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Many tropical fisheries are inherently of a multispecies nature, with any given type of fishing gear harvesting a wide range of species. Species-aggregated relationships between fishing effort and yield or catch per unit of effort (CPUE) provide important information for the management of such fisheries, as well as insights into ecosystemlevel responses to fisheries exploitation. We used a model selection approach to study species-aggregated, yield-effort relationships in spatially replicated, multispecies inland fisheries. Of three alternative models considered, the data strongly supported a sigmoid functional form (Akaike weight 0.95) over the alternative, asymptotic exponential or quadratic (Schaefer) models (Akaike weights 0.03 and 0.02, respectively). The sigmoid form implies the occurrence of an inflexion point in the rising part of the yield-effort curve and no decline in aggregated yield even at the highest effort levels observed. Aggregated CPUE declines steeply near the origin of the effort scale before stabilizing or rising to a local maximum and then declining inversely with further increases in effort. This highly nonlinear response suggests that extreme caution is required when interpreting aggregated CPUE as an indicator of fishing impacts on exploited communities. Further research is required to identify the mechanisms generating the observed relationship.Résumé : Plusieurs pêches tropicales sont multispécifiques de nature et tout type d'engin de pêche y récolte une gamme étendue d'espèces. Les relations pour l'ensemble des espèces entre l'effort de pêche et le rendement ou les captures par unité d'effort (CPUE) fournissent des informations importantes pour la gestion de telles pêches, ainsi que des perspectives sur les réactions écosystémiques à l'exploitation par la pêche. Nous utilisons une méthodologie de sélection de modèles afin d'étudier les relations rendement-effort pour l'ensemble des espèces dans des pêches inté-rieures multispécifiques qui se répètent à l'échelle spatiale. Des trois modèles considérés, les données appuient fortement le choix d'une forme fonctionnelle sigmoïde (pondération d'Akaike de 0,95) plutôt que des modèles de rechange asymptotique exponentiel ou quadratique de Schaefer (poids respectifs d'Akaike de 0,03 et de 0,02). La forme sigmoïde implique l'existence d'un point d'inflexion dans la partie croissante de la courbe rendement-effort et l'absence de déclin du rendement de l'ensemble des espèces même aux niveaux les plus élevés d'effort observés. La CPUE de l'ensemble des espèces décline abruptement près de l'origine de l'échelle des efforts avant de se stabiliser ou de remonter pour atteindre un maximum local, pour ensuite diminuer en fonction inverse des augmentations subséquentes de l'effort. Cette réaction qui est loin d'être linéaire indique qu'il faut être très prudent lorsqu'on interprète la CPUE de l'ensemble des espèces comme indicateur des impacts de la pêche sur les communautés exploitées. Des recherches supplémentaires pourraient identifier le...

Inland fisheries are essential to nutrition and food security in developing countries but remain undervalued. Worldwide, studies of aquatic resource consumption are rare. 'Fish rescue us from hunger' MS 2 We use data from a monthly survey of 40 households over one year in a Tanzanian village, combined with qualitative methods, to analyse consumption of animal aquatic resources across wealth, seasons, fishing vs. non-fishing and male-vs. female-headed households. We find that local freshwater fish are the most frequent source of animal protein, consumed on 57% of survey days. Wealth matters, with better-off households eating fish more often and in larger daily quantities on average. Middle-ranked households catch and sell fish more often, but all households double their consumption on average on days they catch rather than purchase fish. Female-headed households rely on gifts to increase consumption. Our results emphasise the need to preserve the livelihood functions of inland fisheries in the face of increasing threats.

Four different management regimes were identified in small water bodies in Laos: open-access fisheries, both with and without stocking of exotics (mainly Nile tilapia Oreochromis niloticus); community fisheries with restricted access and regular stocking; and fisheries rented out to corporate entities, based on indigenous stocks only. These regimes represent all possible combinations of the two management measures, access (open/restricted) and stocking of exotic species (no/yes) and a test fishing experiment assessed their effects on stock abundance, richness and diversity. The combination of access restrictions and stocking had a strong positive effect on total standing stocks. Stocks of indigenous fish were significantly increased by access restrictions, while stocking of exotics had no effect on indigenous standing stocks. Community fisheries targeted large sizes of exotic species while reducing the exploitation of smaller size groups, which accounted for much of the indigenous stocks. This suggests that stocking can promote active effort regulation and reduce the exploitation of natural stocks. Data on yields and effort were too limited to allow the use of inferential statistics, but indicated that community fisheries were exploited with much lower effort and gave lower yields than open access fisheries, while providing higher returns to fishing effort. This suggests that active management is effective in increasing standing stocks and the efficiency of exploitation, but does not necessarily increase yields unless optimal management regimes can be identified and implemented by the management institutions. No significant effects on wild stock richness or diversity were detected in the test fishing experiment, but wide confidence limits indicated a low statistical power of the test and therefore no definitive conclusions could be drawn. 1998 The Fisheries Society of the British Isles