Case Study

Located 217 m above sea level, Lake Winnipeg is a shallow lake composed of two basins: a wide north basin and a narrow south basin. On average, Lake Winnipeg is only 12 meters deep and receives 517 mm of precipitation annually. Lake Winnipeg provides a habitat for over 50 different species of fish including yellow perch, chestnut lampreys and rainbow smelt. Yellow perch prefer water that has little current. They can tolerate moderate tubidity. Also, they prefer a temperature range of 18 to 20 degrees Celsius. If the temperature of the water varies too much above this range, yellow perch will either move to a new location or die.

Yellow perch spawn in May or early June when water temperatures are above 6 degrees Celsius. First, they migrate to tributaries and then several males attend a female while she releases her eggs. Yellow perch can grow to 302 mm in length. Their life span is approximately 9 years. If there is a lack of resources or too many of them (over-population), yellow perch adapt by stunting. This means that instead of starving, they simply do not grow as large as normal. Thus, they are able to live off less food.

Yellow perch feed in midwater or on the bottom of Lake Winnipeg. They eat a wide variety of invertebrates, and fish such as emerald shiners. The eyes of yellow perch allow them to see almost 360 degrees around them. Thus, they are better able to spot their prey and evade predators. In Lake Winnipeg, yellow perch are eaten by northern pike and walleye. They are also caught for food by commercial fishers and anglers.

Chestnut lampreys are also found in Lake Winnipeg. Lampreys are parasitic fish that attach to other species of fish (such as yellow perch) to feed on their blood and tissues. Recently, rainbow smelt have been introduced into Lake Winnipeg. Rainbow smelt are a very invasive and competitive species. They have been thought to have caused a decrease in the emerald shiner population.

Lake Winnipeg provides a home for many species of fish. However, a severe drought could disrupt this ecosystem greatly. Lake Winnipeg’s water level would drop, the temperature could change and it could become more turbid. Thus, the carrying capacity of the lake would change. But, in its current condition, Lake Winnipeg is an excellent habitat for many species of fish.