Abundance indices and biological traits of juvenile salmon (Salmo salar) sampled in three rivers on the Atlantic and Channel coasts (France)

Abstract

BackgroundAtlantic Salmon (Salmo salar) is an anadromous migratory species adapted to cool temperatures. It is protected by the Bern convention and by the European Habitats Directive. It has been listed as vulnerable by the French IUCN Red List. Salmon decline is the result of combined and cumulated, mainly anthropic, causes: climate change, increasingly high number of impoundments, degradation of water quality and habitat and over-exploitation by fisheries. Monitoring of this species has been carried out on three rivers in France (Southern part of the distribution area) to produce data and knowledge (growth, precocious maturity, survival) for stock management.For 24 years, a specific and standardised electric fishing protocol has been used to target young-of-the-year (0+ parr) Atlantic salmon. Sampling was restricted to areas with shallow running water that flows over a coarse bottom substrate, i.e. the preferred habitat of young salmon. This monitoring and inventory of growing areas thus allows assessment of juvenile recruitment and provides baseline data required to calculate total allowable catches (TACs).New informationThe dataset currently consists of 47,077 occurrence data points from 105 sites spanning up to 24 years in three different watersheds in France. Beyond our project, this dataset has a clear utility to research since it associates abundance measurements with the measurement of biological traits and the collection of tissue samples. It allows for current and retrospective characterisation of individuals or populations, according to life history traits and genetic features in relation to changes in environmental conditions. The fact that the monitoring takes place in France, the southern part of the distribution area, over 24 years, makes the dataset particularly relevant for climate change studies.

Estimating the effective number of breeders from single parr samples for conservation monitoring of wild populations of Atlantic salmon Salmo salar

“…Its population dynamics are closely monitored under the long‐term individual based time series (LITS) framework (Jones et al, ) and maintained by the French Institute of Agronomical Research. (INRA) since 1983 (Lange et al, ; Lange et al, ; Marchand et al, ).…”

“…data) and the distribution of redds is recorded as the number of redds in each patch. These data are all collected under the French Research Observatory Diadromous Fishes in Coastal streams programme (ORE DiaFC), stored in the Long‐term Individual based Time Series (LITS) S. salar Nivelle database (Lange et al, ; Marchand et al, ).…”

“…For returning adults, the same database was also used to retrieve information on phenotypic sex, age at sea migration and time at sea (converted to year of birth and age at returning year). Evidence of precocious male maturity (converted to phenotypic sex) when available and age (converted to year of birth and year of residency in the River Nivelle for parr aged 1+ and 2+ years) were retrieved for electrofished juveniles (Lange et al, ; Marchand et al, ).…”

Effects of spatial aggregation of nests on population recruitment: the case of a small population of Atlantic salmon

“…The study area was divided into 624 stretches of different lengths, defined by habitat features such as dams, bridges, confluences, or river morphodynamic changes (Tentelier et al 2016). Suitable river habitats correspond to the favorable areas for the production of juveniles (nursery stretches), namely shallow running water flowing over a coarse bottom substrate (Marchand et al 2017), wherein available ones define those accessible for salmon (Pr evost et al 1996). 1).…”

“…First, the recruitment, that is, the yearly juvenile number, was estimated from electrofishing within suitable river habitats for juveniles, previously described as shallow running water flowing over a coarse bottom substrate (Marchand et al 2017). This monitoring has been carried out by the Environmental Research Observatory (ERO) on Diadromous Fish in Coastal rivers (DiaPFC; https:// www6.inra.fr/diapfc).…”