Radiocarbon as a novel tracer of extra-Antarctic feeding in Southern Hemisphere Humpback Whales

Bulk stable isotope analysis provides information regarding food web interactions, and has been applied to several cetacean species for the study of migration ecology. One limitation in bulk stable isotope analysis arises when a species, such as Southern hemisphere humpback whales, utilises geographically distinct food webs with differing isotopic baselines. Migrations to areas with different baselines can result in isotopic changes that mimic changes in feeding relations, leading to ambiguous food web interpretations. Here, we demonstrate the novel application of radiocarbon measurement for the resolution of such ambiguities. Radiocarbon was measured in baleen plates from humpback whales stranded in Australia between 2007 and 2013, and in skin samples collected in Australia and Antarctica from stranded and free-ranging animals. Radiocarbon measurements showed lower values for Southern Ocean feeding than for extra-Antarctic feeding in Australian waters. While the whales mostly relied on Antarctic-derived energy stores during their annual migration, there was some evidence of feeding within temperate zone waters in some individuals. This work, to our knowledge, provides the first definitive biochemical evidence for supplementary feeding by southern hemisphere humpback whales within temperate waters during migration. Further, the work contributes a powerful new tool (radiocarbon) for tracing source regions and geographical feeding

Isotopic evidence of a wide spectrum of feeding strategies in Southern hemisphere humpback whale baleen records

Our current understanding of Southern hemisphere humpback whale (Megaptera novaeangliae) ecology assumes high-fidelity feeding on Antarctic krill in Antarctic waters during summer, followed by fasting during their annual migration to and from equatorial breeding grounds. An increase in the number of reported departures from this feeding/fasting model suggests that the current model may be oversimplified or, alternatively, undergoing contemporary change. Information about the feeding and fasting cycles of the two Australian breeding populations of humpback whales were obtained through stable isotope analysis of baleen plates from stranded adult individuals. Comparison of isotope profiles showed that individuals from the West Australian breeding population strongly adhered to the classical feeding model. By contrast, East Australian population individuals demonstrated greater heterogeneity in their feeding. On a spectrum from exclusive Antarctic feeding to exclusive feeding in temperate waters, three different strategies were assigned and discussed: classical feeders, supplemental feeders, and temperate zone feeders. Diversity in the interannual feeding strategies of humpback whales demonstrates the feeding plasticity of the species, but could also be indicative of changing dynamics within the Antarctic sea-ice ecosystem. This study presents the first investigation of trophodynamics in Southern hemisphere humpback whales derived from baleen plates, and further provides the first estimates of baleen plate elongation rates in the species

Effectiveness of mitigation measures to reduce interactions between commercial fishing gear and whales

Effectiveness of mitigation measures to reduce interactions between commercial fishing gear and whales. Objectives: 1. Start to collect additional information required to determine the spatial and temporal extent of migrating whales and how this overlaps with commercial fishing gear. 2. Examine the effectiveness of potential gear modifications to the float rigs of fishing pots/traps to reduce their likelihood of entangling whales

Mitigation measures to reduce entanglements of migrating whales with commercial fishing gear

The West Coast Rock Lobster Managed Fishery (WCRLMF) transitioned to a quota based fishery, and year-round fishing, which corresponded with a spike in whale entanglements in 2013. This presented industry with a challenging social issue, to reduce entanglements without impacting on the financial benefits that the shift to year-round quota fishing had afforded

Collection of baseline data on humpback whale (Megaptera novaeangliae) health and causes of mortality for long-term monitoring in Western Australia

Since 2008 an unprecedented number of humpback whales (Megaptera novaeangliae) have stranded in Western Australia (WA). Between 1989 and 2007 the mean number of humpback whales ashore was between 2 and 3 animals (range: 0-5). In 2008 there were 13 strandings followed by 46 in 2009 and 16 in 2010. The aim of this project was to initiate the collection of data by post-mortem examination of stranded whales in 2011 in order to: 1) identify and characterise factors associated with strandings; and 2) determine baseline and epidemiological information on disease and the nutritional status of stranded whales

Collection of baseline data on humpback whale (Megaptera novaeangliae) health and causes of mortality for long-term monitoring in Western Australia

In 2009, an unprecedented number of humpback whales (Megaptera novaenangliae) (n=46) were found dead or dying on WA beaches. This compares to an average of less than five humpback whales each year in the preceding two decades. Speculation on causes of increased marine mammal mortalities usually focuses on starvation, disease or anthropogenic impacts, or some synergistic combination of these. The current situation is that very little is known about the health of the WA humpbacks in terms of their nutritional status, disease or level of adverse human interactions. We propose to aid in the investigation into increased mortalities by conducting opportunistic post-mortem examinations over a five year period. The project aims to: • identify and characterise factors associated with humpback whale strandings and; • determine baseline and epidemiological information on disease levels and the nutritional status of stranded humpback whales. The data and archived tissues collected will provide an invaluable baseline, thus allowing for the early detection of adverse impacts from natural and anthropogenic pressures and retrospective assessment for the incidence of currently unidentified or poorly-described pathogens

Northernmost record of Shepherd’s beaked whale (Tasmacetus shepherdi) – a morphological and genetic description from a stranding from Shark Bay, Western Australia

Shepherd’s beaked whale (Tasmacetus shepherdi) is one of the least known cetaceans. Based on the location of 45 strandings and two at-sea sightings, T. shepherdi is thought to have a circumpolar distribution in the temperate waters of the Southern Hemisphere between latitudes 33°S and 50°S. On 10 November 2008, a female T. shepherdi was found dead on a beach in Shark Bay, Western Australia, at 113° 16’E, 26° 20’S. DNA sequencing was used to verify the identification of the specimen, which is the northern most record for this species. The age of the specimen was estimated to be between 12 and 15 years, based on counting dentine growth layer groups in two teeth, assuming an annual rate of deposition