Gregory Stone

Site fidelity and along-shore range in Hector's dolphin, an endangered marine dolphin from New Zealand

Abstract To document site fidelity and the alongshore range of individual Hectors dolphins we analysed sightings of 32 photographically identified dolphins, each seen ⩾10 times at Banks Peninsula, New Zealand, between 1985 and 1997. The furthest two sightings of an individual were 106 km apart. All other individuals ranged over less than 60 km ( x =31.0 km, SE=2.43) of coastline. Gender did not significantly influence alongshore range (female x =30.4 km, SE =3.21, n =18; male x =27.4 km, SE=5.68, n =5). Site fidelity was high: for example, on average, individuals were seen in Akaroa Harbour for about two thirds of the years they were known to be alive. These data suggest that impacts on Hectors dolphins are most appropriately managed on a small spatial scale.

Short-term changes of fish assemblages observed in the near-pristine reefs of the Phoenix Islands

Climate change-related disturbances are increasingly recognized as critical threats to biodiversity and species abundance. On coral reefs, climate disturbances have known consequences for reef fishes, but it is often difficult to isolate the effect of coral bleaching from preceding or simultaneous disturbances such as fishing, pollution, and habitat loss. In this study, pre-bleaching surveys of fish family assemblages in the remote Phoenix Islands in 2002 are compared to post-bleaching in 2005, following severe thermal stress. Post-bleaching, total coral cover decreased substantially, as did the combined abundance of all fish families. Yet, changes in abundance for specific fish families were not uniform, and varied greatly from site to site. Of the 13 fish families examined, 3 exhibited significant changes in abundance from 2002 to 2005, regardless of site (Carangidae, Chaetodontidae, and serranid subfamily Epinephelinae). For these families, we explored whether changes in abundance were related to island type (island vs atoll) and/or declining coral cover (percent change). Carangidae on islands experienced larger changes in abundance than those on atolls, though declines in abundance over time were not associated with changes in live coral cover. In contrast, for Chaetodontidae, declines in abundance over time were most dramatic on atolls, and were also associated with changes in live coral cover. The remoteness of the Phoenix Islands excludes many typical local anthropogenic stressors as drivers of short-term changes; observed changes are instead more likely attributed to natural variation in fish populations, or associated with coral loss following the 2002–2003 major thermal stress event.