Temperature and photoperiod induced maturation of southern flounder




Henderson-Arzapalo, A.
Cloura, R.L.
Maciorowski, A.F.

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Texas Parks and Wildlife Department, Coastal Fisheries Branch


Southern flounder (Paralichthys lethostigma) were maintained either in a 9500-L or 2300-L recirculating tank system from October 1983-March 1986 and subjected to controlled photoperiod and temperature conditioning to induce spawning. The fish were first subjected to a 6-month regime to delay natural spawning until spring (1984) followed by 6-month and 4-month regimes to induce either early fall (1984) or late summer (1985) spawning. Regardless of the conditioning regime, female gonadal development and egg release occurred only during December-February when water temperature was 18C and photoperiod maintained at 9-h light: 15-h dark. Male spermatogenesis coincided with female ovarian development but they did not fertilize eggs. The number of eggs released ranged from 66 to 28,900. Injection of 125 g LHRHa/fish failed to induce male courtship and fertilization. Strip-spawning attempts were also unsuccessful because eggs could not be manually extruded despite the presence of hydrated ova within the ovaries.


18 pgs.


southern flounder, Paralichthys lethostigma, spawning, photoperiodicity, temperature effects, animal reproductive organs, sex ratio