Trophic ecology and seasonal occurrence of two Red List fish species in the Western Baltic Sea—two of a kind?

Abstract

Improving the conservation status and the management of Red List species requires knowledge on the biology and distribution of the organisms as well as an evaluation of the appropriateness of management measures. This study provides information on the trophic ecology and seasonal abundances of two Red List fish species from the Western Baltic Sea, snake blenny Lumpenus lampretaeformis (Walbaum, 1792), classified as “critically endangered” according to the German Red List, and eelpout, Zoarces viviparus (Linnaeus, 1758), classified as “near threatened” based on the HELCOM Red List. Beam trawl surveys were conducted to document abundances of both species in summer and winter in a marine protected area (MPA), where mobile bottom-contacting fishing gears will be excluded in the near future. The MPA is located in the German EEZ (exclusive economic zone) and aims to protect sandbank and reef habitats. Stomach content and stable isotope analyses (nitrogen and carbon) were performed to examine the diet of eelpout and snake blenny. To be able to position the two fish species in the food web, stable isotopes of macrozoobenthos, POM (particulate organic matter) and sand goby (Pomatoschistus minutus) were analysed as well. Eelpout and snake blenny were present in the study area in summer and winter, but reached higher abundances in summer. Diet composition overlapped strongly reflected by a similar trophic level, indicating potential food competition of the two species. Prey items were dominated by macrozoobenthos (Mollusca, Annelida, Arthropoda). Our study provides new information on the trophic position and seasonal abundance of the two fish species within an area soon to be placed under protection from mobile bottom-contact fishing. It therefore also provides a baseline to evaluate potential positive repercussions following the exclusion of mobile bottom-contacting fishing gears and might thus help to increase the understanding of fishing impacts on benthic ecosystems contributing to more effective conservation and management measures.