PARTIAL LISTING – UPDATED July 2019
Muskellunge genetics
The Minnesota Department of Natural Resources (MNDNR) has increasingly used genetic information to help manage one of the premier muskellunge fisheries in the U.S. The initial impetus to consider genetics was the poor growth of a strain being stocked statewide. A common-garden experiment demonstrated a likely genetic component to this poor growth and a new broodstock was developed. Microsatellite DNA markers were able to track persisting ancestry from the poor-growing strain and demonstrate that its descendents were not attaining large sizes (Miller et al. 2009, Miller et al. 2012). The study also showed that native genetics persist in several lakes despite years of stocking. Another study examined the current muskellunge stocking program. Reductions in genetic diversity compared with the source population indicated likely fragmentation and bottleneck effects in brood and stocked lakes. Genetic markers are also being used as part of mark-recapture estimates of population size (Miller et al. 2015). The ability to extract DNA from scales has allowed anglers to participate in non-lethal collection of recapture samples. Ongoing studies include ancestry of muskies in the Mississippi River and St. Louis harbor and paternity analysis in the broodstock program.
Coaster brook trout on Minnesota’s North Shore
MNDNR imposed conservative harvest regulations in attempt to restore coaster brook trout populations in tributaries to Lake Superior. “Coasters” are brook trout that use Lake Superior for a part of their lives. In the past, MNDNR had stocked non-local strains of coaster brook trout and other jurisdictions still do today. MNDNR biologists documented increases in larger and older trout following the regulation changes. We used population assignment and ancestry evaluations to show that most of the large fish resulted from Minnesota coasters getting older and larger, not from strays from other coaster stocking programs.
Hatchery rainbow trout in the wild
Steelhead (migratory rainbow trout, Oncorhynchus mykiss) have become naturalized in Lake Superior and maintain their populations through reproduction in many Minnesota tributaries, along with supplemental stocking. In addition to these wild populations, a hatchery strain (kamloops) is stocked in the Duluth area to support a popular fishery. A previous study using crosses made in the hatchery showed that pure kamloops or kamloops x steelhead offspring had poorer survival than pure steelhead offspring in stream environments (Miller et al. 2004). We are studying wild populations to determine if kamloops are reproducing in streams and if they are intermating with wild steelehead.
Walleye population structure and stocking impacts
Walleye are the most desired fish in Minnesota and have been stocked widely. We are evaluating genetic structure among walleye populations to identify distinct strains and determine the impact of stocking on current genetic diversity. We have identified several distinctive strains, generally associated with different watersheds. Stocked populations show varying patterns, with some having ancestry from one or more stocked strains while others retain distinctive, native genetic diversity despite records of extensive stocking. A project started in 2018 compares survival and growth of northern and southern strains stocked simultaneously into several southern MN systems. Intitial results show substantially better performance by the local southern strain in most lakes.
Stocked Northern Pike survival and ageing verification
Although Northern Pike thrive in many Minnesota waters, they are supplementally stocked as fry in some places, especially in southern Minnesota. This stocking has not been rigorously evaluated, in part because of the difficulty ageing Northern Pike to assign them to stocked year-classes. We are using parentage-based tagging to indentify stocked Pike and determine their year-class. All broodstock adults are genotyped and subsequently sampled Pike in stocked lakes will either be compatible with brood parents (i.e., stocked fish) or not (i.e., naturally-produced). This evaluation will determine the contribution of stocking to the adult population and provide known-age fish to compare with ages determined by various structures (e.g., scales, fin rays, cleithra).