Yellow-eyed mullet, known in Aotearoa New Zealand as aua (Aldrichetta forsteri), are a native coastal fish species commonly found around New Zealand's shores. They typically grow between 250 and 400 millimetres in length, with slender, streamlined bodies covered in silvery scales and a distinctive yellow ring around the eye.
Their backs are usually olive-grey, fading to bright silver on the sides and belly. This colouring provides effective camouflage in open coastal and estuarine waters.
Aua are most abundant in estuaries, harbours, coastal lagoons, and shallow inshore waters, though they may also move into lower reaches of rivers. They are a highly social species and are often seen schooling in large numbers near the surface.
Estuaries are particularly important for juveniles, providing sheltered conditions and abundant food. Adults may move more widely along the coast but remain strongly associated with nearshore environments.
Adults spawn in coastal waters, usually during spring and summer
Fertilised eggs develop into free-swimming larvae that drift as part of the plankton
Larvae settle into estuarine and coastal nursery habitats as juveniles
Growth is relatively rapid, reaching maturity within two to three years
The life cycle of Aldrichetta forsteri begins when adults spawn in coastal waters, usually during spring and summer. Fertilised eggs develop into free-swimming larvae that drift as part of the plankton before settling into estuarine and coastal nursery habitats as juveniles. Growth is relatively rapid, and aua typically reach maturity within two to three years. Their life cycle is closely tied to healthy estuaries that function as key rearing grounds.
Morphologically, aua are adapted for fast swimming in open water. They have forked tails for speed and endurance, large eyes for surface feeding, and small mouths suited to grazing and plankton feeding. Their diet consists mainly of algae, detritus, plankton, and small invertebrates, making them one of the few common coastal fish in New Zealand that feeds heavily on plant material and organic debris.
Designed for speed and endurance in open water
Adapted for effective surface feeding
Suited to grazing and plankton feeding
Ecologically, aua play an important role in transferring energy from lower levels of the food web to higher predators. By feeding on plankton and detritus, they help recycle nutrients in estuarine and coastal systems.
They are a major food source for larger fish, seabirds, and marine mammals, making them a key link in coastal food webs. Their schooling behaviour also contributes to nutrient mixing in surface waters.
Despite their abundance, aua face several environmental pressures. Degradation of estuaries through sedimentation, pollution, and coastal development reduces the quality of their main nursery habitats. Agricultural and urban runoff introduces excess nutrients and contaminants that affect water clarity and food availability. Overfishing—particularly by recreational netting in some areas—can place local pressure on populations.
Sedimentation, pollution, and coastal development reduce nursery habitat quality
Agricultural and urban runoff introduces excess nutrients and contaminants affecting water clarity
Recreational netting in some areas places local pressure on populations
Climate change adds further risks through warming coastal waters, altered current patterns, and sea-level rise that threatens low-lying estuarine habitats. Changes in plankton productivity may also affect food availability for juveniles.
In conclusion, aua (Aldrichetta forsteri) are an ecologically important and culturally significant native fish species in New Zealand's coastal and estuarine environments.
Their role in nutrient cycling, food webs, and estuarine ecosystem function highlights the importance of protecting estuaries and managing coastal activities to ensure the long-term sustainability of yellow-eyed mullet populations in Aotearoa.
Exploring the ecology and significance of Aldrichetta forsteri in Aotearoa New Zealand's coastal waters