Marine Debris Project Final Report 2014

Entanglements were primarily observed between July and September. Most entanglements were recordedat Seal Rocks which had a particularly large portion of the observations with location information (N=138).Seal Rocks also had observations in every month except January, based on the 95 records with dates.Seals in the Bass Strait are subject to entanglement dangers from a variety of objects, most of which areassociated with fishing activities. Net characteristics such as material type correlate with strongly with sealentanglement. Our results are consistent with other researchers finding of predominant entanglingmaterials, i.e. trawl nets, monofilament lines and packing straps (Croxall, et al. 1990; Pemberton, et al.1992; Fowler, 1988). We also found incidental entangling items such as plastic bags, plastic sheet, rubber“o” rings and cloth described in other entanglement studies (Shaughnessy, 1980; Fowler, 1988; Croxall, etal. 1990).Net colour also plays an important role in ensnaring Australian fur seals, with green nets being the mostcommon coloured net entangling seals in the region. It is unclear whether this is due to the type of fishingindustries conducted in Bass Strait or because there are more green nets used by the fishing industry ingeneral. It has been noted that green nets can be bought very cheaply and are now used widely (J.Bulbrook, pers. comm., 5 Feb 2014) suggesting the latter. In a sample of nearly 9,000 nets washed ashore innorthern Australia, Wilcox, et al. (2014) found that green nets were overwhelmingly common. With regardto monofilament, seals were most frequently entangled in clear monofilament line. Clear monofilament isused widely in both the recreational (hand line, gill net) and commercial (gill nets, long line) fishingindustries in southern Australian waters.We found that young seals were more likely to be observed as entangled than adult seals, similar to resultsfrom other entanglement studies in Australia (Pemberton, et al. 1992; Page, et. al, 2004) and around theworld (Fowler 1988; Croxall, et al. 1990; Fowler, et al. 1990). This may be because of curiosity andplayfulness of young animals (Pemberton, et al. 1992). It could also be a function of mesh size (smallernecks and limbs pass through easier) (Fowler, 1987; Bengtson, et al. 1988; Fowler, et al. 1990; Pemberton,et al. 1992).Resighting data suggests that on any given survey one would see only a fraction of the animals that areentangled, adding to possible under estimation of entanglement rate. Nine of the sites had resight datawith resighting rates between 32 and 64 percent. So, on any given day between half and two thirds ofentangled seals may not be seen. However, if seals are entangled for long enough, and if the animalsremain at the colony for an extended period, these animals will have additional chances of being seen. Pups38 | Understanding the effects of marine debris on wildlife