The diversity, distribution and status of deep‐water elasmobranchs in the Rockall Trough, north‐east Atlantic Ocean

Abstract

Data from a scientific deep-water trawl fisheries survey in the north-east Atlantic were analysed to determine the spatial and bathymetric distribution of elasmobranch species and assess the change in relative abundance over the period 1998-2013. During this period, commercial fisheries for deep-water sharks went from being entirely unregulated, to being briefly managed, to being completely prohibited. A total of 22 species of shark and 10 species of skate were recorded between depths of 300 and 2030 m. All showed strong species-specific depth-related trends in abundance. Out of the 11 more common species, five showed no change in relative abundance over time, two (Centrophorus squamosus and Centroselachus crepidater) declined significantly and four increased in relative abundance (Apristurus aphyodes, Apristurus microps, Galeus melastomus and Deania calcea). Assuming these populations were depleted by fisheries in the past, the current data do not suggest there has been an overall recovery. Positive signs for some species in the most recent years suggest movement or recruitment back into the area; however, it is of concern that two species continued to decline. There is a continued need to have precautionary management of these elasmobranch species, and the current ban on landing these species in European waters remains appropriate.

Near equal compressibility of liver oil and seawater minimises buoyancy changes in deep-sea sharks and chimaeras

“…Twenty-one species of sharks and chimaeras were captured from the NE Atlantic Ocean from 24 August to 1 September 2018 at depths from 350 to 1830 m on the continental slopes west of Scotland (2.4-9.9°W, 59.1-60.1°N) by the FRV Scotia V using a BT184 otter trawl (Jackson, Peterhead, UK) (Neat et al, 2015). Fish were weighed, measured and the livers removed and frozen.…”

Assessing ecological and molecular divergence between the closely related species Hydrolagus pallidus and H. affinis (Chimaeridae)

“…The north‐east Atlantic Ocean is an area of deep‐water fishing activities (Gordon, ) that experienced a rapid decline in fish stocks in the 1990's (Bailey , ). These populations have since stabilized but have not recovered (Neat & Burns, ; Neat et al, ). Only deep‐water taxa that live below 1500 m escape heavy fishing pressure (Clark & Koslow, ).…”

Preliminary observations on abundance and distribution of fish fauna in a canyon of the Bay of Biscay (ICES Division 8c)

“…Most of the ecological studies of fish assemblages that address geographic distributions, diversity, biomass and abundance in European Continental (Atlantic) waters have been based on trawl surveys. However, these surveys do not usually cover strata deeper than 600 m (ICES, 2018), and few are specifically designed for sampling deep-water species (Massutı & Moranta, 2003;Neat et al, 2015). In many areas, such as the Iberian continental shelf, trawling is not suitable, either due to the rocky bottoms, because they can affect protected areas and coral reefs, or because trawling is forbidden.…”

“…The Basque continental shelf (ICES Division 8c east) is characterized by its narrowness and rocky bottom. Beyond the 200 m depth there is a steep slope with submarine canyons often obliquely oriented to the shelf (Pascual et al ., 2004). These canyons can reach a depth of 2500–3000 m and connect to the Biscay Abyssal Plain below 4500 m in depth.…”