Squawfish ( Northern Pikeminnow )

By Bill and Lori Jollymore's In Species
Northern Pikeminnow
Ptychocheilus oregonensis

The northern pikeminnow is the largest minnow in British Columbia - adults often exceed 400 mm in fork length. There is an old record from Shuswap Lake of a 29-pound (13 kg) pikeminnow. Some minnow ! The largest Squawfish caught on Lac Des Roches weighed 3.7 kg ( slightly over 8 pounds ) and was caught by Randy Michinsky in 2006. Adults are easily distinguished from other B.C. minnows: they lack barbels, possess a large, toothless mouth (the upper jaw extends back beyond the front margin of the eye), and the length of the upper jaw exceeds the diameter of the eye. Juveniles (up to about 200 mm) have a conspicuous black spot at the base of the tail.

Young-of-the-year pikeminnows often occur in mixed schools with young redside shiners and peamouth. They are separable from young redside shiners by the relative position of the dorsal and pelvic fins (the dorsal fin in redside shiners originate well behind the origin of the pelvic fins) and from young peamouth by the dark spot at the base of the caudal fin.

In British Columbia, pikeminnows occur primarily in lakes and slow-moving streams. In the summer, adult pikeminnows cruise the littoral zones of lakes and reservoirs (mainly in water <5 m deep) and on the offshore side of weed beds but within about 45 m of the shore. In the winter, adults move into deeper water and are not as bottom oriented. In a few lakes, some adults even occupy the limnetic zone in both winter and summer. In rivers, there are similar patterns of habitat use with adults in deeper water than juveniles and young-of-the-year in shallow water along the river's edge.

In lakes, juveniles typically occur closer to shore and in shallower water than adults. Unlike adults, they are commonly observed inside weed beds. In rivers, juveniles usually are found in low velocity areas (back channel and sloughs) in water less than 2 m deep. The substrate is usually silt, sand, or fine gravel. In lakes, young-of-the-year pike minnows are typically found in shallow water within a metre of shore. Early in the summer they are usually associated with aquatic vegetation.

Apparently in the spring, rising water temperatures trigger spawning in northern pikeminnows. The threshold temperature is about 12 °C (late April to early July). Spawning occurs in both flowing water and lakes, but most of the known pikeminnow spawning sites in our area are in inlet streams. At these sites, it is rare for pikeminnows to ascend the stream for more than a few hundred metres and spawning usually occurs in the first or second riffle above the lake. There is a dense aggregation of males with females cruising slowly around the edges of the aggregation. Females ready to spawn enter the aggregation and swim more rapidly than cruising females. Many males follow the female down to within a few centimetres of the substrate where eggs and sperm are released. The eggs are adhesive. Fecundity in females is a function of body size and ranges from about 5,000-95,000 eggs. The eggs take about six days to hatch at 18 °C. Newly hatched fry are about 8 mm and strongly nocturnal.

Pikeminnows grow rapidly in their first summer and, depending on spawning time and food availability, usually reach between 35-65 mm by the end of the first growing season. In males, sexual maturity is attained in about 4 to 6 years, while in females sexual maturity is not reached until 6 to 8 years. So far, the oldest pikeminnow recorded in B.C. was in its 19th growing season.

Young-of-the-year pikeminnow consume a wide variety of prey including organisms taken from both the bottom and the water surface (e.g., cladocerans, copepods, ostracods, and chironomid larvae and pupae). As they grow, pikeminnows take larger prey. Juveniles often are surface oriented and at times forage heavily on terrestrial insects. At about 100-125 mm, they start taking fish. Adults above 300 mm are primarily piscivores, although they will eat almost any prey of suitable size (e.g., crayfish, frogs, toads, and even small rodents).

The pikeminnows (Ptychocheilus) are restricted to western North America. The northern pikeminnow is the Columbia representative of the genus. Other species of pikeminnows occur in the Umpqua, Sacramento-San Joaquin, and Colorado River systems.

In B.C., they occur throughout the Columbia and Fraser drainage systems, and from the Fraser, they have colonized the Skeena, Nass, and upper Peace systems. Along the central B.C. coast, they occur in the upper portions of the Klinaklini and Dean rivers. Although primarily an Interior species, pikeminnows reach the coast in large rivers like the Fraser and Skeena; however, they are intolerant of seawater and have not reached any coastal islands.
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