A system dynamics model for the management of the gooseneck barnacle (Pollicipes pollicipes) in the marine reserve of Gaztelugatxe (Northern Spain)

The gooseneck barnacle (Pollicipes pollicipes) is a highly exploited species in Spain and Portugal due to the great commercial demand and the high prices in the market. Due to the inaccessibility of the Gaztelugatxe coastal area (Basque Country, Northern Spain), the gooseneck barnacle has maintained one of the greatest populations of the Basque coast in this area. Declared as a marine reserve by means of the 229/1998 (Basque Government) Decree, a 2 years moratorium in the gooseneck shellfishing was established. Facing the possibility of the gooseneck barnacle fishery opening in the area of the biotope, it was noticed the need for the development of a management tool, capable to think over the different management decisions: from the complete conservation of the system to the sustainable exploitation of the resource, joining together different social and biological factors, allowing the protection of the firsts (protection of the stock) and the development of the seconds (fishery activity). Based on the population dynamics of the gooseneck barnacle, a system dynamic model dominated by one positive and three negative loops was developed. The positive loop portrays the reproductive and maturation process, ultimately producing more adult gooseneck barnacles. The negative loops cause the stabilisation as the different stages of the population expire due by natural causes and exploitation of the resource. According to the model results, the best management decision is the maintenance of the moratorium. Taking into account the dispersion capability of larvae, other areas near the reserve, and subjected to commercial exploitation like Ogoño, Izaro and cape Villano, will benefit from the protection of Gaztelugatxe production. In the case of exploitation, the best management decision, which maximises captures and minimises the stock looses in a sustainable manner, is an alternate exploitation between Aketxe and Gaztelugatxe coastal areas of the marine reserve.