Multi-scale Fish-habitat Associations and the Use of Habitat Surrogates to Predict the Organisation and Abundance of Deep-water Fish Assemblages

Deep-water demersal fishes are an important component of continental shelf and slope ecosystems and play an important role in the economies of many countries. Strong and predictable relationships of fishes with seabed habitats, in conjunction with rapid advances in acoustic seabed mapping capabilities, indicate there is great potential for using habitats as proxies or ‘surrogates’ to predict species distribution and abundance patterns at broad regional scales. However, few studies have evaluated this potential in complex seabed environments. In this study, we examined the spatial distributions, assemblage composition, and benthic habitat associations of deep-water demersal fish species over three spatial scales across Cordell Bank, a deep-water bank in central California. Demersal fishes were counted and habitats quantified from 60 strip-transects allocated over the extent of the bank using in situ observer and video-recorded data from the two-person Delta submersible. Both abundance and distribution of demersal fish species on Cordell Bank were strongly correlated with spatial location and habitat composition on the bank. Habitat structure was heterogeneous at several spatial scales. At broad scales, the rocky bank itself contained the highest diversity of both habitats and fishes. At intermediate scales, transition zones (10-100s of m wide) between the bank and continental slope and shelf sediments supported a diverse and characteristic suite of fish species. Habitats were also heterogeneous at finer-scales (1-10s of m) within these broad-scale zones, and fish responses to these habitat characteristics were taxon-specific, and often contingent on the spatial configuration of fine scale habitats within the broader-scale landscape. The results of this study indicate that for many species it is not sufficient to just know the fine-scale habitat association to predict fish assemblages.

深水底栖鱼类（deep-water demersal fishes）是大陆架与大陆坡生态系统的关键组成部分，对众多国家的海洋经济发挥着重要作用。鱼类与海底生境间存在强且可预测的关联，再加上声学海底测绘（acoustic seabed mapping）技术的飞速进步，表明利用生境作为替代物（proxies/surrogates）在大区域尺度上预测物种分布与丰度模式具备巨大潜力。然而，目前鲜有研究在复杂海底环境中对这一潜力开展评估。本研究以加利福尼亚中部的科德尔班克（Cordell Bank）——一处深水海床——为研究区域，在三个空间尺度上探究了深水底栖鱼类的空间分布、群落组成以及底栖生境关联特征。研究借助双人Delta（德尔塔）潜水器获取的原位观测与视频记录数据，在覆盖整个海床的范围内布设了60条带状样带（strip-transects），对底栖鱼类进行计数并量化生境参数。科德尔班克的底栖鱼类丰度与分布均与该海床的空间位置及生境组成显著相关。生境结构在多个空间尺度上呈现异质性：在大尺度上，岩质海床本身的生境与鱼类多样性均为最高；在中等尺度上，海床与大陆坡、大陆架沉积物之间的过渡带（宽度为数十至数百米）支撑着多样且具有特征性的鱼类类群。在这些大尺度区域内部，生境还存在更精细的空间异质性（尺度为1至数十米），鱼类对这些生境特征的响应具有类群特异性，且往往取决于精细尺度生境在更大尺度景观中的空间配置。本研究结果表明，对于多数物种而言，仅掌握其精细尺度的生境关联特征，并不足以准确预测鱼类群落组成。