Menhaden occupy an important position in estuarine food webs, thus the rate processes associated with their feeding are critical to the ecosystem management of fishery and ecological resources. Atlantic menhaden feed on a wide range of plankton, the size and food quality of which change ontogenetically. We analyzed the functional morphology of the menhaden feeding apparatus in a size series of menhaden representative of juveniles and the adult migratory stock. The physical dimensions of gill arches and rakers increased isometrically with fish length; however, branchiospinule spacing, the dimension that forms the sieve apertures of the branchial basket, scaled allometrically with fish length. Juvenile menhaden from North Carolina have branchiospinule spacings that averaged 12 microm, with three arch subsections of average spacing < 10 microm. Spacings did not increase with juvenile growth until the first allometric inflection point at approximately 100 mm fork length (FL). Spacing data for juveniles from other locations suggests spacing increases with latitude. Spacings increase with fish length in adults until a second inflection at 200 mm FL, after which spacing averages 37 microm. These data suggest menhaden juveniles filter smaller plankton with higher filtration efficiency than previously considered and that regional recruitment may affect adult distribution through foraging preferences.
Southern kingfish Menticirrhus americanus were caught from Cape Fear, North Carolina, to Cape Canaveral, Florida, during seasonal stratified random trawl surveys. Maximum frequency of occurrence and abundance occurred in this area during summer and fall surveys. Analysis of marginal increments on scales showed annulus formation occurred from winter through early spring. Back-calculated mean total lengths at age produced yon Bertalanffy growth equations of Lt = 292(1 -exp[-0.6369(t -0.0045)]} for males and L t = 477(1 -exp[-0.2742(t + 0.2813)]} for females, where L t = total length (ram) at age t (years). Spawning takes place from April through August in the South Atlantic Bight, most intensively from April through early June. Southern kingfish mature at age 1. In South Carolina, 96% of the kingfish landed as by-catch from the penaeid shrimp fishery were southern kingfish, which averaged 23 cm total length (range, 18-36 cm); 81% of these were age 1 and 79% were females. Research catches indicated annual mortality rates of 67-79%, whereas commercial catches implied a rate of about 87%; the higher rate is related to culling operations at sea.
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