Aspects of the growth and life history of the sheepshead minnow, {\it Cyprinodon variegatus}, from Rhode Island and Florida

Walter John Berry, University of Rhode Island

Abstract

The sheepshead minnow, Cyprinodon variegatus, is found from Cape Cod to Mexico. Several subspecies of sheepshead have been described, but little is known about the comparative growth and reproduction of the subspecies.^ The offspring of sheepshead minnows from two populations were reared in the laboratory for six weeks at five temperatures: 15, 20, 25, 30, and 35C. One population (C.v.variegatus) was from the Gulf coast of Florida, and the other (C.v.ovinus) was from Rhode Island. The Rhode Isalnd fish grew at a significantly greater rate (p $<$ 0.05) at 15C than the Florida fish, but growth rates were not significantly different at the other temperatures.^ Individuals from the two populations were crossed in the laboratory and their offspring reared through two generations (F1 and F2). The fish from the two populations interbred freely, and the offspring of the reciprocal crosses were as viable and fertile as those of the self-crosses. Embryos with maternal parents or grandparents from Florida hatched significantly faster than those with maternal parents or grandparents from Rhode Island. There was no significant difference between the mean lengths at hatch or the mean growth rate at 25C of the F2 fish from the four crosses.^ In Rhode Island sheepshead minnows were found in the marshes from May to November, and spawn from May to September. Sheepshead minnow were found in marshes in Florida in all months of the year and apparently spawn there year-round. The growth of juvenile sheepshead at both sites was estimated using the daily growth ring technique. Growth of the RI juvenile fish was not significantly different from that of the Florida juveniles.^ The results of these studies indicated that the sheepshead minnow has conquered its wide latitudinal range through flexibility rather than local adaptation. Its seasonal cycles of activity and spawning are altered to fit the seasonal cycle of its environment. Rate of growth, both in the laboratory and in the field, seems surprisingly consistent from population to population, and by implication, from subspecies to subspecies. ^

Subject Area

Biology, Zoology|Agriculture, Fisheries and Aquaculture

Recommended Citation

Walter John Berry, "Aspects of the growth and life history of the sheepshead minnow, {\it Cyprinodon variegatus}, from Rhode Island and Florida" (1987). Dissertations and Master's Theses (Campus Access). Paper AAI8811550.
http://digitalcommons.uri.edu/dissertations/AAI8811550

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