. Earth Science News .




.
WATER WORLD
Illusion of Plenty Masking Collapse of Two Key Southern California Fisheries
by Staff Writers
San Diego CA (SPX) Sep 30, 2011

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.

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.

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.

The research was supported by Scripps' Center for Marine Biodiversity and Conservation, the Walton Family Foundation and the David and Lucile Packard Foundation. The Vantuna Research Group (Claisse and Pondella) of Occidental College has been supported by Chevron.

Related Links
Scripps Institution of Oceanography at UC San Diego
Water News - Science, Technology and Politics




 

.
Get Our Free Newsletters Via Email
...
Buy Advertising Editorial Enquiries






. Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle



WATER WORLD
New analysis confirms sharks are in trouble
Brisbane, Australia (SPX) Sep 30, 2011
Sharks are in big trouble on the Great Barrier Reef and worldwide, according to an Australian-based team who have developed a world-first way to measure rates of decline in shark populations. "There is mounting evidence of widespread, substantial, and ongoing declines in the abundance of shark populations worldwide, coincident with marked rises in global shark catches in the last half-cent ... read more


WATER WORLD
Japan eases evacuation advisory for zones near nuclear plant

New report reveals the impact of global crises on international development

Plutonium detected outside Fukushima plant: government

Haiti still needs world's help: UN aid chief

WATER WORLD
China cracks down on fake iPhones: report

Apple chief Cook to debut hot new iPhone

Chemistry team produces a game-changing catalyst

Scientists and engineers create the 'perfect plastic'

WATER WORLD
Myanmar suspends dam project after rare outcry

World-first discovery 'can help save coral reefs'

Myanmar suspends dam project after rare outcry

Dead Sea researchers discover freshwater springs and numerous micro-organisms

WATER WORLD
Chinese target Arctic with Iceland land deal: experts

Model provides successful seasonal forecast for the fate of Arctic sea ice

Putin touts Arctic Northeast passage

Understanding methane's seabed escape

WATER WORLD
Climate: Act now to diversify crops at risk, say scientists

Brazil native killing blamed on ranchers: advocates

Weeds are vital to the existence of farmland species

Bigger profits for Asian rice producers?

WATER WORLD
Pakistanis at risk over world inaction on floods: WFP

Aid rushed to Philippine flood victims

Vietnam, China lashed by tropical storm

Hurricane Ophelia strengthens in Atlantic

WATER WORLD
Berkeley Lab Tests Cookstoves for Haiti

Kenya tries to contact French woman's abductors in Somalia

Guyana opposition warns foreign bauxite firms

Zambia's Sata tells Chinese investors to respect labour laws

WATER WORLD
What can magnetic resonance tractography teach us about human brain anatomy?

Many roads lead to Asia

Female promiscuity can rescue populations from harmful effects of inbreeding

DNA study suggests Asia was settled in multiple waves of migration


Memory Foam Mattress Review
Newsletters :: SpaceDaily Express :: SpaceWar Express :: TerraDaily Express :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News
.

The content herein, unless otherwise known to be public domain, are Copyright 1995-2011 - Space Media Network. AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement