Population Characteristics, Food Habits and Spawning Activity of Spotted Seatrout, Cynoscion nebulosus, in Everglades National Park, Florida
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Material Information

Title:
Population Characteristics, Food Habits and Spawning Activity of Spotted Seatrout, Cynoscion nebulosus, in Everglades National Park, Florida Report T-668
Creator:
South Florida Natural Resources Center/South Florida Research Center, Everglades National Park
Edward Rutherford
Edith Thue
David Buker
Place of Publication:
Homestead
Florida
Publisher:
National Park Service, U.S. Department of the Interior
Publication Date:

Notes

Abstract:
Age, growth, mortality, stomach content and spawning activity of 570 spotted seatrout taken from sportfishermen catches in Everglades National Park were studied from November 1978 to January 1980. Fish ranged in length from 220-680 mm and in weight from 0.10-2.24 kg. Ages of fish, determined from scale readings, were mainly 3, 4 and 5 year olds. Fish were fully recruited by age 4. Males lived to at least age 6; females to at least age 7. The sex ratio favored females (1.6711). Fish lengths at age were back calculated from scale annuli. Fish length varied between sexes and among areas of capture and year classes. Males were larger than females at age 1, but smaller at ages 3-6. Calculated fish length and length at capture were greatest in seasonally brackish areas, and smallest in a hypersaline area of the park. Calculated lengths of year classes were significantly smaller in 1978 than in 1974-77. Annual mortality of all fish was 0.77. Annual mortality, exploitation ratio and conditional fishing mortality (0.75) were higher for males than for females. Spotted seatrout in Everglades National Park were carnivorous, eating shrimp and fish. Their diet changed with size; small adults ate proportionately more shrimp than fish while large adults ate more fish than shrimp. Spotted seatrout spawned nearly year round in Everglades National Park with peaks in spring and late summer. Most ripe fish were collected in seasonally brackish areas of the Park. Age 2, 3 and 4 fish contributed most to the spawn. Size at first maturity was 230 mm for males and 237 mm for females. Comparison of the results of this study with an earlier study of park spotted seatrout (Stewart, 1961) showed apparent changes in age distribution, age at full recruitment and mortality since 1959, although mean sizes at age of fish have not changed. Dominant ages shifted from 2 and 3 year olds, to 3 and 4 year old fish. Age at full recruitment shifted from age 3 to age 4. Annual mortality of males decreased slightly since 1959, while annual mortality of females increased slightly. Exploitation ratios of both males and females remained constant. Ratios of conditional fishing to conditional natural mortality increased slightly for males and females. ( English )
Issuing Body:
SuDoc number: I 29.95:T-668

Record Information

Source Institution:
Florida International University
Holding Location:
South Florida Natural Resource Center
Rights Management:
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