Site fidelity and reproductive timing at a spotted seatrout spawning aggregation site:individual versus population scale behavior

摘要

Variability in individual lifetime reproductive success is known to have important consequences for population dynamics, yet it is often poorly understood in marine fishes. We evaluated spotted seatrout Cynoscion nebulosus spawning site fidelity and reproductive timing at both the population and individual level at a resident spawning aggregation site. Because males make sounds associated with courtship, we were able to use aggregation sound as an indicator of population spawning activity, monitoring sound at this site with passive acoustics. To assess individuals, we acoustically tagged and released 32 (19 male, 13 female) fish and monitored the spatio-temporal patterns of their movements with a high-density receiver array. Both aggregation sound and detections of tagged fish indicated a truncated spawning season in 2005, apparently due to a persistent red tide event. Individuals exhibited strong intra-seasonal site fidelity, with 23 tagged fish returning to the site to spawn. Most of the fish spawning at this site were drawn from the estuary and returned to the estuary within a 24 h cycle. However, there was individual variability in this spatio-temporal behavior. Aggregation sound indicated daily spawning at this site, but not by the same individuals. Individual estimates of spawning indicated that males spawned more frequently than females (average spawning interval of 2.2 d compared to 9.3 d for females), and that individuals exhibited variability in the time period between spawning events. The probability of an individual spawning at this site was significantly affected by sex and lunar phase (spawning increased on dates near the full moon), but not by current speed or direction.