Distribution and abundance of skates (Bathyraja spp.) on the Kerguelen Plateau through the lens of the toothfish fisheries

• Published in: Fisheries Research
• Main Authors: Nowara, G.B., Burch, P., Gasco, N., Welsford, D.C., Lamb, T.D., Chazeau, C., Duhamel, G., Pruvost, P., Wotherspoon, S., Candy, S. G., Candy, S.G.
• Other Authors: Australian Antarctic Division (AAD), Australian Government, Department of the Environment and Energy, Institute for Marine and Antarctic Studies Hobart (IMAS), University of Tasmania Hobart, Australia (UTAS), Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: Bathyraja sp; Sub-Antarctic; By-catch; Zero-inflated models; GAM and GLM; [SDV.BID]Life Sciences [q-bio]/Biodiversity; Antarctic; Kerguelen; Heard Island; Kerguelen Islands; Indian; Heard; McDonald Islands; Gam; Antarc*; Icefish; Patagonian Toothfish
• Online Access: https://hal-mnhn.archives-ouvertes.fr/mnhn-01610142; https://doi.org/10.1016/j.fishres.2016.07.022

International audience hree species of skate, Bathyraja eatonii, B. irrasa and B. murrayi, are commonly taken as incidental by-catch in Patagonian toothfish (Dissostichus eleginoides) longline and trawl fisheries, and the mackerel icefish (Champsocephalus gunnari) trawl fishery on the Kerguelen Plateau (KP) in the southern Indian Ocean. Data from fishery observations for 1997–2014 shows that the three skates were widely distributed across the Kerguelen Plateau, showing different spatial distributions, linked mainly with depth. Off Heard Island and McDonald Islands (HIMI), in the southern part of the KP, B. eatonii and B. irrasa were most abundant to the north and northwest of Heard Island, out to the edge of the Australian Exclusive Economic Zone (EEZ), and were caught down to depths of 1790 m and 2059 m respectively. The smallest species, B. murrayi, occurred mainly in the shallower waters down to 550 m, and was most abundant to the north and northeast, close to Heard Island. Around Kerguelen Islands, in the northern part of the KP, skates were most abundant between the 500 m and 1000 m contours circling and extending from the islands.Catch rates were modelled using zero-inflated GAMs and GLMs. The catch rates of skates from the trawl fisheries in the Australian EEZ surrounding Heard Island and McDonald Islands have shown little evidence of depletion on the main trawl fishing grounds, although there is evidence of a decrease in the average total length of B. eatonii. The marine reserves and the conservation measures employed by the Commission for the Conservation of Antarctic Marine Living Resources in the HIMI fisheries, appear to provide effective protection for the skates, at least in the shallower waters where the trawl fisheries operate. B. irrasa taken in the deeper waters where longline fishing occurs have shown a slight decline in catch rate over the years of the HIMI fishery. Although all skates are returned to the water from this fishery, survival rates are unknown and careful monitoring should ...