Juvenile Atlantic cod
Overfishing truncates size and age distributions of fish populations. Female cod responded to harvest levels that exceeded maximum sustainable yield by spawning at an earlier age, and the average spawning age declined from 5-5 years to less than 3 years [2].
This response is thought to be an adaptation to small population sizes. However, younger spawners produce smaller and fewer eggs and, therefore, smaller fry. This makes the new generation more prone to predation and may be contributing to the slow recovery of cod stocks [3].
In addition, the removal of larger, older individuals from the population diminishes the capacity for the population to rebound from declines caused either by overfishing or changing ocean conditions [3].
References
- Auster, P. J. and Langton, R. W. (1998) The Effects of Fishing on Habitat. Committee on Fisheries, Ocean Studies Board, National Research Council. [Online].
- Trippel, E. A. (1995) Age Maturity as a Stress Indicator in Fisheries. Bioscience. 45: 759-771.
- Palakovich, J. and kaufman, L. (2008) Estimating the Importance of Maternal Age, size, and Spawning Experience to Recruitment of Atlantic Cod (Gadus morhua). Biological Conservation. 142: 477-487.