HORMONAL-INDUCED OVULATION OF THE WINTER FLOUNDER, 

 PSEUDOPLEURONECTES AMERICANUS 



Alphonse S. Smigielski' 



ABSTRACT 



The response of winter flounder, Pseudopleuronectes americanus, to human chorionic gonadotropin 

 (HCG), oxytocin, pregnant mare serum gonadotropin (PMSG), deoxycorticosterone (DOCA), and 

 freeze-dried carp pituitary is described. HCG and PMS were successful in some instances in producing 

 viable eggs and larvae while carp pituitary was successful in all instances. These were the first known 

 successful attempts to induce maturation and spawning of winter flounder artificially in the laboratory. 

 Larvae obtained from these hormonal-induced spawnings were normal in all respects and were 

 reared in the laboratory through metamorphosis. Wild plankton obtained from Narragansett Bay, 

 brine shrimp nauplii, and chopped clams were fed as food. The early life history of this flatfish can, for 

 the first time, be completed under controlled laboratory conditions. 



The winter flounder, Pseudopleuronectes 

 americanus (Walbaum), an important species in 

 local New England commercial and sport fishing 

 industries, occurs from Chesapeake Bay to the 

 northern shore of the Gulf of St. Lawrence 

 (Bigelow and Schroeder 1953). Winter flounder 

 spawn from January through April in Rhode 

 Island estuaries with a peak spawning period in 

 February. Demersal eggs are produced which 

 range from 0.74 to 0.85 mm in diameter. 



Investigations to evaluate methods of inducing 

 spawning of winter flounder with the aid of hor- 

 mones under controlled laboratory conditions 

 were undertaken at the National Marine Fisheries 

 Service, Northeast Fisheries Center, Narragan- 

 sett Laboratory in 1970 and continued over a 3-yr 

 period. The use of hormone injections for inducing 

 spawning in other species of fish has been well 

 documented by Pickford and Atz (1957). The in- 

 duction of spawning in winter flounder in the 

 laboratory provides a practical method of supply- 

 ing viable eggs and larvae for physiological 

 studies. By controlling water temperatures, pho- 

 toperiods, and injecting hormones, the research 

 time for this species can be extended. As far as is 

 known, these were the first reported successful 

 attempts to artificially mature and spawn the 

 winter flounder in the laboratory. 



'Northeast Fisheries Center, National Marine Fisheries Serv- 

 ice, NOAA, Narragansett, RI 02882. 



Manuscript accepted June 1974. 



FISHERY BULLETIN: VOL. 73, NO. 2, 1975. 



MATERIALS AND METHODS 



Adult winter flounder were captured by otter 

 trawling in Narragansett Bay in the autumn of 

 1970, 1971, and 1972, and were brought to the 

 Narragansett Laboratory in a 380-liter live car 

 equipped with an aerator. In the laboratory, the 

 fish were held in 1,890-liter circular aquaria (1.2 m 

 in diameter; water depth, 0.8 m). A continual sup- 

 ply of filtered seawater was pumped to the aquaria 

 from Narragansett Bay. 



After acclimating in the laboratory, the fish 

 were segregated by sex, measured and weighed, 

 and tagged with numbered plastic pennants 

 secured through the caudal peduncle with a double 

 barbed stainless steel wire. Winter flounder adults 

 may be sexed easily by placing the fish on its back 

 and running a hand down the white underside. 

 Females are quite smooth while the males are very 

 rough to the touch. Winter flounder lend them- 

 selves quite readily to handling and have proven to 

 be a durable flsh. No anesthesia was required prior 

 to injecting hormones as the fish rarely struggled. 



An artificial photoperiod of 9 h light and 15 h 

 darkness (9L:15D) simulating seasonal light con- 

 ditions was maintained for all experiments by 

 time clocks controlling four banks of 80-W cool 

 white fluorescent lights suspended 1.2 m above the 

 tanks. 



Since winter flounder fast during the spawning 

 season, as many other fish do, their food regimen 

 was not difficult to maintain. A varied diet of 

 clams, squid, chopped menhaden, and silversides 



431 



