Fishes of Canada's National Capital Region
Species Accounts
Clupeidae - Herrings - Harengs
Herrings, shads, sardines, pilchards and menhadens are found world-wide in warmer marine waters with some species anadromous or permanent freshwater residents. There are about 180 species with 9 found in Canada, but only 1 occurs in the NCR.
These fishes have modified scales on the belly forming abdominal scutes with a saw-like edge. The lateral line is usually absent or on only a few scales. Silvery cycloid scales are easily detached and are found only on the body. Teeth are small or absent but gill rakers are long and numerous for sieving plankton. Fins lack spines. There is no adipose fin. The pectoral and pelvic fins have a large axillary scale. The caudal fin is deeply forked. The eye is partly covered by an adipose eyelid. The flesh is particularly oily and is highly nutritional.
Herring are easily caught and are extremely valuable to commercial fisheries. They are the most important fishes economically, both as food for man and also for many other commercial fish species. An estimated 10 billion Atlantic Herring are caught each year and in one year members of the herring family made up 37.3% of all fish caught in the world. Some are used for fish meal, as fertiliser and as an oil source.
Dymond (1939) mentions the American Shad (Alose Savoureuse, Alosa sapidissima (Wilson, 1811)) as occurring in the "Ottawa Region" but this probably refers to the lower Ottawa River outside the NCR. The construction of the dam at Carillon has blocked further upstream migration in recent years and the rapids there before the dam was constructed probably limited access to a few strays, perhaps none of which reached the NCR.
Alewife / Gaspareau
Alosa pseudoharengus (Wilson, 1811)
Taxonomy
Other common names include Gaspereau, Mulhaden, Sawbelly, Spreau, Kyack, Grey Herring, Glut Herring, Branch Herring, Spring Herring, Golden Shad and River Herring.
Key Characters
This herring is the only member of the family in the NCR. It is distinguished by the row of sharp-edged scales on the belly, the adipose eyelid, no lateral line or adipose fin, and scales extending onto each lobe of the caudal fin.
Description
Dorsal fin rays 12-19, anal rays 15-21, pectoral rays 12-16 and pelvic rays 8. Scales along flank 42-54. Gill rakers long, numbering 38-46. Belly scales before the pelvic fin 17-21, behind 12-17.The dorsal fin origin is not far forward of the pelvic fins, there are no enlarged scales before the dorsal fin on the back, there are no teeth on the roof of the mouth, the lower jaw projects and does not fit into the upper jaw notch, eye diameter is longer than the snout length, and there is no diamond-shaped scale pattern, as in related species.
Colour
The back is grey-green and the sides and belly are iridescent silver. The flank may have copper tinges in sea-run specimens or violet tinges in young. Lines run along the flank above the mid-line in some adults. There is a black spot behind the head on the upper flank. Fins are pale yellow or green but can be darkish. The caudal fin is dark with a white leading edge to the lower lobe. The peritoneum is silvery, pearl or pinkish-grey with small spots.Size
Attains 40.0 cm and 0.28 kg.
Distribution
Found from the Gulf of St. Lawrence and northeastern Newfoundland to South Carolina in the sea and tributary rivers. Also in the Great Lakes and tributaries having entered the higher lakes via canal systems. Known only from 2 collections from the Rideau Canal below the locks at Hog's Back Road, Ottawa (Coad, 1983b).
Origin
This species entered the NCR from the Rideau River system where they are known northeast of Kingston. None have been reported from the Ottawa River above the Carillon Dam (Coad, 1983b).
Habitat
The Alewife is a marine species which enters freshwater to spawn but some freshwater populations are land-locked and no longer return to the sea. They are found in both rivers and lakes where their preferred temperature is 18.8°C. The spread of Alewife through the Great Lakes via canals has been rapid. The first appearance in Lake Erie was in 1931, in Lake Huron 1933, and it is now abundant in both these lakes.
Age and Growth
Alewife mature at ages 3-5 with males maturing earlier than females, sometimes as young as 1-2 years. Females are longer and heavier than males of the same age. Life span exceeds 10 years.
Food
Food is the larger zooplankton, items of which may be selected individually, by a dart and suck, as well as filtered indiscriminately while swimming along with the mouth open. Alewife may choose either method depending on available food size. They may also gulp concentrations of plankton. In freshwater zooplankton is eaten too but some bottom amphipods are also taken and the diet may include aquatic insects in late summer when zooplankton numbers fall off. Larval fishes are part of the zooplankton and in freshwaters Alewife may be an important predator on commercial and sport fishes. Introduced Coho Salmon are an important predator on Alewife in the Great Lakes and have reduced mass die-offs.
Reproduction
Spawning occurs in freshwater in spring and early summer (April-July) at water temperatures as low as 8.9°C. The pre-spawning migration in the St. John River, N.B. starts 3 months before spawning. Slow rivers are favoured but spawning does occur in lakes, ponds and streams. In lakes there is a spawning migration from deep water onto beaches in April-July, the timing being dependent on temperature. Spawning occurs in Lake Ontario at 13-16°C. Two or more fish swim in tight circles with flanks touching, rising to the surface. After circling once or twice at the surface, the fish dive and presumably release eggs and sperm over the substrate. Spawning takes place in the evening and at night. Older fish spawn first and may be spawning for the fifth time. Eggs are 1.3 mm in diameter and each female may produce 450,000 eggs. Young return to the sea in late summer and fall. The downstream migration is triggered by increasing rainfall, rapid decrease in water temperature (below 12°C) and the moon phase (dark nights).
Importance
Alewife are commercially important and are caught on the spawning run using weirs, gill nets, dip nets and traps. The 1980 catch, which included Blueback Herring, was 9738 tonnes valued at $2,482,000. The 1988 catch of Alewife alone was 5560 tonnes. They are sold fresh, frozen, smoked, salted or pickled. Some is used as pet food, fish meal or bait in angling and for lobster and snow crab. The flesh is good but bony. Landlocked specimens are thinner and smaller and so are not used much as food for people. In the Great Lakes mass die-offs of Alewife strew beaches with immense numbers of decaying fish, rendering the area unsuitable for human use and a health hazard. They can clog water intake pipes. Recovery of populations is rapid, almost sevenfold in 3 years. Die-offs are caused by sudden temperature changes from cold, deep to warm, shallow waters.
© Brian W. Coad (www.briancoad.com)