Post-Stocking Annual Survival of Fingerling- and Catchable-Sized MYY Brook Trout Salvelinus fontinalis in a Small Stream

The use of hatchery male fish with two Y chromosomes (M_YY) to progressively shift sex ratios of wild populations to 100% male is a novel approach for eradication of undesirable nonnative fish populations, but M_YY fish must survive post-release to successfully reproduce. Post-release apparent survival of 250 mm M_YY brook trout Salvelinus fontinalis stocked in a small stream averaged % annually over the first five years of stocking but increased to 17% once stocking size was reduced to 130 mm. Results suggest that successful M_YY eradication programmes may be contingent in part on M_YY stocking size.