Entanglement of Australian fur seals in man-made debris in Tasmanian waters

Abstract

Observations were made of neck collars of man-made debris on Australian fur seals in Tasmanian waters. These included 47 sightings on six breeding colonies in Bass Strait and 22 on five haul-out sites, one in Bass Strait and four in southern Tasmania. The incidence of entanglement of the population calculated for the southern waters was 1.9 +/- 0.7% (n = 10). Of items identified, polyethylene trawl-net accounted for 40% of neck collars, polypropylene packaging straps 30%, monofilament nets (gill nets) 15% and nylon rope 15%. A variety of colours of polypropylene straps were observed, which indicate a variety of sources of the material. The majority, 66%, of entangled animals were juveniles or subadults; a further 16% were non-breeding adult males and 18% were breeding adults. The neck collars were causing obvious physical injury to 73% of the animals observed and in the two worst cases the collars had cut through the oesophagus. Collars made of traw1.net are the greatest cause for concern as they are large, buoyant and originate from a fishery that is increasing in size and produces a lot of debris. The high incidence of neck collars on Australian fur seals indicates that entanglement is a potential threat to the seal population. This effect may not be reflected in the number of pups born until the animals currently being entangled reach breeding age.