made hundreds of hauls widely distributed 

 inshore as well as offshore at the season when they 

 might be expected. Neither have young butter- 

 fish been reported from the Bay of Fundy. But- 

 terfish fry are very plentiful, however, along the 

 shores of southern New England. 



The eggs are buoyant, transparent, spherical, 

 0.7 to 0.8 mm. in diameter, usually with a single 

 oil globule of about 0.17 to 0.2 mm. In newly 

 spawned eggs, however, there may be two globules, 

 which coalesce as development advances. 11 At a 

 temperature of 65° F. (about the summer state of 

 the surface of Massachusetts Bay) incubation 

 occupies less than 48 hours. And it is probable 

 that development can only proceed in compara- 

 tively warm water, though the lower temperature 

 limit to successful reproduction is not known. 

 The larvae are about 2 mm. long at hatching and 

 they are characterized shortly after by their short 

 deep form, by their 30 muscle-segments, and by 

 the row of black spots along the ventral edge in the 



» Kuntz and RadclifFe, Bull. V. S. Bur. Fish., vol. 35, 1918, p. 112. 



" A large series of butterfish eggs artificially fertilized at the Gloucester 

 hatchery have been available for comparison with the pelagic eggs taken in 

 the tow nets. 



