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.

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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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.

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River infrastructures such as weirs, hydropower stations or water reservoirs represent obstructions to migration for diadromous fish. Knowledge of accurate behaviour of fish in front of such structures is required to protect migrants from hazardous areas, guide them towards safe passage or adapt structure to improve the escapement. We developed and made available a method to process acoustic telemetry data based on Time Difference Of Arrival analysis to accurately locate tagged fish. Improved accuracy allows the detection of escape routes and description of dam‐crossing tactics. Sixteen tagged eels were tracked with high accuracy (1–2 m) and ~1 location min−1 frequency during their exploration period on reaching the dam. Two migration routes (spillways and bottom compensation flow pipe) were used by 77% and 23% of eels respectively. Spillways were the preferred route, but a median of 16 days were required to pass the dam versus 1.1 days via the compensation pipe. A minimal water crest of 40 cm was required for passage via spillways. Eels passing through the compensation pipe were exclusively nocturnal and mainly explored the bottom of the dam. Eels passing through spillways explored the whole dam area by night and day, and were not attracted to the compensation pipe entrance. With global warming, more frequent drought periods are expected, potentially leading to decreased opportunities for eels to migrate across safer dams by spillways. To conserve this endangered species, dam management strategies that account for expected hydrologic conditions and distinct exploration behaviours are needed.

Lampreys are ancestral jawless vertebrates with particularly complex life histories. Population declines resulting from increased anthropogenic pressure have been observed. For semelparous diadromous lampreys, the marine phase remains largely a black box, making targeted management and conservation measures difficult to implement. Here, we collated a database of 168904 hauls from both fisheries-dependent and fisheries-independent surveys between 1965 and 2019. Lampreys were observed in only 254 hauls (<1% lamprey presence); 421 sea lamprey Petromyzon marinus and 300 European river lamprey Lampetra fluviatilis were identified. Sizes ranged from 13 to 92 cm and from 14 to 42 cm, respectively. The majority of lampreys (61%) were caught by mobile demersal gear types. The highest presence of both species was recorded within the Greater North Sea, followed by the Bay of Biscay. L. fluviatilis was observed closer to the coast than P. marinus. For both lampreys, there was an increase in size with distance from the coast. P. marinus were predominantly <60 cm and observed from August to February, indicating that these were sexually immature juveniles migrating out to sea. For L. fluviatilis, the majority were thought to be adults (>20 cm) and occurred in autumn, indicating inshore migration. Our observations provide insight into the ecology of lampreys at sea and highlight study locations and gear types, which may be more pertinent for future research. Greater awareness is needed during surveys to collate catch information on lampreys and improve understanding of their ecology and phenology at sea.

Evaluating the effectiveness of management measures on skates in a changing world ABSTRACT Global declines in elasmobranchs have been observed. Conservation measures such as area closures and fisheries prohibitions have been put in place to support the recovery of vulnerable species. However, the effectiveness of such measures is rarely evaluated in the context of other factors that may affect population abundance. This study investigates the effectiveness of management measures using 1) General additive mixed model derivative changes, taking into account environmental factors that may affect population stochasticity and 2) an age-structured density dependent population dynamic model. The Raja undulata (undulate ray) 2009 targeted fisheries prohibition was used as a case study.Potential beneficial responses on sympatric species Raja clavata (thornback ray) were modelled.A significant increase in abundance was observed in both IUCN red list species during the ban. Surface seawater temperature had a marginal effect on the abundance of both species. The prohibition was in place for an insufficient length of time for long lasting effects to be detected on skate length. The population dynamic model indicated that the increase in abundance was only possible when combining the fisheries ban with increased juvenile discard survival. Our results indicate that species conservation measures may not only have positive effects on the species in question, but also on species with a niche overlap. Nonetheless, due to ongoing fishing for other species, the full potential of fisheries prohibitions may not be realised. For real benefits to be assessed, evaluation of bans should take place once a steady state is observed.