Investigating Black Crappie (Pomoxis nigromaculatus) populations using age and growth data in Whiteshell Provincial Park, Manitoba

Increasing water temperatures due to climate change may offer some warm water fishes the opportunity to establish sustainable populations in systems that were historically not suitable. Black Crappie (Pomoxis nigromaculatus) were introduced into the Whiteshell Provincial Park, in southern Manitoba, in the mid-1940’s, which is at the northernmost edge of their distribution range. However, it was not until recently (in the past 10-15 years) that this population has begun to expand and increase in abundance. With the potential for a shifting distribution as a result of warming temperatures, the purpose of this study was to better understand the characteristics of Black Crappie at the northern extent of their range for the goal of successful management.This thesis examined six lakes within the Whiteshell Provincial Park located in southern Manitoba, as well as Lac du Bonnet located just outside the park boundary. I hypothesized that Black Crappie in Manitoba would show differences in population characteristics in relation to more southern populations as a result of cooler temperatures and a shorter growing season associated with northern latitudes. Results of this study showed that Black Crappie in Manitoba grew slower, but were older and larger than more southern populations. Relative weights indicated the Whiteshell Provincial Park population was within the normal range for body condition for this species. Stock density measurements determined that each lake contained high proportions of large sized fish, which is important for recreational fishing. Values of δ13C and δ15N suggest that Black Crappie feed on different prey items at the same trophic levels between sites. Organ (gonadosomatic and hepatosomatic) indices suggested that Black Crappie begin to spawn in late May and energy stores recover more quickly post-spawn than southern populations. It is apparent that Black Crappie in the Whiteshell Provincial Park have established thriving populations as an introduced species that contribute to a growing fishery. ...