oily deep-water fish, handle with care

Size
Length: 100–150 cm, Weight: 15–30 kg
Lifespan
10–15 years
Diet
Carnivorous feeder on small fish, squid and crustaceans. Hunts in deep water using large mouth and sharp teeth. Swims with snake-like motion. Follows prey into shallower waters at night.
Habitat
Inhabits deep waters of continental slope between 200 and 800 metres during day. Migrates closer to surface at night to feed. Prefers warm, stable waters with high oxygen levels for survival.
Range
Found in tropical and subtropical waters worldwide. In New Zealand it is a summer visitor to northern waters from Northland to Bay of Plenty. Most common in warm summers with high sea temperatures.
Endemism
Native
Main Threats
Bycatch in tuna longline fisheries is primary threat. Also threatened by mislabelling as other fish species. Climate change may expand its range southward into New Zealand waters more frequently.
Population
Global populations considered stable but poorly assessed. Species caught as bycatch in tropical and subtropical longline fisheries. In New Zealand it is rare visitor with no commercial importance. Flesh causes digestive issues.
Conservation Status
Not Threatened
Deep-water predator with a dark brown body. A fearsome set of teeth defines the mouth. This is a fish that is not what it seems. It swims with a snake-like motion. It chases small fish and squid through the dark waters of the continental slope. Its flesh is rich and buttery. This is because it contains a wax ester called gempylotoxin. Eating more than a small portion can cause digestive distress. For this reason it is banned for sale in some countries. A fish that is delicious and dangerous. The appeal is high. The risk is real. The body is elongated and muscular. It has a large head and a terminal mouth. The teeth are sharp and numerous. Colour is a uniform dark brown. This provides camouflage in the deep. The fins are dusky. The scales are small and rough. The morphology supports the lifestyle. Speed is required for the chase. Teeth are required for the capture. Camouflage aids survival. It is a deep-water predator. It spends its days near the seafloor. At night, it migrates closer to the surface to feed. It swims with a snake-like motion. It uses its large mouth to swallow prey whole. The migration is vertical. The feeding is nocturnal. The method is efficient. The energy cost is managed. Its flesh contains a wax ester called gempylotoxin. This wax ester is indigestible to humans. Eating more than a small portion can cause diarrhoea. Other digestive problems may occur. For this reason, escolar is banned for sale in some countries. The regulation is protective. The biology is unforgiving. The consequence is unpleasant. It is not targeted by commercial fisheries in New Zealand. It is occasionally caught as bycatch in tuna longline fisheries. When it is caught, it is often mislabelled as other fish species. The deception is common. The identification is difficult. The consumer is unaware. To see one is rare. They live in the deep. In the warm, dark waters of the continental slope. The longline sets. The escolar takes the bait. It comes up, dark brown and snake-like. The fisherman looks at it and thinks, 'That looks like butterfish.' It is not. The resemblance is superficial. The difference is internal. It is a laxative with fins. The fisherman does not know. He sells it anyway. Someone eats it. Someone regrets it. The outcome is predictable. The warning is ignored. The lesson is learned too late. The escolar does not care. It just wanted a squid. It carries on in the depths. Unseen. Unvalued by the casual observer. But noted by those who suffer. It remains in the dark. A testament to the intact slope. A relic of the wild deep. It waits for the line. Or it does not. The choice is random. The outcome is certain. The fish persists.