Pollock, or pollack, is the common name for either of the two species of marine fish in the Pollachius genus in the cod family (Gadidae), Pollachius pollachius and Pollachius virens. Both of these fish are commercially important and are found in the North Atlantic. They have three dorsal fins and two anal fins separated by a narrow gap and grow to moderately large size (over a meter in length). Other names for P. pollachius include the Atlantic pollock, European pollock, lieu jaune, and lythe, while P. virens is sometimes known as Boston blues (separate from bluefish), coalfish (or coley), or saithe.
Pollock are an important part of the New England and North Atlantic fisheries, though less so than cod and haddock. They are a type of "white fish," having dry or white flesh, unlike oily fish. They are a popular food fish in a number of different preparations, including eaten whole or in fillets or steaks, and steamed, fried, broiled, boiled, smoked, dried, or salted.
Ecologically, pollock also are important to food chains in the North Atlantic, consuming various fish, mollusks (squid), and crustaceans (primarily euphausids, or krill), and being preyed upon by sharks and other larger fishes during various stages of the pollock's life history.
There are also members of the Theragra genus that are commonly referred to as pollock. This includes the Alaska pollock or walleye pollock (Theragra chalcogramma) and the rarer Norwegian pollock (Theragra finnmarchica). While related (they are also members of the family Gadidae) to the above pollock species, they are not members of the Pollachius genus of the North Atlantic. Alaska pollock generally spawn in late winter and early spring on Southeast Bering Sea. The Alaskan pollock fishery in the Bering Sea fishery is the largest single-species food fish fishery in the world. This article will be limited to the two species of Pollachius.
The Pollachius genus is one of twelve genera placed in the subfamily Gadinae (cods and haddock) of the cod family Gadidae (16 genera) of the order Gadiformes and the class Actinopterygii. Members of the Gadiformes are characterized by lacking true spines in the fins, generally long dorsal and anal fins, usually cycloid (rarely ctenoid) scales, a swim bladder without pneumatic duct, and pelvic fins (when present) below or in front of the pectorals. Members of the almost exclusively marine family Gadidae (one Holarctic freshwater species) are typified by having the first dorsal fin posterior to the head, the head of the vomer toothed, and the swim bladder not connected with auditory capsules. Members of the Gadinae subfamily are characterized by having three dorsal and two anal fins, an egg without an oil globule, usually a chin barbel, and a slightly forked or truncate caudal fin (Nelson 2006). In some taxonomic schemes, Gadinae is raised to the family level.
The two species Pollachius species, P. pollachius and P. virens, are similar to each other. However, they can distinguished from one another by the shape of the jaw, the lateral line, and the presence of absence of a chin barbel. P. pollachius, also known as the lythe, has a lower jaw that distinctly projects beyond the upper jaw (Lune and Froese 2008a), while P. virens, also known as the saith and coalfish, has a lower jaw that is approximately even in length with the upper jaw (Picton and Morrow 2005b). In addition, the lateral line in P. pollachius, which is continuous over the whole body, is greenish and has a distinct curve above the region of the pectoral fin (Picton and Morrow 2005a; Lune and Froese 2008a). The lateral line of P. virens is straight and pale (although even being light in color, it is conspicuous against the background of the darker side) (Picton and Morrow 2005b). Furthermore, P. virens has a very small chin barbel, while P. pollachius lacks a chin barbel, which is an unusual trait for members of Gadinae.
P. virens is brownish-green or blackish dorsally, on the side and back, while slightly paler or silvery white ventrally, with fins of the same color as the body (Grzimek et al. 2004; Picton and Morrow 2005b; Lune and Froese 2008b). P. pollachius has silvery-white sides and belly, while the back is dark or greenish brown, and the fins are uniformly dark except for the yellowish pelvic fins (Picton and Morrow 2005a; Lune and Froese 2008a). The first anal fin of P. pollachius begins underneath the first dorsal fin and is considerably longer than the second anal fin, while the first anal fin of P. virens starts beneath the space between the first and second dorsal fins (Picton and Morrow 2005a,b).
Both species, Pollachius pollachius and Pollachius virens, can grow to 4 feet 3 inches (1.3 meters) (Picton and Morrow 2005a,b) and can weigh up to 46 pounds (21 kilograms).
Both species are found in the North Atlantic. Pollachius virens occurs both in the western North Atlantic, from the Hudson Strait to Cape Hatteras in North Carolina, and in the eastern North Atlantic from Spitzbergen to the Bay of Biscay; it also is found in the Barents Sea and around Iceland (Grzimek et al. 2004). Pollachius pollachius is found in the northeast Atlantic near Norway, the Faeroes, and Iceland to the Bay of Biscay, as well as England and Ireland (Lune and Froese 2008a; Picton and Morrow 2005a).
P. virens is a pelagic fish that can be found in water up to 100 fathoms (180 meters or 590 feet) deep over rocks, and anywhere in the water column. They occur in temperatures as low as 0°C (32°F), and do not do well is the water temperature is greater than 11°C (52°F). Younger stages, known as harbor pollock, are often found in bays and estuaries (Grzimek et al. 2004).
P. pollachius are mainly pelagic to benthopelagic and found close to shore over hard bottoms (Lune and Froese 2008a). They are found from the surface to 200 meters (Picton and Morrow 2005a).
P. pollachius mostly spawn at around 100 meters in depth (Lune and Froese 2008a). P. virens spawn in late winter and early spring, over hard, rocky bottoms, with peaks between December and February in water temperature between 4.5°C and 6.0°C (40.1°F-42.8°F) (Grzimek et al. 2004).
P. virens is a gregarious schooling fish. It feeds on fish, mollusks (squids), and crustaceans (largely krill), while the young feed on copepods, amphipods, krill, nematodes, annelids, and crustaceans (krill, shrimps, crabs) (Grzimek et al. 2004; Lune and Froese 2008b). P. pollachius have a similar diet of fish, cephalopods, and crustaceans (Lune and Froese 2008a).
Pollock is largely considered to be a white fish, although it is a fairly strongly flavored one. It has a low-to-moderate fat content, is firm, and has a slightly sweet, delicate flavor (Herbst 2001). It is normally sold in markets between 4 and 10 pounds (1.8-4.5 kilograms) (Herbst 2001). P. pollachius is considered to have dry flesh, but of good flavor (Lune and Froese 2008a). Pollock can be available fresh, frozen, canned, smoked, dried, or salted, and is eaten fried, steamed, boiled, broiled, baked, and microvaved (Herbst 2001; Lune and Froese 2008b).
Although traditionally a popular source of food in some countries like Norway, in the United Kingdom it has previously been largely consumed as an economic and versatile alternative to cod and haddock in the West Country, elsewhere being known mostly for its traditional use as "Pollack for puss/coley for the cat." However, in recent years pollock has become more popular due to over-fishing of cod and haddock limiting those supplies. Pollock can now be found in most supermarkets as fresh fillets or pre-prepared freezer items.
Because of its slightly gray color, pollock is often prepared, as in Norway, as fried fish balls or if juvenile sized perhaps breaded with oatmeal and fried as in Shetland. Year old fish are traditionally split, salted, and dried over a peat hearth in Orkney where their texture becomes wooden and somewhat phosphorescent. The fish can also be salted and smoked and achieve a salmon-like orange color (although it is not closely related to the salmon), as is the case in Germany where the fish is commonly sold as Seelachs or sea salmon.
Alaskan pollock has a much milder taste, whiter color, and lower oil content. Single frozen Alaskan pollock is considered to be the premier raw material for surimi; the most common use of surimi in the United States is "imitation crabmeat" (also known as crab stick). Alaskan pollock is commonly used in the fast food industry, for example the fish filet of Dairy Queen, Arby's, and Burger King are all made from Alaskan pollock.
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