Nakaya and Sato (1999) defined three species groups within Apristurus: the longicephalus-group (two species), brunneus-group (20 species) and spongiceps-group (10 species). The longicephalus-group is characterized by a long, narrow snout. Apristurus longicephalus is readily distinguished from A. herklotsi, the other member of the group, by a higher spiral valve count, a shorter snout, and fewer tooth rows. Apristurus longicephalus is unique amongst the Apristurus species in having a duodenum almost as long as the valvular intestine (Nakaya 1988a, 1988b, 1991; Nakaya and Sato 1999).

The Longhead Catshark (Apristurus longicephalus) is a small (to at least 60 cm total length) deepwater catshark with a patchy distribution in the Indo-West Pacific from Japan to Australia and in the Seychelles and Mozambique. It is likely demersal on the continental slope at depths of 500–1,350 m. No species-specific information is available on interactions with fisheries. It is a potential bycatch of demersal deepwater trawl fisheries off Japan and Taiwan, although it has significant refuge at depth in those waters. If caught, it is likely too small for human consumption but may be retained for fish meal. It may be caught in a few limited effort fisheries in the southern and western Indian Ocean part of its range, but across most of the southern range it occurs beyond the depth of fisheries. The species was possibly captured in deepwater hook and line fisheries during the 1960s–1980s in the Philippines. Across all of its range it has refuge at depth. There is no evidence of population decline and the species is not suspected to be close to meeting the population reduction threshold, and the Longhead Catshark is assessed as Least Concern.

The Longhead Catshark has a patchy distribution in the Indo-West Pacific with records from Mozambique; the Seychelles; and off Java and Sumatra, Indonesia; the Philippines; Taiwan; Okinawa Trough, East China Sea; Tosa Bay of Shikoku Island, southern Japan; off Western Australia and north Queensland, Australia; and New Caledonia (Iglésias et al. 2005, Last and Stevens 2009, Nakaya and Kawauchi 2013, Ebert et al. 2021).

There is no information available on population size, structure, or trend for the Longhead Catshark. The species may be caught by deepwater fisheries in the northern part of its range in Japan and Taiwan, although it has significant refuge at depth beyond the operational depth of the fisheries in that region. In the southern part of its range, it may have previously been fished in the Philippines and may be encountered in a few limited effort fisheries in Australia and in Mozambique at the upper limit of its depth range. Population trend is suspected to be stable based on refuge at depth across its range and limited overlap with fisheries.

The Longhead Catshark is demersal or near the substrate on the continental slope at depths of 500–1,350 m (Ebert et al. 2021). It reaches a maximum size of at least 60 cm total length (TL), males mature at 43–49 cm TL and females mature at 47–51 cm TL (Ebert et al. 2021). Reproduction is oviparous with hermaphroditic individuals recorded (Ebert et al. 2021). Little else is known of its biology.

There is no specific information available on bycatch of the Longhead Catshark. It is possibly a bycatch of Japanese deepwater commercial trawl fisheries which operate to depths of ~700 m (Rigby et al. 2020). It is possibly also a bycatch of deepwater trawl fisheries which operate off the northeast and southwest coasts of Taiwan at depths of 300–700 m; these fisheries target multiple species of prawns with all incidental catch retained (Rigby et al. 2020). In the Philippines, the species' upper-depth limit is beyond the reach of the trawl fisheries that operate to a maximum depth of 200 m (Rigby et al. 2020). It may have previously been encountered in the Philippines by bottom-set multiple hook-and-line gear that targeted dogfish sharks for their liver oil; the fishery was intensive from the 1960s–1980s and still operates but at an artisanal scale (Gaudiano and Alava 2003, Flores 2004, Rigby et al. 2020). In Indonesia, deepwater demersal longline fisheries mostly operate at depths of 100–200 m and thus the species would not be caught. In New Caledonia, there are currently no deepwater fisheries. In Australian waters, it may be encountered in a few fisheries at the upper limit of its depth range but the fisheries effort is minimal (Patterson et al. 2022). In Mozambique, a crustacean trawl fishery operates at depths of 100–600 m and may encounter this species at the upper limit of its depth range. Effort, however, has been declining substantially since 2007; the 2016 effort level was half the 2012 level, which in-turn was only 30% of that in the early 1990s. Currently there are 2–3 vessels operating at any one time, for a total of around 1,000 trawls per year (Pollom et al. 2020). Other trawl fisheries in southern Mozambique (Jacquet et al. 2010, Benkenstein 2013) may threaten this species. Across all of its range, this species has significant refuge in deeper waters from fishing pressure.

No information is available on use and trade; it is likely too small for human consumption but if retained may be used for fish meal in Taiwan.

There are no species-specific measures are in place. In Japan, management measures have been implemented since the mid-1990s to control fishing effort that include total allowable catches, seasonal closures, and gear restrictions (White Paper 2015). In Taiwan, since 1999, all demersal trawling is prohibited within three nautical miles of the coast and within 12 nm for trawlers larger than 50 Gross Registered Tonnage (Fisheries Agency 2019, Liao et al. 2019). In Australia, the species would receive refuge in the network of marine parks (Parks Australia 2023). Further research is needed on population size and trends, and life history, and catch rates should be monitored, particularly if fisheries expand to greater depths across the species range.