Assessing the Viability of Reintroduction of Locally Extinct Migratory Fish Brycon orbignyanus: Successful Growth, Dispersal and Maturation

Juan R Esquivel-Muelbert,Danilo P Streit Jr,Adriane Esquivel-Muelbert,Juan R E Garcia,Luisa Fontoura,Éverton Zardo

doi:10.3390/fishes3040039

Juan R Esquivel-Muelbert, Danilo P Streit Jr + Show 4 more

Open Access

https://doi.org/10.3390/fishes3040039

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Abstract

The reintroduction of threatened fish species in areas where wild populations have been depleted due to anthropogenic impacts is an increasingly popular conservation tool and mitigation policy. Despite the importance of fish reintroduction for conservation purposes, little is known about its efficiency. Here, we assessed the viability of reintroduction of the endangered migratory fish, Brycon orbignyanus, in an area of the Upper Uruguay River basin where the species has not been reported for more than 30 years. We released 4000 yearling juveniles in the Pelotas River in 2014 and maintained 400 juveniles in captivity as a control population. After three years, a total of 13 individuals was recaptured, of which, 10 were considered sexually mature with first maturation being recorded in animals larger than 42 cm in total body length. The age–length comparison with a control population growth curve showed that recaptured fish were slightly bigger than those in captivity. Furthermore, important ecological attributes as schooling behavior and dispersal capacity were recorded for all recaptured individuals. Combined, our results suggest that the re-establishment of a self-sustained population of locally extinct species B. orbignyanus in the Pelotas River may be successful if sustained over time and supported by conservation policies.

Highlights

Anthropogenic disturbances have largely contributed to the recent loss in biodiversity in aquatic ecosystems [1]
Schooling behavior was observed on 3 occasions with up to 5 fish recaptured at the same time
Genetic analysis showed that molecular variance between recaptured and control population was considered low for B. orbignyanus, with a significant pairwise Fixation index (Fst = 0.108, p < 0.001) [18]

Summary

Introduction

Anthropogenic disturbances have largely contributed to the recent loss in biodiversity in aquatic ecosystems [1]. Attempts to recover depleted populations have been implemented worldwide [3] as species loss can affect the stability, resilience, and food web dynamics of aquatic ecosystems and impact the welfare of human populations that depend on fisheries resources [4,5,6]. The establishment of self-sustaining populations in the wild is the principal aim for the long-term viability of fish stocks. The success of reintroduction programs depends on the size and health of released fish, behavioral changes due to domestication and characteristics of the release site as water quality and flow, food availability, and presence of predators [9]. Stocking of endangered fish species into their former habitats have low success rates, often related to post-release mortality and wrong pre and post-release management strategies [2]. Survival to reproductive age is crucial to the establishment of self-sustaining populations in rivers affected by human activities [10]

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