What is the state of our coastal fish community?

Background and Objective

The aim of the European Marine Strategy Framework Directive (MSFD) from 2008 comprises reaching a good environmental status in the seas of the European Union. In this context, EU member states develop strategies for their respective marine areas. This includes:

• assessing the current status of marine areas and describing a good environmental status
• determining environmental targets and developing indicators that adequately mirror the environmental status
• developing monitoring programs and programs of measures to continuously monitor the environmental state and to reach or maintain a good environmental status.

Coastal fish are an important component in marine ecosystems: through their position in food webs as predators, but also as prey organisms, they connect different trophic levels and contribute to ecosystem functioning. Furthermore, they play an essential role in small-scale commercial coastal and recreational fisheries. Therefore, the MSFD also aims to assess the state of the coastal fish fauna. Coastal fish monitoring is already conducted in several neighbouring states of the Baltic Sea considering the HELCOM guidelines. However, various spatial and temporal monitoring gaps exist and methodologies are not yet uniform and standardized across and within countries. So far, no standardized coastal fish monitoring is conducted along the German coast of the Baltic Sea.

Therefore, the aim of the FishNet - project is to develop a concept for a standardized coastal fish monitoring for the coastline of Schleswig-Holstein. The future long-term monitoring will serve to describe and evaluate the state of the coastal fish community by means of suitable indicators. Moreover, information will be gathered on the MSFD descriptors 1, 2, and 4 (biodiversity, non-indigenous species, food webs) and on endangered (red listed) fish species within German coastal waters.

Approach

Sampling of the coastal fish fauna takes place in seven areas along the coast of Schleswig-Holstein between Lübeck Bay in the south and the Inner Fjord of Flensburg in the north. To account for different environments, coastal fish are sampled in five habitat types within these areas, including:

• seagrass meadows
• rocky reefs
• bare sand areas
• blue mussel beds
• bladderwrack belts

To capture a broad size and species spectrum, different active and passive fishing gear are used for sampling:

• multimesh gillnets („Coastal surveynet“)
• fyke nets (“eelfykes”)
• beach seines
• a small bottom trawl (“Youngfish trawl”)

Between 2021 and 2023, the coastal fish community was sampled in all seasons (KüFi3). Based on the data collected, a pilot monitoring will be conducted between 2024 and 2029 (KüFi4). Within each year, fish will be sampled two to three times in spring and summer. FishNet Ostsee is closely working together with its sister project “FishNet Nordsee”, which coordinates the coastal fish monitoring for Schleswig-Holstein’s North Sea coast.

Data and Methods

Data collected during coastal fish sampling comprise: number of individuals, species richness, fish size and weight. Within KüFi4, the feeding ecology and the concentration of contaminants in tissue will be analysed additionally. The habitats, i.e., sampling stations, are characterized by means of recording environmental variables, such as water temperature, salinity and oxygen content. Based on the data collected, the species composition and biodiversity of the coastal fish fauna is described, shedding light on the significance of the examined habitats for coastal fish. In this context, indicators are developed and tested that adequately assess the state of the coastal fish community.

Preliminary Results

In total, 52 fish species were recorded in KüFi3 (2021-2023). The species composition differed distinctly between the five habitat types. For instance, pipefish, gobies and sticklebacks were predominantly caught in seagrass meadows, while small sandeels dominated on bare sand. Species richness was highest in all habitats in summer (August/September) and the majority of small/juvenile individuals was caught between June and September. Since the species composition and biodiversity of fish depended strongly on the fishing method used (selectivity of fishing gear), we will continue sampling with different fishing methods to capture a broad species spectrum.

Links and Downloads

FishNet Nordsee: www.nationalpark-wattenmeer.de/wissensbeitrag/fishnet/