Globally declining fish populations are a frequently cited ecological and commercial calamity, but relatively little attention has been paid to the specific threats faced by fish that gather and spawn in large groups, says Yvonne Sadovy, writing in an article for BioScience. The marine scientist, affiliated with the University of Hong Kong and Science and Conservation of Fish Aggregations (SCRFA), outlines the challenges unique to these populations.
"Many aggregating species face growing threats to their populations from increasing harvest and lack of effective management," she says. Appearing in temporarily high abundances, the fish are particularly vulnerable to overexploitation as a result of both increased catchability and lethal and nonlethal biological factors. According to Sadovy, aggregations in small-scale fisheries in particular could be dangerously overfished by only a few active boats, but large-scale industrial fisheries are also susceptible.
The author also describes how changing economic conditions could contribute to rapid species declines. Many exploited fish populations were once safeguarded from collapses by costs of fishing that rose as fish numbers declined. Given the high catchability of aggregate spawners and consumers' growing ability to pay premium prices for desirable species, this safety valve is vanishing. Instead, fishing pressure could be ramped up, leading to a "downward spiral toward extinction." The Chinese bahaba is a clear example.