Atlantic Herring

- Atlantic Herring QL 626 U52 No 16 1984 2 Underwater World lthough Canadians have been eating The Atlantic herring has a stream- A Atlantic herring canned as sardines lined, elongated body, much deeper since the 1870s, many are not aware that than it is thick, with an iridescent steel- Atlantic Herring they are not the true sardines of the blue or greenish-blue back and silvery genus Sardinops, which are not found sides and belly that provide excellent in Canada. camouflage in the open sea. It has a In 1953, a reduction plant fortrans- deeply-forked tail, large loosely- forming herring into fishmeal and oil attached scales and a single dorsal fin on was opened in the Magdalen Islands, the back. and other plants followed in New Bruns- wick, Newfoundland and Nova Scotia. Life History By 1968, most Canadian herring catches In the northeast Atlantic, the Atlantic were being reduced to low-priced fish herring ranges from northern Labrador meal or oil. However, with the failure and Greenland to North Carolina. On of several major herring fisheries around the other side of the Atlantic, herring is the world in the early l 970s, the demand found from Spitzbergen, north of for food herring increased. Prices to Norway, to Gibraltar, at the entrance to fishermen rose from an average of one the Mediterranean. cent a pound in 1%9 to 12 cents a pound Along the Canadian Atlantic coast, in 1979. spawning may occur in any month be- Now herring is seldom used for fish tween April and October, but it is con- meal production. Most of it is exported centrated in May and September. Most as frozen fillets, sardines, pickled and evidence shows that spring and fall cured fillets, and pickled and cured spawners are biologically independent whole-dressed herring. Whole herring is stock groups. also sold fresh or frozen and is used as It is not clear what factors contrai the lobster bait. The preparation of roe for timing and locality of spawning. How- the Japanese market is a lucrative activ- ever, herring eggs adhere to abjects on ity which bas probably not yet attained the seabed, such as rocks, grave! and its full potential in Atlantic Canada. algae. Less stable surfaces do not provide the necessary conditions for the Description maintenance of a spawning bed. Sorne The Atlantic herring (Clupea haren- fishermen claim that the timing of g us) is one of the best known open sea spawning is precisely related to the lunar fish on Canada's east coast. It is a mem- cycle. This idea bas never been fully ber of the Clupeidae family found in evaluated by scientists and the existing many parts of the world, including some evidence is contradictory. ln the south- species living in inland lakes. Arnong west Gulf of St. Lawrence, the peak of Clupeidae on Canada's east coast are spring spawning is apparently related to the blueback herring, the gaspareau or the water temperature. However, there alweife, the shad and the menhaden. is also evidence of a fixed number of waves of spring spawners regulated by factors other than water temperature. Fall spawners reproduce at very differ- ent temperatures than spring spawners in the same area. 146535 3 AOU 12 19 lmproving knowledge of the subse- quent survival and growth of larvae and juveniles is a frontier of biological researcb. After they have absorbed the yolk sac retained from the egg stage, young larvae risk starvation if their hatching is not followed by a period of adequate food production. They also Quebec may be dispersed if currents are not suitable. Predation by pelagic fish such as mackerel and herring may be a major cause of larval mortality. The larvae of some stocks bave been shown to stay very close to the spawning bed where they were hatched. This is a result of the formation of tidally- induced retention areas, which prevent larvae from being dispersed by water currents. When these larvae metamorphose into juvenile herring, the resulting schools are composed of fish from the same spawning site. Since the members of a school stay together, this results in 30 fathom hne the maintenance of separate stocks, even - - - --- 100 fathom line though mixing with other stocks may occur during feeding or overwintering. The length of time it takes for larvae to metamorphose into juvenile herring is related to the water temperature and the availability of food. Larvae hatched in the early summer will become ju- During spawning, eggs and rnilt veniles that same year, whereas fall (sperm cells of male fish with tbeir rnilky hatched larvae will not metamorphose fluid) are released into the water by until the following spring or summer. herring in scbools. Eggs remain attached The length and age at sexual maturity to the seabed until hatching, which takes have varied in Canadian populations of about 30 days at 5°C, a typical spring the Atlantic herring. As a rule, the spawning temperature, and only 10 days youngest mature herring are three years at 15°C, typical of Gulf of St. Lawrence old, and almost all are mature by age fall spawning temperatures. Fall- five . But it appears that to a certain spawned eggs off soutbwest Nova Scotia extent they will become sexually mature develop at about 10°C. at a younger age as populations dirninish Before 1970, wben most populations under intensive fishing. In 1978 in the were more abundant tban they are now, the water would turn white over inshore spawning beds due to the release of milt from male spawners. Storms would carry waves of eggs onto the beaches, where in some localities tbey were shov- elled into wagons and used to fertilize the fields. Eggs are also eaten by groundfisb like cod and haddock, and various flounders. ÇJL 626 U52 No 16 1984 4 Unde rwater Wo rld Gulf of St. Lawrence, three-year-olds Herring are the prey of a number of were about 25 cm long, while five-year- open-sea predators, such as cod, tuna, olds were 30 cm in length. Growth rates sharks, dogfish, squid, sea birds, seals vary between and within stocks over and whales. Herring may also fall vic- time. These variations are not fully tim to disease. Between 1954 and 1956, understood, but are certainly influenced many herring in the Gulf of St. by the water temperature and popula- Lawrence <lied from a fungus infection. tion size. Higher water temperatures lt is now estimated that about 18 per may be accompanied by faster growth cent of adult herring die each year from rates, while competition for food in a causes other than fishing. But for most dense population may restrain growth. herring populations, fishing is the most Fecundity (the production of eggs per important cause of mortality. Depend- female) increases as fish grow. For ing upon the stock, between 10 and 50 example, 25 cm spring-spawning herring per cent of adult herring are captured in Chaleur Bay produce about 30,000 every year. eggs. At 30 cm they produce 60,000 The herring's principal food is tiny eggs, and at 35 cm, 130,000. The total planktonic (drifting) crustaceans, such weight of eggs produced increases fast- as copepods and euphausids. They also er than the total weight of the fish. For consume eggs, larvae and any other spring spawners in Newfoundland, organisms which are small enough to internal eggs are about 28 per cent of the enter their mouths. Herring are pri- total weight of herring weighing 200 gm, marily particulate feeders ("bite" but 40 per cent of the weight of 400 gm feeders), but they may also filter feed herring. with their gills when food is suitable. Fall spawners produce about 50 per cent more eggs than spring spawners of Major Stocks the same length. Fall spawners meas- A large stock of herring spawns off uring 35 cm in Chaleur Bay produce Southwest Nova Scotia in the fall . more than 200,000 eggs per female. The Spawning activity is concentrated on the high productivity of fall spawners is Trinity Ledge and Lurcher Shoals near probably due to warmer water and Yarmouth. Much of the adult stock then greater availability of food during the migrates up the Nova Scotia coast to summer months before spawning, com- winter in the area around Chedabucto pared to the conditions in March and Bay. In the spring, they migrate to the April before spring spawning. Bay of Fundy where they feed during the summer off the south and southwest coasts of Nova Scotia before moving to the spawning grounds. Juvenile herring from this stock mix with Gulf of Maine juveniles to form large concentrations of "sardines" along the New Brunswick fig. 1. Herring weir coast of the Bay of Fundy during summer, where they support a traditional weir fishery. Both spring and fall spawning herring are found in the southern Gulf of St. Lawrence. Spring spawning occurs mainly in Chaleur Bay, on the eastern shore of New Brunswick, and at the Magdalen Islands. The most important fall spawning sites are in Chaleur Bay, and along the eastern shore of New Brunswick and Nova Scotia. The biologically-separate spring and fall spawners mingle together during summer feeding in the shallow waters along Underwater World 5 these same coasts. They again mix in the Fishery and Stock Trends fall, mainly in Chaleur Bay, in prepar- Prior to the mid l 960s, in most areas ation for the migration to overwintering of Atlantic Canada, herring were caught areas. ln the late l960s, when these by small inshore boats using gillnets or stocks were much more abundant than traps, or in weirs.

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