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Understanding the dynamics of population recovery is particularly complex when an organism has multiple, remote breeding and feeding grounds separated by one of the longest known migration routes. This study reports on the most comprehensive assessment of humpback whale ( Megaptera novaeangliae) movements between remote Antarctic waters south of New Zealand and east Australia (EA), and the migratory corridors and breeding grounds of Australia and Oceania. A total of 112 individual whales were identified; 57 from microsatellites and 61 by fluke with 23 % ( n = 26) matched to sites outside Antarctica. Despite large datasets from other southern regions being included in the comparison, the whales were predominantly linked to EA ( n = 24). Only two matches to the Oceania catalogues directly north was surprising; therefore the primary feeding grounds of these endangered whales still remain unknown. The confirmation of the Balleny Islands as an important feeding ground for EA whales could provide an insight into reasons behind the rapid recovery of this population. Determining the feeding grounds of Oceania's whales may explain whether prey energetics or migration length are limiting factors to their recovery and will allow an understanding of future ecosystem changes in these whales. [ABSTRACT FROM AUTHOR]

Understanding patterns in site fidelity is important for defining the ecological role of species in the systems they use and for gauging the effects of human impacts on their populations. We analyzed long-term movement data of adult spottail sharks ( Carcharhinus sorrah) in Cleveland Bay, Australia, to define the degree of site fidelity this species shows to coastal areas. Individuals were monitored in the study site for 28-566 days, and residency index (i.e., proportion of days present to total monitoring period) ranged from 0.08 to 0.95. Using a randomization procedure, we determined that the movement paths for 90 % of individuals (11 female and 7 male) were more constrained than random, with individuals exhibiting a high degree of site fidelity to consistent areas within the study site. Examining distances moved revealed that individuals used the same areas repeatedly and remained in close proximity (i.e., <6 km) to their location of first detection. While some individuals consistently used and returned back to the same locations, low residency among others suggests that a portion of the population may roam more widely. Long-term site fidelity to consistent areas may be a successful behavioral strategy for C. sorrah by increasing individual fitness through spatial familiarity and knowledge of resources. [ABSTRACT FROM AUTHOR]

The Australasian gannet (Morus serrator) population has increased considerably over the past century, both in New Zealand and Australia. Since 1980, the population in Australian waters has increased threefold, from 6,600 breeding pairs to approximately 20,000 pairs in 1999 2000, a rate of 6% per year. Reasons for the increase in the Australasian gannet population are poorly understood: here we consider the possible effects of recent fluctuations in climatic and oceanographic conditions, and changes in major local commercial fisheries. A significant trend towards more frequent, and stronger, El Niño Southern Oscillation events, warmer summer sea surface temperatures in Bass Strait, increased annual catches and catch per unit effort in the Victorian pilchard (Sardinops sagax) fishery and potential increased discarding of fisheries bycatch may account for at least some of the observed increase in the Australasian gannet population. The potential interactive effects of these factors on prey distribution and abundance and consequently on gannet numbers are discussed. [ABSTRACT FROM AUTHOR]

Daytime sampling of mangrove and seagrass ( Halophila/Halodule community) habitats every 7 wk at Alligator Creek, Queensland, Australia, over a period of 13 mo (February 1985-February 1986) using two types of seine net, revealed distinct mangrove and seagrass fish and crustacean faunas. Total abundance of fish and relative abundance of small and large fish also varied between habitats and seasonally. Post-larval, juvenile and small adult fish captured with a small seine-net (3 mm mesh) were significantly more abundant (4 to 10 times) in the mangrove habitat throughout the 13 mo of sampling. Mangrove fish abundance showed significant seasonality, greatest catches being recorded in the warm, wet-season months of the year. Relative abundances of larger fish (captured in a seine net with 18 mm mesh) in the two habitats varied throughout the year, but did not show a seasonal pattern. At the same site, small crustaceans were significantly more abundant in the mangroves in all but one dryseason sample. Similar comparisons for three riverine sites, sampled less frequently, in the dry and wet seasons of 1985 and 1986, respectively, showed that in general mangrove habitats had significantly more fish per sample, although the relative abundance of fish in mangroves and other habitats changed with season. Crustacean catches showed a similar pattern, except that densities among sites changed with season. Fish and crustacean abundance in mangroves varied among sites, indicating that estuaries differ in their nursery-ground value. The juveniles of two commercially important penaeid prawn species ( Penaeus merguiensis and Metapenaeus ensis) were amongst the top three species of crustaceans captured in the study, and both were significantly more abundant in the mangrove habitat. By contrast, mangroves could not be considered an important nursery for juveniles of commercially important fish species in northern Australia. However, based on comparisons of fish catches in other regions, the results of the present study indicate the importance of mangroves as nursery sites for commercially exploited fish stocks elsewhere in South-East Asia. [ABSTRACT FROM AUTHOR]

Six Tridacna gigas populations were sampled in 1990 from locations throughout the central and northern Great Barrier Reef (GBR). Despite separations in excess of 1000 km, mean Nei's unbiased genetic distances among the populations was 0.0007. The complete lack of spatial variation observed among populations did not results from lack of genetic variability. Genetic variation within populations was high, with mean heterozygosities from 0.221 to 0.250. Gene frequencies were consistent with expectations under conditions of Hardy-Weinberg equilibrium. These data suggest panmixis, or random mating, throughout the highly connected reef system of the central and northern GBR. The large gene exchange among the giant clam populations has important implications for conservation management of one of the few large populations of T. gigas in the world. Small local effects are likely to be overcome in time by inputs from other sources. However, large genetic perturbations, particularly from up-current sources, may spread rapidly through the population. [ABSTRACT FROM AUTHOR]