National Institute of Water and Atmospheric Research Limited, Wellington, New Zealand.
PLoS One. 2011;6(11):e26704. doi: 10.1371/journal.pone.0026704. Epub 2011 Nov 1.
We evaluate hypotheses for meso-scale spatial structure in an orange roughy (Hoplostethus atlanticus) stock using samples collected during research trawl surveys off the east coast of New Zealand. Distance-based linear models and generalised additive models were used to identify the most significant biological, environmental, and temporal predictors of variability in diet, proportion of stomachs containing prey, standardised weight of prey, fish somatic weight, fish total weight, and reproductive activity. The diet was similar to that observed elsewhere, and varied with ontogeny, depth, and surface water temperature. Smaller sized and female orange roughy in warmer bottom water were most likely to contain food. Fish condition and reproductive activity were highest at distances more than 20 km from the summit of the hills. Trawl survey catches indicated greater orange roughy densities in hill strata, suggesting hill habitat was favoured. However, analyses of feeding, condition, and reproductive activity indicated hill fish were not superior, despite fish densities on hills being reduced by fishing which, in principle, should have reduced intra-specific competition for food and other resources. Hypotheses for this result include: (1) fish in relatively poor condition visit hills to feed and regain condition and then leave, or (2) commercial fishing has disturbed feeding aggregations and/or caused habitat damage, making fished hills less productive. Mature orange roughy were observed on both flat and hill habitat during periods outside of spawning, and if this spatial structure was persistent then a proportion of the total spawning stock biomass would remain unavailable to fisheries targeting hills. Orange roughy stock assessments informed only by data from hills may well be misleading.
我们评估了在新西兰东海岸研究拖网调查中采集的橙色粗糙鱼（Hoplostethus atlanticus）种群中中尺度空间结构的假设。使用基于距离的线性模型和广义加性模型来确定饮食、含猎物胃比例、猎物标准体重、鱼类躯体重量、鱼类总重量和生殖活动变化的最显著的生物、环境和时间预测因子。饮食与其他地方观察到的相似，随个体发育、深度和地表水温度而变化。较小体型和生活在温暖底层水中的雌性橙色粗糙鱼更有可能含有食物。在距离山顶 20 公里以上的地方，鱼类状况和生殖活动最高。拖网调查表明，丘陵地层中的橙色粗糙鱼密度更高，表明丘陵栖息地受到青睐。然而，对摄食、状况和生殖活动的分析表明，丘陵鱼类并没有优势，尽管由于捕鱼，丘陵上的鱼类密度减少了，原则上这应该减少了食物和其他资源的种内竞争。对于这一结果的假设包括：(1) 状况较差的鱼类会到丘陵觅食并恢复状态，然后离开；(2) 商业捕鱼扰乱了觅食群集，或造成了栖息地破坏，使被捕捞的丘陵生产力降低。在产卵期以外的时期，成熟的橙色粗糙鱼在平坦和丘陵栖息地都有观察到，如果这种空间结构持续存在，那么总产卵stock 生物量的一部分将无法被针对丘陵的渔业捕获。仅根据丘陵数据进行的橙色粗糙鱼种群评估可能会产生误导。
