Genetic Diversity of an Imperiled Neotropical Catfish and Recommendations for Its Restoration.

Eric M Hallerman,Alexandre W S Hilsdorf,Rodrigo R Domingues,Fernando S Fonseca

doi:10.3389/fgene.2017.00196

Abstract

The long-whiskered catfish Steindachneridion parahybae (Family Pimelodidae) is endemic to the Paraíba do Sul River basin in southeastern Brazil. This species was heavily exploited by artisanal fisheries and faces challenges posed by dams, introduced species, and deterioration of critical habitat. The remaining populations are small and extirpated from some locales, and the species is listed as critically endangered in Brazil. Screening variation at a partial mitochondrial control region sequence (mtCR) and 20 microsatellite loci, we: (i) describe the patterns of genetic diversity along its current distributional range; (ii) test the null hypothesis of panmixia; (iii) investigate the main factors driving its current population structure, and (iv) propose management of broodstock for fostering recovery of wild populations through genetically cognizant restocking. Our microsatellite data for 70 individuals from five collections indicate moderate levels of heterozygosity (HO = 0.45) and low levels of inbreeding (FIS = 0.016). Individual-based cluster analyses showed clear genetic structure, with three clusters of individuals over the collection area with no mis-assigned individuals, suggesting no recent migration among the three clusters. Pairwise DEST values showed moderate and significant genetic differentiation among all populations so identified. The MUR population may have suffered a recent demographic reduction. mtCRs for 70 individuals exhibited 36 haplotypes resulting from 38 polymorphic sites. Overall, mitochondrial haplotype diversity was 0.930 (±0.023) and nucleotide diversity was 0.011 (±0.002). Significant population structure was observed, with ϕST = 0.226. Genetic markers could be used in a hatchery-based restoration program emphasizing breeding of pairs with low kinship values in order to promote retention of genetic diversity and avoid inbreeding. Individual average kinship relationships showed 87.3% advised matings, 11.0% marginal matings, and 1.7% advised against. While these results comprise a contribution toward planning better breeding management and monitoring, parallel actions to be undertaken include surveying healthy riverine habits for reintroduction and continued searching for wild individuals to introduce new variation into the captive broodstock to avoid adaptation to captivity and to minimize inbreeding.

Highlights

The Atlantic Forest is a globally important biome; with high freshwater fish diversity, a high degree of endemism, and threats of many impending extinctions, it is considered a conservation hotspot (Myers et al, 2000; Hubert and Renno, 2006)
All samples of S. parahybae from the five collection areas along the Paraíba do Sul River basin were successfully genotyped at 20 microsatellite loci
Our assessment of the extant S. parahybae populations reflected the endangered status of this Neotropical catfish in its area of occurrence

Summary

Introduction

The Atlantic Forest is a globally important biome; with high freshwater fish diversity, a high degree of endemism, and threats of many impending extinctions, it is considered a conservation hotspot (Myers et al, 2000; Hubert and Renno, 2006). An important component of the fish fauna within this biome is the genus Steindachneridion (Order Siluriformes: Family Pimelodidae), which encompasses six recognized species of migratory long-whiskered catfishes that inhabit deep water in mid-sized streams with rocky bottoms (Agostinho et al, 2003; Garavello, 2005). Referred to “surubim-do-paraíba,” Steindachneridion parahybae (Steindachner, 1877) is a mediumsized, dorsoventrally flattened, whiskered catfish endemic to the Paraíba do Sul River basin in southeast Brazil (Garavello, 2005). Construction of dams, introduced species, and deterioration of critical habitat (Loris, 2008; Moraes et al, 2017), the species is listed as “Critically Endangered” in the official lists of imperiled species in Brazil (Caneppele et al, 2008; Oyakawa et al, 2009)

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Conclusion