Genetic evaluation of migratory fish: Implications for conservation and stocking programs.

Area of Science:

• Ichthyology and Conservation Genetics
• Aquatic Ecology
• Fisheries Management

Background:

• Hydropower dams disrupt natural fish migration, impacting populations.
• Fish stocking is used to mitigate dam impacts but raises genetic concerns.
• Neotropical migratory fish, Prochilodus costatus, are vital to the São Francisco River basin.

Purpose of the Study:

• To assess the genetic diversity, population structure, and gene flow of Prochilodus costatus.
• To evaluate the impact of fish stocking programs on P. costatus genetics in the Três Marias dam region.
• To inform conservation and management strategies for this commercially important migratory fish.

Main Methods:

• Sampled 1,017 Prochilodus costatus from 12 sites and a stocking program.
• Genotyped specimens using high-throughput sequencing at 8 microsatellite loci.
• Analyzed genetic diversity, population structure, and gene flow patterns.

Main Results:

• Populations exhibited low genetic variability and evidence of inbreeding.
• Identified four distinct genetic pools, with one unique to the Paraopeba River.
• Observed high unidirectional gene flow, favoring a specific migratory route.
• Stocking transposed genetic pools but caused genetic homogenization upstream of Três Marias dam.
• Highlighted the genetic fragility of the species.

Conclusions:

• Fish stocking programs can inadvertently lead to genetic homogenization.
• Conservation efforts must consider the genetic integrity of wild fish populations.
• Monitoring genetic diversity is crucial for effective management of migratory fish.