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Gadiformes (Grenadiers, Hakes, Cods, and Relatives)

Gadiformes

(Grenadiers, hakes, cods, and relatives)

Class Actinopterygii

Order Gadiformes

Number of families 11


Evolution and systematics

It is important to note that agreement is lacking among ichthyologists as to the composition, origins, hierarchy, or relationships within the Gadiformes. Nor is there agreement concerning external relationships of members of this rather arbitrary group of fishes. There are no groupings of characteristics that can be assigned to the Gadiformes alone; therefore, synapomorphies (derived characters shared by all members of the group in question) have not been identified for all members of the order to the exclusion of nonmembers. Important recent contributions concerning the phylogeny and systematics of the order Gadiformes include Marshall and Cohen 1973; Markle 1982; Cohen 1984; Fahay and Markle 1984; Cohen (Ed.) 1989 (and several contributions therein); and Cohen et al. 1990. To quote Cohen et al. "The assignment to the order of many species is presently as much a matter of ichthyological convention as it is a result of logic." For the purposes of the present volume, we ground our classification on a taxonomic model proposed by Cohen et al. 1990, wherein taxa are listed alphabetically, in order not to suggest phylogenetic relationships. However, we elevate several genera or groups of genera to family status, not arbitrarily, but based on a consensus of several studies. Those 11 families are listed below (alphabetically) with a tally of genera and species presently understood to be contained in each.

  • Bregmacerotidae (1 genus, 15 species)
  • Euclichthyidae (1 genus, 1 species)
  • Gadidae (12 genera, 22 species)
  • Lotidae (3 genera, 4 species)
  • Macrouridae (19 genera, 300+ species)
  • Melanonidae (1 genus, 2 species)
  • Merlucciidae (3 genera, 18 species)
  • Moridae (18 genera, 89 species)
  • Muraenolepididae (1 genus, 4 species)
  • Phycidae (6 genera, 27 species)
  • Steindachneriidae (1 genus, 1 species)

This listing departs from certain other studies presently available in the following ways: 1) The Gadidae, Lotidae, and Phycidae are usually considered subfamilies (Gadinae, Lotinae, and Phycinae) of the family Gadidae in those studies; 2) the genus Steindachneria is included in the Merlucciidae in some other studies rather than being elevated to full family status; and, 3) the Merlucciidae is included in an expanded family Gadidae in some other studies. The listing above is used here largely because it is the result when ontogenetic evidence is considered. It also better emphasizes the diversity present within the order Gadiformes.

Physical characteristics

The families listed above are diagnosed as follows:

  • Bregmacerotidae: These species are sometimes called unicorn cods. The first dorsal fin is a single, elongate ray arising from a position over the head. The second dorsal and anal fins are long mirrors of each other; there are longer rays at the anterior and posterior ends forming rounded lobes. The elongate, trailing pelvic fin rays arise from the throat position and extend well beyond the anus. The lateral line is high on the body and is parallel to the dorsal margin of the body. There are no chin barbels.
  • Euclichthyidae: The single species is called the eucla cod. The body is long and tapering to a very narrow caudal peduncle. It has a large mouth and no chin barbel. The first dorsal fin is short and high, nearly touching the second dorsal fin, which is shorter and extends the length of the body to the caudal fin. The anal fin is long, with a greatly enlarged anterior lobe. The caudal fin is small and asymmetrical, with the lower rays being longest. Each pelvic fin is comprised of four separate, filamentous rays.
  • Gadidae: This family includes cods, haddock, pollock, tomcod, and others. There are three separate dorsal fins and two separate anal fins. The dorsal and anal fins are either touching at their bases or separated by gaps. A chin barbel is usually present. There are pelvic fins, sometimes with one or more elongate rays.
  • Lotidae: This includes the tusk (or cusk), burbot, and lings. The dorsal fin is single (in Brosme), or there is a short first dorsal followed by a long second dorsal in Lota and Molva. The single anal fin has a long base and includes many fin-rays. There is a well-developed chin barbel. The pelvic fins are normal and are not modified into elongate rays.
  • Macrouridae: This includes rattails and grenadiers. The head and trunk are short, and the tail is compressed and greatly elongate, tapering to a point and lacking a caudal fin (with one exception). The chin barbel is usually present. The head and mouth shape and size vary. Eye size varies, but eyes are usually very large. There are two dorsal fins; the first is high, often including spinous anterior rays. The second dorsal and anal fins are long, meeting at the tail tip. The pectoral fins are narrow based and positioned high on the trunk. The pelvic fins are narrow based, thoracic to jugular in position, and comprised of 5–17 rays. Some species have a light organ on the mid-ventral line of the trunk. The benthic species have a well-developed air bladder, and the bathypelagic species lack an air bladder.
  • Melanonidae: This includes the pelagic cod. It is small, not exceeding 5.9 in (15 cm). The body is long, tapering to a very narrow caudal peduncle. The head has numerous fleshy ridges. There is no chin barbel. The dorsal and anal fins are single and long-based. A slight gap separates the caudal fin from the dorsal and anal fins.
  • Merlucciidae: This includes hakes and grenadiers. The genus Merluccius (hakes) has a large head (1/3 to 1/4 of body length), with a large, oblique mouth. The lower jaw is longer than the upper. There are two separate dorsal fins, with the first being short-based, high, and triangular. The second is long and partially divided by a notch in midsection. The single anal fin is similar in shape to the second dorsal. There are pelvic fins with seven rays. The genera Lyconus and Macruronus are characterized by long, tapering bodies lacking caudal fins. The dorsal fin is single with elevated anterior portion in the former, double with short first dorsal followed by very long second dorsal in the latter. Both have large, oblique mouths. Both have normal pelvic fin without elongate rays. The pectoral fin includes elongate rays in Lyconus.
  • Moridae: This includes the moras. The body tapers to a very narrow peduncle. There are two or three dorsal fins, and one or two anal fins. The pelvic fins are thoracic and are wide apart at the bases. The caudal fin is symmetrical and separated from the dorsal and anal fins by a gap.
  • Muraenolepididae: This includes moray cods. The body is long and compressed. The head is small with a chin barbel. The gill openings are restricted and do not open above the pectoral fin bases. There are two dorsal fins, the first comprised of a single, slim ray, and the second long-based and merging with the caudal fin. The anal fin is single, also merging with the caudal fin. The pelvic fins are thoracic with five rays, 2–3 of which are elongate and not attached to others. The lateral line ends at mid-body.
  • Phycidae: This includes hakes and rocklings. There is a single anal fin. There are two dorsal fins, the first either short-based and moderate in height, or comprised of a single elongate, filamentous ray followed by many, very short hair-like rays. There is a single chin barbel, or 2–4 barbels on the snout as well as on the chin. The pelvic fin is normal in shape and length, or with two very elongate rays, often reaching the level of the anus.
  • Steindachneriidae: This includes the luminous hake. The body is long, compressed laterally, and tapers to a point. The head is compressed laterally, and the mouth is very large. There are two dorsal fins, the first with one spine and 7–9 rays, the second with 123 or more rays. The anal fin is comprised of 123 to more than 125, very short rays. The first ray of the pelvic fin is elongate and filamentous. The anus is between the pelvic fin rays and is separated from the urogenital opening just anterior to the anal fin. A purplish, striated light organ covers the lower body and sides of head.

Distribution

The distribution of gadiform fishes varies by family, but in general, gadiforms are residents of cool water, therefore occurring throughout the water column in high latitudes, but mainly in deeper layers of tropical waters, where temperatures are lower (a phenomenon known as "tropical submergence"). Members of the gadiforms are primarily marine, but a few freshwater or estuarine species occur. The distribution of each family was summarized in Marshall and Cohen (1973). Bregmacerotids differ somewhat from the rest of the order in their distribution in tropical and subtropical seas. The single euclichthyid species occurs in Australian and New Zealand waters, where it lives near the bottom in deep water.

Gadids are centered in continental shelf waters of the temperate and boreal North Atlantic, although a few members

have wandered into cool waters of the North Pacific and some species are circumpolar. Three species in Gadus, including the Atlantic cod, occur circumboreally, extending into Arctic waters north of Europe, where they are found as deep as 1,640 ft (500 m). Melanogrammus aeglefinus, the economically important haddock, is restricted to the North Atlantic where it occurs off the northeastern United States and northern coasts of Europe. Microgadus includes the tomcod, a brackish and freshwater species found along the east coast of Canada and the northeastern United States. Pollachius contains two species, one of which is restricted to the eastern North Atlantic, the other occurring on both sides of the North Atlantic. Theragra chalcogramma, the Alaska pollock, is a North Pacific species that is widely distributed in temperate to boreal waters. Fishes in the family Lotidae are also centered in the North Atlantic, and one genus (Lota) has successfully invaded fresh waters of northern Europe and northern North America.

Members of the speciose family Macrouridae (rattails and grenadiers) occur primarily in deep-water habitats throughout the world's oceans (except for the Arctic). Almost all deep oceanic basins contain a macrourid fauna, and it has been estimated that in the Pacific, members of this family comprise the greatest vertebrate biomass between certain depth strata (Cohen et al. 1990). More macrourid species occur in tropical waters than at high latitudes. Several have very restricted ranges, but the deeper-living species are more widely distributed.

The two species in the family Melanonidae are not well-known or often collected. One species is circumantarctic, the other circumglobal in tropical/subtropical waters. Merlucciids occur in continental slope and deep-shelf habitats along coastlines throughout the world. The several species in Merluccius are found on both sides of the Atlantic Ocean, the eastern Pacific Ocean, and off southern New Zealand. The enigmatic genus Lyconus has been found (rarely) in both the North and South Atlantic oceans. One genus (Macruronus) is restricted to subantarctic waters.

The family Moridae is found in all oceans. Most species have very restricted ranges, although Antimora microlepis occurs in much of the entire North Pacific. Four species in the family Muraenolepididae all occur in the Southern Ocean, near the bottom in cold-temperate waters. Each species is restricted to waters around capes or groups of islands surrounding Antarctica.

The Phycidae are bottom-living fishes with a center around the coastlines of the North Atlantic, but with a few Southern Hemisphere species. Gaidropsarus exhibits a center of abundance in the northeast Atlantic Ocean, but also extends to Japan, New Zealand, and South Africa. Phycis contains two species, which are benthopelagic along the eastern North Atlantic Ocean coast. The several species in Urophycis are distributed in the western Atlantic Ocean from Canada through Argentina. Enchelyopus cimbrius is found on both sides of the North Atlantic, where it occurs along the east coasts of the United States and Canada, the Gulf of Mexico, southern Greenland, Iceland, and the north coasts of Europe. Finally, the monotypic family Steindachneriidae (Steindachneria argentea) is restricted to fairly deep waters of the Gulf of Mexico, Caribbean Sea, and continental slope waters off the eastern United States.

Habitat

Habitats occupied by gadiforms vary by family and by genera. Bregmacerotids occur epi- or mesopelagically in open-oceanic waters, extending at times to shallow, coastal habitats. Some have occasionally been found in estuaries. Euclichthys polynemus, the sole species in the family Euclichthyidae, occurs benthopelagically in depths of 820–2,625 ft (250–800 m).

Most species in the Gadidae occur demersally (on the bottom) or benthopelagically. Very few (e.g. Gadiculus argenteus) are pelagic (live in the water column off the bottom). The demersal species occur over a variety of substrates (rock, sand, mud, gravel, or shell debris), most prefer one over the others, and some undertake seasonal migrations between habitat types. The two species in Pollachius are pelagic, and sometimes form large wandering schools that migrate seasonally. The many species in the Macrouridae are found in all oceans, where they occur over very deep bottoms, including the deep ocean basins. The deepest-occurring species occur at greater than 3.7 mi (6,000 m), and few occur shallower than 328 ft (100 m). Melanonids are widely distributed in open ocean meso- and bathypelagic depths between tropical and subantarctic waters.

Most species in the genera Merluccius and Melanonus occur over continental shelves or upper continental slopes. Favored bottom types occupied by species in the genus Merluccius range from sandy to muddy. The ill-known genus Lyconus is pelagic and occurs in open waters of the Atlantic Ocean.

Morids are pelagic to benthopelagic, and occur from shallow coastal habitats (rarely including estuarine habitats) to deep oceanic waters. Favored bottom habitats range from soft to hard bottoms, and from sand to mud. Muraenolepidids live near bottom in moderate depths in waters surrounding Antarctica. Phycids are demersal fishes living on a variety of substrates ranging from mud to sand to shell debris. Finally, Steindachneria argentea lives in the lower water column over soft bottoms on the deeper parts of the continental shelf and upper continental slope.

Habitat requirements of most gadiforms vary according to their life-history stage or age. It is impossible to propose a generalized model of those varying habitat requirements because each family and each species exhibits its own pattern. For example, within the Phycidae, the white hake, Urophycis tenuis, spawns beyond the continental shelf off the northeastern United States, and the fertilized eggs rise into open ocean layers near the surface in an area known as the "Slope Sea." The larvae hatch and develop into a pelagic-juvenile stage, strongly associated with the surface. As they grow they migrate across the entire breadth of the continental shelf toward shore. They arrive in estuaries as small juveniles and spend one season there growing rapidly, finally leaving the estuary at sizes of about 6 in (15.2 cm) at the end of the summer. One- and two-year-olds may remain segregated from older fish by virtue of their occupation of shallower bays and near coastal waters. Subsequently they mingle with the rest of the adult population on deeper parts of the continental shelf, with seasonal migrations into shallower waters. The white hake's range of habitat requirements, therefore, extends from the estuary, across the breadth of the continental shelf, to the upper part of the continental slope, and also includes the entire water column, from surface to bottom (Fahay and Able 1989).

Another phycid, Urophycis chuss, the red hake, has very specialized habitat requirements. The fertilized eggs occur in near-surface layers of oceanic waters off the northeastern United States. After hatching, the developing larvae occupy the same general layers. The larvae gradually acquire silvery coloration and go through a pelagic-juvenile stage when they occur epipelagically or neustonically, within a few inches of the surface, often associated with floating weed or debris. After about two months of this pelagic existence, red hakes settle to the ocean bottom and seek shelter in a variety of structured habitats including beds of clam shells, anemone or polychaete tubes, depressions made by fishes or crustaceans, or most frequently, beds of scallops, Placopecten magellanicus. The young fishes have been found hiding under scallops, but more frequently they enter into an inquiline association with them whereby they live within the scallops' mantle cavities. The young fish remain in this association through their first winter, finally emerging when they are about 4 in (10.2 cm) long in the spring, and then they remain in coastal or estuarine waters through the next summer. When waters cool in the fall, they join older fish in an offshore migration toward the edge of the continental shelf, where they spend their second winter. Their required habitats, therefore, include the entire water column from surface to bottom, specific beds of invertebrate hosts on the substrate, and the entire breadth of the continental shelf from estuary to shelf edge depending on the season (Able and Fahay 1998).

The Atlantic cod also has habitat requirements specific to its life history stages. The fertilized eggs are pelagic and occur in waters overlying bays, the continental shelf, and important banks and shoals, (e.g. eastern Georges Bank, Grand Banks). Larvae are also pelagic and drift slowly away from spawning areas as they develop. The early juveniles descend to the bottom when they are about 2 in (5.1 cm) long and settle on pebble-gravel deposits on important banks, such as the northeast peak of Georges Bank. After settlement, young fishes appear to favor vegetated habitats (such as eelgrass) in coastal embayments, where they avoid predation by older cod, as well as other predators. After two or three years of segregation from adults, these one- and two-year-olds finally join the adult population. Adults exhibit seasonal movements associated with depth and temperature fluctuations, generally moving into shallower waters during summer and retreating to deeper waters for the winter. Data are available demonstrating habitat preferences based on depth, temperature, and salinity, but surprisingly little is known about bottom types favored. Rocky, pebbly, sandy, and gravelly have all been used to describe cod haunts.

Behavior

In general, gadiform fishes are demersal and highly piscivorus, but there are exceptions to these characterizations. These fishes occur primarily in colder waters, but many exhibit seasonal migrations associated with reproduction or the quest for important prey items. Observations on actual spawning behavior are few, and data on day–night differences in their behavior are also few. Feeding behavior also varies seasonally for many species, with a characteristic pattern involving cessation of feeding activity during spawning seasons.

Feeding ecology and diet

Many gadiform fishes feed on prey items occurring in the substrate, and they are assisted in their search for food by the presence of tactile barbels on their chins. Barbels are well developed in almost all of the gadids, phycids, lotids, macrourids, morids, and muraenolepidids, all of whom feed actively on benthic items. Conversely, the diet of one of the most pelagic of the gadids, the pollock (Pollachius virens), consists primarily of euphausiids and Atlantic herring, and its much-reduced barbel reflects this focus on pelagic prey. Certain other pelagic gadiforms, such as the melanonids, bregmacerotids, and Euclichthys polynemus, lack chin barbels, and although their food habits are not well studied, it can be assumed that their important diet items are also pelagic.

The phycid hakes Urophycis chuss and U. tenuis (red hake and white hake, respectively) have similar food habits, although they do not always occur in the same habitats. Both species focus on crustaceans and eat other fishes only secondarily. Annelids, molluscs, and all other prey constitute a minor fraction of their diets. Their feeding behavior also takes advantage of sensitive pelvic fin rays, which are deployed in advance of the fish and aid in the search for prey through their tactile abilities. The Atlantic cod is primarily a piscivore. Among the fishes it consumes, the herring, Clupea harengus, is perhaps the most important, but redfish, mackerel, and smaller cod are also important prey items, and diet components are likely to vary between different study sites. Certain Newfoundland studies have found the capelin to be critically important. Cod also eat crabs, and in some studies crustaceans have been identified as more important than fishes. The haddock, Melanogrammus aeglefinus, has slightly different food habits than its relative, the cod. Although it focuses on crustaceans as a major dietary component, fishes are unimportant in the remainder of its diet, while polychaetes and echinoderms are secondarily important. The diets of macrourids are highly variable and consist of a wide range of fishes and benthic and pelagic invertebrates. Merlucciids are voracious predators, and the several species of Merluccius are highly piscivorous.

Specific information concerning the species that prey on gadiform fishes is lacking for most species. Adults of larger, commercially important species (cod, haddock, etc.) are probably only preyed upon by sharks, billfishes, and other large predators, and their most important predator is undoubtedly man. Young stages of all species, however, face predation by a large number of species, and this plays a large part in determining year-class strength. Some of their predators are larger members of the same species.

Reproductive biology

More is known about reproduction and egg and larval development in the families Gadidae and Merlucciidae, for those two contain commercially important species that have received the most attention. Gadiform fishes, in general, release masses of eggs that are then fertilized externally. Almost all of those eggs are pelagic (although little is known about reproduction in the deep-water species). The Atlantic cod is one of the world's most fecund fishes. A female of 11.0 lb (5 kg) is capable of producing 2.5 million eggs, and larger females can produce more. The haddock is not far behind. A female just under a meter in length can produce close to 2 million eggs. Eggs of gadiforms range from about 0.02 in (0.5 mm) in diameter in some morids and phycids, to about 0.08 in (2.0 mm) in certain gadids and macrourids. The chorion (outer shell) is smooth in most, but it may have a hexagonal pattern in the Macrouridae. Most gadiform eggs have a single, small oil globule, although eggs of the gadids lack an oil globule. Early life history stages are known for fewer than a third of the species described in the Gadiformes, but some descriptions are available for each family. Gadiform larvae exhibit a diverse array of shapes and specializations. According to Fahay and Markle (1984), "There does not seem to be any character unique or diagnostic for young gadiforms. The features of body shape, anus morphology, and pelvic fin development in combination with specific familial characters appear to be the most useful for initial identification. Transformation is gradual and direct with no striking changes in ontogeny." The gut of most gadiform larvae coils early in ontogeny, and combined with a tapering postanal region and rounded head, contributes to an overall tadpole-like appearance. It has not been documented in all gadiform families and is not always easily observed, but very young gadiform larvae have an anus that exits laterally through the finfold rather than at its edge as in most fish larvae. Another characteristic of gadiform larvae is that some secondary caudal rays develop before some primary rays (in forms that have a caudal fin).

Conservation status

The IUCN lists three gadiform species: Physiculus helenaensis is categorized as Critically Endangered, and Gadusmorhua and Melanogrammus aeglefinus are categorized as Vulnerable. There are no gadiform fishes listed by the United States as endangered or threatened. However, among the factors threatening the sustainability of viable populations of gadiform fishes, overfishing figures high, especially regarding the Atlantic cod, Gadus morhua. In some important areas, for example eastern Canadian provinces, the cod is commercially extinct, meaning its population levels are so low that it can no longer sustain a fishery. The loss of various marine habitats, critically important to the survival of young fishes (as well as older stages), is often cited as contributory to fish populations' declines. For almost all fishes, our knowledge of the critical function of these habitats is lacking or superficial, and increased research in these areas is often cited as necessary for proper management of marine resources.

Significance to humans

Certain gadiforms are among the world's most commercially important fishes. In the late 1980s, for example, some 15,101,665 tn (13,700,000 metric tons [t]), representing fully 17% of the world's landings of marine fishes, were comprised of gadiforms. Of this total, 95% was contributed by the Gadidae (cods and their relatives), followed by the merlucciids, the macrourids, and morids.

The Atlantic cod has been an important fishery for centuries, and this fishery has actually influenced the development of western civilization in countries around the perimeter of the North Atlantic Ocean (Kurlansky 1997). It is said that when John Cabot arrived in Newfoundland waters, supposedly the first European explorer to do so, he was greeted by a well-established fleet of Basque fishermen, who in turn had been fishing for cod in Grand Banks waters for centuries before that. In the days before refrigeration, during the time when the Catholic Church mandated the eating of fish on Fridays and holy days, a good-tasting, lean fish that dried well was in a position to dominate the European markets. The Basques were pioneers and masters both in catching and processing cod and therefore enjoyed a commanding position in the world's economy. Despite the heavy fishing pressure exerted on the cod stocks during past centuries, it sustained a huge fishery until the late 1900s, when increased exploitation, based on increasingly efficient fishing methods (possibly combined with changing environmental trends), finally contributed to the collapse of the cod population. The collapse of the stocks off Labrador and Newfoundland has had particularly devastating and tragic economic consequences in eastern Canada, where the effects have been compared to the Great Depression during the 1930s in the United States.

Other gadiforms are also the basis for valuable fisheries. The Alaska (or walleye) pollock, Theragra chalcogramma, contributes more to the world's fisheries than any other demersal fish species, of any family. The total annual landings of this fish in the late 1980s reached 7,389,750 tn (6,703,868 t). The merlucciids (hakes of the genus Merluccius and two species of Macruronus) were once considered trash fish, but now 11 species are being exploited. In the late 1980s, 2,180,192.1 tn (1,977,837 t) were harvested, making them the second most commercially important family of gadiforms after the Gadidae.

Species accounts

List of Species

Atlantic cod
Haddock
Atlantic tomcod
Pollock
Alaska pollock
Burbot
Roundnose grenadier
Silver hake
Red hake
White hake
Luminous hake

Atlantic cod

Gadus morhua

family

Gadidae

taxonomy

Gadus morhua Linnaeus, 1758, Atlantic Ocean and the coasts of Europe.

other common names

None known.

physical characteristics

Three separate dorsal fins, two separate anal fins. Dorsal and anal fins touching at their bases or separated by very narrow gaps. Chin barbel present. Pelvic fins sometimes with one elongate ray. Head relatively narrow and long. Snout to base of first dorsal fin length <33% of total length. Overall brownish to greenish gray on upper sides, paler ventrally. Body covered with spots, sometimes vague.

distribution

East coast of North America, north of Cape Hatteras, North Carolina, Hudson Bay, both coasts of southern Greenland, Iceland, coast of Europe from Bay of Biscay to Barents Sea.

habitat

Widely distributed in a variety of habitats from close to shore to depths >1,968 ft (600 m), but most common over continental shelf between 492 and 656 ft (150 and 200 m). Mostly demersal, although incursions into water column may coincide with feeding or reproduction. Also found in river mouths from late fall to early winter. Tolerates a wide range of temperatures and salinities, but larger fish generally occur in colder water 32–41°F (0–5°C).

behavior

The Atlantic cod is a highly migratory fish. Patterns of migrations differ somewhat between regions. This pattern is associated with reproduction and seasonal temperature change in the Newfoundland stock (Rose 1993). Here, huge schools of cod leave their wintering areas in deep, oceanic waters, and follow tongues of deep, relatively warm, oceanic waters (or highways) across the continental shelf to summer feeding areas nearer to the coast. Spawning occurs in dense concentrations (>1 fish/m3) as they begin this mass movement, with multiple pairs of spawning fish observed in columns above the mass. As this huge mass migrates inshore, it periodically encounters important prey aggregations (such as capelin or shrimp) and disperses in order to feed. The mass is led by the largest fish (or scouts), and the smallest bring up the rear. After reaching nearshore waters, they turn and move northward along the Newfoundland coast in late summer, then eventually return to their deep-water wintering areas.

Off New England, Atlantic cod typically move into coastal waters during the fall, and then retreat into deeper waters during spring. A slightly different pattern occurs in the Great

South Channel area where they move southwesterly during the fall, spend the winter off southern New England and the Middle Atlantic coast, and then reverse this movement during the spring.

feeding ecology and diet

Diet changes with life history stage. The cod is generally omnivorous and voracious. For most ages, feeding occurs in twilight (dawn and dusk), but young fish feed almost continuously. Larvae feed on plankton; juveniles feed on invertebrates, especially small crustaceans; older fish feed on invertebrates and fishes, including young cod. Important diet items are likely to vary between study areas. Herring and capelin are important items in some areas.

reproductive biology

Size and age at maturity have declined in recent years, most likely as a response to the fishery harvesting older and larger fish, or to a general decline in the stock biomass due to intense exploitation. A Scotian Shelf study (Beacham 1983) found that median age at maturity declined about 50% from 1959 (when age at 50% maturity was 5.4 years in males; 6.3 years in females) to 1979 (when age at 50% maturity was 2.8 years in both sexes). Median lengths at maturity declined from 20.1 to 15.4 in (51 to 39 cm) in males; 21.3 to 16.5 in (54 to 42 cm) in females. This smaller-and-younger-at-maturity trend continued between 1972 and 1995 in all zones between Georges Bank and Labrador, until presently in United States waters, maturity is reached between 1.7 and 2.3 years (median age) and 12.6 and 16.1 in (32 and 41 cm) (average length). Off the northeastern United States, the distribution of eggs indicates that important spawning occurs over the northeast peak of Georges Bank and around the perimeter of the Gulf of Maine. Reproduction peaks in winter and spring, but continues weakly throughout the year. The North Sea is a major center for reproduction in the eastern Atlantic, where spawning peaks between December and May. Eggs and larvae are pelagic, and juveniles begin descending to the bottom at sizes between 1.0 and 2.4 in (2.5 and 6.0 cm).

conservation status

The Atlantic cod is listed as Vulnerable by the IUCN. Populations are heavily overexploited by fisheries and are at reduced levels of abundance. Both commercial landings and estimates of spawning stock size are at their lowest levels since 1960. Catch limits are strictly managed, and several important fishing grounds, e.g. portions of Georges Bank, have been closed to all fishing, largely in response to these low levels.

significance to humans

The importance of the Atlantic cod through history can hardly be overemphasized. For the past 1,000 years, the capture, preparation, and distribution of the cod has influenced the development of Western Civilization, especially around the perimeter of the North Atlantic Ocean. The Vikings crossed the Atlantic in pursuit of the cod. The Basques turned the cod into a commercial product in medieval times. Cape Cod was named in honor of the cod in 1602. The cod has actually been the cause of wars between countries, from American colonial times to recent conflicts between Iceland and Great Britain in the twentieth century. Newfoundland was settled by Irish and English natives in the early eighteenth century, largely because of opportunities in the cod fishery. Throughout most of the nineteenth century, this fishery was the most important source of employment and income for people in Newfoundland and much of Eastern Canada. In 1992, the cod population nearly reached a point of commercial extinction in waters off eastern Canada and Newfoundland, and a fishing moratorium was imposed. This moratorium has removed the main source of employment and income for thousands of fishermen from hundreds of small fishing communities and has truly devastated the Canadian economy.


Haddock

Melanogrammus aeglefinus

family

Gadidae

taxonomy

Melanogrammus aeglefinus Linnaeus, 1758, Oceano Europeo.

other common names

None known.

physical characteristics

Three separate dorsal fins, two separate anal fins. Dorsal and anal fins separated by narrow gaps. Small chin barbel present. Pelvic fins sometimes with one elongate ray. Lateral line dark. A prominent blotch on side over the pectoral fin.

distribution

Eastern North Atlantic from Bay of Biscay to Spitzbergen; Barents Sea; around Iceland and southern tip of Greenland; Western North Atlantic from Labrador to Cape Charles, Virginia. In the western Atlantic, highest abundance occurs over Georges Bank, Scotian Shelf, and southern Grand Bank. The highest concentrations off the United States are associated with the two major stocks located on Georges Bank and in the southwestern Gulf of Maine.

habitat

Haddock are most common at depths of 148–443 ft (45–135m) and temperatures of 36–50°F (2.2–10°C). Substrates preferred include rock, sand, gravel, or broken shell. Gravelly sand and gravel are preferred in the Western Atlantic. Haddock exhibit age-dependent shifts in habitat use, with juveniles occupying shallower water on bank and shoal areas, and larger adults associated with deeper water.

behavior

Adult haddock do not undertake long migrations, but seasonal movements occur in the western Gulf of Maine, the Great South Channel, and on the northeast peak of Georges Bank.

feeding ecology and diet

Crustaceans, echinoderms, polychaetes, and mollusks are the most important prey items for juveniles and adults combined. Juveniles prey mostly on crustaceans. Other fishes are of minor importance in the haddock's diet.

reproductive biology

Spawning occurs between January and June, with peak activity during late March and early April. An average-sized 21.7 in (55 cm) female produces approximately 850,000 eggs, and larger females are capable of producing up to three million eggs annually. Spawning concentrations occur on eastern Georges Bank, to the east of Nantucket Shoals, and along the Maine coast. Growth and maturation rates of haddock have changed significantly over the past 30 to 40 years. During the early 1960s, all females age four and older were fully mature, and approximately 75% of age three females were mature. Presently, growth is more rapid, with haddock reaching 18.9 to 19.7 in (48 to 50 cm) at age three. Nearly all age three and 35% of age two females are mature. Although early maturing fish increase spawning stock biomass, the degree to which these younger fish contribute to reproductive success of the population is uncertain.

conservation status

Listed as Critically Endangered by the IUCN. The spawning stock biomass of Georges Bank haddock declined from 76,000 tn (69,000 t) in 1978 to 12,125 tn (11,000 t) by 1993, and has since increased to 41,900 tn (38,000 t) in 1998. However, spawning stock biomass is presently below the minimum threshold level of 58,400 tn (53,000 t), indicating the stock is in an overfished condition. Observed increases in spawning stock biomass of Georges Bank haddock have resulted from conservation of existing year classes. This is a necessary first step in the stock rebuilding process. Recent research vessel surveys provide indications that the 1998 year class may be the strongest in two decades. If this recruitment is realized, there is a potential for significant stock rebuilding.

significance to humans

An extremely valuable fishery on both sides of the North Atlantic. In 1987, the FAO reported that landings of this species amounted to 439,295 tn (398,522 t), of which total most (400,530 tn; 363,353 t) was taken in the northeastern Atlantic. Leading fishing countries are United Kingdom, Russia, Norway, and Iceland, followed by France, Denmark, and others. Northwest Atlantic landings are dominated by Canada, followed by the United States.


Atlantic tomcod

Microgadus tomcod

family

Gadidae

taxonomy

Microgadus tomcod Walbaum, 1792, Artedi.

other common names

English: Frostfish.

physical characteristics

Three separate dorsal fins, two separate anal fins. Dorsal and anal fins separated by gaps and rounded in outline. Chin barbel present. Pelvic fins with one elongate ray. Caudal fin rounded.

Olive brown to green dorsally, paler ventrally, with darker mottling on sides.

distribution

Once reported to occur along the coast of North America from Labrador to North Carolina, the tomcod now occurs only as far south as the Hudson River in New York, where it is common.

habitat

The tomcod is a coastal fish, ascending rivers into habitats with very low salinities, and living near or on the bottom. It is strictly riverine in the Hudson River, but also can survive landlocked in lakes. Young stages are found in estuaries throughout its range, but not those with limited (or no) freshwater input.

behavior

No migrations to offshore waters, but tomcod prefer colder temperatures and move into deeper waters during summer, returning to shallow waters during fall and winter.

feeding ecology and diet

Feeds mostly on small crustaceans (especially shrimps and amphipods), worms, small molluscs, squid, and very young fishes.

reproductive biology

Tomcod spawning is accomplished during winter, and involves elaborate courtship behavior of small groups. Most egg deposition occurs well upstream, in the lowest salinities available, and eggs are weakly adhesive. In the Hudson River, 93–99% of spawners are young-of-the-year fish approaching their first birthday. Larvae hatch at 0.2–0.24 in (5–6 mm) total length and grow rapidly during their first spring. Growth is then depressed during summer and resumes in the fall.

conservation status

Not threatened.

significance to humans

Tomcod is a popular sport and food fish, mostly in Canada and New England states. In addition to a limited hook and line fishery, tomcod are taken with bag nets, pocket nets, and weirs.


Pollock

Pollachius virens

family

Gadidae

taxonomy

Pollachius virens Linnaeus, 1758, Oceano Europeo.

other common names

English: Coalfish, saithe.

physical characteristics

Three separate dorsal fins, two separate anal fins. Dorsal and anal fins separated by narrow gaps. A very small chin barbel present. Lateral line pale. Brownish-green dorsally, slightly paler ventrally. Fins same color as body.

distribution

The pollock occurs on both sides of the North Atlantic. In the western North Atlantic, it is found from the Hudson Strait to Cape Hatteras, North Carolina. In the eastern North Atlantic, from Spitzbergen to Bay of Biscay. Also found in Barents Sea and around Iceland.

habitat

The pollock is strongly pelagic and occurs most frequently over depths of 361–590 ft (110–180 m), although its range can vary with food supply and season. Adult fishes occur in temperatures as low as 32°F (0°C), and they do not tolerate temperatures >52°F (11°C). Young stages are known as harbor pollock and are commonly found in bays and estuaries throughout their range.

behavior

The pollock is a schooling species and is found throughout the water column, not just near bottom. Pollock engage in short migrations associated with temperature changes or for spawning, but otherwise remain fairly stationary within their range.

feeding ecology and diet

The pollock feeds most actively on pelagic prey. Important prey items include euphausiids (especially Meganyctiphanes norvegica), fishes, and molluscs (especially the squid Loligo). Crustaceans are most important in juveniles' diets. Fishes comprise only 12% of juveniles' diets and 28% of adults' diets.

reproductive biology

In the western Atlantic, spawning occurs from September to April with peaks between December and February. Both sexes reach sexual maturity during their third year, at lengths of 19.9 and 18.9 in (50.5 cm and 47.9 cm) in males and females, respectively. Spawners occasionally form huge aggregations. Spawning occurs over hard, rocky bottoms, and activity peaks when temperatures are between 40.1 and 42.8°F (4.5 and 6.0°C). Eggs and larvae develop pelagically, and small pelagic juveniles begin to enter inlets in February and March, when they are <2.0 in (50 mm) long.

conservation status

Not listed by the IUCN. Although there are recognized western Atlantic centers of abundance of pollock on the Scotian Shelf, Georges Bank, and Gulf of Maine, tagging studies suggest considerable movement of pollock between these centers and accordingly, pollock from Cape Breton, Nova Scotia, and south continue to be assessed as a single, unit stock by United States scientists. The total nominal catch from this stock, including commercial and recreational, has been steadily declining since 1986, and the 1996 total represents an 82% reduction from 1986 landings. Spawning biomass is increasing, but within the Gulf of Maine, stock abundance and biomass remain low. Overall the stock is considered to be fully exploited, but not yet in an overfished condition.

significance to humans

Pollock is an important commercial species, and it is marketed in several ways: fresh, as chilled fillets, frozen, canned, dried and salted, and in brine. A large percentage of the 1987 total landings 524,680 tn (475,981 t) was landed in the northeast Atlantic by Norway, Iceland, France, Germany, the United Kingdom, and Denmark. Most of the catch in the northwest Atlantic is landed by Canada, the United Kingdom, and France.


Alaska pollock

Theragra chalcogramma

family

Gadidae

taxonomy

Theragra chalcogramma Pallas, 1811, sea of Okhotsk and the shores of Kamchatka.

other common names

English: Walleye pollock.

physical characteristics

Three separate dorsal fins, two separate anal fins. Dorsal and anal fins separated by gaps. A very tiny chin barbel present. Pelvic fins sometimes with one ray elongate. Olive green to brown dorsally, silvery on sides, pale ventrally. Often mottled or blotchy.

distribution

Found in temperate and subarctic waters of the Northern Pacific Ocean from Sea of Japan, through Okhotsk Sea, Bering Sea, and Gulf of Alaska, then south to waters off central California. Separate stocks (as many as 12) occur in the North Pacific, including those in the Gulf of Alaska, Aleutian Islands, and Bering Sea.

habitat

A schooling fish found on or near the bottom, but also in mid-water to near-surface depths. Heaviest catches made at depths between 164 and 984 ft (50 and 300 m).

behavior

Alaska pollock perform vertical migrations on a daily basis. Juveniles ascend at night to feed on zooplankton near the surface. Migrations of the entire population associated with spawning and feeding. Alaska pollock follow a circular pattern of migrations in the Bering Sea, moving inshore in the spring to spawn and feed, and offshore to warmer, deeper waters in winter.

feeding ecology and diet

Young fish feed on copepod adults and eggs. Adults prey on shrimps, sand lance, and herring off British Columbia; on pink, chum, and coho salmon in Alaskan waters; on mysids, euphausiids, silver smelt, and capelin in Asian waters.

reproductive biology

Alaska pollock begin spawning at age two, but ages four and five contribute most to reproduction. Most spawning begins late February in the Bering Sea, March or April in the Gulf of Alaska. Major spawning aggregations are found in Shelikof Strait, Straits of Georgia, Aleutian Basin, and off the Pribilof Islands. Spawning fish form dense schools high in the water column. Fecundity ranges from 37,000 eggs per female to nearly one million off the coast of Canada. In the western Bering Sea, an 11-year-old female can produce 15 million eggs. Eggs are pelagic and occur mostly within 98 ft (30 m) of the surface.

conservation status

Not listed by the IUCN. Based on estimates of spawning stock biomass and projections into the near future, the Gulf of Alaska stock is not in an overfished condition, nor is it predicted to be.

significance to humans

The Alaska pollock has become an increasingly important human food resource. In the early 1990s, landings of this species were the largest of any demersal fish. The FAO Yearbook of Fishery Statistics for 1987 reported 7,389,750 tn (6,703,868 t) were landed, primarily in the western part of the North Pacific by USSR, Japan, Poland, and Republic of Korea. The largest catches are made over the outer shelf and slope of the eastern Bering Sea, between the Aleutian Islands and the Pribilofs.


Burbot

Lota lota

family

Lotidae

taxonomy

Lota lota Linnaeus, 1758, Europe.

other common names

English: American burbot (Canada), lush (Alaska), lawyer, ling (Canada), eelpout.

physical characteristics

Short first dorsal fin followed by long second dorsal fin. Anal fin single, nearly as long-based as second dorsal. Pelvic fins normal, not modified into elongate rays. Well-developed chin barbel. Anterior nostril has barbel-like flap. Color yellow, light tan, to brown, overlain with a blotchy pattern of darker brown or black.

distribution

The burbot occurs in freshwaters of northern North America and Europe and Asia. Occurs farther north than 40° N (to nearly 80° N).

habitat

Occurs on the bottoms of lakes and rivers, from depths of 1.6 ft (0.5 m) to more than 755 ft (230 m).

behavior

The burbot moves into shallower waters during summer nights. They also move into shallower water to spawn in some parts of their range.

feeding ecology and diet

The burbot has been characterized as a voracious predator and night feeder. Young fish feed on insect larvae, crayfish, molluscs and other invertebrates, whereas adults >19.7 in (50 cm) feed almost exclusively on other fishes.

reproductive biology

Burbot spawning occurs from November to May, but primarily between January and March in Canada, and December in parts of Russia. Spawning usually occurs under the ice, over sand or gravel substrates, at night, and in shallow water (<9.8 ft [3 m] depth). Eggs are semi buoyant. Fecundity ranges from 45,600 eggs per 13.4-in (34-cm) female to 1,362,077 eggs in a 25.2-in (64-cm) female.

conservation status

Not listed by the IUCN. The burbot may occur in considerable numbers in many inland lakes, but has declined over past levels in the Great Lakes, where it had been considered a nuisance species.

significance to humans

The burbot is an important competitor for food of other species, such as lake trout and whitefish. It is fished commercially in Finland, Sweden, and the European part of Russia, but it is only moderately important as a commercial species in Canada and Alaska. Often marketed salted or as pet food.


Roundnose grenadier

Coryphaenoides rupestris

family

Macrouridae

taxonomy

Coryphaenoides rupestris Gunnerus, 1765, Trondheim.

other common names

English: Black grenadier, rock grenadier.

physical characteristics

Abdominal region (tip of snout to beginning of anal fin) short. Snout broad and rounded. Head broad, soft and deep, with tiny chin barbel. First dorsal fin with two spines and 8–11 rays. Pelvic fin has 7–8 rays, with one elongate. A modified scutelike scale at tip of snout. A wide gap between first and second dorsal fins. Anal fin rays much longer than dorsal fin rays. Color brownish gray, with blackish fins. Reaches greater than a meter in length.

distribution

Occurs in the North Atlantic north of Cape Hatteras, North Carolina to Baffin Island, Greenland, off Iceland and Norway, south to Spain in the Eastern Atlantic. Isolated occurrences off North Africa and Bahamas.

habitat

Found between 590 and 7,217 ft (180 and 2,200 m) depth, but concentrated between 1,312 and 3,937 ft (400 and 1,200 m). Adults may be distributed in shallower waters than younger fishes.

behavior

Undertakes a post-spawning migration during the winter, back into relatively shallow waters.

feeding ecology and diet

Undertakes diurnal, vertical feeding migrations that may take it well off the bottom >3,280 ft (1,000 m). Consumes a variety of fishes and invertebrates, primarily pelagic crustaceans such as shrimps, amphipods, and cumaceans. Also feeds on lantern-fishes and cephalapods.

reproductive biology

Undertakes spawning migrations during the summer into deeper waters, particularly near Iceland. Females mature at about 23.6 in (60 cm), males at about 15.8 in (40 cm). Fecundity estimates range from 12,000 to 35,500 eggs per female. In

some areas, may spawn year-round. The eggs are pelagic, spherical, and 0.091–0.095 in (2.3–2.4 mm) in diameter. Their shell is honeycombed and they contain a single oil globule. The larva has been illustrated by Merrett (1978).

conservation status

Not listed by the IUCN. A valuable commercial fish species currently facing overexploitation in the North Atlantic.

significance to humans

The roundnose grenadier is a fish with excellent taste and texture. Some 22,000 tn (20,000 t) are landed annually, primarily by fishing fleets from Russia, Germany, and Poland. Its liver is rich in fats and vitamins.


Silver hake

Merluccius bilinearis

family

Merlucciidae

taxonomy

Merluccius bilinearis Mitchill, 1814, New York.

other common names

English: Atlantic whiting.

physical characteristics

Genus (hakes) characterized by large head (1/3 to 1/4 of body length), with large, oblique mouth. Lower jaw longer than upper. Two separate dorsal fins, the first short based, high, and triangular, separated from the second, which is long and partially divided by a notch in the midsection. Single anal fin similar in shape to second dorsal. Pelvic fins with seven rays. Silver hake has 16–20 gill rakers on the first arch (cf. 8–11 in closely related Merluccius albidus). Color purplish gray dorsally, silvery white lower on sides.

distribution

Occurs on the continental shelf of the northwest Atlantic Ocean from Gulf of St. Lawrence and Grand Banks to offings of North Carolina. Silver hake are most abundant between Nova Scotia and New Jersey. Two stocks have been identified in American waters. One occurs in the Gulf of Maine and northern edge of Georges Bank, the other from the southern edge of Georges Bank to Cape Hatteras, North Carolina.

habitat

Silver hake apparently prefer temperatures between 44.6 and 51.8°F (7 and 11°C) in the summer and fall, and 44.6 and 55.4°F (7 and 13°C) in the spring. They occur in depths between 33 and 4,100 ft (10 and 1,250 m), moving into deeper waters during the coldest time of year. Little is known about substrates they prefer, although juveniles 0.6–2.0 in (1.5–5.0 cm) are most abundant on silt-sand bottoms with concentrations of amphipod tubes. During the colder times of year, silver hake become concentrated in deep basins of the Gulf of Maine and along the upper continental slope.

behavior

All stocks of silver hake exhibit inshore-offshore migrations associated with temperature changes and availability of important diet items. They are primarily demersal fish, but often move upward in the water column, especially at night, presumably following prey items.

feeding ecology and diet

Young silver hake <7.9 in (20 cm) eat mostly crustaceans, such as euphausiids and shrimps. As they grow, they consume increasing proportions of fishes, and adults >13.8 in (35 cm) feed almost exclusively on fishes. Said to be a voracious predator, their diet sometimes includes smaller silver hake.

reproductive biology

Major spawning areas include coastal Gulf of Maine, southern Georges Bank, and waters south of Rhode Island. In these areas spawning reaches a peak in June and July. Spawning occurs during late summer off Sable Island Bank in Canadian waters. Females are asynchronous spawners and lay their eggs in several batches through the season. Age and length at maturity have both declined in recent years. In the early 1960s, silver hake reached maturity at two to three years of age and lengths between 11.4 and 13.0 in (29 and 33 cm). By 1989, these figures had declined to 1.6–1.7 years old and 8.8–9.1 in (22.3–23.2 cm), respectively. Another study found that 20% of two-year-olds had reached maturity in 1973, while 80% of two-year-olds had reached maturity in 1990.

conservation status

Not listed by the IUCN. The decline in size and age at maturity are usually the result of a stock that has been overfished. In both the northern and southern stocks, significant mortality of juvenile silver hake has occurred through discarding in the large mesh and small mesh otter trawl fisheries directed at other species. Annual discard estimates over 1989–1992 ranged from 1,430–11,020 tn (1,300–10,000 t [10 million to 81 million fish]) per year. Excessive discard mortality on juveniles may severely limit opportunities to rebuild either silver hake stock. The southern stock is considered to be in an overfished condition.

significance to humans

The silver hake fishery is important to the United States, Russia, and Cuba. Centers of the fishery are Nova Scotia, Gulf of Maine, and Georges Bank. The total catch in 1987 was 85,950 tn (77,975 t), down from 479,500 tn (435,000 t) in 1973. Silver hake flesh is flaky and good tasting. It is marketed frozen or filleted, and preparation methods include smoking, boiling, and frying.


Red hake

Urophycis chuss

family

Phycidae

taxonomy

Urophycis chuss Walbaum, 1792, Artedi.

other common names

English: Squirrel hake.

physical characteristics

Single anal fin. Two dorsal fins, the first short based and moderate in height, with one elongate ray. A single chin barbel. Pelvic fin comprised of two very elongate rays, tip of the longest reaching level of anus. Upper limb of gill raker with three gill rakers; caudal fin with 28–34 rays.

distribution

Western North Atlantic Ocean from Cape Hatteras, North Carolina to Nova Scotia, rarely to Gulf of St. Lawrence. Two

stocks occur off the northeastern United States: a northern stock from the northern slopes of Georges Bank and Gulf of Maine, and a southern stock, from the southern slopes of Georges Bank to North Carolina.

habitat

Found on muddy or sandy bottoms, less common on gravelly or hard bottoms. Adults found between 16.4 and >984 ft (5 and >300 m), but some seasonal migrations take place. Early settled juveniles live in an inquiline association with sea scallops, Placopecten magellanicus, or other structured habitats, after which they remain in relatively shallow coastal waters until their second year. Thereafter, they are most common in depths <328 ft (100 m) in warmer months, >328 ft (100 m) in colder months.

behavior

Red hake migrate seasonally in reaction to changing temperatures. During summer, they are quite common in nearshore bays and estuaries in New England. During the winter, they migrate into deeper waters.

feeding ecology and diet

Hakes use their pelvic fin rays as sensory organs to find food (Bardach and Case 1965). Juveniles leave their shelters at night and prey on small benthic organisms such as crustaceans. Adults also prey on crustaceans, but consume a wide variety of fish and squid as well.

reproductive biology

Spawning occurs spring through fall off the coast of northeastern United States, but may be restricted to mid-summer in the Gulf of Maine. Eggs and larvae develop pelagically, and the larvae transform into a specialized pelagic–juvenile stage that is highly neustonic (lives very near the surface), often gathering around floating debris. They settle to the bottom at sizes of 1.4–1.6 in (35–40 mm).

conservation status

Not listed by the IUCN. During the early 1960s, total landings from both stocks (northern and southern) peaked at 125,220 tn (113,600 t) in 1966. Annual landings then declined sharply to only 14,220 tn (12,900 t) in 1970, increased again to 84,220 tn (76,400 t) in 1972, and then have declined steadily since. Red hake landings averaged only 1,870 tn (1,700 t) per year during 1990–1999, a decline of over 40% from the 1980–1989 average. Red hake landings in 1999 were well below historic levels. Despite these declines, neither stock is presently considered to be in an overfished condition, and recruitment of younger fish appears to be strong.

significance to humans

A variable constituent of the United States and Canadian trawl fisheries. Large fish marketed fresh or frozen, and small fishes sometimes sold for animal feeds.


White hake

Urophycis tenuis

family

Phycidae

taxonomy

Urophycis tenuis Mitchill, 1814, New York.

other common names

English: Mud hake (Canada).

physical characteristics

Single anal fin. Two dorsal fins, the first short based and moderate in height, with one elongate ray. A single-chin barbel. Pelvic fin comprised of two very elongate rays, not quite reaching level of anus. Upper limb of gill raker with two gill rakers; caudal fin with 33–39 rays.

distribution

Most commonly from Newfoundland to Cape Hatteras, North Carolina, as far south as Florida in deeper water and around the coasts of Iceland.

habitat

Soft, muddy bottoms of the outer continental shelf and upper continental slope. Most occur deeper than 656 ft (200 m). Also found in deeper basins in the Gulf of Maine and submarine canyons along the edge of the continental shelf. Juveniles depend on estuaries during their first spring and summer, where they are common in eel grass beds and other structured habitats.

behavior

Young white hake engage in sand-hiding behavior, whereby they bury themselves in sand with only their heads protruding. The entire population typically moves into deeper waters in the fall, although the largest sizes occur in depths of 656 ft (200 m) and deeper and move very little, if at all.

feeding ecology and diet

Juveniles feed on polychaetes, shrimps, and other crustaceans. Adults also feed on crustaceans, but augment their diet with fishes, including juvenile white hake.

reproductive biology

Spawning occurs in early spring off the northeastern United States, with a separate spawning event during summer over the Scotian Shelf and Gulf of St. Lawrence (Able and Fahay 1998). Larvae develop into a silvery pelagic–juvenile stage that is strongly associated with the ocean surface. These soon migrate into estuaries, where they settle to their first bottom stage, and remain through the summer.

conservation status

Not listed by the IUCN. Total landings of white hake increased from about 1,102 tn (1,000 t) during the late 1960s to 9,150 tn (8,300 t) in 1985. Landings then declined to 5,622 tn (5,100 t) in 1989, rose sharply to 10,582 tn (9,600 t) in 1992, and have since steadily declined to levels not seen since the early 1970s. Total landings in 1998 were 2,866 tn (2,600 t), a 30% decline from 1996. Results of the most recent assessment indicate the Gulf of Maine–Georges Bank white hake stock is in an overfished condition.

significance to humans

Since 1968, the United States fishery has accounted for approximately 90% of the Gulf of Maine–Georges Bank white hake catch, but Canadian fishermen also land significant amounts from Newfoundland and northern Gulf of Maine. Larger fish are marketed fresh or as frozen fillets. Smaller fish are sometimes used for animal feed.


Luminous hake

Steindachneria argentea

family

Steindachneriidae

taxonomy

Steindachneria argentea Goode and Bean, 1896, off Mississippi River delta.

other common names

None known.

physical characteristics

Body long, compressed, tapering to a fine point and tiny caudal fin. Anus separated from urogenital opening, the former situated between the pelvic fin bases, the latter just ahead of the anal fin. A light organ present on the ventral part of body and sides of head, appearing as purplish, striated area. First dorsal fin has one spine and 7–9 rays; second dorsal and anal fins each has more than 123 rays. Anterior portion of anal fin elevated, containing 10–12 rays. Pectoral fin has 14–17 rays. First ray of pelvic fin filamentous. Body silvery, upper part somewhat brownish, belly purplish.

distribution

Found in the central western Atlantic Ocean and off the East Coast of the United States, Gulf of Mexico, and Caribbean Sea as far as Venezuela.

habitat

Occurs on outer part of continental shelf and upper continental slope, usually over soft bottoms.

behavior

Unknown.

feeding ecology and diet

Unknown.

reproductive biology

Eggs of this species are undescribed. The larvae are pelagic and are uncommonly collected in the Gulf of Mexico. They have large heads and large eyes, and the pectoral fins are somewhat stalked as they develop. The striated luminous organ begins to develop in larvae as small as 0.9 in (24.0 mm), when fin rays are completely formed. The anus and urogenital opening initially are found together, but the anus migrates forward with development.

conservation status

Not listed by the IUCN.

significance to humans

No fishery is directed at this species, although large quantities are sometimes landed between depths of 1,300 and 1,640 ft (400 and 500 m) in the northern Gulf of Mexico.


Resources

Books

Able, K. W., and M. P. Fahay. The First Year in the Life of Estuarine Fishes in the Middle Atlantic Bight. Piscataway, NJ: Rutgers University Press, 1998.

Kurlansky, M. Cod. A Biography of the Fish That Changed the World. New York: Walker and Company, 1997.

Periodicals

Bardach, J. E., and J. Case. "Sensory Capabilities of the Modified Fins of Squirrel Hake (Urophycis chuss) and Searobins (Prionotus carolinus and P. evolans)." Copeia 2(1965): 194–206.

Beacham, T. D. "Variability in Size or Age at Sexual Maturity of White Hake, Pollock, Longfin Hake, and Silver Hake in the Canadian Maritimes Area of the Northwest Atlantic Ocean." Canadian Technical Report of Fisheries and Aquatic Sciences 1157: iv+43p.

Cohen, D. M. "Gadiformes: Overview." In Ontogeny and Systematics of Fishes, edited by H. G. Moser, W. J. Richards, D. M. Cohen, M. P. Fahay, A. W. Kendall, Jr. and S. L. Richardson. American Society of Ichthyology and Herpetology, Special Publication no. 1 (1984): 259–265.

——, ed. "Papers on the Systematics of Gadiform Fishes." Science Series No. 32; Los Angeles County Museum of Natural History (1989): 143–158.

Cohen, D. M., T. Inada, T. Iwamoto, and N. Scialabba. "Gadiform Fishes of the World (Order Gadiformes)." An Annotated and Illustrated Catalogue of Cods, Hakes, Grenadiers, and Other Gadiform Fishes Known to Date. FAO Fisheries Synopsis 10, no. 125 (1990): 1–442.

Fahay, M. P. "The Ontogeny of Steindachneria argentea Goode and Bean with Comments on Its Relationships." In Papers on the Systematics of Gadiform Fishes. Science Series No. 32, edited by D. M. Cohen. Los Angeles County Museum of Natural History (1989): 143–158.

Fahay, M. P., and K. W. Able. "The White Hake, Urophycis tenuis in the Gulf of Maine: Spawning Seasonality, Habitat Use, and Growth in Young-of-the-Year, and Relationships to the Scotian Shelf Population." Canadian Journal of Zoology 67 (1989): 1715–1724.

Fahay, M. P., and D. F. Markle. "Gadiformes: Development and Relationships." In Ontogeny and Systematics of Fishes, edited by H. G. Moser, W. J. Richards, D. M. Cohen, M.P. Fahay, A. W. Kendall, Jr., and S. L. Richardson. American Society of Ichthyplogy and Herpetology, Special Publication no. 1 (1984): 265–283.

Fahay, M. P., P. L. Berrien, D. L. Johnson, and W. W. Morse. "Essential Fish Habitat Source Document: Materials for Determining Habitat Requirements of Atlantic Cod, Gadus morhua Linnaeus." NOAA Technical Memorandum (1999) NMFS-F/NEC: 41 p.

Markle, D. F. "Identification of Larval and Juvenile Canadian Atlantic Gadoids with Comments on the Systematics of Gadid Subfamilies." Canadian Journal of Zoology 60, no. 12(1982): 3420–3438.

Marshall, N. B., and D. M. Cohen. "Order Anacanthini (Gadiformes): Characters and Synopsis of Families." Memoirs of the Sears Foundation for Marine Research 1, no. 6(1973): 479–495.

Merrett, N. R. "On the Identity and Pelagic Occurrence of Larval and Juvenile Stages of Rattail Fishes (Family Macrouridae) from 60 N, 20 W, and 53 N, 20 W." Deep-Sea Research 25 (1978): 147–60.

——. "The Elusive Macrourid Alevin and Its Seeming Lack of Potential in Contributing to Intrafamilial Systematics." In Papers on the Systematics of Gadiform Fishes. Science Series No. 32, edited by D. M. Cohen. Los Angeles County Museum of Natural History. (1989): 175–185.

Rose, G. A. "Cod Spawning on a Migration Highway in the North-west Atlantic." Nature 366 (1993):458–461.

Scott, W. B., and E. J. Crossman. "Freshwater Fishes of Canada." Fisheries Research Board of Canada Bulletin. 184(1973): 1–966.

Michael P. Fahay

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"Gadiformes (Grenadiers, Hakes, Cods, and Relatives)." Grzimek's Animal Life Encyclopedia. . Encyclopedia.com. 21 Sep. 2018 <http://www.encyclopedia.com>.

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