The scope of this paper is to quantify, for a wide selection of European fisheries, fishing tactics and strategies and to evaluate the benefits of adjusting the definition of fishing effort using these elements. Fishing tactics and strategies were identified by métiers choices and a series of indices. These indices have been derived to reflect shifts in tactics (within a fishing trip) and in strategies (within a year). The Shannon-Wiener spatial diversity indices of fishing tactics (FT_SW) and strategies (YE_SW) had the greatest impact on catch rates. In particular, FT_SW was always negatively correlated to catch rates. One may anticipate that during a fishing trip, vessels with high FT_SW have been searching fish aggregations for a long time, while vessels with low FT_SW have been more efficient in finding these aggregations. The linkage between YE_SW and catch rates was of a more complex nature. Adjusting fishing effort by means of (i) the métier effect and (ii) the indices of tactics and strategies generally led to a substantial gain in the precision of the relationship between fishing mortality and fishing effort. Résumé : L'objectif de cette étude est de quantifier, pour une large sélection de pêcheries européennes, les tactiques et stratégies de pêche, et d'évaluer dans quelle mesure ces éléments peuvent être utilisés pour mieux ajuster l'effort de pêche. Les tactiques et stratégies de pêche ont été identifiées par les choix de métiers et une série d'indices. Ces indices ont été calculés pour quantifier les changements de tactique (au cours d'une marée) et de stratégie (au cours d'une année). Les indices de Shannon-Wiener décrivant la distribution spatiale de l'effort de pêche au cours d'une marée (FT_SW) et d'une année (YE_SW) ont eu l'effet le plus important sur les taux de capture. En particulier, FT_SW était négativement corrélé aux taux de capture pour tous les cas d'étude. Ce résultat était prévisible. Au cours d'une marée, les bateaux caractérisés par un FT_SW élevé ont vraisemblablement cherché les agrégations de poisson pendant une longue période, tandis que les bateaux caractérisés par un faible FT_SW auront été plus efficaces pour localiser ces agrégations. Le lien entre YE_SW et les taux de capture était d'une nature plus complexe. L'ajustement de l'effort au moyen, (i) de l'effet métier et, (ii) des indices de tactique et de stratégie, conduit généralement à un gain substantiel de précision de la relation entre effort de pêche et mortalité par la pêche. Marchal et al. 533

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Compared with diploid species, haplodiploids suffer less inbreeding depression because male haploidy imposes purifying selection on recessive deleterious alleles. However, alleles of genes only expressed in the diploid females are protected in heterozygous individuals. This leads to the prediction that haplodiploids suffer more from inbreeding effects on life-history traits controlled by genes with female-limited expression. To test this, we used a wild population of the haplodiploid mite Tetranychus urticae. First, negative effects of inbreeding were investigated by comparing maturation rate, juvenile survival, oviposition rate and longevity between lines created by three generations of either outbreeding or mother-son inbreeding. Second, purging through inbreeding was investigated by comparing the intensity of inbreeding depression between outbred families with known inbreeding/outbreeding mating histories. Negative effects of inbreeding and evidence for purging were found for the female trait oviposition rate, but not for juvenile survival and longevity. Both male and female maturation rate were negatively affected by inbreeding, most likely due to maternal effects because inbred offspring of outbred mothers was not affected. These results support the hypothesis that, in haplodiploids inbreeding effects and genetic variation due to deleterious recessive alleles may depend on gender.

Since inbreeding in Tetranychus urticae can reduce offspring fitness, sexual selection may favour disassortative mate choice with respect to relatedness of the mating partners. We tested whether T. urticae shows this preference for mating with unrelated partners. We chose an experimental set-up with high potential for female choosiness, since females only mate once and are therefore expected to be the choosier gender. An adult virgin female was placed together with two adult males from the same population. One male was unrelated and the other male was related—a brother with whom she had grown up. Significantly more copulations (64%) took place with the unrelated male. Time to mating did not depend on the female-to-male relatedness. The remaining (non-copulating) male tried to interfere with the ongoing mating in the majority of cases, but this interference did not depend on the female-to-male relatedness. These results imply that T. urticae (a) can recognize kin (via genetic and/or environmental similarity) and (b) has the potential to avoid inbreeding through mate choice.

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