Australia’s only endemic pinniped, the Australian sea lion (ASL) Neophoca cinerea, is one of the rarest sea lions (~ 14,700) worldwide and listed as “threatened” under Australian Commonwealth legislation and as “Specially Protected Fauna” under the WA Wildlife Conservation Act.

There is considerable concern among some researchers and community sectors that incidental bycatch of ASLs by commercial gillnetting may be preventing the recovery of ASL populations from their current depleted states. Goldsworthy et al (2010) recently estimated that several hundred ASLs die annually in SA due to gillnetting, indicating that there is an urgent need to explore the extent to which ASLs in WA are affected by commercial gillnetting.

WA temperate gillnet fisheries will soon commence Marine Stewardship pre-assessment and their members are acutely aware of the urgent need for research on ASL/gillnet interactions in WA, without which, they cannot achieve certification and are vulnerable to the Commonwealth’s Marine Park planning process (if that process is not based on sound information).

As the distribution of ASL colonies, foraging areas of ASL individuals, and of gillnet fishing in WA are very different from SA, the results of the SA study cannot be applied directly to the WA situation.

Goldsworthy et al. (2009) based their analyses on distance from colonies and depth, but possibly because of limited tagging and/or observer data, did not consider the direction of ASL foraging trips from breeding colonies and haul out points and may have thus overestimated ASL mortality rates due to commercial gillnetting. The accuracy of estimates of ASL/gillnet interactions has major implications for both the conservation of ASL populations and for the viability of important fisheries. Developing improved methods of analysis, e.g. the agent-based modelling approach proposed here, and comparison of results with those from existing approaches are key to facilitating sound risk assessments.