There and back again: migration in freshwater fishes

Abstract

Animal migration is an amazing phenomenon that has fascinated humans for long. Many freshwater fishes also show remarkable migrations, whereof the spectacular mass migrations of salmonids from the spawning streams are the most well known and well studied. However, recent studies have shown that migration occurs in a range of freshwater fish taxa from many different habitats. In this review we focus on the causes and consequences of migration in freshwater fishes. We start with an introduction of concepts and categories of migration, and then address the evolutionary causes that drive individuals to make these migratory journeys. The basis for the decision of an individual fish to migrate or stay resident is an evaluation of the costs and benefits of different strategies to maximize its lifetime reproductive effort. We provide examples by discussing our own work on the causes behind seasonal migration in a cyprinid fish, roach (Rutilus rutilus (L., 1758)), within this framework. We then highlight different adaptations that allow fish to migrate over sometimes vast journeys across space, including capacity for orientation, osmoregulation, and efficient energy expenditure. Following this we consider the consequences of migration in freshwater fish from ecological, evolutionary, and conservation perspectives, and finally, we detail some of the recent developments in the methodologies used to collect data on fish migration and how these could be used in future research.Key words: fish migration, seasonal, evolution, consequences, cyprinids.Résumé : L'étonnant phénomène des migrations animales fascine les humains depuis belle lurette. De remarquables migrations caractérisent de nombreux poissons d'eau douce, les migrations massives des salmonidés à partir de leur cours d'eau d'origine étant les plus connues et les plus étudiées. Cela dit, des études récentes ont démontré l'existence de migrations chez divers taxons de poissons dulcicoles d'habitats nombreux et variés. Dans la présente synthèse, nous nous penchons sur les causes et conséquences de la migration chez les poissons dulcicoles. Nous abordons en premier lieu les concepts importants et les catégories de migration, puis examinons les causes évolutionnaires qui amènent des individus à accomplir ces déplacements migratoires. La décision d'un poisson donné de migrer ou de demeurer en place repose sur une évaluation des coûts et avantages de différentes stratégies visant à optimiser son effort de reproduction durant sa durée de vie. Nous présentons des exemples basés sur nos propres travaux sur les causes de la migration saisonnière chez un poisson cyprinidé, le gardon (Rutilus rutilus (L., 1758)), dans ce cadre. Nous décrivons ensuite différentes adaptations qui permettent dans certains cas à des poissons de migrer sur de grandes distances, dont une capacité d'orientation, l'osmorégulation et l'efficience des dépenses énergétiques. Nous examinons ensuite les conséquences de la migration chez les poissons dulcicoles des points de vue écologique, évolutio...

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