Instituto Patagónico para el Estudio de los Ecosistemas Continentales, IPEEC-CONICET, Puerto Madryn, Argentina.
Grupo de Investigación y Desarrollo Tecnológico en Acuicultura y Pesca, Facultad Regional Chubut, Universidad Tecnológica Nacional, Puerto Madryn, Argentina.
J Fish Biol. 2022 Oct;101(4):925-936. doi: 10.1111/jfb.15151. Epub 2022 Aug 3.
This study evaluates the influence of marine and freshwater conditions on the timing of river entry and upstream migration of sea trout (Salmo trutta) in the Grande River of Tierra del Fuego, Patagonia. We analysed the in-river catch-and-release records from a group of fishing lodges that dominate the Grande River fishery during January-April 2008 (n = 5029 fish) as a function of environmental variables: tidal amplitude, stage in the lunar cycle, river discharge, and river water temperature along the homeward migration season. We discuss the value of the daily catch rate as an abundance index in the Grande river, then analyse the temporal structure of the tidal cycle in the Grande River estuary, a macro-tidal environment with a mean tidal amplitude of 5.7 m, and analyse the fit of a generalized additive model to trout catches on a daily basis in four sections along the river to identify the environmental variables that may affect trout abundance throughout the homeward migration. Fish catches in each section of the river were differentially affected by specific environmental variables: tidal amplitude had a positive and significant effect on catches in the lower river sections, whereas water temperature and river discharge significantly affected catches in upper sections (positive effect of temperature; negative effect of discharge). Catches in the lower section clearly reflect the river entry stage of the homeward migration, with a bi-modal shape significantly correlated with the tidal cycle. The first peak was composed mainly of larger multi-sea-winter trout that move upstream, whereas the second one had a wider range of fish lengths, including a large proportion of small and maybe nonreproductive trout that overwinter in the lower river. Based on our results, we conclude that the large tides in the Grande River estuary strongly affect the river entry timing of sea trout. The underlying mechanisms of this effect may be a combination of increased olfactory recognition and increased tidal transport modulated by the seasonal tidal cycle, which operates on trout during coastal migration to produce the pulses observed in the Grande River sea trout run. In the middle and upper sections of the river, where the tidal effect at river entry was dissipated as upstream migration progressed, trout catches increased with water temperature and decreased with river discharge, which may operate through their influence on in-river migration rate and abundance, but also through changes in catchability.
本研究评估了海洋和淡水条件对火地岛格兰德河（Grande River）洄游三文鱼（Salmo trutta）进入河流和溯河洄游时间的影响。我们分析了 2008 年 1 月至 4 月期间，主导格兰德河渔业的一组钓鱼小屋的河流捕捞记录（n=5029 条鱼），作为环境变量的函数：潮幅、月相阶段、河流流量和河流水温。我们讨论了每日捕捞率作为格兰德河丰度指数的价值，然后分析了格兰德河河口潮汐周期的时间结构，该河口潮汐周期具有 5.7 米的平均潮幅，分析了广义加性模型在河流四个部分的每日基础上对鳟鱼捕捞的拟合情况，以确定可能影响整个溯河洄游期间鳟鱼丰度的环境变量。河流各部分的鱼类捕捞受到特定环境变量的不同影响：潮幅对下游部分的捕捞有积极且显著的影响，而水温和河流量对上游部分的捕捞有显著影响（温度有积极影响；流量有消极影响）。下游部分的捕捞明显反映了溯河洄游的进入阶段，与潮汐周期呈双模态形状，具有显著相关性。第一个高峰主要由较大的多龄海三文鱼组成，这些三文鱼向上游洄游，而第二个高峰则有更广泛的鱼长范围，包括大量可能在下游越冬的小型和非繁殖性三文鱼。根据我们的结果，我们得出结论，格兰德河河口的大潮强烈影响三文鱼的进入时间。这种影响的潜在机制可能是嗅觉识别增强和季节性潮汐周期调制的潮汐运输增强的组合，在沿海洄游期间作用于三文鱼，产生在格兰德河三文鱼洄游中观察到的脉冲。在河流的中游和上游部分，随着溯河洄游的进行，进入河流的潮汐效应逐渐消散，鳟鱼捕捞量随着水温的升高而增加，随着河流量的减少而减少，这可能通过对河流洄游速度和丰度的影响以及通过渔获物可捕捞性的变化来起作用。
