Atlantic Herring 2 Underwater World
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QL 626 U5313 no.16 c.2 o u 1 Au - Atlantic Herring 2 Underwater World Atlantic Herring Description Distribution and migration Atlantic herring (Clupea harengus), In the northeast Atlantic, the herring one of the best known of open-sea fish is found from Spitzbergen, north of lthough Canadians have been on Canada's east coast, comprise more Norway, to Gibraltar, at the entrance eating Atlantic herring canned as than one fifth of the area's annual fish- of the Mediterranean. It is also found Asardines since the 1870s, many are not eries catch, with a total value in 1978 of in the Baltic Sea and the Gulf of Fin- aware that these are not the true sar- more than $125 million. land. In the northwest Atlantic, the dines of the genus Sardinops, which The Atlantic herring is a member of Atlantic herring ranges from northern are not found in Canada. Over the the Clupeidae family found in many Labrador and Greenland to North years, Atlantic herring also have been parts of the world, including some Caroli na. salted, smoked, or used as bait or ferti- species living in inland lakes. Among Herring form schools and migrate to lizer and by 1968 most Canadian her- Clupeidae on Canada's east coast are "spawning grounds" in order to repro- ring catches were being reduced to fish- the blueback herring, the gaspereau or duce. Those that spawn in the spring meal or oil. alewife, the shad and the menhaden. In usually do so in shallow, inshore However, with the failure of several the Bay of Fundy, juvenile herring are waters, while fall spawners reproduce major herring fisheries around the known as sardines. in somewhat deeper water, or on off- world in the early l 970s, demand in- The Atlantic herring has a stream- shore banks. creased for Canadian herring. Prices to lined, elongated body, much deeper It is not clear what factors control fishermen rose from an average of one than it is thick, with an iridescent steel- the timing and locality of spawning. cent a pound in 1969 to 12 cents a blue or greenish-blue back and silvery Some fishermen daim it is precisely pound in 1979. sides and belly that provide excellent related to the lunar cycle. Because of Now herring is seldom used for fish- camouflage in the open sea. It has a manpower and funding restrictions, meal production. It is more often deeply-forked tail, large loosely- this idea has never been fully evaluated found on the shelves of supermarkets attached scales and a single dorsal fin by scientists and the existing evidence is as Canadian sardines, and a good pro- on the back. contradictory. ln the southwest Gulf of portion is sold in Europe as frozen St. Lawrence, the peak of spring fillets . spawning is apparently related to the water temperature. However, there is also evidence of a fixed number of waves of spring spawners regulated by factors other than water temperature. Fall spawners reproduce at very dif- ferent temperatures than spring spawn- ers in the same area. On Canada's east coast, tagging studies have shown that herring migra te extensively. Tagging in the southern Gulf of St. Lawrence in 1970 and 1971 showed that the main compo- nent of the adult stock overwinters in the deep fjords of southwest Ouebec Newfoundland. In the spring the fish migrate across the Cabot Strait toward the spawning grounds and rich feeding areas of the Gulf. Spring spawning occurs along the Gaspé and Maritimes coastline, and fall spawning is locally important mainly in the Gaspé and northern New Brunswick areas. Feeding concentra- , tions of herring may be found on American Bank, Bradelle Bank, Or- phan Bank and Fisherman's Bank. In November, most adults return to New- foundland. But the large overwintering concentrations in that area disappeared 30 fathom line in the early 1970s, probably as a result ------ 100 fathom line of high fish catches during that period. Underwater World 3 An early spring fishery on the "Edge" For example, 25-centimetre spring- and slowed when year-old herring (year of the Laurentian Channel started at spawning herring in Chaleur Bay were classes) are abundant. Still other the same time but has recently been dis- found to contain about 30,000 eggs. At studies show fewer larvae survive if continued. 30 centimetres they produced 60,000 adults are abundant, due to predation The major stock of fall-spawning eggs, and at 35 centimetres there were by adult herring. There is also evidence herring off southwest Nova Scotia al- 130,000 eggs. The total weight of eggs that in the Gulf of St. Lawence fewer so undertakes complex migrations. produced also increases faster than the larvae and juvenile herring survive if Spawning is concentrated on the Trin- total weight of the fish. For spring the abundance of mackerel, a major ity and Lurcher Shoals area off Yar- spawners in Newfoundland, internai predator, increases. mouth. Much of the adult stock then eggs are about 28 per cent of the total Clarifying these relationships for migrates up the Nova Scotia coast to weight of herring weighing 200 grams, specific stocks could be very useful for winter in the area around Chedabucto but 40 per cent of the weight of stock management. For example, while Bay. In the spring they migra te to the 400-gram herring. it may be desirable to maintain a high Bay of Fundy where they feed during Fall spawners are about 50 per cent population biomass to encourage egg the summer off the south and more fertile than spring spawners of production, a high abundance of southwest coasts of Nova Scotia before the same length. Thirty-five-centimetre adults may lead to excessive preying on continuing to the spawning grounds. fall spawners in Chaleur Bay produce larvae, or too many larvae could mean Large concentrations of juvenile more than 200,000 eggs per female. slower growth rates. The information herring (sardines) also spend the The high productivity of fall spawners now available on any one stock is not summer along the New Brunswick is probably due to warmer water and sufficient to make management deci- coast of the Bay of Fundy and their greater availability of food during the sions on the basis of these relation- presence supports a large weir fishery summer months before spawning, ships. there. compared to the conditions in March Herring are the prey of a number of Life History and April before spring spawning. pelagic, or open-sea, predators, such as The length and age at sexual matu- Obviously, maintaining an abundant cod, silver hake, salmon, tuna, sharks, rity have varied in Canadian popula- fishable population of herring is not as dogfish, squid, sea birds, seals and tions of the Atlantic herring. It appears simple as the production of eggs. Egg whales. Herring may also fall victim to that to a certain extent herring become and larval mortality is very high, and disease. The most disastrous incident sexually mature at a smaller size as the only a tiny minority of fertilized eggs of this sort occurred between 1954 and population diminishes. Also, they have survive to become juvenile herring. 1956 when most herring in the southern been exploited by the fishery at During spawning, eggs and milt (sperm Gulf of St. Lawrence <lied from a fun- younger ages as the population dimin- cells of male fish with their milky fluid) gus infection. lt is now estimated that ishes. This happened in the Bay of are released into the water by herring about 18 per cent of adult herring die Fundy between 1971 and 1978. The schools. Eggs normally remain on the each year from causes other than fish- standing stock of juvenile fish de- seabed until hatching, which takes ing. But for most herring populations, creased considerably, while the length about 30 days at 5°C, a typical spring fishing is still the most important cause of the majority of mature males and spawning temperature, and only 10 of mortality. Depending on the stock, females dropped from 27 .3 centimetres days at 15 °C, typical of Gulf of St. between 10 and 40 per cent of adult to 25 .6 centimetres. Lawrence fall spawning temperatures. herring are captured every year. As a rule, the youngest mature her- Fall-spawned eggs off southwest Nova The herring's principal food is tiny ring are three years old, and almost all Scotia develop at about 10°C. crustaceans, such as copepods and are mature by age five. ln 1978 in the Before 1970, when most populations euphausids. They also consume eggs, southern Gulf of St. Lawrence, three- were more abundant than they are larvae and any other organisms which year-olds were about 25 centimetres now, the water would turn white over are small enough to enter their mouths. long, while five-year-olds were 30 inshore spawning beds due to the Herring are filter feeders - they use centimetres long. Growth rates, how- release of milt from male spawners. their gills to filter food organisms from ever, vary between and within stocks Storms would carry waves of eggs onto the plankton in the water. over time. These variations are not the beaches, where in some localities fully understood, but are certainly they were shovelled into wagons and influenced by the water temperature used to fertilize the fields. Eggs are also and population size. Higher water eaten by groundfish like cod and had- temperatures often mean faster growth dock, and various flounders. rates, white competition in a larger The subsequent survival and growth population will restrain growth.