Mark Fincel

Proposal Seminar

Abstract: Standardized monitoring has become a vital component of fisheries assessments.  Annual variation in fish growth and abundance is often used to monitor changes in fish populations and develop strategies for fisheries management.  Although variation in fish abundance provides insight about the status of fish populations, it can be difficult to link these changes to environmental conditions without concurrent information about productivity.  Measures of nutrient concentration, algal biomass, and zooplankton composition/abundance can provide important insight into productivity; however, standardized approaches for collecting this information have not been developed by South Dakota Game, Fish and Parks for use on Missouri River reservoirs.  Development of protocols that account for spatial and temporal variation in these parameters, when coupled with standardized fisheries assessments would enhance knowledge of factors affecting fish populations.  Further complicating management efforts are inter- and intra- reservoir variation in prey fish composition and abundance and fluctuating water levels.  Recently, low water levels combined with an expansion of gizzard shad into Lake Oahe have resulted in a unique food web previously unobserved in this system.  As a result, factors affecting gizzard shad abundance and distribution in Lake Oahe and their influence on sportfishes are poorly understood.  The objectives of my study are to 1) develop standardized sampling protocols for quantifying nutrient concentrations, chlorophyll a, zooplankton biomass and composition, and water quality attributes in Oahe, Sharpe, Francis-Case, and Lewis and Clark reservoirs, 2) determine gizzard shad population characteristics in Lake Oahe and compare them with shad population characteristics in the lower Missouri River impoundments, 3) quantify the energetic contribution of gizzard shad to walleye growth and compare/contrast energy flow to walleyes among Missouri River impoundments, 4) compare ¹³C and ¹⁵N signatures of three tissue types (muscle, fins and scales) to determine if non-lethally collected tissues can be readily substituted for white muscle in stable isotope analyses and 5) document carbon and nitrogen isotope signatures in Lake Oahe walleye and compare these signatures to those of walleye populations in the lower Missouri River impoundments both presently and historically.  This research will aid managers in understanding the complex interactions between fluctuating water levels, reservoir productivity, and trophic interactions allowing them to make more informed management decisions.