How much biomass must remain in the sea after fishing to preserve ecosystem functioning? The case of the sardine fishery in the gulf of California, Mexico

One of the great scientific challenges for the management of fish resources is to address the question of how much biomass must remain in the sea after fishing in order to maintain the functions of the ecosystem. We define this fishing limit as an ecosystem limit reference point, ELRP, that could be used for marine resource management. The basic concept is that the entropy of the ecosystem changes when biomass is removed, and if the removal exceeds a certain threshold, the ecosystem will lose its capacity to recover and its ability to adopt a different organizational pattern. For fishing, we can define the ELRP as a harvest rate to be applied to each species group in the ecosystem. We illustrate this concept with the sardine fishery of the central Gulf of California and offer a criterion for approaching concerns about the exploitation of small pelagic fishes in many parts of the world. The ELRP shown here also contributes to the maintenance of ecosystem function by providing a specific harvest rate. This rate permits the estimation of the remaining biomass at sea as a limit for maintaining ecosystem sustainability by adopting a precautionary management policy.