Chionoecetes bairdi
Encyclopedia
Chionoecetes bairdi is a species of crab
known alternatively as bairdi crab and tanner crab. C. bairdi is closely related to Chionoecetes opilio
, and it can be difficult to distinguish C. opilio from C. bairdi. Both species are found in the Bering Sea
and are sold commercially under the name "Snow crab". Tanner crabs have suffered from overfishing
and as a result strict controls have been placed on tanner crab fisheries.
with pincer claws on their frontmost pair of legs. They can live over a decade with most adults reaching 1 lbs by the time they reach adulthood, usually after about five years. Females will incubate fertilized eggs for a full year before hatching during spring plankton
blooming season. The larvae are at first able to swim, but lose this ability and settle to the bottom after about two months. The tanners' diet consist mostly of other ocean bottom crustaceans, clams and worms. Bottomfish and humans are their main predators. Little is known about their social structure except that the sexes remain mostly separate except during mating season.
. The Bering Sea fishery for tanners opened in 1961 and soon became a major fishery in the North Pacific, with record catches as high as 332000000 lbs. Before the passage of the Magnuson Fishery Conservation and Management Act of 1976 much of the Bering Sea tanner crab was caught by Japanese and Soviet fishing vessels.
Due to the massive harvests, numbers declined sharply, with only 1200000 lbs harvested in 1984. Sensing the danger of overfishing
tanner crab to the point of extinction, legislators and fisheries managers closed tanner crab fishing entirely in 1986 and 1987. Policy adjustments were made to limit the catch, but the fishery was closed again in 1997 due to a very poor harvest in 1996. In the mid 2000s fisheries managers introduced a "Crab Rationalization Program" based on similar programs in the North Atlantic and New Zealand. The program introduced individual fishing quota
s based on each crab fishing boat's previous catches and a requirement that a percentage of the catch be offered for sale in the regions where it was caught. This program was popular with environmental and conservation groups, although some small-scale crab fisherman complained that it placed them at a disadvantage as they could never catch more than their alloted share even if there were more crab available. In addition to overfishing, researchers from the School of Fisheries and Ocean Sciences
have hypothesized that prevailing winds may affect crab population numbers from one year to the next.
Tanner crabs are among the commercial species whose market value is ruined by dinoflagellate
s, species of Hematodinium
, that cause bitter crab disease.
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
known alternatively as bairdi crab and tanner crab. C. bairdi is closely related to Chionoecetes opilio
Chionoecetes
Chionoecetes is a genus of crabs that live in the northern Pacific and Atlantic Oceans.Other names for crabs in this genus include "queen crab" and "spider crab" – they are known by different names in different areas of the world....
, and it can be difficult to distinguish C. opilio from C. bairdi. Both species are found in the Bering Sea
Bering Sea
The Bering Sea is a marginal sea of the Pacific Ocean. It comprises a deep water basin, which then rises through a narrow slope into the shallower water above the continental shelves....
and are sold commercially under the name "Snow crab". Tanner crabs have suffered from overfishing
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
and as a result strict controls have been placed on tanner crab fisheries.
Biology
Tanner crabs are considered a short-tailed or "true" crab. They are decapodsDecapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
with pincer claws on their frontmost pair of legs. They can live over a decade with most adults reaching 1 lbs by the time they reach adulthood, usually after about five years. Females will incubate fertilized eggs for a full year before hatching during spring plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
blooming season. The larvae are at first able to swim, but lose this ability and settle to the bottom after about two months. The tanners' diet consist mostly of other ocean bottom crustaceans, clams and worms. Bottomfish and humans are their main predators. Little is known about their social structure except that the sexes remain mostly separate except during mating season.
Fisheries
Tanners are normally caught through the use of crab pots similar to those used to catch the larger King crabKing crab
King crabs, also called stone crabs, are a superfamily of crab-like decapod crustaceans chiefly found in cold seas. Because of their large size and the taste of their meat, many species are widely caught and sold as food, the most common being the red king crab, Paralithodes camtschaticus.King...
. The Bering Sea fishery for tanners opened in 1961 and soon became a major fishery in the North Pacific, with record catches as high as 332000000 lbs. Before the passage of the Magnuson Fishery Conservation and Management Act of 1976 much of the Bering Sea tanner crab was caught by Japanese and Soviet fishing vessels.
Due to the massive harvests, numbers declined sharply, with only 1200000 lbs harvested in 1984. Sensing the danger of overfishing
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
tanner crab to the point of extinction, legislators and fisheries managers closed tanner crab fishing entirely in 1986 and 1987. Policy adjustments were made to limit the catch, but the fishery was closed again in 1997 due to a very poor harvest in 1996. In the mid 2000s fisheries managers introduced a "Crab Rationalization Program" based on similar programs in the North Atlantic and New Zealand. The program introduced individual fishing quota
Individual fishing quota
Individual fishing quotas also known as "individual transferable quotas" are one kind of catch share, a means by which many governments regulate fishing. The regulator sets a species-specific total allowable catch , typically by weight and for a given time period. A dedicated portion of the TAC,...
s based on each crab fishing boat's previous catches and a requirement that a percentage of the catch be offered for sale in the regions where it was caught. This program was popular with environmental and conservation groups, although some small-scale crab fisherman complained that it placed them at a disadvantage as they could never catch more than their alloted share even if there were more crab available. In addition to overfishing, researchers from the School of Fisheries and Ocean Sciences
School of Fisheries and Ocean Sciences
School of Fisheries and Ocean Sciences,or SFOS, is part of the University of Alaska Fairbanks. SFOS offers a bachelor of arts and a bachelor of science in fisheries, and master’s and doctoral degrees in oceanography, fisheries and marine biology....
have hypothesized that prevailing winds may affect crab population numbers from one year to the next.
Tanner crabs are among the commercial species whose market value is ruined by dinoflagellate
Dinoflagellate
The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth...
s, species of Hematodinium
Hematodinium
Hematodinium is a genus of dinoflagellates. Species in this genus, such as Hematodinium perezi, the type species, are internal parasites of the hemolymph of crustaceans such as the Atlantic blue crab and Norway lobster...
, that cause bitter crab disease.