Zooplankton Analysis of Blue Lake October 23 rd, 2010 Ben Majsterek, Mary Coyle, Jackie Hancock, and Mary Ruskovich

Introduction Kettle lake formation, heavy macrophytes, and extremely thick sediment along bottom “bottomless lake” 100’s of bullhead catfish as well as 60 hatchery rainbow trout stocked ~2 years ago Used for fishing, boating, swimming, and as aesthetic appeal Goal: reduce macrophytes and algae, increase zooplankton abundance, properly manage fish stocks, maximize recreational use

Methods Site selection –Li-Cor meter – aphotic vs photic –Temperature profile – unstratified Northeast to Southwest transect –Five locations, 3 replicates, entire water column with a 12.5 cm closing plankton net Preserved with formalin for 2 weeks and analyzed at the U of I lab to determine zooplankton density and species distribution

Location of Sites Blue Lake Oct. 23 rd,

Site 1 Mean individuals/L for ceriodaphnia, cyclopoid, and diaphanosoma: 6.33, 7.66, and.333 individuals/L

Site 2: Mean individuals/L for ceriodaphnia, leptodora, cyclopoid, diaphanosoma, calanoid, harpacticoid: 8.33, 0.66, 9.33, 1.66, 2 and 0.66 individuals/L Site 2

Site 3 Mean individuals/L for ceriodaphnia, leptodora, cyclopoid, and bosmina: 10, 0.33, 3.33, and 0.33 individuals/L

Mean individuals/L for ceriodaphnia, leptodora, cyclopoid, and bosmina: 7.33, 0.33, 5.33 and 0.33 individuals/L Site 4

Mean individuals/L for ceriodaphnia, leptodora, cyclopoid, diaphanosoma, and calanoid: 6, , 0.33, and 1 individuals/L Site 5

Total individuals/L for sites 1-5. Individuals/L for ceriodaphnia, leptodora, cyclopoid, diaphanosoma, calanoid, harpacticoid, and bosmina are 38, 3, 28, 2.33, 3, 0.67, and 0.67

Zooplankton CeriodaphniaCyclopoid copepod Calanoid copepod Bosmina (Jones, B )

Fish Species Bullhead Catfish (Ameiurus spp.) –Diet: plants, detritus, small fish, worms and zooplankton Rainbow Trout –Diet: midges, Diptera, Ephemeroptera, and Nemouridae larvae, fish, large zooplankton Largemouth Bass –Diet: crustaceans, variety of invertebrates, fish, and odonate nymphs

Discussion Significant absence of large zooplankton –Fast growth in trout when first stocked –Large bullhead population Changes (recent rainbow trout addition) may have long term effects –increased eutrophication –Increased dependency on human supplied feed Current management structures and goals cannot be met without change in other aspects

Alternatives Ecological Improvement (swimming, aesthetic improvement, improved clarity) –Reduction of trout and bullhead stocks Fishery Improvement –Continual feeding of trout –Cons: may have long term effects – increased eutrophication Change fishery structure –Movement from trout fishery to bass –Removal of a large portion of bullhead population

Conclusion Zooplankton stocks are depleted and cannot sustain current fish populations alone To improve any aspect of the lake, another factor will have to change i.e. continued fish stocks at these numbers and nutrient levels will may result in murky, algae filled water

References Ahrenstorff, T. D. and M. R. Helmus The influence of littoral zone coarse woody habitat on home range size, spatial distribution, and feeding ecology of largemouth bass (Micropterus salmoides). Hydrobiologia 623: Cisneros, R., E. Hooker, and L.E. Velasquez Natural diet of herbivorous zooplankton in Lake Xolotlan (Managua). Aquatic Ecology. 25: Jones, B Limnology. Indiana University. Newell, A. E Biological survey of the lakes and ponds in Coos, Grafton and Carroll Counties. New Hampshire Fish Game Surv. Rep. 8a:297. Harlan, J. R. and E. B. Speaker Iowa fish and fishing. 3rd Ed. State of Iowa. 377pp. Steiner L Pennsylvania Fishes