Otolith mass asymmetry in the Australian anchovy Engraulis australis (White, 1790) predated by Australasian gannets Morus serrator (Gray, 1843), Hauraki Gulf, New Zealand

Water disturbance can be developed to a certain degree from nature, but human activities increase the level of disturbance through pollution of aquatic habitats. Fish species are directly and indirectly harmfully disturbed by water pollution. Like other living species in the aquatic system, fish are confronted with various sources of different pollutants such as pesticides, insecticides, herbicides, and heavy metals in their habitats. Otolith mass asymmetry may reflect some growth disarrays of fish caused by environmental pressure. Especially high-level otolith mass asymmetry can adversely affect fish life, so the determination of the asymmetry is very vital for species management. The aim of the present study is to calculate the otolith mass asymmetry of Engraulis australis recovered from the food of a piscivorous bird Gannet inhabiting islands in the Hauraki Gulf, New Zealand. The mean asymmetry value computed was found to be 0.0107 (within -0.25483 and + 0.41220) in the samples of E. australis (n = 55, 19.5-23.0 cm TL). The otolith mass asymmetry and absolute otolith mass asymmetry of this species is not related to the total length.