seal shark, follows deep-water prey upward

Size
Length: 1–1.5 m, Weight: 10–30 kg
Lifespan
30–50 years
Diet
Small fish, squid and crustaceans. Hunts near seafloor in deep, dark waters. Uses large, comb-like teeth to saw through flesh. Also scavenges on dead animals. Feeds on whatever found.
Habitat
Deep continental slopes and seamounts between 200 and 1,500 metres depth. Prefers muddy and sandy bottoms with stable, cold temperatures. Found near seafloor in darkest waters.
Range
Deep waters around New Zealand from Northland to Campbell Plateau. Most common on Chatham Rise and off east coast of South Island. Also found in Atlantic, Indian and Pacific Oceans.
Endemism
Native
Main Threats
Bycatch in deep-sea trawl and longline fisheries is primary threat. Extremely slow reproduction makes populations highly vulnerable. Habitat damage from bottom trawling. Valued overseas for liver oil.
Population
Global populations declined significantly due to overfishing. Listed as Vulnerable by IUCN. Caught as bycatch in orange roughy and oreo fisheries. Slow growth means recovery takes decades.
Conservation Status
Not Threatened
The teeth are unlike those of any other shark. Upper teeth are narrow and pointed. They are for gripping. Lower teeth are large, serrated and blade-like. They are for sawing through flesh. A shark that bites, then saws. A shark that does not let go. The design raises questions. The answers are in the deep. The mechanism is brutal. It is efficient. It works. The seal shark gets its name because it occasionally preys on seals. Its diet consists mainly of fish and squid. It is a deep-sea sleeper shark. The body is dark, almost black. The snout is short and rounded. It lives between 200 and 1,500 metres down. Sunlight never reaches this depth. It is a shark that has never seen the sun. The darkness is total. The cold is constant. The pressure is immense. The shark adapts. It survives. It persists. The liver is filled with low-density oils. These provide buoyancy in the deep sea. This adaptation allows the shark to hover effortlessly near the seafloor. It saves energy in an environment where food is scarce. Every calorie counts. Every movement is calculated. The shark can live for half a century. This happens in the cold, dark waters of the deep sea. It is a slow life. It is a long life. The pace is glacial. The growth is incremental. The survival is hard-won. Global populations have declined significantly due to overfishing. The seal shark is listed as Vulnerable by the IUCN. In New Zealand it is caught as bycatch in deep-sea trawl and longline fisheries. These fisheries target orange roughy and oreo. No one targets the seal shark directly. But it dies in the nets anyway. The catch is incidental. The death is real. Slow growth and low reproduction mean recovery could take decades. The biology cannot keep up with the industrial scale of extraction. The deficit grows. The population shrinks. A deep-sea sleeper shark with a saw for a mouth fights for survival. The world fishes too deep and too hard. The nets drop. The shark hovers, unaware. The net sweeps past. The shark is caught. It does not know why. It was just hovering. It was just living its half-century life. Now it is on a deck. It is dying in the light. The transition is abrupt. The air is foreign. The gills fail. The end comes quickly. The saw-like teeth are useless on deck. The buoyant liver is drained. The flesh is discarded or sold. The value is extracted. The life is spent. The seal shark remains a mystery to most. It lives out of sight. It dies out of mind. The deep sea offers no refuge from modern fishing technology. The trawl reaches down. The longline extends far. The seal shark intersects with both. The outcome is rarely positive. The vulnerability is structural. The status is Vulnerable. The trend is downward. The future is uncertain. It carries on in the dark. For now.