Year Established: 2014 Start Date: 2014-07-01 End Date: 2015-06-30
Total Federal Funds: $10,027 Total Non-Federal Funds: $35,457
Principal Investigators: Lance Yonkos
Abstract: Intersex in the form of testicular oocytes (TO) has been reported with high prevalence in smallmouth bass (Micropterus dolomieu) and largemouth bass (Micropterus salmoides) populations. Prevalence in males from Potomac, Shenandoah, Susquehanna, and several Eastern Shore Watersheds often exceeds 80%. The presence of TO is generally accepted as evidence of exposure to endocrine disrupting compounds and suggestive of reproductive compromise and population level effects. Potential sources of estrogenic contaminants are numerous (e.g., wwtp effluent, agricultural and urban runoff, etc), but, as yet, no single source or contaminant has been identified that adequately explains the spatial heterogeneity of TO occurrence. Current methods for identification of TO require collection and sacrifice of fish for histological identification of oocytes within testis of male specimens. Where populations are already imperiled, experimental collection necessarily places an additional impact on population number. Thus, populations in regions where analysis of fish is most warranted are among those least able to accommodate the additional pressure. Employing a non-lethal means of determining TO prevalence will serve to alleviate this pressure while still allowing field assessment of endocrine disruption within impacted populations. Further, targeted regions can be re-sampled over multiple seasons or years to observe temporal shifts including recovery or further decline without undue influence to fish populations. The proposed project compliments a larger effort to identify the windows-of-sensitivity of largemouth bass to endocrine disrupting chemicals (EDCs) by exposing hatchery-reared fish to estrogenic solutions at various sensitive developmental stages. After exposures fish will be grown to maturity before sacrifice and examination for the presence of TO using routine histological methods. This will necessarily require sacrifice of research fish. The proposed project will compliment this work by employing a non-lethal laparoscopic technique (pioneered by MD DNR Fish Pathologist Mark Matsche) to collect testes biopsy samples prior to tissue collection via dissection. Comparison of efficacy of TO detection by non-lethal laparoscopic methods versus routine histological methods will determine the appropriateness of the laparoscopic method for field assessment of TO prevalence. Working in compliment with the on-going project provides an opportunity to compare method results on 300 to 500 hatchery-reared and laboratory controlled fish, a number more than adequate to validate the laparoscopic method. Field collection and sacrifice of a similar number of native largemouth bass would be extremely costly, effort-intensive, and potentially damaging to population structures.