ABSTRACT

Composition and length-frequency are important attributes considered in the management of fish communities and can be affected by both exploitation and environmental forces. Vulnerability to these effects varies among species depending on environmental tolerance, ecological traits, and life-history strategies. In the present study, data from scientific bottom trawl surveys conducted between 1991 and 2018 were analysed to identify long-term changes in community structure and length-frequency of demersal fish species of the east coast of the South Island, New Zealand. Analysis of variance, hierarchical clustering analysis and multidimensional scaling relationships demonstrated that community composition has changed significantly over the last three decades, with a tendency towards greater spatial overlap among species in the most recent periods. Changes in depth distribution were identified but were mainly correlated with shifts in relative biomass. Total catch rate (kg km⁻²) of the whole community has increased significantly over time, while the average trophic level decreased, primarily explained by an increase in relative biomass of intermediate trophic level species. Fishing activity was significantly related to the variation in length-frequency of species at intermediate trophic levels, confirming that the impacts of fisheries are heterogeneous throughout the community, providing vital information to support multi-species management of fishery resources.

摘要

组成和长度频率是鱼类群落管理中考虑的重要属性，可能受到开发和环境力量的影响。不同物种对这些影响的脆弱性各不相同，具体取决于环境耐受性、生态特征和生活史策略。在本研究中，分析了 1991 年至 2018 年间进行的科学底拖网调查的数据，以确定新西兰南岛东海岸底层鱼类群落结构和长度频率的长期变化。方差分析、层次聚类分析和多维标度关系表明，群落组成在过去三十年中发生了显着变化，最近时期物种之间的空间重叠有更大的趋势。确定了深度分布的变化，但主要与相对生物量的变化相关。总捕获率（公斤·公里^-2 ) 的整个群落随着时间的推移显着增加，而平均营养级下降，主要是由于中间营养级物种的相对生物量增加。捕捞活动与中等营养级物种长度频率的变化显着相关，证实了渔业对整个社区的影响是异质的，为支持渔业资源的多物种管理提供了重要信息。