Assessment of Caspian Seal By-Catch in an Illegal Fishery Using an Interview-Based Approach

Abstract

The Caspian seal (Pusa caspica) has declined by more than 90% since 1900 and is listed as endangered by IUCN. We made the first quantitative assessment of Caspian seal by-catch mortality in fisheries in the north Caspian Sea by conducting semi-structured interviews in fishing communities along the coasts of Russia (Kalmykia, Dagestan), Kazakhstan and Turkmenistan. We recorded a documented minimum by-catch of 1,215 seals in the survey sample, for the 2008–2009 fishing season, 93% of which occurred in illegal sturgeon fisheries. Due to the illegal nature of the fishery, accurately quantifying total fishing effort is problematic and the survey sample could reflect less than 10% of poaching activity in the north Caspian Sea. Therefore total annual by-catch may be significantly greater than the minimum documented by the survey. The presence of high by-catch rates was supported independently by evidence of net entanglement from seal carcasses, during a mass stranding on the Kazakh coast in May 2009, where 30 of 312 carcasses were entangled in large mesh sturgeon net remnants. The documented minimum by-catch may account for 5 to 19% of annual pup production. Sturgeon poaching therefore not only represents a serious threat to Caspian sturgeon populations, but may also be having broader impacts on the Caspian Sea ecosystem by contributing to a decline in one of the ecosystem’s key predators. This study demonstrates the utility of interview-based approaches in providing rapid assessments of by-catch in illegal small-scale fisheries, which are not amenable to study by other methods.

Inter-year variation in pup production of Caspian seals Pusa caspica 2005–2012 determined from aerial surveys

“…It is classified as Endangered by the IUCN , and continues to be affected by a number of threats, including humancaused mortality and habitat loss (Härkönen 2008, Härkönen et al 2012, Dmitrieva et al 2013. Reliable estimates of abundance and reproduction are crucial for monitoring the status of the species and facilitating discussions with regional stakeholders on mitigation, conservation and management issues.…”

Individual variation in seasonal movements and foraging strategies of a land-locked, ice-breeding pinniped

“…During formation of the ice sheet most animals moved into the centre of the north basin and were located along the ice edge or within the ice field around the 'Saddle' area. Their locations overlapped with areas of high seal density identified from concurrent aerial population surveys in February in 2010 to 2012 (Dmitrieva 2013, Dmitrieva et al 2015.…”

“…The tagging of moulted pups on the ice would contribute to understanding movement and habitat use of juveniles. Overall, the data suggest that Caspian seals are likely to have little population structure since they disperse throughout the whole Caspian from the Komsomolets Bay moulting site, and during the winter animals ranged through the whole breeding distribution in the ice pack identified from aerial surveys (Dmitrieva 2013, Dmitrieva et al 2015. Such long range dispersal, high mobility, and aggregated breeding is comparable with other ice-breeding species with weak population structure, such as ringed seals in the Arctic, where the annual life history is governed by seasonal and spatial separation of breeding substrate and food resources (MartinezBakker et al 2013); hooded seals in the North Atlantic where migration patterns reflect favourable foraging conditions (Coltman et al 2007, Andersen et al 2013; and in Weddell seals (Chambert et al 2015).…”

“…Areas used by seals along the western coast also overlap with commercial fishing grounds. The north Caspian, which is an important year round habitat used for moulting, transit, foraging, resting and breeding, is an area of intensive oil and gas development and has high levels of sturgeon poaching activity which generates substantial bycatch of seals (Dmitrieva et al 2013). In view of these environmental pressures, telemetry data can help assess impacts from human activities and contribute to conservation measures such as defining protected areas which encompass critical habitats for Caspian seals.…”

“…It is subject to a range of threats including high levels of mortality from fishing by-catch and other anthropogenic sources, and habitat loss and disturbance caused by industrial and urban development. Impacts on food webs from invasive species and overfishing, disease, pollution and climate change may pose additional threats but are poorly studied (Härkönen 2008, Här -könen et al 2008a, Dmitrieva et al 2013.…”