Modelling the management of clam (Ruditapes decussatus) exploitation in the Plentzia estuary (Basque Country, Northern Spain)

摘要

Some of the estuaries of the Basque Country (Northern Spain) have beenareas of exploitation of clam populations, both by professional and illegalfishermen. There is a real possibility of overfishing and, therefore, theDepartment of Fisheries of the Basque Government needs to: (a) understandthe situation relating to these populations; and (b) provide a tool to establishthe most adequate management for the exploitation of clams.In order to simulate different alternatives for the exploitation, based uponscientific data on the population, the best tool available is a systemdynamics model. Here the VENSIM? model was employed, utilising dataon clam populations: summer stock and biomass in the Plentzia estuary, in1998, 2000; winter stock in 1999, 2000, and 2001; the area occupied by thespecies; the length and weight class distribution; the number of fishermen;mean of biomass, captured by the fishermen; natural mortality, by lengthclass; maturation; fertility rate; etc. This study improves previousexperiences in modelling clam exploitation in the Plentzia and Mundakaestuaries.Following validation of the model, after running it for 1 and 10 years, somecases were simulated. This analysis was undertaken in order to establish theeffect of modifying the number of fishermen, the aperture-close season ofcaptures, the minimum sustainable biomass, the exploitation area and theminimum legal length for shellfishing. This approach tries to establish thesustainable exploitation of the clam populations in the Basque Country.