Understanding meta-population trends of the Australian fur seal, with insights for adaptive monitoring

Abstract

Effective ecosystem-based management requires estimates of abundance and population trends of species of interest. Trend analyses are often limited due to sparse or short-term abundance estimates for populations that can be logistically difficult to monitor over time. Therefore it is critical to assess regularly the quality of the metrics in long-term monitoring programs. For a monitoring program to provide meaningful data and remain relevant, it needs to incorporate technological improvements and the changing requirements of stakeholders, while maintaining the integrity of the data. In this paper we critically examine the monitoring program for the Australian fur seal (AFS) Arctocephalus pusillus doriferus as an example of an ad-hoc monitoring program that was co-ordinated across multiple stakeholders as a range-wide census of live pups in the Austral summers of 2002, 2007 and 2013. This 5-yearly census, combined with historic counts at individual sites, successfully tracked increasing population trends as signs of population recovery up to 2007. The 2013 census identified the first reduction in AFS pup numbers (14,248 live pups, -4.2% change per annum since 2007), however we have limited information to understand this change. We analyse the trends at breeding colonies and perform a power analysis to critically examine the reliability of those trends. We then assess the gaps in the monitoring program and discuss how we may transition this surveillance style program to an adaptive monitoring program than can evolve over time and achieve its goals. The census results are used for ecosystem-based modelling for fisheries management and emergency response planning. The ultimate goal for this program is to obtain the data we need with minimal cost, effort and impact on the fur seals. In conclusion we identify the importance of power analyses for interpreting trends, the value of regularly assessing long-term monitoring programs and proper design so that adaptive monitoring principles can be applied.

Remotely piloted aircraft improve precision of capture–mark–resight population estimates of Australian fur seals

“…Performing CMR, whether by ground or RPA, required that pups be marked. The focal populations in this study had previously been subject to monitoring once every five years, yet recent analysis has indicated this program lacked the necessary power to detect and interpret changes in the population, reducing the efficacy of the monitoring program (McIntosh et al 2018b). By contrast, at the larger of the sites (Seal Rocks), the two RPA-derived CMR estimates and the RPA-derived count were similar but estimated a smaller pup abundance than the ground-based CMR estimate.…”

“…Error bars show 95% confidence intervals. spatial areas (Forcada and Aguilar 2000, McMahon et al 2003, Shaughnessy and Goldsworthy 2016, McIntosh et al 2018b. In most examples, the researchers using traditional estimates are resigned to the fact that they are working with underestimates and a poor understanding of accuracy.…”

“…Additionally, survey frequency can be increased using RPAs for direct counts, because these surveys can be deployed with greater ease and less disturbance when compared to traditional techniques (Sarda-Palomera et al 2012). The focal populations in this study had previously been subject to monitoring once every five years, yet recent analysis has indicated this program lacked the necessary power to detect and interpret changes in the population, reducing the efficacy of the monitoring program (McIntosh et al 2018b). Increased survey frequency, combined with the greater precision of RPA monitoring, will improve capacity to detect change and implement management strategies.…”

“…The traditional ground-based techniques for the specific sites have been well developed and used for the past three censuses (Kirkwood et al 2005, McIntosh et al 2018b). However, RPA surveys are a novel technique that has not previously been tested for this species.…”

“…Two fur seal colonies (Seal Rocks and The Skerries of the coast of SE Australia) were surveyed using RPA in coastal southeastern Australia during December 2017 and January 2018 as part of a five-yearly monitoring program (McIntosh et al 2018b). Pups are generally the selected age class for fur seal abundance estimates, as they are easily recognizable, more manageable when handled by researchers (as is required for CMR estimates), and are least likely to be in the water at this age (Kirkwood et al 2010).…”