Navigation Links
Fishing throws targeted species off balance, Scripps study shows
Date:4/16/2008

Fishing activities can provoke volatile fluctuations in the populations they target, but its not often clear why. A new study published in the journal Nature by scientists at Scripps Institution of Oceanography at UC San Diego and colleagues has identified the general underlying mechanism.

Research led at Scripps with a distinguished team of government and international experts (including two chief scientific advisors to the United Kingdom) demonstrates that fishing can throw targeted fish populations off kilter. Fishing can alter the age pyramid by lopping off the few large, older fish that make up the top of the pyramid, leaving a broad base of faster-growing small younglings. The team found that this rapidly growing and transitory base is dynamically unstablea finding having profound implications for the ecosystem and the fishing industries built upon it.

The data show that fished species appear to be significantly more nonlinear and less stable than unfished species, said Professor George Sugihara of Scripps. We think the mechanism involves systematic alteration of the demographic parametersand especially increases in growth rates that magnify destabilization in many wayswhich can happen as fishing truncates the age structure.

Imagine a container of water with a 500-pound fish. With food, it grows a little bigger. Without food it gets a bit smaller. Imagine the same container with 500 one-pound fish. They eat, reproduce and the resulting thousands of fish boom, quickly outstripping the resources and the population crashes. These many smaller fishwith the same initial biomass as the larger fishcant average out the environmental fluctuations, and in fact amplify them through higher turnover rates that promote boom and bust cycles.

The study that included academic and government scientists from Alaska, Asia and Great Britain is based on data from the California Cooperative Oceanic Fisheries Investigations (CalCOFI), a program based at Scripps that has monitored fish and oceanographic activities of the California Current for more than 50 years. To arrive at their results, the researchers compared the CalCOFI records of larvae, a key indicator of adult populations, of both fished and non-fished species in the California Current.

Fishing typically extracts the older, larger members of a targeted species and fishing regulations often impose minimum size limits to protect the smaller, younger fishes.

That type of regulation, which we see in many sport fisheries, is exactly wrong, said Sugihara. Its not the young ones that should be thrown back, but the larger, older fish that should be spared. Not only do the older fish provide stability and capacitance to the population, they provide more and better quality offspring.

Thus the danger, according to Sugihara, is that current policies that manage according to current biomass targets (without significant forecast skill) while ignoring fish size pose risks that can further destabilize the population. This instability can in principle propagate systemically to the whole ecosystem, much like a stock market crash or a domino effect, and magnify risk for the fishing industry itself as well as those of ecologically related fisheries.

This is especially true when trying to rebuild fish stocks, Sugihara says.

This may be the most important implication of this work, as we attempt to rehabilitate fisheries, said Sugihara. Regulations based solely on biomass harvest targets are incomplete. They must also account for age-size structure in the populations, he said. Current policies and industry pressures that encourage lifting bans on fishing when biomass is rehabilitatedbut where maximum age and size are notcontain risk.

This is currently the case with Atlantic swordfish, for which industry pressures to resume fishing are based on the restoration of historic biomass levels, even though the swordfish are clearly undersized.

In the extreme case, the danger of such unstable dynamics for certain populations for management is that harvest targets may lag the population, potentially making things worse, said Sugihara. A high harvest target may be set after an especially abundant period when the population may be poised to decline on its own. Likewise future abundant periods may represent missed opportunities, despite current low abundances. As senior officials of the Canadian Department of Fisheries and Oceans have said, we are often a year behind in our stock projections.

Sugihara cautioned that nonlinearity is not unique to fished species. Nonequilibrium overshooting and undershooting occurs in unexploited stocks, but to a lower extent. Therefore, classical single-species population models that require equilibrium are unlikely to be very successful in stock forecasts, except perhaps in the very short term.

"Other methods that do not rely on these assumptions may be more promising," suggests Christian Anderson, paper co-author.


'/>"/>

Contact: Mario Aguilera
scrippsnews@ucsd.edu
858-534-3624
University of California - San Diego
Source:Eurekalert  

Related biology news :

1. Oceanic sharks worldwide at serious risk from high-seas fishing, rising demand for shark products
2. Small-scale fishing in Mexico rivals industrial fisheries in accidental turtle deaths
3. Research shows loggerhead sea turtles threatened by small-scale fishing operations
4. Researchers combat slowing yields with targeted fertilizer applications
5. Microarray sequence capture speeds large-scale resequencing of targeted genomic regions
6. St. Jude finds factors that accelerate resistance to targeted therapy in lymphoblastic leukemia
7. Species explorers ask: Whats on Your planet?
8. Destruction of Sumatra forests driving global climate change and species extinction
9. Scientists discover new species of giant elephant-shrew
10. Scientists call for urgent research into real impacts of invasive species
11. Multiple species of bacteria may cause trachoma: Implications for treatment
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Fishing throws targeted species off balance, Scripps study shows
(Date:5/16/2016)... --  EyeLock LLC , a market leader of iris-based ... IoT Center of Excellence in Austin, Texas ... embedded iris biometric applications. EyeLock,s iris authentication ... with unmatched biometric accuracy, making it the most proven ... platform uses video technology to deliver a fast and ...
(Date:4/28/2016)... India , April 28, 2016 ... Infosys (NYSE: INFY ), and Samsung SDS, a ... that will provide end customers with a more secure, ... services.      (Logo: http://photos.prnewswire.com/prnh/20130122/589162 ) , ... services, but it also plays a fundamental part in enabling ...
(Date:4/19/2016)... The new GEZE SecuLogic access ... "all-in-one" system solution for all door components. It can ... door interface with integration authorization management system, and thus ... minimal dimensions of the access control and the optimum ... offer considerable freedom of design with regard to the ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... 2016 Houston Methodist Willowbrook Hospital has ... Association to serve as their official health care ... Willowbrook will provide sponsorship support, athletic training services, ... coaches, volunteers, athletes and families. "We ... Association and to bring Houston Methodist quality services ...
(Date:6/23/2016)... , June, 23, 2016  The Biodesign Challenge ... envision new ways to harness living systems and biotechnology, ... Art (MoMA) in New York City ... 130 participating students, showcased projects at MoMA,s Celeste Bartos ... Paola Antonelli , MoMA,s senior curator of architecture and ...
(Date:6/23/2016)... (PRWEB) , ... June 23, 2016 , ... STACS DNA ... Technical Leader at the Arkansas State Crime Laboratory, has joined STACS DNA as a ... STACS DNA team,” said Jocelyn Tremblay, President and COO of STACS DNA. “In further ...
(Date:6/23/2016)... 2016  Blueprint Bio, a company dedicated to identifying, ... community, has closed its Series A funding round, according ... "We have received a commitment from Forentis Fund ... to meet our current goals," stated Matthew Nunez ... to complete validation on the current projects in our ...
Breaking Biology Technology: