Frontiers in Marine Science (Jul 2014)
Mismatch between biological, exploitation, and governance scales of sea urchin (<i>Paracentrotus lividus</i>) fisheries in Galicia
Abstract
The spatial structure of fishery resources influences stock dynamics and finally the fishery. Therefore, this aspect should be included as a key topic in the assessment and management of fisheries [1, 2]. Here we use the case study of the fishery of the sea urchin Paracentrotus lividus in Galicia to demonstrate how the mismatch between biological, fishery and management scales causes failures in the governance, giving rise to over-exploitation. P. lividus is spatially distributed in nested biological units [3]: patches, micro-stocks, local populations and metapopulations. While fishing operations are local exploiting micro-stocks, management units in Galicia are regional and comprise more than one local population. This pattern allows the depletion of several micro-stocks without any short-term signals in the exploitation rates over the complete managed territory. Moreover, there are examples where local populations are divided between two fishing territories and consequently are exploited according to the different management plans running in each area. We suggest that management units should be redefined to include complete local populations. In addition, the implementation of reserve networks or a rotation system could allow to effectively managing the resource at a small-scale. Any of both regulations could compensate the inverse denso-dependency that regulates recruitment and fecundity in this species [4]. Specifically in the first case, we suggest to establish multiple reserves in shallow habitats, where the recruitment of P. lividus takes place [40]. The migratory pattern of P. lividus heading to deeper areas [4, 5] would secure the spillover of biomass towards the fishery areas. On the other hand, rotations are based in the delimitation of fishing subareas where harvest alternates [6]. One relevant design aspect for rotations is the definition of the sizes of the subareas. If the spatial scale is too large fishers could overexploit several micro-stocks and continue to harvest others without any short-term signal of the decrease of the profitability of the subarea. This is the reason because micro-stocks should be the units for rotations to allow controlling effectively density after a harvest pulse.
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