Mass marking of juvenile Schizothorax wangchiachii (Fang) with alizarin red S and evaluation of stock enhancement in the Jinping area of the Yalong River.

Kun Yang,Yezhong Tang,Zhaobin Song,Shu Li,Weixiong Gan,Xiaoshuai Liu,Longjun Deng

doi:10.7717/peerj.4142

Abstract

Schizothorax wangchiachii is a key fish species in the stock enhancement program of the Yalong River hydropower project, China. Alizarin red S (ARS) was used to mark large numbers of juvenile S. wangchiachii in the Jinping Hatchery and later used to evaluate stock enhancement in the Jinping area of the Yalong River. In a small-scale pilot study, 7,000 juveniles of the 2014 cohort were successfully marked by immersion in ARS solution, and no mortality was recorded during the marking process. The ARS mark in the fish otoliths remained visible 20 months later. In the large-scale marking study, approximately 600,000 juveniles of the 2015 cohort were successfully marked. Mortalities of both marked and unmarked juveniles were very low and did not differ significantly. Total length, wet mass and condition factor did not differ significantly between unmarked and marked individuals after three months. On 24 July 2015, about 840,000 Jinping Hatchery-produced young S. wangchiachii, including 400,000 marked individuals, were released at two sites in the Jinping area. Recapture surveys showed that (1) marked and unmarked S. wangchiachii did not differ significantly in total length, wet mass and condition factor; (2) stocked individuals became an important part of recruitment of the 2015 cohort; (3) instantaneous growth rate of marked individuals tended to slightly increase; and (4) most stocked individuals were distributed along a 10–15 km stretch near the release sites. These results suggest that the ARS method is a cost-efficient way to mass mark juvenile S. wangchiachii and that releasing juveniles is an effective means of stock recruitment.

Highlights

Habitat degradation and overexploitation contribute to the decline of fisheries around the world
To optimize marking quality and minimize juvenile mortality, several preliminary experiments were conducted in 2013, and results showed that immersing juvenile S. wangchiachii in water containing alizarin red S (ARS) doses ≤100 mg L−1 for 24 h resulted in the lowest death rate while producing a mark that could be seen clearly in the otolith
The surveys conducted in this study showed that, there are some spawning grounds for Schizothorax fishes in the Jinping area of the Yalong River, where some naturally born juveniles were caught in April 2014

Summary

Introduction

Habitat degradation and overexploitation contribute to the decline of fisheries around the world. The effectiveness of stock enhancement can be assessed by mark-release-recapture studies (Blaxter, 2000), which require effective tagging or marking methods Various marking techniques, such as otolith marking (Volk, Schroder & Grimm, 1999), coded wire tags (Bernard, Marshall & Clark, 1998) and passive integrated transponders (Navarro et al, 2006), have been developed to monitor released fish. Among these techniques, otolith marking is a feasible method that allows long-term identification of small fish (Caraguel et al, 2015; Crook et al, 2009). ARS offers better mark quality and lower cost and is viewed as a promising dye for mass marking fish at early life stages (Taylor, Fielder & Suthers, 2005; Yang et al, 2016)

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Discussion

Conclusion