Using fish ‘feeding guilds’ reveal ecosystem structure and function
Analysis of food webs can reveal system-level phenomena, such as whether the structure and functioning of an ecosystem is stable or changing, that cannot be detected by studying focal species or assemblages alone.
Food web indicators have been explicitly called for to inform policy via status assessment as part of the indicator toolkit supporting the OSPAR Convention, the EU’s Marine Strategy Framework Directive and national reporting (e.g. UK Marine Strategy). However, the substantial investment required to routinely monitor marine food webs and the lack of internationally agreed approaches to assessing them has hampered the development of marine food web indicators.
Our new research uses cluster analysis to classify fish into ‘feeding guilds’ based on diet and life stage information (Fig. 1). These include fish which tend to feed on zooplankton (‘planktivores’), prey found on the seabed (‘benthivores’) or other fish (‘piscivores’). We then show how the distribution (Fig. 2) and dynamics of feeding guild biomasses in the North Sea can be used to understand change in marine ecosystem structure and functioning in response to environmental change. Our approach is designed so it can be routinely updated with new data (including new diet data) and replicated globally where similar information exist.
For more information, read the paper in the Journal of Applied Ecology.
Fig. 1. Our proposed fish feeding guilds based on diet and life stage (letter codes represent taxa and size category, e.g. COD.L = large cod) applicable as a food web indicator to support ecosystem-based management via food web status assessment.
Fig. 2. Mean feeding guild biomass distribution between 1985 and 2014 across ICES statistical rectangles in the North Sea.