Flesh-footed Shearwaters Puffinus Carneipes Research Articles

Seabird population changes following mammal eradication at oceanic Saint-Paul Island, Indian Ocean

The eradication of invasive mammals on islands is important for protecting seabird populations and insular ecosystems. However, the impacts of such eradications are insufficiently known because monitoring of potentially beneficiary species is often sporadic and limited. We performed a survey of all seabird species on Saint-Paul Island, southern Indian Ocean, 20 years after successful eradication of invasive black rat (Rattus rattus) and European rabbit (Oryctolagus cuniculus). Using complementary sampling designs including adaptive cluster sampling, stratified random sampling and entire sampling, we estimated population changes and colonization by new seabird species. A total of 13 seabird species were found breeding on Saint-Paul post-eradication compared to six before the eradication. Among the seven species that colonized the island, five (MacGillivray’s prion Pachyptila macgillivrayi, fairy prion P. turtur, white-bellied storm petrel Fregetta grallaria, Antarctic tern Sterna vittata, sooty tern Onychoprion fuscatus) had relictual populations breeding on a nearby islet, and one (brown skua Catharacta antarctica) was a new breeding species. We also found breeding subantarctic little shearwaters Puffinus elegans. For species that were breeding on the Saint Paul pre-eradication, the mean annual population growth rate was 1.030 ± 0.093 (SE). Species known to be vulnerable to rat predation (prions, great-winged petrel Pterodroma macroptera, flesh-footed shearwater Puffinus carneipes, subantarctic little shearwater, white-bellied storm petrel, Antarctic tern) had the highest population growth rates. Two decades after the eradication of invasive mammals on a remote oceanic island, seabird populations were high beneficiaries. These findings further highlight the importance of invasive mammal eradication on islands as a conservation tool. Results are encouraging for the planned eradication of invasive mammals from nearby Amsterdam Island, and suggest this will mainly benefit terns and small burrowing petrels.

Overlap between flesh-footed shearwater Puffinus carneipes foraging areas and commercial fisheries in New Zealand waters

Although the flesh-footed shearwater Puffinus carneipes is a species with large population sizes (tens of thousands of breeding pairs) and widespread sub-tropical distribution across Australasian water masses, it is among the species most threatened by longline fisheries mortality in this region. While bycatch mitigation measures have been very successful in reducing mortality in some species, bycatch of flesh-footed shearwaters is still high, with captures estimated to exceed the sustainable take of 514 birds yr-1 by nearly 200 birds for New Zealand fisheries alone. Management agencies aiming to reduce the impact of fisheries mortality on the populations need to understand which marine areas are being used by flesh-footed shearwaters to better target fishery monitoring and mitigation efforts. Foraging studies of seabirds tell us about their use of resources, i.e. the way species segregate the available habitat and help to identify threats that may affect population viability. Breeding shearwaters were tracked from 2 New Zealand colonies using GPS loggers. Individuals foraged over shelf and deep oceanic waters up to 1200 km from their nesting sites during incubation but were mainly within 370 km during early chick rearing. The intensity of potential interactions increased for trawl and surface longline fishing between the January and February study periods but remained at a similar level for bottom longline fishing. Following the field data collection, changes to fishery monitoring were implemented in the areas where shearwaters foraged.

Linking at-sea mortality of a pelagic shearwater to breeding colonies of origin using biogeochemical markers

An emerging issue in seabird conservation is the ability to link at-sea mortality with observed demographic changes at breeding colonies. Applications of modelling and biochemical markers can be used to assign mortalities of unknown provenance to a colony of origin ensuring conservation actions are targeted at those colonies identified as the most affected. We analysed feathers (n = 120) from flesh-footed shearwater Puffinus carneipes collected from 5 breeding colonies throughout their range. Using stable isotopes (δ15N and δ13C) and trace element concentrations (Mn, Ni, Cu, Mo, Ag, Ba, Pb), we assigned birds recovered from fishing vessels off Australia, New Zealand, and the North Pacific to colony of origin, and investigated the rate of correct assignment at 3 spatial scales. Using quadratic discriminant analysis, samples of known origin were correctly assigned to basin, region, and breeding colonies at similar rates (92.3, 81.3, and 88.1%, respectively). Stable isotopes succeeded in assigning individuals among basins (72.8%), performing less well at the region and colony level (52.5 and 36.4%, respectively). In contrast, correct assignment was consistent at all 3 scales using only trace elements (93.2, 95.7, and 96.6%, respectively). Applying our final model based on trace elements to 116 flesh-footed shearwaters taken as bycatch in eastern Australia (n = 30), Western Australia (n = 32), New Zealand (n = 16), eastern North Pacific (n = 27) and western North Pacific (n = 11), we assigned individuals to colonies in New Zealand (35.3%), Western/South Australia (36.2%), Western Australia (27.6%), and Lord Howe Island (0.9%). Bycatch in fisheries may help explain ongoing declines in fleshfooted shearwater populations across the species’ range, highlighting the utility of assignment tools to account for unobservable mortality of wildlife at-sea.

Environmental determinants of the at-sea distribution of encounters between flesh-footed shearwaters Puffinus carniepes and fishing vessels

Fisheries observer data were used to model the distribution of seabird encounters in order to identify potential areas for fisheries closures. Data from the Australian Eastern Tuna and Billfish Fishery (ETBF) in the Tasman Sea were used, and the focal species was the flesh-footed shearwater Puffinus carneipes Gould, 1844 (the species most commonly killed in this fishery). Encounters between flesh-footed shearwaters and longline fishing vessels varied with season, distance from Lord Howe Island, and a number of environmental and oceanographic variables. Encounters were most common south-west of Lord Howe Island, in waters associated with the Tasman Front and the East Australian Current. The resulting model was used to predict overlaps between fisheries and flesh-footed shearwaters during 3 years (1997-98, 2003-04 and 2006-07). During 2003-04, high rates of interaction were predicted in areas with high fishing effort and high observed mortality rates of shearwaters. In 2006-07 most fishing was well to the north of areas with predictions of high interaction rates, and seabird bycatch was low. The shift in fishing locations coincided, and was likely driven by, a change in the fish species targeted by the majority of the fishery. This indicates that the most likely reason for falling bycatch rates in this fishery were movements of the fishing effort away from the birds, rather than changes in fishing technique. These results emphasise the potential of area closures as a method of bycatch mitigation for species that are proving intractable to standard bycatch reduction methods. Our results demonstrate that data collected from fisheries vessels can be used to identify characteristic areas of interactions.

Migration and diving activity in three non-breeding flesh-footed shearwaters Puffinus carneipes

The flesh-footed shearwater Puffinus carneipes is a medium-sized shearwater and transequatorial migrant within the Pacific Ocean. We used archival data loggers to study the non-breeding migration and diving behaviour of three flesh-footed shearwaters following breeding in New Zealand. In early April, the birds migrated to the western North Pacific Ocean in 23±2 days, occupying core distributions within the Kuroshio/Oyashio transition system for 91±17 days. Subsequent movements were made into the Sea of Okhotsk prior to return migrations to New Zealand in mid September (19±1 days). Diving depths during migration (2.5±2.4 m), and in the western North Pacific (2.4±2.6 m) were shallower than during the onset of breeding (4.8±8.7 m). Non-breeding flesh-footed shearwaters occupy a region of high fisheries activity and the impact of these fisheries on adult survival in this declining species warrant further study.

The impact of pelagic longline fishing on the flesh-footed shearwater Puffinus carneipes in Eastern Australia

The flesh-footed shearwater (Puffinus carneipes) is a medium-sized seabird (ca. 700g) that is incidentally killed during longline fishing operations. We examined the levels of bycatch in Australia’s Eastern Tuna and Billfish Fishery and developed a model to examine the impact of this fishery on the eastern Australian population of flesh-footed shearwaters, which breeds at only one site, Lord Howe Island. Observed bycatch rates for flesh-footed shearwaters were 0.378 birds/1000 hooks for night sets, and 0.945 birds/1000 hooks for day sets. The mean number of birds killed from 1998 to 2002 was estimated to be 1794–4486 birds per year, with the estimated total killed over this period ranging from 8972 to 18,490 birds. Models incorporating both density-independent and density-dependent scenarios were applied to levels of bycatch representative of that observed in the fishery. Density-independent scenarios showed that fishing mortality levels caused declines in the majority of simulated populations. In contrast, density-dependent scenarios produced populations that were more resilient to fishing mortalities. Although some modelling scenarios led to population growth, under most stochastic simulations median population halving and quasi-extinction times were less than 55 and 120 years, respectively. We conclude that the level of bycatch observed in the fishery is most likely unsustainable and threatens the survival of the Lord Howe Island population. This situation can be improved only with the development and implementation of mitigation measures that will halt or greatly reduce the level of bycatch currently observed. Improved knowledge on a range of demographic parameters for the species, combined with a clearer idea of the at-sea distribution of breeding and non-breeding shearwaters, will greatly assist in improving understanding and the management of this population.