A temperature-dependent reproductive model for spotted seatrout (Cynoscion nebulosus) explaining spatio-temporal variations in reproduction and young-of-the-year recruitment in Florida estuaries

Abstract

Abstract Spotted seatrout (Cynoscion nebulosus) exhibit various seasonal patterns of reproduction and juvenile recruitment in estuaries across their range. To explain this variability, data on the reproductive state of 1674 individual females from the Indian River Lagoon were used to develop a generalized additive model (GAM) describing the relationship between reproduction and local environmental conditions. The model predicted that optimum spawning conditions exist at a water temperature of 29°C, indicating that if this temperature was exceeded during the spawning season, spawning activity would be temporarily curtailed, which would lead to a bimodal recruitment curve. In contrast, daily mean water temperatures below the optimum condition would result in a single recruitment peak. The reproductive model was largely consistent with historical information on spotted seatrout spawning seasonality along the gulf and Atlantic coasts of the US. Factors other than temperature (i.e., hours after sunset, lunar period and size and condition factor of females) were also found to regulate reproductive activity. Model predictions of the number of recruits based on local temperature regimes during the spawning season were compared to actual catches of juvenile spotted seatrout in three Florida estuaries. The reproductive model was able to predict the timing and modality of recruitment, but the relative amplitude of the fluctuations in abundance was dampened considerably compared to the observed variation.