deep-water beryx, long-lived and slow-growing

Size
Length: 30–50 cm, Weight: 0.5–1.5 kg
Lifespan
20–30 years
Diet
Small fish, squid and crustaceans. Hovers in deep water using long, trailing fins. Uses large eyes to detect prey in low light. Feeds near the seafloor at night.
Habitat
Deep continental slopes and seamounts between 200 and 800 metres depth. Prefers rocky bottoms and steep underwater topography. Often found in aggregations near submarine canyons and underwater mountains.
Range
Deep waters around New Zealand from Northland to the Campbell Plateau. Most common on the Chatham Rise and off the east coast of the South Island. Also found in the Atlantic, Indian and Pacific Oceans.
Endemism
Native
Main Threats
Bycatch in deep-sea trawl and longline fisheries. Habitat damage from bottom trawling on seamounts. Slow reproduction makes populations vulnerable. No targeted commercial fishery in New Zealand waters.
Population
Population trends are poorly understood due to the deep-water habitat. Caught as bycatch in orange roughy and oreo fisheries. Quota management limits total bycatch. Better species-specific data is needed for accurate stock assessments.
Conservation Status
Not Threatened
Brilliant red in the sun. Invisible in the dark. That is the longfinned beryx. Its striking colour is the first wavelength absorbed by seawater. At depth the fish effectively disappears. It becomes a ghost in the twilight zone. Large eyes and long, trailing fins complete the picture. This is a creature built for hovering in deep water. It waits for something edible to drift past. You will not see one on a reef or in a harbour. The longfinned beryx lives between 200 and 800 metres down. It inhabits continental slopes and seamounts. Rocky bottoms and steep topography create hiding places there. It aggregates near submarine canyons and underwater mountains. It hangs in the current with those long fins trailing behind like ribbon. It feeds on small fish, squid and crustaceans. It uses those big eyes to detect prey in the dim light. At night it rises closer to the seafloor to hunt. Nobody targets this fish. It arrives on deck only as bycatch. Nets aimed at orange roughy and oreo sweep it up. That is both good news and bad news. Good because there is no directed fishery. Bad because deep-sea trawling damages the rocky habitats where beryx live. The species reproduces slowly. A long life of two or three decades sounds impressive. But it also means populations cannot bounce back quickly from pressure. New Zealand's quota management system caps the bycatch. The truth is we do not know enough about this deep-water red ghost. We cannot say whether those caps are right. Population trends remain poorly understood. The fish lives so far down that studying it requires expensive research vessels and deep-sea cameras. What little we know comes from fisheries data. This only counts the ones that get caught. Until we invest in better species-specific data, the longfinned beryx continues its slow, hovering existence in the dark. Red and unseen. Waiting. That is the deep sea for you. It is full of mysteries we have only begun to unravel. It contains fish like this one that have been doing just fine until we showed up with our trawl nets. It carries on.