ABSTRACT

This study describes some of the characteristics of the spawning runs of rainbow and brown trout from Lake Otamangakau, into Te Whaiau Stream. More than 55,000 fish undergoing spawning migrations were enumerated in a fish trap between 1994 and 2013. During that period, the spawning run size increased for both species, but particularly for rainbow trout, which exhibited a concurrent decline in average weight. The timing of the runs was consistent across both species, sexes, and maturation statuses but was affected by the average weight of the fish and the run size. The level of iteroparity revealed that 40% and 55% of the runs were made up of previous spawner rainbow and brown trout, respectively. Detections of PIT-tagged fish at the trap indicated that rainbow and brown trout could spawn up to six and eight times, respectively. Remarkably, repeat spawning fish of both species and sexes returned within a few days of the same date each year over consecutive spawning events. Rainbow and brown trout grew substantially after spawning up to the 3rd and 4th spawning, respectively. The results of this study are relevant for informing management of the popular Lake Otamangakau trout fishery, in particular achieving a balance between satisfactory CPUE and large fish size.

摘要

本研究描述了从 Otamangakau 湖进入 Te Whaiau 溪流的虹鳟鱼和褐鳟鱼产卵路线的一些特征。1994 年至 2013 年期间，在一个捕鱼器中统计了超过 55,000 条正在进行产卵洄游的鱼。在此期间，这两个物种的产卵数量都有所增加，但虹鳟鱼尤其如此，它们的平均重量同时下降。运行的时间在两个物种、性别和成熟状态中都是一致的，但受到鱼的平均重量和运行大小的影响。迭代级别显示 40% 和 55% 的运行分别由之前的产卵彩虹和褐鳟鱼组成。在陷阱处检测到带有 PIT 标签的鱼表明，虹鳟鱼和褐鳟鱼可以分别产卵 6 次和 8 次。值得注意的是，在连续的产卵事件中，每年同一日期的几天内返回的物种和性别的重复产卵鱼。虹鳟鱼和褐鳟鱼在产卵后分别大幅增长到第 3 次和第 4 次产卵。这项研究的结果与广受欢迎的 Otamangakau 湖鳟鱼渔业的管理有关，特别是在令人满意的 CPUE 和大鱼尺寸之间取得平衡。