Egg production, fertility, and hatch success of American plaice held in captivity

The reproductive performance of individual female American plaice Hippoglos soides platessoides was monitored during a spawning season under laboratory conditions. The majority (74%) of females produced eggs at some point in a 2-month period (May-July) during which they were checked every 2 d for ovu lated eggs. Most females produced several batches of eggs during an average production period of 26 d. Approximately 12% of the total number of eggs p roduced by each female were obtained in the first egg batch. There were per iodic peaks of egg production for the group in increasing intervals at abou t 8, 20, and 34 d after the first eggs were collected. The mean relative fe cundity was 1.5 x 10(5) eggs/kg body weight, but there was no relationship between actual fecundity and either length or weight. The mean percentages of viable and fertile eggs were 44.7% and 13.7%, respectively. A significan t decline in the percentage of fertile eggs was observed with time, such th at percent of fertile eggs by the sixth batch was significantly (P < 0.05) lower than in the first batch. There was no significant decline in viable e ggs with time, although there was a positive correlation (r = 0.72, P < 0.0 01) between viability and fertility. The number of larvae hatched from viab le eggs varied widely during the spawning period with a mean hatch success rate of 23%; A significant positive correlation was observed between the nu mber of larvae hatched and the percentage of fertile eggs (r = 0.82, P < 0. 001).