Are aggregation-fisheries sustainable? Reef fish fisheries as a case study

Reef fish spawning aggregations are attractive and often lucrative to fish but particularly vulnerable to fishing, with many cases of declines or extirpations. While awareness of the risks of aggregation exploitation has grown substantially in the tropical western Atlantic in the last decade, the phenomenon of aggregation-spawning is little known in the vast Indo-Pacific region where few aggregations are managed or monitored, and are rarely considered in marine-protected area designations. Even in the tropical western Atlantic and Caribbean, marine-protected area planning, until recently, did not typically consider spawning aggregations. Available data and analyses of aggregation-fisheries and aggregating species strongly suggest that: (1) the majority of known aggregations that are exploited are yielding declining landings; (2) aggregating species show greatest overall declines in local fisheries when their aggregations are also exploited; (3) from an economic perspective, aggregation fishing may yield lower prices for fish, or aggregations may be more valuable unexploited, as a source of fish for local fisheries or as tourist attractions; (4) hyperstability can mask declines in aggregation-fisheries, based on fishery-dependent data; (5) monitoring of aggregation catches by either fishery-dependent or fishery-independent means is deceptively challenging. There are also possible ecosystem-level consequences of reducing or eliminating spawning aggregations. We conclude that aggregation-fisheries are likely to be sustainable only for limited subsistence-level use, that the precautionary principle should be more widely applied in aggregation-fisheries and that, despite growing interest in aggregations over the last decade, few of the key biological questions necessary for effective management have been, or are being, addressed.