Sentinel Fisheries - Redfish
The Prince of Wales, later Edward VII, feasted on redfish in 1883 at the great international Fisheries Exhibition.
If redfish, members of the family Scorpaenidae, were virtually unknown in England in 1883, they were hardly more so in the Canada of that day. Yet in the twentieth century, redfish were to become the basis of an important fishery of Canada’s Atlantic coast, with the United States currently acting as our most important customer for redfish products.
Swimming in the deep waters at the edge of the great fishing banks and in deep channels carved in the ocean floor, redfish are mainly noted for the brilliant scarlet colour from which they take their name.
Aside from its deep colour, which ranges from orange to flame-red, sometimes with a brownish cast, the beaked redfish is distinguished from other spiny-rayed fish by a bony protusion on the lower jaw, by a fan of bony spines that radiates out from around the gill cover, and by its large eyes.
Two types of redfish are known in the Northwest Atlantic, Sebastes mentella being the more common. It is found at depths of greater than 200 meters, has a bright red colour, a relatively large eye and a long, well developed beak. Recent studies indicate that this species may, in fact, be further subdivided to include S. fasciatus. The S. marinus, usually found at depths of less than 240 meters, is orange in colour rather than red, has a smaller eye and a small, blunt beak that is relatively weak. It generally grows to a much larger size than its close cousins. As far as the commercial fishery or fisheries management is concerned, the two (or three) species are managed together as a single unit.
In the North Atlantic, the family of Scorpaenidae is most significantly represented by the redfish, also known as ocean perch or rosefish. The fish live in cool, northern waters (3° to 8°C) on both sides of the Atlantic.
The deep waters off New Jersey form the southern limit of redfish range in the West Atlantic. Redfish usually inhabit waters from 100 to 700 meters in depth in the Gulf of Maine, off the Nova Scotia and Newfoundland banks, in Gulf of Saint-Lawrence, along the continental slope from the southwestern Grand Banks to Hamilton Inlet Bank, and in the area of Flemish Cap. Occasionally, in some areas of Maine, Newfoundland and the Bay of Fundy, where the waters are very cool, redfish have been caught in shallow waters near shores and around wharves. However, this is unusual. Redfish generally are stratified by depth, with smaller fish being found in shallow and larger fish in deep waters. Redfish are known to move upward from bottom at night, returning downward during the day.
Redfish are viviparous, which means that eggs are fertilized internally, and eggs develop within the female’s body. After hatching, some 25 000 to 40 000 fry are retained in the ovaries of the female until the yolk sac of each is absorbed. Then the young fish are born, alive and free-swimming.
Mating generally occurs in September or October, and the young are born sometime between April and July. The young are about 7 mm at birth and swim freely in the surface waters until they reach a length of approximately 25 mm, at which time they move into deeper waters over rock and mud bottom.
Redfish are slow growing and long-lived. Growth varies somewhat from population to population, but generally fish have reached some 15 cm by about the age of four, 25 cm by 10, 32 cm by 20, and 38 cm by the age of 30 years.
During the first six to seven years, males and females grow at about the same rate, but afterward the growth of males slows somewhat. The maximum size of S. marinus, the largest of the redfish, is 50 to 55 cm for males and 65 to 70 cm for females. S. mentella males reach a maximum length of only 40 to 45 cm and the females 45 to 60 cm. Redfish reach sexual maturity at eight to 10 years of age on the Grand Banks, but slightly later in the northern part of their range.
Redfish feed on a combination of small invertebrates, and small fish. They are in turn preyed upon by such species as cod and Greenland halibut (turbot). However, the effect of predation on redfish stocks is not yet well understood.
Redfish in the West Atlantic first became commercially important in the Gulf of Maine around 1935. Since then, the fishery has expanded greatly with the discovery of other stocks, such as those in the Gulf of Saint Lawrence, the Grand Banks, Hamilton Bank, and on Flemish Cap. These discoveries were mostly made between 1947 and 1952 from the deck of the research vessel INVESTIGATOR II.
The commercial fishery expanded extensively in those years to reach a maximum weight of 389 000 metric tons (t) in 1959. The Canadian landings decreased from 103 000 t in 1975 to 12 300 t in 1999. At first, redfish were caught in bottom trawls that dragged along the sea floor during the daytime. Subsequently (with the discovery of off-bottom movement by redfish at night), the commercial fishermen found they could make large catches at night by using a midwater trawl. A midwater trawl is shaped like a bottom trawl but the fisherman is able to adjust the depth at which the trawl is pulled through the water.
The minimum commercially acceptable size of redfish landed in Canada is approximately 25 cm. Most of the catch is destined to be turned into fillets, skin on or off, which is the major product of shore-based plants, and they are marketed as ocean perch throughout North America.
Redfish are distributed throughout a wide area of Canada’s eastern coastal waters. The resources are divided into seven separate stocks, each of which is managed separately. Since 1974, all of these stocks have been regulated by a Total Allowable Catch (TAC) which sets the upper exploitable limit for each stock.
Adaptation of document : Redfish, by McKone W.D., LeGrow E. M., Coll. Underwater World, published by Communications Directorate, Fisheries and Oceans Canada, 6 p. 1984.