Temperature and food‐level effects on reproductive investment and egg mass in vendace, Coregonus albula

Individual variation in reproductive investment is important for recruitment and population dynamics in fish populations. Thus, it is crucial to understand how these decisions are influenced by environmental con- ditions. Here, the influence of growth variation during gonadogenesis or early life on reproductive investment in vendace, Coregonus albula (L.) was investigated. A set of cohorts of mature females were sampled over two different years with contrasting climate conditions and food levels, using total length at age 1 year as a proxy for juvenile growth. Relative reproductive investment and individual egg mass were lower in the favourable year (elevated temperatures and zooplankton densities) when the females were in better condition compared with a less favourable year (lower temperatures and zooplankton densities). Female vendace demonstrated plasticity in their allocation to relative reproductive investment and egg mass, probably induced by diverging environmental conditions. This phenotypic response to growth may have strong effects on recruitment and population growth rate.