Featured Research

from universities, journals, and other organizations

Killing Young Fish Paradoxically Results In Population Growth, Study Finds

Date:
March 19, 2009
Source:
Universiteit van Amsterdam (UVA)
Summary:
If you kill more fish, the total population of the species declines. However, kill only small, young fish, the total number of small, young fish increases. This seemingly paradoxical conclusion has far reaching implications for the sustainable management of oceans.

Research shows that selectively removing specimens of certain size classes not only results in compensation induced by changes in competition for resources, but in fact results in over-compensation.
Credit: iStockphoto/Viacheslav Lvov

If you kill more fish, the total population of the species declines. However, kill only small, young fish, the total number of small, young fish increases. This seemingly paradoxical conclusion has far reaching implications for the sustainable management of oceans, and is the result of a theoretical study conducted by a research team led by Prof. André de Roos of the Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam.

A follow up study conducted by the same team now provides experimental evidence to support their initial findings.

When fish are killed, by fishing or predation, a first obvious effect is that the total number of fish of the species in question declines. However, the removal of fish also results in less competition for food among the remaining individuals.  For example, young, small fish, one can imagine that when a certain percentage of young small fish is selectively removed, the remaining ones  have more food available to grow into bigger and stronger adults. These adults in turn, are able to produce more offspring, i.e. more young small fish, to compensate for the ones that were killed. In fact, the increased reproduction more than compensates for the number of small fish that were selectively removed in the first place.

This is a simplified version of the type of relationships that Prof. De Roos and his team revealed in a theoretical study that was published in the American Naturalist in 2007. The modeling study indeed predicted that selectively removing specimens of certain size classes not only results in compensation induced by changes in competition for resources, but in fact results in over-compensation.

The seemingly paradoxical implication is that selectively fishing away small, young fish results in an increase in the number of small, young fish. In a similar manner, the modeling study also predicted that the selective removal of large, adult individuals can lead to an increase in small, young fish densities. To test their predictions, Prof. De Roos and his team performed an experimental follow up study in Sweden that was recently concluded and supports their theoretical conclusions in all respects. This includes the specific example of selectively culling a certain percentage of small, young fish, which indeed was found to lead to an increase in their total numbers.

The results of the experimental study were published in the Proceedings of the National Academy of Science in February 2009.

Together, both studies show once more that marine food webs are very complicated and that interfering with them may lead to unanticipated results.  However, they also show that by carefully studying the relationships, they can be understood and modeled. Both these conclusions have far reaching implications for the sustainable management of oceans. For example, in a forthcoming publication in the Canadian Journal for Fisheries and Aquatic Sciences it is shown that this type of overcompensation may prevent a marine reserve from functioning as a source of young fish. This latter is one way in which marine reserves were believed to contribute to a sustainable exploitation of marine fish stocks.


Story Source:

The above story is based on materials provided by Universiteit van Amsterdam (UVA). Note: Materials may be edited for content and length.


Journal References:

  1. A. Schröder, L. Persson, and A. M. de Roos. Culling experiments demonstrate size-class specific biomass increases with mortality. Proceedings of the National Academy of Sciences, 2009; 106 (8): 2671 DOI: 10.1073/pnas.0808279106
  2. Tobias van Kooten, Lennart Persson, and André M. de Roos. Size-Dependent Mortality Induces Life-History Changes Mediated through Population Dynamical Feedbacks.. The American Naturalist, 2007; 170 (2): 258 DOI: 10.1086/518947

Cite This Page:

Universiteit van Amsterdam (UVA). "Killing Young Fish Paradoxically Results In Population Growth, Study Finds." ScienceDaily. ScienceDaily, 19 March 2009. <www.sciencedaily.com/releases/2009/03/090317143155.htm>.
Universiteit van Amsterdam (UVA). (2009, March 19). Killing Young Fish Paradoxically Results In Population Growth, Study Finds. ScienceDaily. Retrieved July 24, 2014 from www.sciencedaily.com/releases/2009/03/090317143155.htm
Universiteit van Amsterdam (UVA). "Killing Young Fish Paradoxically Results In Population Growth, Study Finds." ScienceDaily. www.sciencedaily.com/releases/2009/03/090317143155.htm (accessed July 24, 2014).

Share This




More Plants & Animals News

Thursday, July 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Stone Fruit Listeria Scare Causes Sweeping Recall

Stone Fruit Listeria Scare Causes Sweeping Recall

Newsy (July 22, 2014) — The Wawona Packing Company has issued a voluntary recall on the stone fruit it distributes due to a possible Listeria outbreak. Video provided by Newsy
Powered by NewsLook.com
Michigan Plant's Goal: Flower and Die

Michigan Plant's Goal: Flower and Die

AP (July 22, 2014) — An 80-year-old agave plant, which is blooming for the first and only time at a University of Michigan conservatory, will die when it's done (July 22) Video provided by AP
Powered by NewsLook.com
Huge Schizophrenia Study Finds Dozens Of New Genetic Causes

Huge Schizophrenia Study Finds Dozens Of New Genetic Causes

Newsy (July 22, 2014) — The 83 new genetic markers could open dozens of new avenues for schizophrenia treatment research. Video provided by Newsy
Powered by NewsLook.com
CDC Head Concerned About a Post-Antibiotic Era

CDC Head Concerned About a Post-Antibiotic Era

AP (July 22, 2014) — Sounding alarms about the growing threat of antibiotic resistance, CDC Director Tom Frieden warned Tuesday if the global community does not confront the problem soon, the world will be living in a devastating post-antibiotic era. (July 22) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins