Aquatic Sciences Meeting, Albuquerque 2001

CS16 Invasive Species: Benthic and Pelagic Organisms

Date: Friday, February 16, 2001, Time: 8:45:00 AM

Location: Dona Ana

Lester, O, , Utah State University, Logan, UT, USA, olester@cc.usu.edu

Flinders, J, , Utah State University, Logan, UT, USA, flinders@cc.usu.edu

Luecke, C, , Utah State University, Logan, UT, USA, luecke@cnr.usu.edu

INVASION OF THE EXOTIC CLADOCERAN DAPHNIA LUMHOLTZI TO WILLARD BAY UTAH: ALTERATION OF THE PELAGIC FOOD WEB

Willard Bay is a shallow reservoir located in Box Elder County in Northern Utah. The exotic Cladoceran Daphnia lumholtzi, characterized by an enlarged helmet and an elongated tail spine, was first observed in Willard Bay in the autumn of 1999. Bimonthly sampling began May 2000, with the reservoir being sectioned off into four transects. Zooplankton abundance was monitored using three, six meter, vertical zooplankton tows taken in each transect. Results of zooplankton analysis indicated that Daphnia pulicaria dominated zooplankton populations until mid July, with abundance peaking in mid June. Daphnia lumholtzi reached high abundance after August 1, with peak densities present in mid September. Fish feeding experiments indicated that juvenile Bluegill (average size 32 mm), when exposed to similar abundances of D. pulicaria and D. lumholtzi, strongly select for D. pulicaria. Comparison of seasonal dynamics of zooplankton over the past five years suggests that patterns of energy transfer have been dramatically altered since the invasion of D. lumholtzi. These changes could reduce fish production in the reservoir’s recreational fisheries.

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Aquatic Sciences Meeting, Albuquerque 2001

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