Life history and secondary production of predaceous aquatic macroinvertebrates in managed ephemeral ponds




Holmes, Anita J.

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Fish hatchery ponds are nutrient rich waters designed to support abundant phytoplankton and zooplankton populations to enhance fish fry production. Such enhanced waters can also secondarily lead to an increase in secondary production of predaceous aquatic insects. One objective of this study was to determine and compare the secondary production of predaceous aquatic insects found in fertilized and unfertilized lined fish hatchery ponds at the National Fish Hatchery and Technology Center, San Marcos, Hays County, Texas. Quantitative benthic dipnet and vacuum samples were collected from replicate fertilized and unfertilized ponds once a week, for sixteen weeks, beginning April 1st 1995. Organisms were sorted, identified to genus, headwidth and body length recorded, and dry weight (mg) measured. The secondary production of most predators was higher in fertilized ponds. However, the secondary production of Pantala (Libellulidae: Odonata) was an order of magnitude higher in unfertilized (0.31 g/m2/year) than fertilized ponds (0.04 g/m2/year). Whereas, production of the dominant predator Berosus (Hydrophilidae: Coleoptera) had higher production in fertilized ponds (0.53 g/m2/year) than unfertilized ponds (0.02 g/m2/year). Higher production of Pantala in the unfertilized ponds may have been a response to visual cues provided by unfertilized ponds to ovipositing females. Overall, production values are comparatively lower than in other studies and are the result of low standing stock biomass. The second objective was to determine the functional feeding response of the predators at different prey densities. Functional feeding responses were determined by placing predators of the same size-class/instar into individual replicated cubitainers with different prey densities. All predators increased consumption with increased prey density, but only Pantala showed a typical type-2 functional response. Species diversity was highest in the fertilized ponds. Pantala was dominant in the unfertilized ponds; whereas, Berosus was dominant in the fertilized ponds.



predatory insects, aquatic macroinvertebrates, fish hatcheries, ephemeral ponds


Holmes, A. J. (1999). Life history and secondary production of predaceous aquatic macroinvertebrates in managed ephemeral ponds (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.


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