ABSTRACT

Age compositions from eight blue cod (Parapercis colias) subpopulations off the South Island of New Zealand were compared to investigate recruitment patterns temporally and spatially. Findings indicate (1) recruitment is highly variable between years, (2) subpopulations closer to each other have similar age compositions, and (3) strong and weak recruitment events are linked and the key processes that drive recruitment strength are acting on a large spatial scale. Recruitment variability among years and similarities between areas are likely to be density-independent, due to environmental fluctuations. Age compositions exhibited modal progression of age classes providing validation of ageing based on counts of rings on otoliths. Sex ratio by age and length were compared in relation to their reproductive strategy of changing sex from female to male (protogynous hermaphrodites). Sex ratio pattern differed for each of the eight subpopulations but was most similar in those from the same area. Males dominate at younger ages and sex ratio swings in favour of females with increasing age. Patterns in sex ratio with size are virtually the opposite to those of age because the largest fish are invariably males. These results support the theory that the form of protogyny in blue cod is diandric.

摘要

八条蓝鳕（Parapercis colias ）的年龄成分) 新西兰南岛附近的亚群进行了比较，以调查时间和空间上的招募模式。研究结果表明：(1) 招聘在不同年份之间存在很大差异，(2) 彼此距离较近的亚群具有相似的年龄构成，以及 (3) 强招聘事件和弱招聘事件相互关联，驱动招聘强度的关键过程作用于大空间规模。由于环境波动，不同年份的招募变化和地区之间的相似性可能与密度无关。年龄组成表现出年龄等级的模态进展，提供基于耳石上环计数的老化验证。将年龄和长度的性别比例与它们将性别从女性变为男性（雌雄同体）的生殖策略进行了比较。八个亚群的性别比例模式各不相同，但在同一地区的人群中最为相似。男性在年轻时占主导地位，性别比例随着年龄的增长而有利于女性。性别与体型的比例模式实际上与年龄相反，因为最大的鱼总是雄性。这些结果支持蓝鳕鱼的母体形式是双雄性的理论。