Pacific Cod fish identification, its habitats, characteristics, fishing methods.
The Pacific cod is one of the most desirable of the North Pacific Ocean's groundfish; a bottom dweller, it is found mainly along the continental shelf and upper slopes down to the depths of 900 meters in huge schools. Pacific cod is very different from cod and its subspecies, living in the seas of the Atlantic Ocean in the Atlantic basin by having sticking on the ground and not floating pelagic fish eggs. It has 3 separate dorsal fins and the catfish whiskers on its lower jaw. It is similar in appearance to the Atlantic cod (Gadus morhua), coloured brown to grey on the back, lighter on the sides, with a belly shading grey to white, and has the typical chin barbel of the cod. The head is a relatively larger and wider than the Atlantic cod. It is very different from Atlantic cod by shorter horn-like extension in front end of a swimming bladder.
Typically 60 cm in length with a weight of 2.5 to 3.6 kg, the Pacific cod is an important commercial food species with a good source of low fat protein, phosphorus, niacin, and vitamin B12. Pacific cod has a moisture content a little higher than that of Atlantic cod, making it less firm. The cooked meat is white, low fat content and a dense, lean and flaky with a mild taste. Cod livers are processed to make cod liver oil, an important source of vitamin A, vitamin D, vitamin E and omega-3 fatty acids (EPA and DHA). Larger cod caught during spawning are sometimes called skrei. Young Atlantic cod or haddock prepared in strips for cooking is called scrod.
The Pacific cod, Gadus macrocephalus, species family Gadidae, also known as gray cod, gray goo, gray wolf, grayest or grayfish, Morue du Pacifique in French, Bacalao del Pacifico in Spanish, Ma-dara in Japanese, is widely distributed in the North Pacific Ocean from Yellow Sea to the Bering Strait, along the Aleutians. In western North America they are found from Japan to the southeastern Bering Sea and to Santa Monica, in the waters of the Aleutian Islands, along the Pacific coast of the Alaska Peninsula, and around the Gulf of Alaska, southwards to northern California, Los Angeles (but rare).
Pacific cod are moderately elongated and heavy body species with large eyes and small scales. They have large mouth and upper jaw projects, square-cut caudal fin, 3 separate and distinct dorsal fins and soft rays, 2 anal fins - 1st anal fin begins below front of 2nd dorsal fin. The first dorsal fin is the highest, with rounded apex, and begins somewhat behind the perpendicular from the upper angle of the pectoral fin, at a distance from the tip of the snout that is about 1/3rd of the length of the body. It contains from 12 to 15 rays, the first two simple, the rest, with the exception of the last or the last two, branched, the third, fourth, or fifth the longest, measuring about 1/6 to 1/7th of the length of the body. The second dorsal fin, varying in length between 17 and 20 % of the length of the body begins at a distance from the tip of the snout. The third dorsal fin begins at a distance from the tip of the snout that measures 62—68 % of the length of the body. In height and shape it resembles the second, but is shorter. It generally contains 17—19 rays, the first three rays and sometimes the last ray simple, the others branched at the tip, and the third, fourth or fifth ray is the longest.
The two anal fins are analogous to the two posterior dorsal fins in shape and position, the distance between the first anal fin and the tip of the snout is somewhat less than that between the second dorsal fin and the same point. The first anal fin with 19 rays has the length of about 20—17% of the body, the first two, three, or four, as well as in many cases the last ray, simple, the rest branched at the tip, and the sixth ray the longest, measuring 10'/2—12 % of the length of the body. The second anal fin with 17 or 18 rays, the first more than half as long as the second and the third ray the longest. The caudal fin is truncate, with 23 to 27 (usually 24-26) divided rays; and the length of the middle rays varies between 7 and 9 % of the body. The pectoral and ventral fins are about equal in length in young and middle-sized Cod, while in old specimens the latter are somewhat shorter. The pectoral fins are rounded at the tip. The ventral fins are set in front of the pectoral, their tips extending to the middle of the latter, when depressed along the body. They contain 6 rays, the second ending in a long, filamentous tip.
Pacific cod has the long chin barbel on lower jaw (equal in length to width of entire eye diameter). Head relatively broad wit interorbital space 1/4 of head length. Predorsal distance more than about 1/3rd of length; anterior part of swimbladder with 2 relatively short, horn-like extension. The lateral line is broad, but narrower in front, and lies much nearer to the back than to the belly, highest with a prominent arch under the 1st and 2nd dorsal fins and straight from the middle or end of the first anal fin to the caudal fin, ending under the 3rd dorsal. It has a chain-like or articulated appearance, oblong projections. The body is covered with fine, thin, and imbricated scales, which, though here of smaller size, also clothe the head and the bases of most of the fins, especially the caudal.
Head relatively broad; interorbital space 18 to 25% of head length. Predorsal distance more than about 33% of length; anterior part of swimbladder with 2 relatively short, horn-like extensions. Long chin barbel equal in length to eye diameter. Space between the 2nd and 3rd dorsal fins is shorter than the eye diameter.
37-57 soft rays on 3 dorsal fins.
31-42 soft rays on 2 anal fins.
Max length: 48 in/120cm.
Max weight: 50 lb/22.7kg.
Max age: 18 years.
The color of Pacific cod is highly variable from dark ash-gray or brown to olive-gray or gray above, with dense, yellow or brownish round spots or pale areas on back and side, on the anterior part of the head and more scattered down the sides. The lower parts of the body are lighter below on the sides and belly, becoming paler ventrally, pale lateral line and pale gray below, without spots. All the vertical fins are dusky or gray, with more or less distinct, dark spots, which sometimes form transverse bands. Dorsal, caudal, and anal fins are usually edged with white on their outer margins that are wider on anal and caudal than on dorsal. The pectoral and ventral fins are lighter and plain, the latter being often of the same colour as the belly. In old and large Cod the iris is silvery, in younger ones yellowish, and in the dark olive-green or red variety more or less reddish.
Pacific cod is very similar to Atlantic cod. However, they usually have smaller body and the pointedness of its fins, and range in weight from 4-11 lbs (2-5 kg). Atlantic cod average weight is 11–26 lb (5–12 kg). The head is a relatively larger and wider than the Atlantic cod. It is very different from Atlantic cod by shorter horn-like extension in front end of a swimming bladder. Also Atlantic cod can change color at certain water depths and has two distinct color phases: grey-green and reddish brown. The harvesting of Pacific cod increased as the harvest of Atlantic cod decreased.
Adults usually occur near bottom, wide-ranging from 40 to 1800 feet (12-549 meters) and could be as deep as 875 m, but the vast majority occur between 50 and 300 m. Usually shallower in spring, deeper in fall adults and large juveniles prefer mud, sand and clay, although coarse sand and gravel substrates. In summer they form small and distinct schools, as opposite to the large aggregations formed by the Atlantic cod.
They are not considered to be a migratory species as the Atlantic species but moves only for short distances, such as seasonal migrations from coast to coast in winter and to and from the shore, or from one bank to the other within a limited region on depths of 30-60 m, in summer. Pacific cod migrate from areas where they feed during most of the year to winter spawning areas, where the water is between 6º-7º C. Spawning migrations have been definitely linked to annual changes in temperature of the ocean in various parts of the geographical range.
At the southern Pacific cod move from deep water to cool shallow water to spawn in the winter and then return to deeper offshore waters to feed when the shallower coastal waters warm. In the northern they make a seasonal movement from deep spawning areas of the outer shelf and upper slope in fall and winter to shallow middle-upper shelf feeding grounds in the spring and early summer. In the eastern Bering Sea and regions of Kamchatka and the Sea of Okhotsk, in response to the autumn-winter drop in temperatures in the littoral waters Pacific cod move off the inner and central shelf regions as summer ends, concentrate in deeper water on the outer shelf and along the shelf edge during winter. They migrate back toward the inner shelf as the ice pack recedes northward in the spring (post-spawning / feeding migration), and are broadly dispersed over much of the inner and central shelf, as well as the outer shelf and along the continental slope, during the summer.
Pacific cod appear to be indiscriminate predators upon dominant food organisms present. They evidently feed very little when they are close to spawning. Adult Pacific cod is an euryphages because the main part of their diet is whatever prey species is most abundant. The diet of adults includes fish, octopuses, and large benthic and bentho-pelagic crustacea such as the Kamchatka crab and shrimps. The fish species consumed include saffron cod, pollock, smelt, and herring, as well as flounders, cottids, salmon and sardines. Larvae at about 20 mm eat copepods.
Juveniles and adults are carnivorous, and feed at night. Young juveniles in the Bering Sea eat copepods, small shrimps and amphipods, and switch to more crabs with increased size. 20-40 cm Pacific cod in the Bering Sea eat shrimp, mysids and amphipods; 40-50 cm Pacific cod eat crabs and amphipods; 50-70 cm Pacific cod prefer mainly sandlance; and 70+ cm Pacific cod consume almost exclusively walleye pollock when available.
Male Pacific cod bacome sexually mature at 2-3 years and 40-53 cm, and females mature at 47-56 cm, but it vary with areas. The overall sex ratio is nearly 1:1, with males dominating in the younger age groups, and females in the older age groups. During the spawning season the females keep near the bottom, the males probably joining them there, but seeming generally to swim higher in the water. Spawning occurs at depths of from 40 to 265 m. on a coarse sand and cobble bottoms from late fall, winter to early spring. Over the North Pacific Ocean, Pacific cod spawn within the period from December to May. Pacific cod in northern areas spawn at lower temperature 1º-5º C (in the Bering Sea), in southern areas at temperature 7º-9º C (Japan) and 6º-9º C (in the Strait of Georgia).
Fecundity in Pacific cod has been estimated between 225,000 and 9+ million eggs per spawning female. The eggs are extremely numerous, their number varies with the size of the fish, a 60-cm female (3-4 years) may produce 1.2 million eggs. A 78-cm female (5-7 years) may have up to 3.3 million eggs, a 75 lbs female may produce 9,100,000. Pacific cod are oviparous and have external fertilization. They are single-batch spawners, releasing all ripe eggs in a single spawning event in a few minutes time ones a year. However Pacific cod do not spawn simultaneously, the older generally spawn earlier than the younger and each Cod requires several weeks and sometimes two months to deposit its spawn, as the whole larvae does not ripen at once, but only partially and gradually. Eggs are demersal, slightly adhesive, and are found sublittorally in polyhaline to euhaline waters between 1º C and 10º C. Fertilized eggs are spherical, approximately 1 mm in diameter. The size as well as the number of the eggs varies with the size of the fish. A 32kg fish has eggs 2.8mm in diameter, while 117kg females can have 3.2-3.6mm eggs.
Optimal hatching temperature is in the range of 3º-6º C. Eggs hatch in 8-9 days at 11º C, 20 days at 5º C, and 28 days at 2º C. Larvae hatch at about 3-4 mm with a yolk sac that is absorbed in about 10 days while floating in the water, and rises higher and higher towards the surface, where the first stages of the development are passed. Larvae metamorphose at 20-25 mm and settle into the benthic community by 35 mm. Larvae and small juveniles are pelagic; large juveniles and adults are parademersal. Larvae are found in the upper 45 m of the water column; highest abundances are between 15 and 30 m. Small juveniles (between 60 and 150 mm in length) usually settle into intertidal/subtidal habitats, commonly associated with sand and eel grass, and gradually move into deeper water with increasing age.
It is possibly hypothesized that spawning of Pacific cod must take place over a shorter period of time than that of the Atlantic species because of the greater instability in the Pacific marine temperatures and Pacific cod are very dependable on a temperature.
Growth of Pacific cod is rapid during early stages.
The Pacific cod fishery is the second largest fishery in Alaskan waters. There are several gear types that are used in the Alaskan and Canadian fishery, each with their own habitat effects. Hook and line, or jigging are deemed the least damaging of the gear types used, while traps, pots, and bottom longline all have varying degrees of bycatch levels and/or habitat effects.
Cod meat is white in color, is moist and lean, medium- to firm-textured, and delicately flavorful with a mild taste. Tender, thick fillets with large flakes that "gape" (separate) when cooked. It is a good source of low fat protein, phosphorus, niacin, and vitamin B12 with a mild flavor and a dense, flaky white flesh. Cod livers are processed to make cod liver oil, an important source of vitamin A, vitamin D, vitamin E and omega-3 fatty acids (EPA and DHA).
Cod is excellent for poaching, broiling, baking, braising, and frying. A popular main ingredient in chowders, which are creamy and binding enough to support the big flakes of meat that fall apart when cooked. Whole cod are often stuffed and baked. Heads and bones make fine soup stock.