RESUMEN

Male sneaking behaviour can lead to interspecific hybridisation if sneakers attempt to fertilise ova in heterospecific mating, contributing to break down of interspecific barriers. In south European rivers, sneaking Atlantic salmon males fertilise an important proportion of ova from adult females in heterospecific crosses, up to 65%. In a south French flow-controlled stream, we found that they were able to naturally fertilise brown trout ova in absence of brown trout males. Aggressiveness of brown trout males towards sneaking salmon males and low survival of hybrids issued from salmon sneakers are found to be interspecific barriers.

Asunto(s)

Salmonidae/genética , Animales , Cruzamientos Genéticos , Femenino , Francia , Agua Dulce , Hibridación Genética , Masculino , Reacción en Cadena de la Polimerasa , ARN Ribosómico 5S/genética , Salmonidae/clasificación

RESUMEN

By screening variable number of tandem repeat (VNTR) loci, multiple paternity within clutches has been found in wild populations of southern European Atlantic salmon (Salmo salar) and brown trout (Salmo trutta). For Atlantic salmon, we determined the relative contribution of alternative male phenotypes to the next generation. Individual males that are morphologically juvenile yet sexually mature fertilized a large proportion of eggs, and they thereby contributed to an increase of genetic variability in wild populations via (1) balancing the sex ratio, (2) increasing outbreeding, and (3) enlarging the effective population size, in part a consequence of (1) and (2). In addition, these precocious males ensured that interspecific spawns involving Atlantic salmon females and brown trout males (a fairly common occurrence in southern Europe where the two species are sympatric) resulted mostly in Atlantic salmon progeny. For brown trout, preliminary genetic results indicated that multiple paternity, when present, was not due to alternative mating strategies by males, but rather to successive fertilizations by adult suitors.

Asunto(s)

Repeticiones de Minisatélite/genética , Salmo salar/fisiología , Trucha/fisiología , Animales , Animales no Consanguíneos , Quimera/genética , ADN Mitocondrial/análisis , Femenino , Fertilización/fisiología , Variación Genética , Glucosa-6-Fosfato Isomerasa/genética , Masculino , Proteínas Musculares/genética , Paternidad , Fenotipo , Fosfoglucomutasa/genética , ARN Ribosómico 5S/genética , Reproducción/genética , Salmo salar/genética , Razón de Masculinidad , Maduración Sexual , Especificidad de la Especie , Trucha/clasificación , Trucha/genética

RESUMEN

Genetic analyses were performed on the progeny of Atlantic salmon (Salmo salar L.) sampled in natural redds of three rivers flowing into the Bay of Biscay, the Nivelle, the Mandeo and the Sella. These rivers are at the southern limit of the European distribution of the species and their populations are small and endangered by human activities. Nine variable number of tandem repeat (VNTR) loci (five minisatellites and four microsatellites) were used for parentage analysis. Multiple male participation was recognized in the fertilization of eggs. A large proportion was fertilized by precociously mature parr. We demonstrate that multiple paternity derived from mature parr is crucial for the conservation of genetic variability in small populations of Atlantic salmon.

Asunto(s)

Salmo salar/genética , Animales , Ecosistema , Femenino , Francia , Variación Genética , Genética de Población , Humanos , Masculino , Repeticiones de Minisatélite , Paternidad , Densidad de Población , España

RESUMEN

We studied 12 size-matched pairs of Atlantic salmon, Salmo salar, in an experimental stream in southwest France, to determine whether fish activity and motivation changed during the course of reproduction. The absolute weight of spawners did not affect their spawning activity. On average, females deposited their eggs within 3 days in nine nests. Male and female breeding behaviours changed throughout the reproductive period. This cyclic variation in behaviour appeared to be determined in part by the activity of the other sex, as a consequence of complex interplay between the sexes, but also largely by the stage of the spawning period. During the first three ovipositions, male-female stimulus-reaction chaining became more consistent just before spawning, which may help synchronize gamete release for successful fertilization. During the last three ovipositions, sequence chaining between the sexes was less coherent, possibly as a result of reduced mate attractiveness and/or physiological limitations. Copyright 1999 The Association for the Study of Animal Behaviour.