Intensive fishing leads to smaller fish

May 07, 2010 by Hans Wolkers

(PhysOrg.com) -- Intensive fishery activities in the North Sea have resulted in evolutionary changes in fish. Fish remain smaller, grow slower and mature sexually earlier. This is postulated by Fabian Mollet, fishery researcher at Imares, The Netherlands, who will graduate on 7 May with these findings.

Mollet simulated fishery activities and their effects on the Dutch sole and plaice populations with complex models which he has developed. He studied how fishery affects the growth and the age at which the animals are sexually active. 'Fish mortality caused by efficient fishery is very high', Mollet says. 'A fish needs a lot of luck to survive the first five years of its life; this chance is only about eight percent.'

Due to strict fishing regulations based on size, it is a disadvantage for a fish to be big; big fish are being caught quickly. It is better to stay small and be able to procreate at a younger age. 'Intensive fishing has resulted in smaller fish which are sexually mature earlier,' says Mollet: For smaller fish to be able to produce enough , the animals also devote a lot of energy to their , which causes them to grow slower themselves. These take place very fast, and can be completed within a few decades.

According to Mollet, the current fishery policy - which stipulates that fish be selected based on size - nurtures the evolution of less marketable smaller fish. As a result, this reduces the maximum size of the permitted catch so that the would not be endangered through overfishing. It is a lose-lose situation. However, there is hope for the declining fish populations. According to Mollet, fishery-induced evolution can be halted. 'It is even possible at this moment to turn this fishery-induced evolution around', the PhD student thinks. 'Fishermen would then have to spare the big fish and go after medium-sized fish more . This letting go of big could cause the catch to be smaller in the short run, but if this is not done, future gains would become less anyway because of negative evolutionary effects.'

Explore further: New study charts the global invasion of crop pests

Provided by Wageningen University

4.3 /5 (3 votes)
add to favorites email to friend print save as pdf

Related Stories

Over-fishing: Fewer eggs, smaller fish

Jan 19, 2006

A University of California-Riverside study suggests harvesting the largest individuals from a fish population introduces harmful genetic changes.

Overfishing and evolution

Jul 20, 2009

Using snorkelers and SCUBA divers is not the best way to monitor fish populations, if we want to know the evolutionary effects of overfishing.

Fight over bringing Aussie carp to Britain

Jul 03, 2006

A private fishery in England is being inundated with letters and e-mails from anglers over plans to stock an 11-acre lake with imported Australian carp.

Recommended for you

New study charts the global invasion of crop pests

14 hours ago

Many of the world's most important crop-producing countries will be fully saturated with pests by the middle of the century if current trends continue, according to a new study led by the University of Exeter.

Zambia lifts ban on safari hunting

15 hours ago

Zambia has lifted a 20-month ban on safari hunting because it has lost too much revenue, but lions and leopards will remain protected, the government said Wednesday.

The devastating spread of the mountain pine beetle

22 hours ago

When the mountain pine beetle began blazing a path across forests in British Columbia and Alberta, nobody could have imagined the extent of the damage to come. But as the insect devastated pine forests and ...

User comments : 0