Effects of the Iron Baron oil spill on little penguins (Eudyptula minor). I. Estimates of mortality

The bulk ore carrier Iron Baron ran aground on Hebe Reef at the mouth of th e Tamar River in northern Tasmania, Australia, on 10 July 1995. It released an estimated 325 tonnes of bunker fuel oil. Of the wildlife species affect ed, the most readily detected was the little penguin (Eudyptula minor); 189 4 were collected and treated for oiling. This study estimates the impact of the oil spill on populations of little penguins. At Ninth Island (approxim ately 40 km from Hebe Reef), one of the most affected little penguin coloni es, pre-oil-spill population estimates were available. Extensive regular tr apping and mark-recapture of birds at this site during the course of the oi l spill provided longitudinal data on oiling rates from a known population size. Using these data, we estimate that 19.6% of birds from Ninth Island w ere oiled and survived to come ashore. This represents about 526 (1932-3108 , 95% CL) adult birds, or up to 5566 (4197-6917) birds in total (adults and juveniles). For estimates of the impact on little penguin populations in t he region, we provide three scenarios of the possible numbers of penguins o iled. After considering the biases of each risk assessment, we believe that between 10 000 and 20 000 penguins were killed as a result of the oil spil l. The study indicates that, despite the relatively small amount of oil spi lt by the Iron Baron, the impact on penguin populations was extensive. This study also highlights the difficulties and requirements in assessing the i mpact of oil spills on wildlife populations.