Maturation and spawning of marine finfish
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Fish utilized for spawning experiments were taken near Port Aransas, Tex., from estuarine and gulf populations of each species. Red drum, Sciaenops ocellata, were taken by hook-and-line and beach seine. Spotted seatrout, Cynoscion nebulosus, and red snapper, Lutjanus campechanus, were collected by hook-and-line. Southern flounder, Paralichthys lethostigma, were taken by hook-and-line and trammel net. Red drum and southern flounder were taken during their fall spawning period and spotted seatrout in the early spring season. Immature red snappers taken in early fall were placed in the spawning tank. The snapper tank was covered with nylon netting to prevent fish from jumping out of the tank. Red drum (750 mm TL), spotted trout (356 mm TL), and southern flounder (males 254 mm TL, females 305 mm TL) were kept as brood fish. Fish were transferred to the laboratory in fiber glass tanks (300-1,900 1) and placed into 1,000-30,000 l fiber glass spawning tanks. Fish were handled carefully to avoid surface abrasions which could result in infections. External parasites were removed with a 25-50 ppm bath of malachite green and Formalin. After this treatment the fish were placed in spawning tanks. Details of the seawater holding facilities are described by Arnold et al. (1976). Photoperiod and temperature data were gathered from U.S. Coast Guard and U.S. Weather Service records for Port Aransas, Tex. By comparing larval collections or adult spawning records of redfish (Simons and Breuer 1962), southern flounder (Stokes 1975), spotted trout (Miles 1950), and red snapper (Mosely 1966), the photoperiods and temperatures for the natural spawning seasons were determined. The laboratory photoperiod and temperature regimes for induced spawning of these four species were based on these meteorological and hydrological records.