Presentation on theme: "August 5, 2013. Topics to be Discussed Brief history of gizzard shad in Roosevelt Prior survey results Confounding issues Key findings from UT surveys."— Presentation transcript:
August 5, 2013
Topics to be Discussed Brief history of gizzard shad in Roosevelt Prior survey results Confounding issues Key findings from UT surveys at Lake Powell Future plans Surveys – Roosevelt and Apache Lakes Bass genetics - statewide Habitat improvement Stocking Literature Review Trophic evaluation of gizzard shad effects at Roosevelt and Apache Lakes
Gizzard Shad First detected in Roosevelt Lake in January 2007 Fall 2008 survey noted gizzard shad lake-wide with multiple year classes present, but composed primarily of smaller (6”-10”) shad. By fall 2011 survey gizzard were most prevent species in gill net catch (>50%) and size classes had shifted to primarily larger (13”-17”) shad with very few small shad present.
Gizzard Shad CPUE
Confounding Issues Roosevelt Lake has experienced declining water levels post-spawn throughout the recent survey period
Confounding Issues Largemouth bass virus (LMBV) detected in the population during the 2011 survey. Fish kills have been documented in the southeast US and Indiana and Michigan. Typically occurs in the summer and affects largemouth bass over 12” Fish lose equilibrium and float at surface and can have lesions on the swim bladder but usually not external signs. Golden algae detected in Roosevelt Lake in Minor kill associated with golden algae in Roosevelt in August/September 2012 but only a few dead bass noted. Extensive kill (July 2012) in the Salt River from Roosevelt Lake upstream to at least Horseshoe Bend.
Lake Powell Findings Gizzard shad took only 3-years to expand lake-wide in Powell and now account for 36-44% of gill-net sample YOY gizzards make up a large percentage (up to 40%) of open water trawl samples Adults are up to 20+ inches in size and constitute a large part of Lake Powell biomass Anectdotal evidence show a declining carp population that coincides with the establishment of Gizzard Shad Have not seen any negative impact on black bass growth It's been a good thing for Striped Bass population as it dampens the Boom/Bust cycles historically experienced with a Threadfin Shad
Future Activities (Surveys) Planned for Roosevelt Lake in October 2013 and Apache Lake in April 2014 Additionally, crappie surveys will take place at Roosevelt Lake spring 2014 to determine most effective sampling techniques All gizzard shad collected associated with these effort will be euthanized.
Future Activities (Bass Genetics) Chris worked out an agreement with Texas Parks and Wildlife Department to looks at largemouth bass genetics for 10 AZ lakes, including Roosevelt Lake Will be able to determine the contribution of Florida strain genetics to AZ bass populations Samples to be collected in association with planned surveys or tournaments
Future Activities (Habitat) Habitat mapping and development of a Habitat Improvement plan and Implementation timeline for Roosevelt Lake AGFD will starting to work on compliance for conducting habitat improvements (reef balls deployment, gravel…) at Roosevelt lake – with coordination and approval by Forest Service AGFD has dedicated a full time position to reservoir fish habitat Don McDowell seeking funding and angler support to conduct habitat mapping and evaluation (possibly via diving) and identification of suitable locations to implement habitat improvement projects Don McDowell seeking funding to build reef balls
Future Activities (Stocking) AGFD Fish Program has budgeted annually for warmwater fish stockings statewide beginning in FY15 (July 2014). A portion of the budget may be used for stocking bass at Roosevelt Lake pending genetic testing results and completion of compliance AGFD will match any money raised (up to $50K) for fish stocking at Roosevelt Lake
Future Activities ($50k) AGFD Commission approved $50k for Gizzard Shad Management (2014) – Possible Options Conduct a literature review of the impact of gizzard shad on fish communities in reservoirs Will check with UT to see if they conducted a review Would require a 1 time funding; 1-year project Trophic evaluation of the impacts of gizzard shad at Roosevelt and Apache lakes Use some or all of the funding for habitat enhancement
Future Activities ($50k) Trophic evaluation of the impacts of gizzard shad at Roosevelt and Apache lakes Likely to be a multiyear project implemented externally through award of a contract or pass-through of funding Cost likely to significantly exceed $50k annually Evaluation of the Apache Lake bass populations in response to gizzard shad presence and growth would help identify the severity of the impact of gizzard shad on the fish community (trophic impact) in absence of drastic water elevation fluctuations