SMIGIELSKI: OVULATION OF WINTER FLOUNDER 



16 fish. The three differing dosage levels of each 

 test hormone were injected into groups consisting 

 of four fish per group, and the remaining four fish 

 in each tank served as uninjected controls. At the 

 termination of the trial, test fish were sacrificed, 

 ovaries examined, and gonosomatic index (GSI) 

 levels recorded. 



A final series of experiments was initiated to 

 evaluate the effectiveness of carp pituitary 

 (freeze-dried powder) at the dosage levels of 5.0 

 mg and 0.5 mg/454 g fish injected daily. Two 

 groups of test fish with each group consisting of 

 three trial fish and three uninjected controls were 

 established and held in two 1,890-liter tanks. Dur- 

 ing the trials, water temperatures ranged 

 between 1.5° and 3.5°C with a mean at 2.5°C. 



RESULTS AND DISCUSSION 



In the group of test fish that received HCG in- 

 jections at 300 lU daily, one fish hydrated after a 

 single injection (Table 1). Hydration, an increase 

 in total body weight due to water uptake by the 

 ovaries resulting in higher GSI levels, was rapid, 

 and the following morning this fish was grossly 

 bloated. Externally, hydrated fish may become 

 slightly swollen or grossly bloated. The majority of 

 the eggs stripped were opaque and misshapen, and 

 approximately 5% of the total egg mass in the 

 ovaries were viable. These eggs, numbering 

 approximately 10,000, were fertilized but 

 embryonic development ceased in the blastula 

 stage and none survived to hatch. This rapid 

 hydration may have been responsible for the poor 

 quality of the eggs. A long development period for 

 oocytes with a minimum of 2 or 3 yr from the time 



Table l.-Effects of human chorionic gonadotropin (HCG) on 

 Pseudopleuronectes americanus, temperature range 5°-7°C (J 

 6.2°C). Photoperiod 9L/15D. 



oocytes become histologically recognizable until 

 they are spawned has been suggested for winter 

 flounder by Dunn and Tyler (1969). Our observa- 

 tions in the past have noted that the natural 

 hydration and ovulation process of winter flounder 

 can occupy a lengthy period of time (unpubl. data). 

 The remaining fish in this test group were refrac- 

 tory after receiving a total of 12 injections. 



The group of five test fish that received injec- 

 tions of 300 lU every other day (for a total of seven 

 injections in 13 days) contained three fish which 

 were refractory at the conclusion of the trial; one 

 fish displayed signs of slight hydration, but did not 

 ovulate. The remaining fish in the group ovulated 

 and was spawned 10 days after the last injection. 

 Approximately 95% of the eggs were fertilized but 

 development ceased at the blastula stage and none 

 survived to hatch. 



The group of test fish which received daily in- 

 jections of 150 lU for 12 days contained three fish 

 which were refractory and two which hydrated 

 slightly but did not ovulate. Of the six fish that 

 served as uninjected controls, five displayed no 

 signs of hydration, and the remaining fish 

 hydrated slightly but did not ovulate. 



At the termination of the trials, the fish were 

 not sacrificed. The only criterion for evaluating 

 the success of the hormone was obtaining viable 

 eggs. It was reasoned that the relatively warm- 

 water temperatures (5°-7°C) coupled with sus- 

 pected low GSI levels inhibited the effectiveness 

 of the hormones. Observations made in the inner 

 parts of the Gulf of Maine, (Bigelow and Schroeder 

 1953) have shown that extensive spawning of 

 winter flounder does not occur in water tempera- 

 tures above 6°C. 



At the conclusion of the second series of 

 experiments, four fish hydrated and ovulated after 

 receiving from two to nine injections (Table 2). 

 Fertilization was high for all fish but embryonic 

 mortalities were high in the blastula and gastrula 

 stages, and hatches were poor, ranging from 2 to 

 20%. Larvae obtained from these spawnings ap- 

 peared to be normal in all respects and several 

 were reared through metamorphosis. Three addi- 

 tional test fish became grossly bloated after 

 receiving a total of 10 injections in 10 days and 

 hydrated to the point of dying. Membranous plugs 

 formed in their oviducts and the eggs were water 

 hardened. The formation of these plugs is not un- 

 derstood as prior to receiving their last injection 

 they were hydrating at a normal rate. Shehadeh 

 and Ellis (1970) reported plugs forming in striped 



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