Abstract

Collapses of marine fish populations are a global concern. Some collapses are attributed to hyperstability, where catch per unit effort remains stable while the population declines. Hyperstability is difficult to detect until after a population is depleted, thus nearly all such studies on the hyperstability phenomenon are retrospective. Using whole-island acoustic arrays to track an endangered, aggregating reef fish on two Caribbean islands, we demonstrate for the first time behavioral mechanisms that might lead to hyperstability. We show that: i) Every reproductive-aged fish aggregates each year, ii) Older, more fecund fish aggregate longer, iii) Individuals will visit multiple aggregation sites during the spawning period, yet every fish always aggregates and spawns at a single location, and iv) Overfishing extends the time spent aggregating, increasing vulnerability to harvest as the population declines.

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