'Illusion of plenty' masking collapse of 2 key Southern California fisheries

[Croaker Dave]

Scripps-led study finds overfishing of spawning areas, environmental conditions behind collapse of 2 bass species

		IMAGE:Kelp bass represent one of the two most important recreational fisheries off Southern California. Click here for more information.

The two most important recreational fisheries off Southern California have collapsed, according to a new study led by a researcher from Scripps Institution of Oceanography at UC San Diego.
Scripps postdoctoral researcher Brad Erisman and his colleagues examined the health of regional populations of barred sand bass and kelp bass-staple catches of Southern California's recreational fishing fleet-by combining information from fishing records and other data on regional fish populations. Stocks of both species have collapsed due to a combination of overfishing of their breeding areas and changes in oceanographic conditions, the researchers found.
As they describe in the most recent edition of the Canadian Journal of Fisheries and Aquatic Sciences, the researchers say the total amount, or biomass, of each bass species decreased 90 percent since 1980. Yet fisheries catch rates have remained stable for a number of years, even as overall population sizes dropped drastically. This is due, the authors say, to a phenomenon known as "hyperstability" in which fishing targets spawning areas at which large numbers of fish congregate, leading to a misleading high catch rate and masking a decline in the overall population.
"The problem is when fish are aggregating in these huge masses, fishermen can still catch a lot each trip, so everything looks fine-but in reality the true population is declining," said Erisman, a member of the Scripps Center for Marine Biodiversity and Conservation. "So as the true abundance is declining, the fisheries data used to assess the health of the fisheries are not showing that and give no indication of a collapse-this is referred to as 'the illusion of plenty.'"
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.

		IMAGE:This is Larry Allen, a coauthor of the study, with a barred sand bass. Click here for more information.

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."

http://www.eurekalert.org/pub_releas...--op092611.php

[Croaker Dave]

I have no comment on the quality of this bass study.

It's interesting that they mention the atlantic cod fishery. IIRC, it was the continual advancing of commercial fishing technology that enabled the fishery to maintain good fish counts even as they decimated the cod population to almost nothing.

[mazilla]

Sounds like junk science tailored to fit their agenda...the world is full of these types of "studies".

[Ed]

Originally Posted by mazilla

Sounds like junk science tailored to fit their agenda...the world is full of these types of "studies".

All they did was compare historical catch rates since 1980. It is more history than science. Pretty good study by Scripps.

[blitzburgh]

I work for a company that supplies product to THE major home improvement chain in the U.S.. We conduct and/or pay for, study, after study after survey, after survey for various sales purposes. The results we receive from any one of these are always mixed at best. I find it hard to believe they can come to such a assertive conclusion with the massive amount of variables that would come into play in something like this.

[Phatford]

I doubt Scripps would risk their reputation on shaky science... The mention Environment in the beginning article. You can't get a good feel for what all they measured in a few short paragraphs and certainly can't fit 30 years of data on one page.

There is no doubt changes need to be made in my mind, but what kind of fair changes can we help make? Calling every study bad science is not going to help our cause. Pretending we are catching the same quality of fish we used to catch is also bad science or poor memory... ha ha

But it's a damn good thing we have people out there saving the seals... oh wait!