Westland petrels and hoki fishery waste: opportunistic use of a readily available resource?
The importance of fisheries waste in the diet of Westland petrels (Procellaria westlandica) was assessed using 3 different techniques. Dietary studies showed that during the hoki (Macruronus novaezelandiae) fishing season (mid June - early September), fish waste formed c. 63% of the solid food brought back to the colony and fed to chicks. After the hoki season, fisheries waste contributed only c. 25% to the diet. A survey of Westland petrels at sea found that, although vessels fishing for hoki influence the petrels' distribution, only a small proportion of the population appears to use this food resource at any one time. Satellite tracking showed that, on average, birds spent 1/3rd of each foraging trip near vessels, but they foraged over much wider areas than those occupied by the fishing fleets. Although fishery waste now forms a substantial component of the Westland petrel's diet, the situation suggests opportunistic use of a readily available resource, rather than dependence.... [Show full abstract]