Evidence Gap FF.10: Essential fish habitat (EFH)
Review of current knowledge
Essential Fish Habitats (EFH) are those necessary to support critical fish life stages, such as spawning, feeding or growing to maturity. These habitats are of key importance to ensuring the viability of fish populations and the provision of associated ecosystem services. As a result, EFH are of interest when considering the potential impacts of marine activities, including MRE projects.
Early information on the distribution of sensitive fish habitats around the UK (i.e. spawning and nursery grounds identified in Coull et al 1998, Ellis et al 2012) is considered insufficiently resolved for the use in marine planning (MMO 2013a). The lack of high-resolution data on EFH constitute a major limitation for the reliable identification of high value habitats and their practical consideration in the marine planning process (MMO 2016). In order to address this data gap and develop methodologies to improve the resolution of EFH, significant research has been undertaken in recent years.
For instance, the MMO developed spatial models of EFH in respect of the South Inshore and Offshore Marine Plan areas in 2013 (MMO 2013a). Under this project models were produced to identify the environmental conditions associated to the presence of adult foraging habitats, nursery habitats and spawning grounds for selected fish species. These models informed the production of maps showing the spatial distribution of EFH, illustrating probability of occurrence of adult, juvenile and eggs/larval stages. In 2016 a follow up study was undertaken to validate the EFH maps produced in 2013 against new data and expert judgement. In addition, the follow up study aimed to identify additional data from fish surveys and environmental data layers and assess the acceptability of the MMO (2013a) approach as a tool to support marine planning (MMO 2016).
EFH maps have also been produced for key commercial fish species in the Irish Sea by the Agri-Food and Biosciences Institute (AFBI 2021) and various models to predict spawning across the North Sea have been recently developed for species such as cod (González-Irusta and Wright 2015), haddock (González-Irusta and Wright 2016) and whiting (González-Irusta and Wright 2017). In addition, existing UK fisheries sensitivity maps were updated in 2014, based on models which combine observations of species occurrence with environmental data, to provide information on the most likely locations for aggregations of fish during their first year (Aires et al 2014).
Research is currently on-going to develop new spatially predictive EFH models nationally under project "Essential Fish Habitat Validation (MMO1133)" (MMO, 2021). Whilst this is expected to continue development of previous MMO commissions (MMO 2013a, MMO 2016) it is also considering other models. In addition to fish, future research should give consideration to the possibility of modelling shellfish species, particularly species of commercial importance (MMO 2016).
In the particular case of inshore waters, it should be noted that their inclusion in EFH models is constrained by the reduced spatial coverage of suitable fish survey data that exists for these areas (MMO 2016). Further information on this topic is provided under "Evidence Gap FF.12. Inshore populations/distribution".
Next steps in research
As described in the literature review presented above, high-resolution data on EFH is currently only available in specific areas within the UK and, in some cases, data is only available for specific species. To date, the mapping of essential habitats has been focused on fish with limited consideration of shellfish species. In addition, there is limited data currently available in relation to the distribution of fish and shellfish in inshore areas.
In order to address current evidence gaps, the development of consistent EFH mapping approaches across the UK is strongly recommended. In addition, the inclusion of shellfish species, particularly those of commercial importance (i.e scallops, Nephrops, crab, lobster, whelk), should be given due consideration in future mapping exercises.
The above would facilitate assessing impacts on essential habitat across different regions in a consistent manner for key fish and shellfish receptors and improve the evidence base available to inform cumulative assessments.
Next steps in research specifically focused on improving data on the distribution of fish and shellfish species in inshore waters are discussed in detail "Evidence Gap 12: Inshore populations/distribution".
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