Brown catshark - Apristurus brunneus

The brown catshark Apristurus brunneus is a small, slender deep-sea shark with an elongated body. The head is broad and flattened, the muzzle is long and narrows towards the front. On its underside there are numerous sensory pores with which the shark detects movements and weak electrical signals from prey near the ground.

The eyes are small and located on the sides of the head. The wide, curved mouth sits on the underside; There are clearly visible lip furrows at the corners of the mouth. The numerous small teeth have several points and are suitable for holding small fish and invertebrates, not for cutting up large prey.

Fins and coloring

Both dorsal fins are small, similar in size and set far back. The first begins approximately above the posterior area of ​​the pelvic fins. What is striking is the long anal fin, the base of which extends almost to the caudal fin. The caudal fin is low and has a significantly larger upper than lower lobe.

• Slender, soft body with broad, flat head.
• Long snout with prominent rows of sensory spores.
• Five short gill slits on the sides behind the head.
• Two small dorsal fins far back on the body.
• Very long anal fin immediately in front of the caudal fin.
• Uniform light to dark brown coloring with contrasting fin edges.

Oregon Sea Grant states a maximum total length of around 68 to 69 centimeters. On average, females are larger than males. The simple brown color, the elongated body and the dorsal fins located far back are important identifying features.

The brown catshark lives in the eastern Pacific. It is certainly documented by Canada across the west coast of the USA to Baja California in Mexico. Further evidence and distribution models extend along Central America and the South American Pacific coast.

The extended known area includes bodies of water Guatemala, Honduras, Nicaragua, Costa Rica and Panama as well as before Ecuador, Peru and Chile. In the southern parts of the area, finds are much more patchy than in North America.

Continental margin and deep sea floor

FishBase states a depth range of 33 to 1,306 meters. The species lives close to the ground on the outer continental shelf and on the upper continental slope. It is primarily observed over soft mud and sand bottoms, but can also occur in more structured deep-sea habitats.

The water at these depths is cold, dark and often low in oxygen. Most direct observations come from research catches, bottom trawling surveys and remotely operated submersible robots. A lack of reporting in a coastal section does not automatically mean that the species does not occur there.

The map is a historical, schematic representation from 2007. It shows the occurrence summarized at that time and not a current, precise database of finds. More recent evidence and the larger depth range known today cannot be fully deduced from this.

The brown catshark stays close to the seabed and slowly searches for small prey. Its snout pores and keen sense of smell help it locate animals in mud or in complete darkness. Little is known about daily activity rhythms and migrations.

food

According to the Monterey Bay Aquarium The species mainly eats shrimp, small squid and fish. Studies also mention euphausiids. The wide mouth and small, multi-pointed teeth are suitable for hunting small, soft or only weakly armored prey on the deep sea floor.

Eggs with long adhesive threads

The species lays eggs. An egg capsule usually develops in each of the two oviducts, allowing a female to carry two capsules at the same time. The embryo is nourished exclusively by the yolk and, after developing, hatches as an independent young animal.

The Study on the morphology of egg capsules describes egg capsules about 52 to 72 millimeters long. There are long threads at both ends; the rear ones in particular are strongly and tightly rolled up. They can anchor the capsule to corals, sponges or other solid substrate and prevent it from being carried away in the current.

Females with egg capsules were found off Canada between February and August. It is unclear whether egg laying has the same rhythm further south. Gestation period of the capsules, hatch size, age at sexual maturity and life expectancy are still poorly known.

The current assessment of the IUCN Red List classifies the brown catshark as not endangered (Least Concern). The assessment, published in 2025, replaces the previous classification as insufficiently researched. The population trend is stated to be stable.

There is no known targeted fishing for this small species. However, it can occur as unintentional bycatch in bottom trawls, bottom longlines and other deep fishing gear. Animals from great depths can be injured by changes in pressure and capture, even if they are subsequently released.

Why further observation remains necessary

• Large parts of the area are only sampled scientifically on an irregular basis.
• Species identification within the species-rich genus Apristurus is difficult.
• By-catches are not identified or reported down to species in all fisheries.
• Egg capsules and delicate deep-sea beds can be damaged by ground-based equipment.
• Growth, age, maturity and natural mortality are poorly understood.

The broad distribution area and occurrence at great depths probably offers some protection from local interference. This does not exclude regional pressures on the continental slope. Standardized bycatch data and photographically documented species identification are therefore important for future assessments.

Protective measures should particularly focus on limiting bottom-touching fishing in sensitive deep-sea habitats and treating unavoidable by-catch with care. The protection of coral and sponge fields also benefits the egg capsules of numerous deep-sea catsharks.

The brown catshark poses no danger to humans. With a body length of less than 70 centimeters, small teeth and a life well below normal diving depths, there are practically no direct encounters with bathers or scuba divers.

Live animals are primarily observed using deep-sea cameras and remote-controlled vehicles. Such recordings are scientifically valuable because body shape, behavior and habitat can be documented without catching the shark or removing it from the seabed.

Bycatch and scientific reporting

Fisheries and Oceans Canada requests that shark encounters in British Columbia be documented and reported. For a usable report, the location, date, depth, fishing gear, total length, gender and clear photos of the head, fins and the entire side of the body are particularly helpful.

• Only keep an animal on deck for as short a time as possible and protect it from dehydration.
• Fully support body and tail; never carry on gills or fins.
• Carefully remove hooks and fishing gear without damaging the mouth or gills.
• If there is severe pressure damage, follow regional scientific release protocols.
• Report unusual catches with photos to fishing or research institutions.

Keeping them in public aquariums is rare because of the cold water, pressure, depth and bottom habitat requirements. For research and education, high-resolution ROV images and correctly assigned egg capsules are often more meaningful than living exhibits.

The greatest human impact comes not from encounters but from fishing on the continental margin. Bycatch documentation that is as accurate as possible can at least generate data from an unintentional catch without having to specifically remove additional animals.