CCAMLR

Acoustic harassment devices (AHDs) have been increasingly implemented in various fisheries that suffer significant losses caused by odontocete depredation. However, the efficacy of AHDs to deter odontocetes from fishing gear remains poorly investigated. To determine the effectiveness of AHDs in deterring depredation we experimentally tested a high amplitude device (195 dB re 1 μPa 6.5 kHz 1 m from the source) from a Patagonian toothfish longliner operating off the Crozet Islands while it was subjected to heavy depredation by killer whales. This species usually depredates longlines within a 10 - 300 m range from the vessel, as they only have access to fishing gear during hauling. We expected this distance to increase in response to the acoustic disturbance created by the AHD. The distances of 29 killer whales from the vessel (n = 1,812 records) were collected during 45 phases of AHD activation and 30 phases during which the AHD was turned off. Two multi-exposed killer whale social units fled over 700 m away from the vessel when first exposed to the AHD. However, they remained within a 10 - 300 m range and depredated longlines again past the 1st and 7th exposures respectively showing insignificant behavioural response to further activations of the AHD. When tested through Generalized Linear Mixed Models (GLMMs), the effect of AHD activation was only significant when killer whales were first exposed to the device. However, the effect disappeared after successive exposures suggesting that killer whales became habituated to the AHD and may sustain potentially harmful hearing disturbance to access the resource made available by longliners. In addition to raising significant conservation concerns, this rapid return of initial depredation behaviour strongly suggests that AHDs are ineffective at deterring depredating killer whales and that fisheries should favour the use of other mitigation techniques when facing repeated depredation by this species.
 

Three fish biomass surveys have been recently undertaken in the northern part of the Kerguelen Plateau (POKER 1, 2006; POKER 2, 2010; POKER 3, 2013) with the chartered trawler FV “Austral” repeating the same random and stratified sampling stations in the bathymetric range 100 – 1000 m. Data on the bathymetric and geographical fish distribution are available for 19 bottom-dwelling species (13 neritic and 6 deep-sea for their upper bathymetric range).  The high number of stations (up to 200 each time) allows to be confident with the estimation of fish biomass ranging from 247 000 to 268 000 tons for a ground area of about 183 000 km². Patagonian toothfish (Dissostichus eleginoides), with up to 40% of the total biomass on the shelf and surrounding deep-sea, is the dominant species in terms of biomass but other species (Notothenia rossii, Channichthys rhinoceratus, Zanclorhynchus spinifer, Lepidonotothen squamifrons, Champsocephalus gunnari, Bathyraja eatonii) including never exploited fish form the bulk of the biomass. Local densities are often specific to some species. Previously overexploited species by the trawl fishery show clear and recent strong recovery. It is the case for mackerel icefish Champsocephalus gunnari and marbled notothen Notothenia rossii. Evolution of biomass of other unexploited species (i.e. Channichthys rhinoceratus), unrelated to fishery impact seems still unclear. Such study is the first ones taking into account all the fish components of a surveyed area in the Southern Ocean.
 

Proposed Research plan for the survey of Ukrainian longliner in 48.2 subarea.