Presence of European sea bass and other species in proposed bass nursery areas
Presence of European sea bass (Dicentrarchus labrax) and other species in proposed bass nursery areas
Applies to England and Wales
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Juvenile sea bass occupy nursery grounds in estuaries and coastal areas for up to their first six years of life during which time they are subject to being bycatch in fisheries. Bass Nursery Areas (BNAs) were designated in England and Wales in the 1990s to reduce the impact of commercial and recreational fishing in areas where the majority of sea bass were likely to be below the minimum conservation reference size (MCRS – formerly, minimum landing size (MLS)) established in UK and EU legislation. In total, 37 estuaries and other coastal sites were designated as BNAs and additional restrictions on commercial and recreational fishing were imposed. These are thought to have played an important role in protecting the stock, possibly generating changes in size distribution, increased juvenile survival, and improvements in the productivity of the stock.
In 2015, Defra assessed the need for changes to existing BNAs and new designations. A questionnaire was sent to the nine mainland Inshore and Fisheries Conservation Authorities (IFCAs) and the Marine Management Organisation (MMO) requesting information to support the review of BNAs. Responses were received from eight IFCAs and the MMO, that included 48 proposed amendments to the existing BNA legislation (39 new site designations, five changes of extent, and four no longer required).
In this report, the evidence for each of the 48 proposed BNA amendments was compiled to assess their importance for juvenile sea bass and related fishing activity. The importance for juvenile sea bass was evaluated from the presence, abundance, and distribution of sea bass, and the extent of important sea bass habitat (e.g., salt marsh, intertidal areas). Juvenile was defined as fish being of length less than 36 cm. No comprehensive data sets were available, so it was necessary to collate a number of different sources. Data were compiled for abundance of sea bass from the Environment Agency (EA) sampling of estuaries and coastal waterbodies, Solent and Thames bass surveys, Thames Herring Survey, Cefas Young Fish Survey, power station screens, local IFCAs, and non-governmental organisations (NGO) surveys, and other sources (e.g., species records). Physical data on the temperature, salinity, and size, and habitat characteristics were sourced from the EA. Commercial fishing was assessed from landings in the adjacent International Council for the Exploration of the Sea (ICES) statistical rectangle and presence of commercially exploited fish within the BNA.
Different levels of evidence existed that were collected in varying ways for each area; hence, making direct comparison across areas impossible. Sufficient data were available to ascertain the presence of juvenile sea bass for 22 out of the 48 proposed amendments, but for another 22 limited or no evidence existed. Where data were available, they were not of sufficient resolution to generate spatial distributions of juvenile sea bass within each area or changes throughout the year. The remaining four proposed amendments related to the removal of BNAs no longer benefiting from warm water outflows due to decommissioned power stations. In those cases, the proposed amendment was reasonable as the feature had been removed, but broader protection could be considered where there was evidence of the presence of juvenile sea bass in the estuaries within which the power stations were located (e.g., Bradwell in the Blackwater, Kingsnorth in the Medway).
Site designation amendments that extend the BNAs will provide additional protection, but this depends on how much of the total recruitment of sea bass to local populations is sourced from each area. This could not be assessed from the current data as the report uses a range of local surveys to indicate the presence and size of juvenile sea bass, not the total abundance of juveniles in the water body. Further work is recommended within nursery areas to understand the distribution of sea bass, the nature and extent of commercial fisheries, levels of discarding, and the relative contribution of individual nursery areas to the stock.