Larvae of migratory fish (Teleostei: Ostariophysi) in the lotic remnant of the Paraná River in Brazil

ABSTRACT Fish larvae and adults are morphologically distinct from each other and have different ecological requirements. Research on the dynamics of ichthyoplankton provides valuable information about the early stages of the life cycle of fish. This study analyzed the temporal and spatial distribution of the larval stages of three migratory species - Salminus brasiliensis (Cuvier, 1816), Prochilodus lineatus (Valenciennes, 1836) and Pseudoplatystoma corruscans (Agassiz, 1829) - to identify possible spawning areas in the last lotic remnant of the upper Paraná River, in the Brazilian territory. A total of 26 points were sampled monthly from October 2003 to November 2004. The PERMANOVA detected significant differences between the months only for S. brasiliensis (Pseudo-F = 3.88, p = 0.0021) and P. corruscans (Pseudo-F = 3.35, p = 0.004). Among the environmental variables, temperature was the most important and the Mantel test detected a significant correlation between temperature and the densities, only for P. lineatus (r = 0.09, p = 0.03). The species in our data chose for spawning tributaries that are not dammed, of which most are outside conservation areas. Therefore, recruitment, maintenance and possible actions aiming to recover the stocks of these species are dependent on the conservation of tributaries and floodplain lakes in the region, in addition to monitoring to prevent fishing during the reproductive period.

摘要：鱼类幼体与成体在形态学上存在显著差异，且具有截然不同的生态需求。对鱼类浮游生物（ichthyoplankton）动态的研究，可为鱼类生命周期早期阶段的相关研究提供宝贵参考信息。本研究针对3种洄游性鱼类——巴西大脂鲤（Salminus brasiliensis, Cuvier, 1816）、线纹原鳍鲮（Prochilodus lineatus, Valenciennes, 1836）以及斑纹扁鲇（Pseudoplatystoma corruscans, Agassiz, 1829）——的幼体时空分布展开分析，以期在巴西境内巴拉那河上游最后一处流水生境残留河段中定位潜在产卵场。2003年10月至2004年11月期间，研究团队对共计26个采样点开展了月度采样工作。置换多元方差分析（PERMANOVA）结果显示，仅在巴西大脂鲤（Pseudo-F=3.88, p=0.0021）与斑纹扁鲇（Pseudo-F=3.35, p=0.004）中检测到不同月份间的群落分布显著差异。在所有环境变量中，水温为影响最为显著的因子；曼特尔检验（Mantel test）结果显示，仅对线纹原鳍鲮而言，水温与其幼体密度间存在显著相关性（r=0.09, p=0.03）。本研究涉及的3种鱼类均选择未筑坝的支流作为产卵场，而其中多数支流并未纳入保护范围。因此，要实现这些鱼类种群的自然补充、种群维持以及后续的种群恢复工作，除需在繁殖期开展禁渔监测外，还需对该区域的支流与泛滥平原湖泊实施保护。