A comparison of fishing methods to sample coastal fish communities in temperate seagrass meadows

Abstract

In the face of ongoing habitat destruction and biodiversity loss, adequate sampling methods for coastal fish communities are required to conduct sound ecological research and reduce sampling impacts in vulnerable habitats like seagrass meadows. However, different active and passive fishing methods might only capture specific fragments of fish diversity, varying in their catch efficiency for certain species and traits. To aid scientists with their choice of sampling methodology, we compared 5 common fishing methods (multimesh gillnet, eelfyke, minnow trap, bottom trawl, beach seine) to test how efficiently they display taxonomic and trait diversity of seagrass fish communities and whether their catchability differs between seasons. Among passive methods, gillnets captured the highest and minnow traps the lowest fish diversity (abundance, species richness, Shannon index, trait richness, trait dispersion). Seasonal differences in fish diversity were observed when comparing beach seines and bottom trawls to gillnets. Active methods displayed increased fish diversity from summer until autumn, which is likely linked to seasonal variations in community composition among methods, i.e. active methods had a higher catchability for gobies, sticklebacks and pipefish, representing typical seagrass inhabitants. Abundances of specific species and traits (e.g. body size, vertical habitat use) differed among methods, suggesting that fishing methods complement each other in sampling fish communities. Therefore, to obtain a holistic picture of fish diversity in seagrass meadows, at least 2 fishing methods should be combined (e.g. gillnet and 1 active method), while specific methods might be sufficient to target certain species or traits dependent on the research objective.