Age and growth of the bighead carp Hypophthalmichthys nobilis (RICHARDSON 1845) in the middle Mississippi River

Abstract

An age and growth study was conducted on the bighead carp Hypophthalmichthys nobilis population from the middle Mississippi River (MMR) using pectoral fin ray cross-sections. Bighead carp (N = 92) were collected from the MMR and from Pool 26 (N = 40) during 1998 and spring of 1999 using trammel and gill nets, AC electrofishing, and seining. Length-frequency distributions were dominated by the 800-900 mm length class in both the MMR and Pool 26. Age classes 1-6 were represented in the MMR sample, and only ages 4-6 in the Pool 26 sample. Age 4 (1994 year class) was dominant in 1998 in the MMR. The mean condition factor (K) was 1.03 for all bighead carp collected, and ranged from 0.58 to 2.04. Condition factor was significantly higher for Pool 26 than for the MMR (ANOVA; p ≤0.0001), but not significantly different between sexes (ANOVA; p = 0.60). Condition factor peaked in May and decreased sharply during June and July of 1998. An unconstrained von Bertalanffy growth equation was obtained. Growth was fast in both the MMR and Pool 26, but no significant differences in relative or absolute growth were found between the two populations. Bighead carp is much more abundant in the MMR than reported in the literature or commercial fisheries harvest reports. Recruitment of bighead carp from the MMR was not consistent, but fast growth (reaching 1 kg by age 2), and high abundance suggest that a commercial fishery for bighead carp could be sustained in the MMR.