These are two final reports for INT2016-04: Indirect effects of commercial fishing on Buller's shearwater and red-billed gulls. The reports assess available information on seabird population status and trends, and interactions with fish shoals.
These reports investigate the possible indirect effects of commercial fishing on surface- and near surface-feeding seabirds. Shoals of predatory fsih species such as kingfish, kahawai and trevally often concentrate thier prey-small fish and krill- close to the sea surface, producing 'biol-ups' that attract large numbers of surface-feeding seabirds. In New Zealand, these include several shearwater, petrel and prion species, Australasian gannet (Morus serrator), red-billed gull (Larus novahollandiae), white-fronted tern (Sterna striata), and grey noddy (Procelsterna albivitta).
Most of these species seem to depend on these boil-ups to obtain much of the high quality food needed to rear their chicks successfully. There is some concern that the frequency, size and duration of these events may be declining due to changes in fish stocks, for whatever reason. If so, then this could reduce the birds overall foraging efficiency and compromise breeding success.
Frost, P. 2017. Population status and trends of selected seabirds in northern New Zealand. Report prepared for the Conservation of Services Programme, Department of Conservation, Wellington. 37 p.
Gaskin, C. 2017. Procellariiformes associating with shoaling fish schools - northern New Zealand. Report prepared by Northern NZ seabird trust for the Conservation of Services Programme, Department of Conservation, Wellington. 52 p.