PRODUCTION OF A YY MALE BROOK TROUT BROODSTOCK FOR POTENTIAL ERADICATION OF UNDESIRED BROOK TROUT POPULATIONS

Abstract -. Exotic Brook Trout often negatively impact native aquatic fauna or provide marginal fisheries and are often targeted for manual or piscicide removal in lakes and streams. Unfortunately, complete eradication of established Brook Trout populations via these approaches is rarely achieved. A potential alternative is a Trojan Y Chromosome (TYC) program, where hatchery-produced genetically YY male fish would be regularly released into an undesired population over time, skewing the population towards 100% males, theoretically resulting in population extirpation upon stocking cessation.  

We sought two genetic sex markers for Brook Trout and employed juvenile sex reversal methods commonly used in commercial aquaculture to develop a YY Brook Trout 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 both assays matching the observed phenotype for 90 of 90 individuals.   Estradiol-infused food readily feminized XY fish at a high rate (99.6%, n = 224) in the first phase of the program.   Survival of progeny from egg-laying F_XY females 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 egg-producing supermales (F_YY fish), a vital step towards development of YY technology on a large aquaculture scale.  Study results also show that estradiol treatment does not reduce long-term Brook Trout growth performance.    This study demonstrate that hatchery production of a YY male Brook Trout broodstock is feasible, modest in cost (less than US $10,000), and can be completed in less than 5 years.