New Zealand Bigeye

Fascinating facts about the New Zealand Bigeye

• A fish only 15.8 cm long can slip into crevices as shallow as the surface and dive down to 70 m (230 ft) – a vertical range that rivals many reef dwellers, showing how flexible its habitat needs are.
• When night falls, these night-time foragers leave their rocky hideouts and actually "talk" – popping sounds let the shoal stay together.
• Some groups have been seen swimming far upstream after dark to hunt shrimp, amphipods and crab larvae, proving they can cross into estuaries and chase prey far from the open sea.
• Gravid females appear from mid-November through February, and the same period sees spawning, with juveniles settling between January and April – a tight seasonal window that ties their life cycle to New Zealand’s summer.
• Their hearing relies on a modified swim bladder, Baudelot's ligament and the lateral line.

At a glance

About the New Zealand Bigeye

The New Zealand bigeye, Pempheris adspersa, is a sleek, dark-coloured sweeper distinguished by its disproportionately large eyes and a deeply keeled, laterally compressed body dotted with countless tiny spots. Growing to a modest 15.8 cm (6.2 in) standard length, this nocturnal fish inhabits the rocky shores of New Zealand’s northeastern North Island, favouring crevices, overhangs and caves from the surface down to 70 m (230 ft). By day it remains concealed, but at night it emerges in shimmering shoals, using a repertoire of vocalisations and popping sounds, produced through a specialised swim-bladder-lateral-line system, to keep the group together as they hunt. Their diet is a mixed banquet of planktonic fare and benthic critters; observations record them drifting upstream under cover of darkness to snatch shrimps, amphipods, crab larvae and other zooplankton. A surprising trait is their occasional forays into estuarine mangrove forests, where they feed on zooplankton among the roots, demonstrating a flexibility that belies their seemingly niche coastal habitat. Reproductive activity peaks from mid-November to February, with gravid females spawning as juveniles settle from January to April, often found among rock-shore weed in the late summer, continuing the cycle of night-time foraging and day-time refuge.

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