Seijo-Gutiérrez, J.C. & G., Ponce Díaz (2023). Addressing spatial management questions through dynamic bioeconomic modelling of fisheries targeting sedentary species: A brief review. INAPESCA (Eds.), Ciencia Pesquera. 31(1): 115-122.
Juan Carlos Seijo-Gutiérrez 1 y Germán Ponce Díaz 2
This manuscript reviews the scientific contributions by Professor John F. Caddy for properly understanding and modelling the heterogeneity over space and time of resource abundance and spatial behavior of fishing intensity in fisheries targeting sedentary species. As spatial data on patch distribution of stocks become available for low or null mobility sedentary resources, responsible management requires relaxing the dynamic pool assumptions. It also involves proper understanding of fisher behavior driving the spatial allocation of fishing intensity over time. As pointed out by Caddy (1975), Seijo & Caddy (2008) and Anderson & Seijo (2010), the Schaefer-Gordon and Beverton-Holt models are based on dynamic pool assumptions, which establish that: i) the resource is homogeneously distributed in space; ii) ages are perfectly mixed; and either iii) fishing effort is applied uniformly over the range of resource distribution, or iv) after fishing effort has been applied, the resource is able to redistribute itself according to i) and ii). For sedentary and low mobility resources, models based on dynamic pool assumptions are inadequate and may result in serious model error for fisheries targeting sedentary species of bivalve molluscs, gastropods, and echinoderms. This type of resources exhibits stock patchiness with heterogeneous distribution of patch size, density, and age structure. As a result, fishers respond by allocating their fishing intensity over space and time by considering the heterogeneous stock abundance, the distance and associated costs and corresponding quasi-profits of the variable costs of fishing in alternative sites. As pointed out by Caddy (1975) the main consequence of this spatial heterogeneity is that under dynamic pool assumptions the productive potential of the stock is overestimated, increasing the risk of over-exploitation and collapse of the fishery targeting sedentary or low mobility species. This manuscript summarises the fisheries science contributions of the first dynamic age-structured spatial model, published in by John F. Caddy in 1975. Also, reviews how this model evolved into a geographic spatial bioeconomic model for fisheries targeting sedentary species to answer questions such as: How to model the age-structured spatial dynamics of sedentary species recruiting in patches of random size and location? How to determine the seasonal and long-run spatial dynamics of stocks and the corresponding fishing intensity targeting sedentary species over space and time? Which is the bioeconomic optimal rotating harvest strategy for sedentary species with heterogeneous renewability capacity? Which are the dynamic biomass and resource rent effects of alternative states of nature of uncertain biologic and economic parameters? What is the bioeconomic effect of port location in relation source and sink areas of metapopulations recruiting in patches over space and time? What is the bioeconomic effect of location of area closures (mPa’s) with identifiable source and sink areas of targeted stocks of sedentary species? This manuscript also identifies research and management questions of a high value species targeted by a small-scale fleet of Mexico which could consider spatial analysis approaches to aid decision making for stock recovery of sedentary highly vulnerable stocks.
Palabras clave: spatial; patch density; heterogeneous distribution; fishing intensity; sedentary species; metapopulations; source; sink; Spatial management; bio-economics.
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