Spawning aggregations in reef fishes: Control that is tight in time but sloppy in space

Background/Question/Methods

Spawning aggregations are a common phenomenon among many commercially-important reef fish populations.  For some species, these aggregations are highly predictable in space and time, suggesting that spawning aggregations may be optimizing fitness by spawning at these particular times and locations.  Here, we define the spatiotemporal objective function for the lane snapper (Lutjanus synagris) spawning aggregation located off Punta Hicacos-Cayo Mono, Cuba.  We test whether larvae released at the observed aggregation site and observed time are more likely to survive than larvae released at adjacent spatial and temporal locations.  We track virtual larvae from release to settlement, incorporating changes in larval behavior through ontogeny, using a multi-scale biophysical model, the Connectivity Modeling System.  

Results/Conclusions

Larval success was sensitive to the timing of spawning: propagules released during the observed spawning period had a lower probability of recruitment failure than those released outside the observed spawning period.  Larval success rates were comparatively insensitive to the location of the release site along the adjacent shoreline up to 20 km from the aggregation site along the same isobath.  We pose a simple optimization model to interpret the length and timing of the spawning period as a life history tradeoff between the mean and variance of larval success.