Towards responsible and sustainable fisheries

A billion people dependent on fish in the world  |  From years of  “miraculous fishing” to stock collapse  |  An unlikely return to initial state  |  Impacts
of fisheries on the marine ecosystem as a whole
  |  A worrisome reduction
in fish size
  |  Dynamics of exploitation systems  |  Towards
responsible and sustainable fisheries
  |  The Centre de Recherche
Halieutique Méditerranéenne et Tropicale

A worrisome reduction in fish size

An essential qualitative evolution in fish landings shows the indirect effects that my be engendered by fisheries on the ecosystem as a whole: fishes of small size and at the bottom of the trophic chain constitute a growing proportion of catches. More and more sardines, anchovies, herrings and other small pelagic fishes are caught, and fewer and fewer codfish, halibut, hake, etc. This phenomenon is not linked to a change in targeting by fishers, quite the contrary. Indeed, fishers most frequently target large carnivorous fishes, situated at the top of the trophic chain, because these have high commercial value.
In Canada, where the codfish seems to have in fact disappeared, the ecosystem today is dominated by pelagic fishes and other species located lower down the trophic chain, in particular shrimps and crabs. Several decades ago, it was still possible to catch three-meter long halibut and two-meter long codfishes. Today, their size rarely exceeds one meter. This reduction in fish size found in catches is a clear symptom of the generalized overexploitation of fish stocks, especially of the larger species. Scientists are beginning to take the measure of the problem.  Knowledge of the functioning of the marine milieu, even if incomplete, allows us to foresee that the massive reduction of these predatory species will have important effects on marine ecosytems as a whole, upsetting their structure and functioning. Dominated by species of small size and short life expectancies, ecosystems will become more and more affected by environmental and climatic variations.

Poissons pélagiques