A bió-socio-economic simulatión model for management of the red sea urchin fishery in Chile.

Abstract

This study focused on the management of the red sea urchin Loxechinus albus fishery in Chile. The main objective was to design, consuct, implement and assess a computerbased simulation model to analyse the biological effects, socio-economic consequences and spatial dynamics resulting from coastal management plans applied to this resource under the system of AMEBR. This was accomplished by using systems dynamics (SD) and geographical information systems (GIS) modellmg, in a process of model development, run, optimisation, sensitivity analysis and risk management, and a series of fleid-based activities carried out at the cove of Quintay. The GIS model developed for allocating sea urchins restocking sites offered a flexible, cost-effective, user-friendly and descriptive technique for support decision-making on management of this species and other benthic resources. Final site selection for restocking was based on the identification, quantification and selection of higher suitabilityavailability combinations (site categories). This map showed 16 different suitabilityavailability combinations or site categories, ranging from 4:100 to 8:100 (suitability pointsavailability %). These had an average of 6.446937 (covering an area of 82.5 Ha overali equivalent to 81.21% of the study area. This site classification demonsfrated high heterogeneity between options, and revealed the fuli variety of altematives for decision-making. More iinportantly, the generaily high suitability indexes as well as available area emphasised the prospects for restocking sea urchins in this study area. Over and aboye of the quantitative outcomes obtained from running the GISRM (suitable and available restocking sites) and the BSESM (alternative strategic management plans), the case study-based analysis made it possible to disc lose the wider issues related to the red sea urchin coastal management. These results demonstrated the biological inefficiency of traclitional size/seasonal restriction-based approach (macro-scenario 1) for sustainable management of the target species. More importantly, final outcomes strongly suggested that a combination of adaptive restocking-based enhancement activities and flexible exploitation constituted a highly attractive approach (macro-scenario 3) for stock management of this fishery in terms of harvestable stock and related incomes. However from the economie analysis, stocking was also found to be economically unfeasible, bemg a rather cost intensive exercise negatively affected by high natural mortality rates. A single-variable optimisation analysis demonstrated that a higher survival rate is needed to generate sufficient profits to cover major restocking costs and a positive payment, or a cost reduction is essential to make up for the loss. On top to these practical constraints, based on the distinctive modest economic situation prevailing for most Chilean co yes and hence their limited capacity to pay for stocking material, unless adequate and constant funding is available to support artisanal associations, they are vety unlikely to develop mass release programrnes. Given the economic (i.e.: high operatmg costs) and technical (i.e: low survival rates) limitations conditioning stocking-based management cost-effectiveness and applicability, wide imp lementation of mass releases as a major approach for management of the red sea urchin fishery is very unlikely to take place in Chile. This study presents a methodology and offers a tool to design, evaluate and optimise coastal management plans for the red sea urchin in a dynamic, interactive, systematic, integrated and flexible way. The optional strategic management plans proposed on this study may not be applied equally to any AMEBR, as they are the outputs arising from a single cove-specific analysis. Still, the complete methodological framework and analysis procedures developed may be applied to run the BSESM and optimise management of a red sea urchin fishery at any other AMEBR case of study.