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床生境中的底栖鱼类与十足目甲壳动物集合群落的微尺度空间分布格局展开评估。研究采用沿样线布设样方的方法，原位调查了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。本研究共记录到6种优势鱼类与4种优势甲壳动物，其中岩生隆头鱼（Ctenolabrus rupestris）为鱼类群落的绝对优势种，鳞形铠甲虾（Galathea squamifera）则为甲壳动物群落的优势种。底质类型差异对微尺度分布的影响显著强于优势藻类的密度。海藻床对鱼类丰度具有负调控效应：相较于邻近开阔区域，海藻床内的鱼类平均密度显著更低。综合所有底质类型来看，鱼类最偏好的底质为大卵石。与之相反，甲壳动物并未表现出特定的底质偏好性。研究结果明确显示，与其他复杂生态系统类似，北部硬质底质生境中存在显著的微尺度物种-生境关联。然而，由于该区域环境条件常较为严酷，此类生境主要通过搭载采样装置的船只进行采样，所得数据无法用于解析小型尺度的物种-生境关联。因此，详细的底质分类与群落评估（通常仅可通过水肺潜水完成），对于深化理解北温带海域物种与环境间的功能关系至关重要；在全球气候变化引发的环境压力日益加剧的背景下，此类认知具有极高的现实意义。