KINGDOM ANIMALIA: VERTEBRATES

FISHES

All fish share a few characteristics. They live in water and have fins. They are cold-blooded, which means their body temperatures are determined by the temperature of their environment. Oxygen is obtained from water by breathing through gills. In Nova Scotia, there are 20 fish species that occur in freshwater, 51 species that occur in coastal marine waters, and 18 species that are found in both habitats.

AMERICAN EEL (Anguilla rostrata)

An eel's appearance is unmistakable. Adults are slender and snakelike in shape, have strong jaws and sharp teeth, and are covered in a thick mucous coating. They are bronze black with silvery white bellies. An average adult is 600 g to 800 g and measures 60 cm to 80 cm in length. Individuals weighing as much as 7 kg and measuring 1.2 m have been reported. Not much is known about how long eels live.

Eels occur throughout Nova Scotia, inhabiting ponds, lakes, harbours, estuaries, and rivers. Their mucous coating enables them to travel over land when the ground is wet. Consequently, eels can appear in isolated farm ponds and detached lakes.

For many years, the life cycle of an eel puzzled scientists. They are catadromous, meaning they spend most of their life in fresh water, returning to salt water spawn and then die--the reverse to what salmon do. Nobody knew what happened to eels once they left fresh water. Eventually, it was discovered that all American eels migrate to the Sargasso Sea near the Bahamas to spawn. Once hatched, the young begin migrating to fresh water. Eels have a true larval stage, a form drastically different from the adult stage. Larval eels are like transparent spear-shaped leaves. Young eels, or glass eels, are also clear, about 5 cm long, and shaped like adults when they finally reach fresh water. During their years in fresh water, young eels develop colour and mature sexually.

Eels are mainly creatures of the night. They rest on the bottom and bury themselves in mud during the day. At dusk these carnivores emerge to prowl the shallows for prey, feeding on such things as small fishes, amphibian larvae, and aquatic insects. Predators of eels include ospreys, eagles, cormorants, and humans.

ATLANTIC WHITEFISH (Coregonus huntsmani)

Whitefish are part of the salmon family and are streamlined in appearance. The Atlantic, or Acadian, whitefish has an elongated body and a fairly small head. The overall colouration is silvery with dark blue to dark green on the back and silver white below. The mouths of Atlantic whitefish and most other whitefish are relatively small and delicate. They grow between 30 cm and 50 cm long and can weigh up to 900 g.

Currently, Atlantic whitefish are only found in Nova Scotia. They are known to occur only in the Tusket River and Petite Riviere watersheds. They have been observed to move into estuaries and salt water.

For many years people considered Atlantic whitefish to be the same as lake whitefish, Nova Scotia's most common whitefish. The small population of Atlantic whitefish in the Tusket River wasn't identified as a separate species until 1966. Consequently, little is known about the species. Their regular upstream and downstream movements indicate that Atlantic whitefish are anadromous, meaning they spawn in fresh water and mature in salt water. They eat a variety of invertebrates, including marine worms, small snails, and aquatic insect larvae.

Prior to 1960, Atlantic whitefish were more widespread and abundant in Nova Scotia. A small commercial industry exported Atlantic whitefish until the 1950s. However, several factors contributed to the whitefish's decline. The construction of a hydroelectric dam severely disrupted their migratory movements and made the whitefish more vulnerable to predators. Acid rain, overfishing, and destruction of habitat further reduced their abundance. The Atlantic whitefish is designated as a species-at-risk.

BROOK TROUT (Salvelinus fontinalis)

Trout species in Nova Scotia include the native brook and rainbow, as well as the introduced brown trout. The brook, or speckled, trout is probably one of the province's most beautiful freshwater fishes. The back is various shades of green and brown, almost black, with lighter sides highlighted by cream, orange, and red spots. The lower fins are orange with a distinctive white band on the leading edge. At spawning time, males become orange red on their bellies. Brook trout that have gone to sea and returned are known as sea trout and have become silvery with a purple, green, or blue back.

Spawning occurs in late summer or autumn in small streams across the province. Brook trout occasionally spawn in gravel shoals of lakes, especially where springs are present. Females use their tails to scoop out depressions, called redds, in the stream gravel where they lay eggs. Females lay about 3,000 to 4,000 eggs per kilogram of body weight, and males will fertilize the 3.5 mm to 5 mm eggs. These spawning sites often occur where water from springs can seep through the gravel, carrying oxygen to the eggs. Young fish, or fry, emerge in the spring when the water warms. They usually reach sexual maturity in two years.

Through their growth stages, trout feed on aquatic larvae, nymphs, and the hatching adults of insects such as mayflies and stoneflies. Large brook trout also feed on small fishes of their own species or others. The brook trout is actually not a trout, but belongs to the char family, along with lake trout and arctic char. Its scientific name, Salvelinus fontinalis, means "fish of the springs." Its char characteristics require it to live in very clear and cold water. The best water temperatures are around 15° C. Water over 25° C can kill trout or salmon. Clear and cold water is necessary for most of the prey species on which brook trout depend.

Brook trout seldom live longer than five years, never achieving the size of other trout species. In Nova Scotia, their average length in brooks and rivers is 25 cm to 30 cm, and they usually weigh less than 1 kg. Sea-run trout tend to be larger. One fish caught in Halifax County was 60 cm long and weighed 3.4 kg.