Crustaceans and fish abundances and species at and around artificially introduced tetrapod fields in the southern North Sea, 2009

The micro-scale spatial distribution patterns of a demersal fish and decapod crustacean assemblage were assessed in a hard-bottom kelp environment in the southern North Sea. Using quadrats along line transects, we assessed the in situ fish and crustacean abundance in relation to substratum types (rock, cobbles and large pebbles) and the density of algae. Six fish and four crustacean species were abundant, with Ctenolabrus rupestris clearly dominating the fish community and Galathea squamifera dominating the crustacean community. Differences in the substratum types had an even stronger effect on the micro-scale distribution than the density of the dominating algae species. Kelp had a negative effect on the fish abundances, with significantly lower average densities in kelp beds compared with adjacent open areas. Averaged over all of the substrata, the most attractive substratum for the fish was large pebbles. In contrast, crustaceans did not show a specific substratum affinity. The results clearly indicate that, similar to other complex systems, significant micro-scale species–habitat associations occur in northern hard-bottom environments. However, because of the frequently harsh environmental conditions, these habitats are mainly sampled from ships with sampling gear, and the resulting data cannot be used to resolve small-scale species–habitat associations. A detailed substratum classification and community assessment, often only possible using SCUBA diving, is therefore important to reach a better understanding of the functional relationships between species and their environment in northern temperate waters, knowledge that is very important with respect to the increasing environmental pressure caused by global climate change.

本研究针对北海南部硬质底质海藻生境中的底栖鱼类与十足目甲壳动物群落的微尺度空间分布格局展开系统评估。研究采用沿样带布设的样方法，原位测定鱼类与甲壳动物的丰度，并分析其与底质类型（岩石、砾石及大卵石）及藻类密度的关联。本次调查共记录6种优势鱼类与4种优势甲壳动物，其中岩锦鱼（Ctenolabrus rupestris）为鱼类群落的绝对优势种，鳞突铠甲虾（Galathea squamifera）为甲壳动物群落的优势种。底质类型对微尺度分布的影响强度显著高于优势藻类的密度。海藻对鱼类丰度存在负调控效应：海藻床内的鱼类平均密度显著低于邻近开阔区域。综合所有底质类型来看，大卵石是对鱼类吸引力最强的底质。与之相反，甲壳动物未表现出明确的底质偏好。研究结果清晰表明，与其他复杂生态系统类似，北温带硬质底质生境中存在显著的微尺度物种-生境关联。但由于该类生境的环境条件通常较为严苛，其采样工作主要依赖搭载采样设备的船舶完成，所得数据无法解析小尺度的物种-生境关联。因此，细致的底质分类与群落评估（通常仅可通过水肺潜水实现），对于深入理解北温带水域物种与环境间的功能关系至关重要——在全球气候变化带来的环境压力日益加剧的背景下，这类认知具有极高的实践价值。