PROGRESS IN BIOLOGICAL INQUIRIES, 19 3 2 97 



the bay from the deeper channels which form the wintering grounds 

 of the species. No recoveries have been reported since the spring 

 season. 



Observations in ni)per Chesapeake Bay showed that the striped 

 bass spawn in the Susciuehanna Kiver, above Havre de Grace, during 

 the latter part of May. The large and rather delicate eggs of the 

 species were taken in abundance by townets in the Susquelianna and 

 supplied the first, evidence on record concerning a natural spawning 

 area of the striped bass. 



EXPERIMENTAL REARING OF MARINE FISH LARVAE 



The cause of fluctuation in commercial fisheries has been traced to 

 a corresponding fluctuation in the survival of the young of the various 

 species. To determine the physical and chemical factors efl'ecting 

 their survival, Louella E. Cable continued experiments on rearing 

 marine fish larvae at the Woods Hole station during the summer of 

 1932. 



It was shown that the most critical period of development comes 

 a few days after hatching, when the yolk sac is nearly or wholly 

 absorbed and the young fish are ready to take food. Very few lar- 

 vae feed in the laboratory in standing water, and those that do seldom 

 survive the critical period. Apparently stimulus is needed to nuike 

 them sufficiently alert to catch food and keep them active after feed- 

 ing and to create the need and desire for more food for after feeding 

 they sink to the bottom making little eft'ort to swim about. The 

 current rotor devised by Dr. P. S. GaltsofT and Miss Cable while 

 allowing for a constant change of water without danger of loss or 

 injury to the larvae, provides a gentle current which buoys up the 

 larvae, stimulates them to action, and keeps the food suspended. 

 Such gentle currents were found to be a definite aid to the fish larvae 

 in catching their food. 



The larvae of those species studied, mackerel, sand dab, Prionot us, 

 Paralichthys oblongus, tautog, cunner, and Urophycis, respond in like 

 manner to similar conditions. All develop more rapidly at high than 

 at low temperatures; all are injured by contact with rough surfaces 

 and are very sensitive to water pollution, and all die within a few 

 hours after absorption of the yolk sac unless they begin to feed at 

 that time. In the labaratory the early post larvae of these species 

 will feed on copepods and nuike rapid growth. Under sanitary con- 

 ditions mortahty before the critical period is almost negligible, being 

 less than 10 percent in many cases. 



Mackerel larvae, at least, are able to adapt themselves to salinities 

 varying from 20 to 32 per mille. The limits of adaptabihty may be 

 found to be even more widely separated. 



SOUTH ATLANTIC AND GULF FISHERY INVESTIGATIONS 



INVESTIGATIONS OF THE SPAWNING HABITS, EMBRYOLOGY, LARVAL 

 DEVELOPMENT, AND RATE OF GROWTH OF FISHES 



Studies pertaining to the spawning habits, the embryology, larval 

 development, and rate of growth of fishes of the South Atlantic States 

 were continued by Dr. Samuel F. Hildebrand, assisted during most 

 of the year by Louella E. Cable and the rest of the year by Nell Henry. 

 Besides the collection of additional material and data, and preliminaiy 



