Case Studies in Fisheries Conservation and Management: Applied Critical Thinking and Problem Solving
Case 8: Predators Eat Prey: Effects of an Inadvertent Introduction of Northern Pike on an Established Fish Community
Approximately one million years ago, an area of north-central Nebraska was modified by wind to form sand hills. Approximately 1,500 natural lakes occur within lowlands in this region, and nearly half are capable of supporting fish communities. All of these lakes are shallow. Most have limited surface water drainage and are maintained by surface runoff and groundwater connections. These lakes provide some of the best angling opportunities in Nebraska. The nature of Sandhill lakes can both limit and promote fish production. Their shallow basins with clear water and abundant vegetation can result in fish kills, especially in winter. During the growing season, the basin of a Sandhill lake amounts to littoral habitat throughout. Invertebrates are abundant and fish growth rates can be fast by the standards of this geographic location. See Figure 8.1 for a view of a typical Sandhill lake.
Sandhill lakes are popular with both resident and nonresident anglers, with ice fishing opportunities for panfish species such as bluegill and yellow perch being especially common. Because of the high productivity and abundant zooplankton and macroinvertebrate communities in these lakes, many lakes produce exceptional sizes of bluegill (e.g., >25 cm) and yellow perch (e.g., >30 cm).
The northern pike was likely native to Sandhill lakes (Jones 1963), and this locale represents the southwestern-most native distribution for this species. As the top-level predator in many aquatic systems in both North America and Europe, northern pike can structure fish communities through predation. The purpose of this case study is to investigate the effects of a northern pike introduction on established populations of bluegill, yellow perch, and largemouth bass.