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Related Experiment Video

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Modeling the Size Spectrum for Macroinvertebrates and Fishes in Stream Ecosystems

Modeling the Size Spectrum for Macroinvertebrates and Fishes in Stream Ecosystems

Published on: July 30, 2019

Evolutionary response to size-selective mortality in an exploited fish population.

Douglas P Swain¹, Alan F Sinclair, J Mark Hanson

¹Fisheries and Oceans Canada, Gulf Fisheries Centre, Moncton, New Brunswick E1C 9B6, Canada. swaind@dfo-mpo.gc.ca

Proceedings. Biological Sciences

|February 1, 2007

Summary

Fisheries can cause rapid evolutionary changes in fish size. This study shows Atlantic cod evolved smaller sizes due to fishing, explaining their slow recovery even with reduced fishing pressure.

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Area of Science:

Marine Biology
Evolutionary Biology
Fisheries Science

Background:

Many depleted fish populations fail to rebound after fishing cessation.
Evolutionary changes driven by fisheries-induced mortality are a potential cause.
Previous lab studies confirmed rapid genetic shifts in growth rates due to size-selective harvesting.

Purpose of the Study:

To investigate if size-selective fishing has caused genetic changes in growth rates in a wild Atlantic cod (Gadus morhua) population.
To analyze a 30-year dataset of fish lengths-at-age to detect evolutionary responses.

Main Methods:

Utilized a 30-year time-series of back-calculated lengths-at-age for Atlantic cod.
Controlled for environmental factors like density and temperature affecting growth.
Correlated changes in mean length-at-age between cohorts with estimated fishing selection differentials.

Main Results:

A significant positive correlation was found between the change in mean length of 4-year-old cod and the parental selection differential.
This indicates genetic changes in growth rate in response to size-selective fishing in the wild.
The observed smaller size-at-age in cod persists despite favorable growth conditions and reduced fishing.

Conclusions:

The study provides evidence for evolutionary changes in growth in Atlantic cod due to size-selective fisheries.
These genetic shifts may explain the lack of population recovery and continued small fish size.
Management strategies must consider the evolutionary impacts of fishing to ensure sustainable fisheries.