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 the Tamar River in northern Tasmania, Australia, on 10 July 1995. It released an estimated 325 tonnes of bunker fuel oil. Of the wildlife species affected, the most readily detected was the little penguin (Eudyptula minor); 1894 were collected and treated for oiling. This study estimates the impact of the oil spill on populations of little penguins. At Ninth Island (approximately 40 km from Hebe Reef), one of the most affected little penguin colonies, pre-oil-spill population estimates were available. Extensive regular trapping and mark–recapture of birds at this site during the course of the oil 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 were 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 the region, we provide three scenarios of the possible numbers of penguins oiled. 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 spill. The study indicates that, despite the relatively small amount of oil spilt by the Iron Baron, the impact on penguin populations was extensive. This study also highlights the difficulties and requirements in assessing the impact of oil spills on wildlife populations.

Effects of the Iron Baron oil spill on little penguins (Eudyptula minor). II. Post-release survival of rehabilitated oiled birds

The post-release survival of rehabilitated oiled little penguins (Eudyptula minor) was monitored over 20 months following the Iron Baron oil spill (10 July 1995) in northern Tasmania, Australia. During rehabilitation, over 1800 little penguins were individually banded and detailed records kept of factors including their degree of oiling, sex, capture and release mass and capture and release condition. Post-release survival of rehabilitated oiled little penguins was assessed through regular trapping of birds over two breeding sites (Ninth Island and Low Head). The minimum estimate of post-release survival was 59% for penguins from Ninth Island and 44% for penguins from Low Head. Rehabilitated oiled little penguins had significantly lower survival than non-oiled birds at both sites. The main factor affecting post-release survival was the extent of oiling, which itself had a significant influence on the capture mass and condition of birds. Combined, these factors had the greatest power to predict post-release survival. Other factors that significantly affected post-release survival included release mass and condition, and the sex of the bird. The duration of rehabilitation and whether birds were translocated (200–410 km) from their capture site prior to release did not significantly affect survival. The results of this study indicate how aspects of oiling, the condition of birds and rehabilitation affect post-release survival. As such, they will help improve the success of wildlife rehabilitation in future spills, and highlight the importance of individually marking rehabilitated oiled wildlife and post-release monitoring in assessing the success of rehabilitation programs.

Effects of the Iron Baron oil spill on little penguins (Eudyptula minor). III. Breeding success of rehabilitated oiled birds

The long-term effects of oiling on the breeding success of rehabilitated oiled little penguins (Eudyptula minor) were examined over two consecutive breeding seasons following the Iron Baron oil spill in 1995. The commencement of egg laying was delayed among rehabilitated oiled penguins compared with non-oiled birds during the 1995/96 breeding season. During that season, hatching success (number of eggs hatched from those laid) was no different in nests containing rehabilitated oiled penguins than in those containing non-oiled birds, but overall egg success (number of pre-fledging chicks from the number of eggs laid) was significantly lower among rehabilitated oiled birds. This effect was predominant in nests containing a rehabilitated oiled female, where the probability of successfully fledging any chicks was 22% lower than in nests containing a non-oiled female. During the 1996/97 breeding season, there was no significant difference between either the hatching or egg success of rehabilitated oiled penguins and non-oiled birds. In both seasons, the pre-fledging masses of chicks from rehabilitated oiled penguins were significantly lower than those from non-oiled birds. The chicks of rehabilitated oiled penguins were therefore expected to have lower survival than chicks raised by non-oiled parents. Results indicate that oiling not only reduced the number of chicks raised by rehabilitated oiled penguins in the short term, but also decreased the quality of young produced for at least two seasons following the spill.

Prey harvest of the Australasian gannet (Sula serrator) in Tasmania

This study investigated the diet of the Australasian gannet (Sula serrator) at Pedra Branca, an island off the south coast of Tasmania. A total of 109 regurgitations representing 394 prey items was collected from the gannets between 1986 and 1991. Pelagic schooling fish, with fork length less than 200 mm, were the most common prey items. Redbait (Emmelichthys nitidus) and jack mackerel (Trachurus declivis) were the dominant prey species, with redbait being the most numerous, contributing 72% by number and 56% by mass. The diet of the Australasian gannet was compared with the fish taken by the commercial purse seine fishery in which jack mackerel was the target species and redbait a bycatch. The mean size of commercially caught fish of both species was greater than that taken by the gannets. We suggest that there is a threshold (in the size of the fish) above which the birds cannot capture and handle the prey, effectively limiting the resource available to them. It appears that the commercial fishery and the gannets, while harvesting the same species, exploit schools of different-size fish. The potential of Australasian gannets as indicators of fish stocks is discussed.

DDT and dieldrin: effects on resident Peregrine Falcon populations in south-eastern Australia

Organochlorine residues in eggs and prey species of the Peregrine Falcon,Falco peregrinus, were determined in parts of three south-eastern Australian States: Tasmania (1975-91), Victoria (1975-83) and South Australia (1977-1981). Relationships between residues detected and eggshell thickness, nest site occupancy and productivity were examined. Temporal changes and, in particular, the relative effects of DDE and dieldrin were also investigated. DDE was detected in all 137 eggs analysed. The concentration of DDE residues in eggs peaked in the late 1970s to early 1980s in Victoria, but peaked earlier and had declined to low concentrations by the 1980s in Tasmania. Maximum concentrations reached 82 ppm, in Victoria. The geometric means were: Victoria 12.4 ppm; Tasmania 1970s 10.1 ppm, 1980s 1.5 ppm; and South Australia 1.95 ppm. Dieldrin was detected in approximately half the eggs, but all except one egg (1.5 ppm) contained concentrations considered noncritical (<1 ppm). The degree of shell-thinning and reproductive success were related to DDE content, but not to that of dieldrin.Organochlorine concentrations in prey reflected general concentrations in eggs and, with a few exceptions, were low. In Tasmania, reproductive success increased as DDE contamination declined. In Victoria, despite mean concentrations of DDE well above that considered to be critical for successful reproduction (>15-20 ppm) for at least seven years, the breeding population declined by <2% a year. We interpret this result as evidence that DDE causes a slow decline in population and that the dramatic declines observed in some other parts of the world were mainly attributable to contamination by dieldrin or to other confounding factors.

Status of Australian and New-Zealand Fur Seals at Maatsuyker Island, Southwestern Tasmania

Surveys were carried out between 1987 and 1989 on Maatsuyker I. and nearby Needle Rocks off southern Tasmania to establish the status and identification of the seals present. New Zealand fur seals, Arctocephalus forsteri, were found on Maatsuyker I. There were at least 15 pups born on the island in 1987/88. Australian fur seals, Arctocephalus pusillus doriferus, use the islands as a haulout site but do not breed here. The distribution of New Zealand fur seals can now be amended to include Tasmanian waters. Records discussed here also alter aspects of the status of Australian fur seals because the Maatsuyker group is not a breeding site for this species and breeding colonies are therefore restricted to Bass Strait waters.

Water, Sodium and Energy Turnover in Free-Living Little Penguins, Eudyptula-Minor

Water influx rates of adult little penguins ranged from 20 ml kg-' day-' in fasting (incubating and moulting) birds to about 650 ml kg-' day- ' in birds that were foraging at sea over extended periods. The sodium influx rates of adults ranged from almost zero up to 87 mmol kg-' day-', depending on the activity patterns of the birds, and were closely correlated with water influxes. The metabolic rates of adult penguins were 1.7 and 2.8 times standard metabolic rates during fasting and foraging respectively, and were also closely correlated with water influx rates. The mean food consumption rate for the maintenance of chicks was about 236 g kg-' day-', equivalent to a maintenance energy intake of 1460 kJ kg-' day-'. Partitioning calculations show that sea water ingestion during foraging represented about 10% of total water influx, but about 40% of total sodium influx. Nasal salt secretions were hyperosmotic to serum and it was calculated that daily sodium influxes could be totally eliminated via this route within 4 hours.

The isolation of arboviruses including a new flavivirus and a new Bunyavirus from Ixodes (Ceratixodes) uriae (Ixodoidea: Ixodidae) collected at Macquarie Island, Australia, 1975-1979

Pools of ticks, Ixodes (Ceratixodes) uriae collected between 1975 and 1979 at Macquarie Island, yielded 33 strains of at least 4 different viruses: Nugget virus (Kemerovo group), 1 strain; Taggert virus (Sakhalin group) 9 strains; a previously undescribed flavivirus, related to Central European Tickborne encephalitis virus, for which the name "Gadgets Gully" is proposed, 9 strains; a virus serologically related to the Uukuniemi serogroup, family Bunyaviridae, for which the name "Precarious Point" is proposed, 10 strains. Three isolates were mixtures of Nugget and Gadgets Gully viruses; the remaining virus strain remains unidentified.