Production of a YY Male Brook Trout Broodstock for Potential Eradication of Undesired Brook Trout Populations

Abstract

Brook Trout Salvelinus fontinalis introduced outside of their native range often negatively impact native aquatic fauna or provide marginal fisheries and are frequently targeted for manual or piscicide removal in lakes and streams. Unfortunately, complete eradication of exotic Brook Trout populations via these methods is rarely achieved; new approaches are needed. A potential alternative is a Trojan Y Chromosome (TYC) program in which hatcheryproduced genetically YY male fish would be regularly released into an undesired population over time, skewing the population towards 100% males, theoretically resulting in wild population extirpation. We developed two genetic sex markers for Brook Trout and employed juvenile sex reversal methods commonly used in commercial aquaculture to develop a YY broodstock that can produce offspring for possible future use as biological control agents. Our search for genetic sex markers proved successful, with genotypic sex determination for two assays matching the observed phenotype for 90 out of 90 individuals. In the first phase of the program, estradiol-infused feed readily feminized genetic XY males into neofemales (F XY fish) at a high rate (99.6%; n = 224). Survival of progeny from such egg-laying F XY fish averaged 88% to eye-up and 91% from eye-up to ponding, values similar to untreated Brook Trout reared at the same facility. In the second program phase, we cultured both sperm-and egg-producing supermales (YY fish), a vital step towards development of TYC technology on a large aquaculture scale. Results showed that, in the hatchery, estradiol treatment does not reduce Brook Trout growth. This study demonstrates that hatchery production of a YY Brook Trout broodstock is feasible, modest in cost (less than US$10,000), and can be completed in 4 years. Although several hurdles remain before a full-scale stocking program could occur, we believe that future work on the TYC strategy for Brook Trout is warranted.

Demonstration of viability and fertility and development of a molecular tool to identify YY supermales in a fish with both genotypic and environmental sex determination

“…A similar strategy of using qPCR from genomic DNA to distinguish YY and XY genotypes has been successfully employed to screen for YY supermales in brook trout Salvelinus fontinalis (Schill, Heindel, Campbell, Meyer, & Mamer, 2016) and in the vegetable crop Asparagus officinalis (Mutoh, Watanabe, Nii, & Kanno, 2009). In addition to being very fast, the qPCR showed 100% agreement with the results of genotypic sex inferred by progeny test, which demonstrates its reliability and potential usefulness for field studies.…”

Effects of Air Exposure During Simulated Catch‐and‐Release Angling on Survival and Fitness of Yellowstone Cutthroat Trout

“…The phenotypic sex of each fish was identified in the field and confirmed using genetic analysis to produce accurate sex assignments (i.e., 99% accuracy in field‐based assignments; Schill et al. ). While remaining underwater, each fish had a 1/0 barbed circle hook manually inserted through the middle of the lower jaw and was randomly assigned a treatment of 0 s (control), 30 s, or 60 s of air exposure.…”

“…Estimates of survival were considered significantly different between groups when 95% CIs around the differences did not contain zero (Fleiss ; Johnson ; Schill et al. ). Such an approach is a direct statistical test, with the added benefit of clearly identifying both an effect size and the associated precision (Johnson ).…”

Comparison of body composition and sensory quality of wild and farmed whitefish (Coregonus macrophthalmus [Nüsslin, 1882])

“…One possible solution to this problem could be to use sterile fish. Triploidisation is a common practice in other species of farmed fish such as rainbow trout, which results in enhanced growth and avoids negative effects of maturation (Bye & Lincoln, 1986;Schill, Heindel, Campbell, Meyer, & Mamer, 2016); this technique has already been successfully tested in whitefish (Goebel et al, in prep. ).…”