The Impact of Stocking on the Current Ancestry in Twenty Native and Introduced Muskellunge Populations in Minnesota

Abstract

Fish stocking, often from multiple source populations, is a common management practice frequently conducted without the means or effort to determine the reproductive contributions of stocked fish. Historically, the Minnesota Department of Natural Resources (MNDNR) has stocked four strains of muskellunge Esox masquinongy, but the contribution of these strains to current populations was unknown. Two strains came from Minnesota lakes, Shoepack Lake and Leech Lake, and the other strains came from Wisconsin and Iowa hatcheries and were of uncertain origin. The MNDNR discontinued stocking the Shoepack strain in the 1980s when that strain displayed poor growth in stocked waters. Managers were concerned that ancestry from this strain might be limiting the genetic potential for muskellunge to attain trophy size in stocked populations. Using 13 microsatellite DNA markers, we determined the ancestry of muskellunge in 10 supplemented native populations and 10 introduced populations. The ancestry from each of the four stocked strains of muskellunge was detected in some populations, but the level of ancestry was unrelated to the amount of stocking of a strain. Ancestry from native populations persisted in six of the supplemented populations despite years of stocking. The potential effects of Shoepack strain ancestry on fish size were limited in most lakes because of its low persistence. All stocked strains reproduced in at least some of the lakes, but some lakes had no evidence of reproduction by any stocked strain. Our results will help MNDNR manage genetic diversity among muskellunge populations and direct efforts toward appropriate actions to improve size structure. This study reinforces how genetic data are often useful for evaluating ancestry in stocked fish populations, whereas stocking histories may be poor indicators of current genetic composition.

Combining population genomics and forward simulations to investigate stocking impacts: A case study of Muskellunge (Esox masquinongy) from the St. Lawrence River basin

“…Our results are congruent with these observations where PIG lake, initially used as a stocking source (from 1950 to 1965), left few traces of admixture in our populations. Significant Managers responded by altering stocking policies and the strain mixing has since declined over time via dilution (Miller et al, 2012). We hypothesize a similar dilution of individual ancestry through time has occurred with respect to the PIG stocking source although we are aware of no negative effects of its introduction.…”

“…Stocking was also performed as species introductions to support new recreational fisheries and as a predator to control invasive fish species (Crane et al, ; Jennings et al, ; Kapuscinski, Belonger, Fajfer, & Lychwick, ; Wingate, ). Studies regarding Muskellunge genetic divergence and stocking effects primarily used microsatellite markers and mainly focused on the Laurentian Great Lakes and Upper St. Lawrence River (Kapuscinski et al, ; Miller, Mero, & Younk, ; Turnquist et al, ; Wilson, Liskauskas, & Wozney, ). These studies revealed pronounced genetic differentiation among weakly connected populations at small spatial scales.…”

Stocking activities for the Arctic charr in Lake Geneva: Genetic effects in space and time

“…The common practice is to raise and release the offspring of few adults (artificially obtained by in-farm fecundation), yielding a disproportionate amount of siblings among released stocks and thus low effective size and genetic diversity. Fishes from this period also seem substantially different than original wild stocks (disruptive clustering on the PCA, Figure (Miller, Mero, & Younk, 2012;Perrier, Guyomard, Bagliniere, & Evanno, 2011;Perrier et al, 2013), an effect intimately linked to stocking intensity (Valiquette et al, 2014). In addition, it is not excluded that demographic processes (i.e., historical decline, as reported during the 1970s in the lake) may have contributed to this genetic bottleneck.…”

From regionally predictable to locally complex population structure in a freshwater top predator: river systems are not always the unit of connectivity in Northern Pike Esox lucius

“…; Miller et al. ). Knowledge of contemporary distributions of genetic variation is therefore a prerequisite for gaining an understanding of population structuring processes in general and to guide conservation measures in particular.…”

“…In consequence, restocking of Esocids has in a multitude of cases been attempted as a means to counteract population decreases. However, only few such programs have adhered to the otherwise generally established paradigm of taking intraspecific diversity into consideration (Larsen et al 2005;Launey et al 2006;Lucentini et al 2009;Jennings et al 2010;Miller et al 2012). Knowledge of contemporary distributions of genetic variation is therefore a prerequisite for gaining an understanding of population structuring processes in general and to guide conservation measures in particular.…”