Sea bottom geomorphology of multi-species spawning aggregation sites in Belize

Abstract

Large, commercially important coral reef fishes such as Nassau grouper Epinephelus striatus are known to spawn at specific places and times in a so-called transient fish spawning aggre- gation (FSA). Traditional E. striatus spawning sites also serve as multi-species FSA sites. Many sites have been extirpated by overfishing or have shown dramatic declines. The objectives of this paper are to: (1) characterize the sea bottom geomorphology of all known transient FSA sites in Belize; (2) provide an evaluation of the multi-species aspects of known FSA sites; and (3) evaluate a prediction of 2 potential FSA sites based on the relationship between seafloor characteristics and fish aggrega- tions. The reef structures surrounding FSA sites were defined in relation to their depth and proxim- ity to shelf edges, deep water, reef channels, and reef promontory tips. All (n = 14) transient FSAs occurred at convex-shaped reef structures jutting out over steep walls into deep water. All FSA sites were located <100 m from shelf edges and <200 m from reef promontory tips, and at a mean of 78 ± 62 m from 100 m depth. Geomorphologically distinctive features at known FSAs allowed us to iden- tify 2 new multi-species FSA sites exhibiting similar characteristics. All the primary FSA sites in Belize are reef promontories, but the reasons why fish aggregate at these sites remain unclear.