Fishing and other anthropogenic impacts have led to declines in many fish stocks and modification of the seabed. As a result, efforts to restore marine ecosystems have become increasingly focused on spatially explicit management methods to protect fish and the habitats they require for survival. This has led to a proliferation of investigations trying anthropogenic impacts and identify fish resource requirements in order to meet conservation and management needs.A wide range of habitat-related concepts, with different uses and understandings has arisen as a consequence. Inconsistencies in terminology can cause confusion between studies, making it difficult to investigate and understand the ecology of fish and the factors that affect their survival. Ultimately, the inability to discern the relationships between fish and their environment clearly can hinder conservation and management measures for fish populations.This review identifies and addresses the present ambiguity surrounding -related concepts currently used in spatial management of demersal marine fish populations. The role of spatial and temporal scales is considered, in addition to examples of how to assess fish habitat for conservation and management purposes.

The protection of species requires an understanding of their habitat requirements and how habitat characteristics affect their distribution, survival and growth. This need is especially important in areas where anthropogenic pressures can not only have a significant direct impact on the survival of the species but also damage their habitat. The Firth of Clyde in southwestern Scotland was an important commercial fishing area for a variety of demersal fish species up until 1973. However, stocks rapidly declined thereafter and the catch of targeted species ceased in 2005, despite fisheries measures put in place to aid recovery. Changes in the availability and quality of fish habitat are possible explanations for this lack of recovery. Here, we report on stereo baited remote underwater video surveys in the Firth of Clyde between June and September in 2013 and 2014 to determine the habitat of juvenile Atlantic cod Gadus morhua, haddock Melanogrammus aeglefinus and whiting Merlangius merlangus. Habitat predictor variables explored included substratum type, depth, wave fetch, and epibenthic and demersal fauna diversity. G. morhua were most abundant in shallow, sheltered areas composed of gravel−pebble containing maerl. M. aeglefinus and M. merlangus predominated over deeper sand and mud. Ontogenetic shifts in all 3 species were also observed. Relative abundances of G. morhua and M. merlangus were positively related to the diversity of epibenthic and demersal fauna. Our results indicate that spatial conservation measures to benefit demersal fish should be advised by patterns of epibenthic and demersal fauna diversity as well as physical substratum types.

Distribution and life history trait models indicate vulnerability of skates. Progress in Oceanography, Elsevier, 2020, 181, pp.ABSTRACT Elasmobranchs are k-strategy species with low reproduction rate and slow growth lending to increased anthropogenic vulnerability. Specific management measures to improve the conservation of elasmobranchs can be problematic due to insufficient information on their biology and ecology. Here, three sympatric skates occupying north-eastern Atlantic waters, which have differing conservation status were studied within ICES divisions 4.c, 7.d-e, 7.f-h and 8a-b and d. Fisheriesdependent data on skate bycatch and a series of environmental variables were used to model spatio-temporal differences in habitat use between the three species. Raja undulata, the undulate ray (IUCN red listed as 'Endangered') was observed to have a coastal distribution within the English Channel and the Bay of Biscay (ICES division 7.d-e and 8.a-b). Raja clavata, the thornback ray ('Near threatened'), had a broader distribution with higher presence in the eastern English Channel and the southern North Sea (ICES division 7.e and 4.c). Raja montagui, the spotted ray's probability of presence ('Least concerned') was higher 1 Corresponding author. E-mail address: sophie_elliott@yahoo.com, telephone: (+33) (0) 2 23 18 58 83 off the coast of southern Ireland (ICES division 7.g). Seasonal and life-history trait differences were also observed.From the fisheries-dependent data, wider skate distributions than previously studied were modelled. Although the species do co-occur, spatio-temporal differences between these species were observed. This study contributes to a greater understanding of skate habitat during their different life history stages, and indicates reasons for R. undulata's increased vulnerability than R. clavata and R. montagui. Information from the distribution models could be used for specific spatio-temporal management measures. Better understanding of the distribution of species can also help reduce bycatch of protected species such as R. undulata.

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