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Grey Mullet (Kanae)
An ecologically important and culturally valued fish species in New Zealand's estuarine and coastal environments
Grey mullet, known in Aotearoa New Zealand as kanae (Mugil cephalus), are a large, silvery coastal fish found in warm-temperate seas around the world, including throughout New Zealand's coastal waters. They typically grow between 350 and 600 millimetres in length, though some individuals can exceed 750 millimetres. Kanae have long, cylindrical bodies with large, shiny scales, dark backs, and pale silver sides and bellies. Their blunt heads and small mouths are well adapted for feeding on fine organic material and algae.
Habitat and Distribution
Kanae are most commonly found in harbours, estuaries, coastal lagoons, and shallow inshore waters, though they can also enter the lower reaches of rivers. They are a highly mobile and social species, often schooling in large numbers near the surface. Estuaries are especially important habitats for juvenile kanae, providing sheltered conditions, warm water, and abundant food.
Life Cycle
Offshore Spawning
Adults migrate offshore to spawn, usually in late summer and autumn. Fertilised eggs develop into free-swimming larvae that drift with ocean currents.
Estuarine Settlement
Larvae settle into estuaries and coastal nursery areas. Juveniles grow steadily in these sheltered environments.
Adult Migration
Juveniles gradually move into more open coastal waters as adults. Kanae typically reach sexual maturity between three and five years of age and may live for over ten years.
Morphological Adaptations
Physical Features
Morphologically, kanae are adapted for sustained swimming in shallow coastal waters. They have powerful forked tails for long-distance movement and strong pectoral fins for manoeuvring in tidal currents.
Feeding Adaptations
Their gizzard-like stomach and specialised mouthparts allow them to feed by grazing on algae, biofilms, detritus, and organic material scraped from sediments and surfaces. This makes them one of the most important detritus-feeding fish in coastal ecosystems.
Ecological Importance
Ecologically, kanae play a vital role in recycling nutrients and maintaining the health of estuarine and coastal environments. By feeding on detritus, algae, and fine organic matter, they help prevent excessive nutrient build-up and contribute to water clarity. They are also an important food source for larger fish, sharks, seabirds, and marine mammals, making them a key link in coastal food webs.
Environmental Pressures
Despite their wide distribution, kanae face several environmental pressures. Degradation of estuaries from sedimentation, pollution, and coastal development reduces the quality of their main nursery habitats. Agricultural and urban runoff introduce excess nutrients and contaminants that affect food availability and water quality. Overfishing—particularly through netting in estuaries and harbours—can place significant local pressure on kanae populations.
Habitat Degradation
Sedimentation, pollution, and coastal development reduce nursery habitat quality
Water Quality
Agricultural and urban runoff introduce excess nutrients and contaminants
Overfishing
Netting in estuaries and harbours places significant local pressure on populations
Climate Change Impacts
Climate change adds further risks through rising sea temperatures, altered current patterns, and sea-level rise that threatens low-lying estuarine habitats. Changes in algae and plankton productivity may also affect feeding conditions, especially for juveniles.
Conclusion
In conclusion, kanae (Mugil cephalus) are an ecologically important and culturally valued fish species in New Zealand's estuarine and coastal environments. Their role in nutrient recycling, food webs, and estuary health highlights the importance of protecting estuarine ecosystems and ensuring sustainable fishing practices to support the long-term survival of grey mullet in Aotearoa.