Swampfish (Chologaster cornuta) occur from southeastern Virginia to east-central Georgia and are often considered to be uncommon. We obtained swampfish from January–April 1976 and January 1977–January 1978 in an east-central North Carolina stream (tributary ditch to Black Swamp Creek, Jones Co.). Swampfish reached sexual maturity by the end of its first year and exhibited a spring (early March–middle April) spawning season. Ovaries were developing by late fall, increasing to a mean gonosomatic index of 7–11% before spawning. Females (n = 156, 20–48 mm SL) had an overall mean of 24.7 mature ova (range 6–98) prior to spawning. The positive relationship between fecundity (F) and standard length (SL) was described by the linear regression: F = 2.67(SL) - 25.71 (r = 0.67). Mean mature ova diameter increased from 1.09 mm in January to 1.48 mm in late March and April. Females were nearly always more numerous and larger than males. Of the 14 taxa eaten by swampfish (n = 289, 13–48 mm SL), amphipods were dominant, occurring in 60.3% of the specimens and representing 41.1% of the foods by number. Chironomids were the next most frequent and abundant food, followed by cladocerans. The preference for amphipods was maintained across all seasons and size groups. Two year classes of swampfish were apparent on every sampling date. We estimated a maximum age of 26 months. Length frequency data suggested very slow or no growth during the summer. Weight (W) and length were highly correlated, and the formula (both sexes combined) was: W = 0.23 × 10−4(SL)2.88, (r = 0.95). The appendage that develops on the snout of male swampfish was not noticeable in age 0 fish through about 16 mm SL. By late age 0 (23–25 mm SL) males could be sexed by locating the organ, and it was fully developed by early age 1 (25 mm). The anterior migration of the vent was most rapid between 10 and 17 mm SL, with little change in fish ≥ 19 mm. The low species richness in the diet, the low fecundity, and the generally greater than reported longevity of these fish could be related to life in the ephemeral ditch.
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1 March 2003
LIFE HISTORY OF THE SWAMPFISH FROM A NORTH CAROLINA STREAM
Steve W. Ross,
Fred C. Rohde
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