Influence of seasonal changes in relative liver size, condition, relative gonad size and variability in ovarian development in multiple spawning fish species used in environmental monitoring programmes

Basic biological information was collected to assist in understanding the biology of selected small‐bodied fishes for use in environmental monitoring programmes. Gonado‐somatic index (IG) and hepato‐somatic index (IH) profiles of female blacknose dace Rhinichthys atratulus, mummichog Fundulus heteroclitus and golden shiner Notemigonus crysoleucas were similar, decreasing gradually during the spawning season. IG and IH profiles of female northern redbelly dace Phoxinus eos peaked twice suggesting oocyte recruitment was continuous throughout the spawning season. Regressions of ovary mass to adjusted body mass (MA) were more variable in dace relative to the other fish species. For female blacknose dace, variability in the relationship between ovary mass and MA was minimized by selecting either 2 year‐old fish and fish that weighed 2–4 g.