Animalia Life

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.

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