Learning about TURFs and natural variability: Failure of surf clam management in Chile

Abstract

Territorial User Rights for Fisheries (TURF) is considered an appropriate tool for small-scale fishery management. In Chile a TURFs system called Management Exploitation Areas for Benthic Resources (Áreas de Manejo y Explotación de Recursos Bentónicos-AMERB) were developed as a solution for the fishery crisis of Concholepas concholepas, a hard bottom snail. The success of these AMERBs led to its widespread application across different fisheries resources and social-ecological contexts, among them the surf clam Mesodesma donacium which has a highly variable population. Traditionally, fishermen followed the sporadically appearing M. donacium beds, migrating along the coast, a behavior now suppressed under the AMERB regime. We examined the dynamics of the M. donacium fishery, evaluating the performance of the AMERB system for its sustainable exploitation. Fishermen extracted surf clams based on monthly quotas, which were conservative. Despite this, after three years the fishery of M. donacium within the AMERB collapsed because of lack of recruitment and high natural mortality. The resulting low abundances made the fishery unattractive, causing the abandonment of the AMERB. This suggests that implementation of an AMERB system must integrate knowledge of the spatial scales over which different clam beds (subpopulations) are connected. While still ignoring the structure of the metapopulation, as occurs at present for M. donacium stocks in Chile, it could be evaluated to increase capture during the periods of boom, taking advantage of surf clams that will disappear in any case due to natural mortality. A spatial reserve within each clam bed could also be established in order to conserve the unknown but potentially important role of the subpopulation for the metapopulation.