Type of Document Master's Thesis Author Small, Ron Author's Email Address email@example.com URN etd-10022002-132132 Title Trophic interactions between larval gizzard shad and resident zooplanktivores in Claytor Lake, Virginia Degree Master of Science Department Fisheries and Wildlife Sciences Advisory Committee
Advisor Name Title Ney, John J. Committee Chair Copeland, John R. Committee Member Murphy, Brian R. Committee Member Orth, Donald J. Committee Member Keywords
- larval fish
- diet composition
- gizzard shad
Date of Defense 2002-09-20 Availability unrestricted AbstractAnglers unlawfully introduced gizzard shad Dorosoma cepedianum into Claytor Lake, Virginia in the late 1980s, apparently with the intention of improving the sportfishery by adding an additional clupeid prey resource. This study examined the trophic interactions between larval shad and resident zooplanktivorous fishes, in an attempt to discover the potential for trophic competition and negative impacts to these fish species.
Ichthyoplankton sampling in 1997 and 1998 showed that peak abundances of larval shad overlapped temporally and spatially with both larval Lepomis spp. and larval alewife Alosa pseudoharengus. Peak larval shad density (0.04-0.06 fish/m3) was two to three orders of magnitude less than that reported from other reservoir systems, slightly less than that of larval alewife in Claytor Lake (0.05-0.07 fish/m3), and significantly less than that of larval Lepomis spp. in Claytor Lake (0.28-0.51 fish/m3). Diet overlap values indicated potential resource overlap among all three larval taxa. Diet of larval shad did not overlap with that of either age-0 Micropterus spp. or adult alewife. All species of limnetic larvae examined showed feeding preferences for Diaphanosoma and copepod nauplii. Crustacean zooplankton densities did not respond negatively to peak larval fish abundances, and never dropped below 250-400 organisms/L. In Claytor Lake, the impact of trophic competition with larval gizzard shad on other zooplanktivores currently appears to be minimized by low densities of larval shad and abundant crustacean zooplankton.
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