Intrinsic rate of increase is unknown. Age at sexual maturity is 10 to 12 years for females, and 7 to 11 years for males (DFO 2003). Once they reach maturity, males grow slower than females, so growth rate of the species is varied (Archambault, pers. comm., 2004). Maximum age is over 50 years (NAFC 1999).

Atlantic Halibut spawn annually in groups on slopes of the continental shelf and the offshore banks of the Western Atlantic. Spawning occurs in deep water over mud or clay bottom off the coast of Norway, and has been reported over rough or rocky bottom in the Western Atlantic (NOAA 1999). Juvenile Atlantic Halibut remain in well-defined nursery grounds for about 90 days (NOAA 1999). Larger animals may not disperse widely and may return annually to spawning grounds, although this is not well-documented (NOAA 1999; Brodziak, pers. comm., 2004).

There is limited support, however, for substantial spawning aggregations, which may be in part due to low density, so we chose not to subtract points here (Brodziak, pers. comm., 2004).

Atlantic Halibut are found on both sides of the North Atlantic and in some parts of the Arctic Ocean (NOAA 1999). They are distributed from Disko Bay, Greenland to Long Island, and have been found as far south as Virginia (NOAA 1999; Zwanenburg et al. 2003). In the Eastern Atlantic, they range from the Bay of Biscay to the Barents Sea and eastern Greenland (Fishbase 2004). We consider this to be a medium size range.

Abundance of Atlantic Halibut is low throughout its range. The Scotian Shelf and Southern Grand Banks and Gulf of St. Lawrence populations in Canadian waters are stable at very low levels of abundance compared to levels in the early 20th century (Zwanenburg et al. 2003; DFO 2004).

In U.S. waters, biomass in the Gulf of Maine and Georges Bank is assessed through both fishery dependent and independent surveys. In 2001, population biomass was estimated at 232 metric tons (mt), which is 9% of BTHRESHOLD and 4% of BMSY. (GARM 2002).

Some researchers believe biomass is at such critically low levels that Atlantic Halibut could go extinct (Krisstensson 2002).

Atlantic Halibut in Canadian waters suffered intensive fishing pressure by mostly American fishers in the first half of the 20th century. Since then, their populations have not recovered, and Atlantic Halibut remain at very low levels of abundance (Zwanenburg et al. 2003; DFO 2004).

Recruitment to the Scotian Shelf and Southern Grand Banks population has been low since 1993 and declined further in 2002, but the numbers of pre-recruits increased from 1998-2001 (Zwanenburg et al. 2003). Likewise, increases in the number of small halibut in the Gulf of St. Lawrence population have been identified and may indicate that recruitment increased in the 1990s (DFO 2004).

Atlantic Halibut have shown no recovery in U.S. waters, and stock assessment biologists do not expect the population to rebuild in the near future (GARM 2002). Also, little or no recovery of Atlantic Halibut populations has been seen in Greenland, Iceland, or Norway (EU Commission 2003).

The IUCN classifies Atlantic Halibut as Endangered—facing a very high risk of extinction in the wild in the near future—on the IUCN Red List by virtue of population reduction of at least 50% caused by exploitation (IUCN 2004). The species is listed as "overfished" in the U.S (NMFS 2003).

In Canada, where most of the Atlantic Halibut in U.S. markets is caught, fishers use bottom longlines to catch them. In the U.S. the only fishery for Atlantic halibut is an experimental fishery in the Gulf of Maine that uses longlines and tub trawls (NOAA 2003). We consider bottom longlines to be less damaging than bottom trawling, but not as habitat friendly as pelagic longlines.

In Canada, where the vast majority of Atlantic Halibut sold in the U.S. are caught, management is divided between two management units: the Gulf of St. Lawrence and the Scotian Shelf and Southern Grand Banks. Landings in the Gulf of St. Lawrence have not met the Total Allowable Catch (TAC) limit in the last 5 years. In 1999, the Department of Fisheries and Oceans (DFO) increased the TAC for the Scotian Shelf and Southern Grand Banks population from 850 metric tons (mt) to 1150 mt. Catch limits are not well-enforced: between 1997 and 2003, landings exceeded the TAC five times (Zwanenburg et al. 2003).

Also, the minimum size limit does not sufficiently protect spawning females, and the majority of commercial catches includes fish smaller than the age at which 50% of females reach maturity (DFO 2004). This is a major liability for the future of the Atlantic Halibut fisheries in Canadian waters.

The Gulf of Maine and Georges Bank population is managed by the New England Fishery Management Council. This population is grossly overfished and is not expected to rebuild in the near future. The New England Fishery Management Council has discussed developing a recovery plan, but none exists. Currently there is a very low limit on the number of Atlantic Halibut that may be taken in the recreational fishery, and Atlantic Halibut are allowed only as bycatch in the groundfish fisheries (GARM 2002).

In European waters, the Atlantic Halibut fishery is managed with gear limitations, annual quotas, minimum size restrictions and area closures. There is a TAC on Atlantic Halibut, as well as a bycatch cap. If bycatch of Atlantic Halibut is reached in directed fisheries for other species, the bycatch cap will close the directed fishery (EC 2002).

A low score of 1.00 point was awarded here to account for the poor enforcement of catch limits in Canadian waters, which supply the majority of Atlantic Halibut to U.S. waters. Despite existent management schemes, the poor status of Atlantic Halibut throughout its range indicates that the species is not being managed for sustainability.

Although catches are monitored and stock assessments are performed in both Canadian and U.S. waters, biological research of Atlantic Halibut is lacking. The Department of Fisheries and Oceans in Canada monitors Atlantic Halibut with research vessel and longline surveys, the latter of which provides the best data. These surveys generally take place when the fish are not spawning and do not collect important data about the maturation process of Atlantic Halibut. The minimum size limit (81 cm) may not be high enough to protect spawning females (Zwanenburg 2003; Archambault, pers. comm., 2004), but there are limited resources available to collect the data needed to assess this (Archambault, pers. comm., 2004). Also, the high variability in abundance estimates among groundfish surveys in the Gulf of St. Lawrence population is cause for concern (DFO 2004).

In Canada, Atlantic Halibut is at very low levels of abundance compared to its population size in the early 1900s (Zwanenburg et al. 2003; DFO 2004). It is not designated as overfished, however, and no recovery plan is in place.

Atlantic Halibut is classified as overfished in the U.S., because population biomass is below the population size threshold (NFMS 2003). The New England Fishery Management Council has discussed developing a recovery plan, but none exists.

Quantitative estimates of bycatch are not available. Most directed fisheries for Atlantic Halibut are limited, and Atlantic Halibut is generally caught incidentally in generalized groundfish fisheries, so it is difficult to assess this issue (Zwanenburg et al. 2003).

White Hake, Cusk, Atlantic Cod, Dogfish, and several other species are caught in association with Atlantic Halibut. Incidental capture of these species is estimated to be high, between 46 and 69% of the catch (Zwanenburg et al. 2003). It is unknown to what degree these other species are landed or discarded.

In the U.S., Atlantic Halibut is primarily captured incidentally in other groundfish fisheries.

Halibut are taken as bycatch in trawl fisheries for groundfish in Canada and the U.S. Managers are concerned that the bycatch of immature halibut in these fisheries is inhibiting recovery of the species. In Canada, shrimp trawlers are now using bycatch reduction devices for groundfish, called Nordmore grates (DFO 2004). Increases in the abundance of small Atlantic Halibut in the Gulf of St. Lawrence in recent years is likely the result of moratoria on Cod and Redfish trawling operations and the adoption of Nordmore grates by shrimpers (Archambault, pers. comm., 2004; DFO 2004).