Burbot Early Life History Strategies in the Great Lakes

摘要

Burbot Lota lota exhibit four previously known reproductive strategies in the Great Lakes region. In this paper we review those strategies and provide evidence for a fifth onedelayed deepwater spawning. The four known, shallow-water strategies are as follows: (1) spawning by self-sustaining, landlocked populations, (2) spawning in tributaries in winter and the exit of larvae to a Great Lake, (3) spawning by residents in a spawning stream with access to a Great Lake, and (4) spawning on unconsolidated and rocky areas in shallow water in winter in the lake proper. Resident, landlocked populations exist in some Michigan and Wisconsin rivers (e.g., the Muskegon River in Michigan). The evidence for winter tributary spawning is the appearance of newly hatched Burbot in the St. Marys and Bark rivers during April-June. Evidence for Burbot juveniles leaving spawning streams is U.S. Fish and Wildlife Service tributory mouth trap data. The evidence for winter nearshore spawning comes from power plant monthly entrainment studies (Mansfield etal. 1983). Our proposed fifth strategy is spring and summer spawning at deep reefs, where there is probably cobble or boulder habitat. Our evidence comes from midlake reefs in Lake Michigan and offshore areas of Lake Huron: (1) we collected adult Burbot at midlake reefs in Lake Michigan, (2) we collected many Burbot larvae (many of which were newly hatched) from Lakes Michigan and Huron in June-August, and (3) we collected a Burbot egg in a PONAR grab in mid-July from 73m in southern Lake Huron. An important question remains, namely, which life history strategy provides the highest recruitment success for this species. It may be that adaptability ensures the survival of this important, top-predator fish during periods of crisis (e.g., encounters with dams, Sea Lamprey Petromyzon marinus predation).