A Scripps Institution of Oceanography-led study finds overfishing of spawning areas and environmental conditions are behind the collapse of two important recreational fisheries off Southern California.
We talked with Scripps postdoctoral researcher Brad Erisman to find out more about why the health of regional populations of barred sand bass and kelp bass have collapsed.
Brad Erisman is a member of the Scripps Center for Marine Biodiversity and Conservation.
Erisman says the cod fishery that collapsed in the North Atlantic Ocean is the world's most famous example of fisheries data masking an impending collapse, but other fish stocks in regions where fish congregate to spawn are declining as well.
In order to grasp a clear picture of the true health of the barred sand bass and kelp bass in Southern California, Erisman and his colleagues looked outside fisheries data. They tapped into fish population numbers tracked by power plant generating stations, which are required to log fish entrapments as part of their water cooling systems, and underwater visual censuses conducted by Occidental College since 1974.
The authors acknowledge that both bass species began declining in the early 1980s, a drop other studies have directly linked with a climatic shift in regional water temperatures. But they say fishing impacts exacerbated the declines.
"The combined evidence from this study indicates that persistent overfishing of seasonal spawning aggregations by recreational fisheries brought about the collapse of barred sand bass and kelp bass stocks in Southern California," the authors write in their paper.
"The relationship between catch rate and stock abundance suggests there is an urgent need to incorporate fisheries-independent monitoring to create something sustainable and monitor the fisheries effectively," said Erisman. "While fisheries monitoring remains a key part of management, it is clear that such data alone do not provide an accurate assessment of stock condition."
Larry Allen of California State University Northridge; Jeremy Claisse and Daniel Pondella II of Occidental College; Eric Miller of MBC Applied Environmental Sciences; and Jason Murray of the University of South Carolina coauthored the study.
