The influence of catch-and-release on mortality of Salminus brasiliensis (Cuvier, 1816)

Abstract Catch-and-release (CR) angling has been used to assist management programs seeking to promote the conservation and recovery of some recreational fish stocks by decreasing mortality from fishing. However, without appropriate fish handling, this activity may cause damage and injuries to individual fish, causing mortality. Therefore, CR should be allowed under some circumstances that ensure higher rates of survival to achieve the goals of the conservation measures. Thus, we experimentally tested the CR effects on dourado (Salminus brasiliensis) by comparing caught-and-released fish (CR fish) with uncaught fish (control fish) in a pond and estimating individual mortality rates related to seven air exposure times (AET: 120 s, 240 s, 360 s, 480 s, 600 s, 720 s and 840 s). We also determined a safe limit for fish handling and investigated the length and weight gain variations. We found that an increase in AET affects fish survival and that the limit of handling time for this species was 546 s; after this threshold, the individual probability of death exceeds 5%. The length and weight gain of CR fish did not differ significantly from the control fish. We believe that CR is efficient for S. brasiliensis because it does not significantly impair their organic growth and causes little or no mortality if handling is performed properly; thus, it could be employed to assist conservation programs.

摘要 钓获放流（Catch-and-release, CR）垂钓常被用于辅助渔业管理项目，通过降低捕捞致死率，助力部分休闲垂钓鱼类种群的保护与恢复。然而，若未采用恰当的鱼类处理方式，该活动可能对个体鱼类造成损伤与伤害，进而引发死亡。因此，为达成保护措施的既定目标，钓获放流应在可保障更高存活率的场景下开展。为此，本研究通过在池塘中对比钓获放流个体（CR组鱼类）与未捕捞个体（对照组鱼类），并针对7种空气暴露时长（Air Exposure Time, AET：120 s、240 s、360 s、480 s、600 s、720 s及840 s）估算个体死亡率，实验探究了钓获放流对巴西大鳞脂鲤（Salminus brasiliensis，俗称多拉多鱼）的影响。本研究同时确定了该鱼种的安全操作时长阈值，并探究了其体长与体重增长变化情况。研究结果显示，空气暴露时长的增加会对鱼类存活率产生负面影响，该鱼种的安全操作时长阈值为546秒；超过该临界值后，个体死亡概率将超过5%。钓获放流组鱼类的体长与体重增长幅度与对照组无显著差异。本研究认为，针对巴西大鳞脂鲤（S. brasiliensis），钓获放流是一种高效的管理手段：只要操作得当，该方式不会显著损害其机体生长，且几乎不会造成死亡，因此可用于辅助相关鱼类保护项目。