Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ocean Data Confirms Fishing Puts Targeted Species in 'Double Jeopardy'

20.10.2006
Groundbreaking study gives new insight for conservation and management efforts of exploited fish populations Scripps Institution of Oceanography/UC San Diego

For the first time, a research study has shown that fishing can promote relative boom and bust swings in supplies of targeted fish stocks. The study, authored by scientists at Scripps Institution of Oceanography at UC San Diego, the Southwest Fisheries Science Center (National Marine Fisheries Service), Imperial College London and the University of Oxford, shows that beyond the potential for fishery exploitation to cause systematic declines in targeted fish stocks, fishing carries with it a "double jeopardy" impact by also amplifying the highs and lows of natural population variability. This increases uncertainty in estimating population levels and could put fisheries at greater risk of collapse than previously believed.

For decades, theoretical debates have swirled in scientific circles regarding how much impact—if any—commercial fishing activities held for the fish populations they target. Statistics and recent studies have shown that many commercially important fish populations have been declining over the past several decades, but how much can be traced to fishing rather than environmental influences?

The new study, published in the October 19 issue of the journal Nature, is based on data obtained by the California Cooperative Oceanic Fisheries Investigations (CalCOFI), a program that has been investigating the ecological conditions of the California Current for more than half a century. "We found that the temporal variability of the targeted (exploited) populations was much higher, meaning that fishing tends to amplify both the peaks and the valleys of population numbers," said George Sugihara, a coauthor of the paper and a professor in the Physical Oceanography Research Division at Scripps. "Fishing can potentially not only lead to declining stock levels, but we show it actually causes populations to fluctuate more through time, which could put them at greater risk of collapse than we previously thought."

The researchers differentiated between environmental and fishing impacts by analyzing the populations of exploited versus unexploited species living in the same environments. Normally this comparison cannot be made with traditional fisheries data that are based on "landings" records, as there are no landings records for unfished species. The CalCOFI data was unique in this regard because it gathered data on larval abundances of both fished and non-fished species. Larval abundance is a well-known indicator of adult abundance. The study analyzed the quantity of larval fish recorded during systematic CalCOFI research cruises, which focus on the California Current, the large current originating in the northern Pacific Ocean that passes along the western coast of North America.

The authors believe that the reason fished populations become more variable is a consequence of the fact that fishing selectively culls the larger, older individuals, thereby removing the fish that are more able to buffer random environmental variation and add year-to-year continuity to the population. These individuals also tend to be the most reproductively active in their populations. As fishing proceeds, there is a tendency for the size and age of individuals in the population to decline, potentially leaving a stock of near-juveniles that are less able to cope with environmental pulses such as El Niño events.

"This so-called 'age truncation effect' (ATE) suggests that fisheries need to be managed not only to maintain a harvest target or total biomass level, but also to maintain a certain age structure in the stock," said Sugihara, who indicated that the fluctuations they identified tend to precede systematic declines of populations, meaning they can be viewed as a kind of early warning sign prior to collapse. "Instituting practical maximum size limits or encouraging the use of marine reserves to protect the larger individuals are possible solutions."

Beginning in the 1960s and '70s, debates over fishing impacts, which included coauthors John Beddington of Imperial College London and Robert May of the University of Oxford, were largely speculative arguments where some scientists argued that fishing activities would act to stabilize populations (through density-dependent harvesting), while others said that it would increase fluctuations. There were no data at the time to resolve the controversy. Sugihara says the new study, motivated by his student Chih-hao Hsieh's doctoral work, was made possible only through the unique and highly valuable data provided by the CalCOFI program. Data from fisheries are, by definition, plagued with a catch-22 situation in that they can only provide information about fished species and virtually no information about non-fished species. Without data on unexploited species, control comparisons for evaluating fishing effects are not possible.

"Our study points to the foresight of long-term observational programs like CalCOFI and the Long-Term Ecological Research (LTER) program, and helps to further justify the public investment in such nationally important programs," said Sugihara.

"The most immediate implication for fisheries management is that beyond the potential for causing a decline in abundance, fishing can provoke greater variability in exploited populations (and therefore reduced resilience) and thereby increase the risk of collapse of a fishery from (random) environmental events," the authors conclude in their study. "Obviously, this risk increases if fishing results in both higher variability and declining populations. That these two undesirable consequences of fishing can occur together represents double jeopardy and should be of concern to fisheries managers." In addition to Hsieh, Beddington, May and Sugihara, the study was coauthored by John Hunter of Scripps Oceanography and Christian Reiss of the Southwest Fisheries Science Center.

The study was funded by the National Oceanic and Atmospheric Administration (NOAA) Fisheries and the Environment (FATE), the National Marine Fisheries Service, the National Science Foundation/LTER California Current Ecosystem "Nonlinear Transitions in the California Current Coastal Pelagic Ecosystem," the Deutsche Bank Complexity Studies Fund and the Sugihara Family Trust.

Mario Aguilera | EurekAlert!
Further information:
http://www.calcofi.org
http://scripps.ucsd.edu
http://www.ucsd.edu

More articles from Ecology, The Environment and Conservation:

nachricht Successful calculation of human and natural influence on cloud formation
04.11.2016 | Goethe-Universität Frankfurt am Main

nachricht Invasive Insects Cost the World Billions Per Year
04.10.2016 | University of Adelaide

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>