Difference between revisions of "'''Oviposition and Egg Desiccation'''"

Aquatic insects exhibit complex life cycles that include egg, larval, adult, and, in some instances, pupal stages. Disturbances at any of these life stages can affect overall population dynamics. Yet, efforts to understand the effects of disturbances, such as hydrologic alterations, overwhelmingly focus on the larval life stage of aquatic insects. We evaluated the potential for load-following flows associated with hydroelectric power production to act as a population bottleneck for aquatic insects via reductions in the availability and temporal persistence of optimal oviposition habitats. Specifically, we quantified the oviposition habitat selectivity of Baetis spp. (Baetidae), Brachycentrus occidentalis (Brachycentridae), Chironomidae (Diptera), and Hydropsyche occidentalis (Hydropsychidae) downstream of Flaming Gorge Dam, Utah, USA. We found that all taxa except H. occidentalis preferentially laid eggs on large emergent substrates located along the river edge. Peak discharge associated with load-following flows substantially reduced the number of emergent substrates available for oviposition, and daily low flows exposed eggs in these habitats to desiccation and drying. When subjected to experimental drying, both Baetis and H. occidentalis eggs experienced nearly 100% mortality after 2 h, whereas most B. occidentalis remained viable after 8 h. Our paired field and experimental results are consistent with the hypothesis that load-following flows from hydroelectric dams produce a population bottleneck for aquatic insects by short circuiting recruitment processes. Environmental flows that seek to improve the health of tailwater aquatic insect populations would benefit from consideration of habitat requirements for all life stages of aquatic insects. [1]

BioScience Paper

BioScience Paper

BioScience Paper

BioScience Paper

https://www.usbr.gov/uc/rm/amp/twg/mtgs/17jan26/AR19_Kennedy.pdf

• Aquatic Foodbase
• USU Buglab
• GCMRC Aquatic Food Base Lab
• The Bugflow Experiment Page

2020

• Miller et al. 2020. Macroinvertebrate oviposition habitat selectivity and egg-mass desiccation tolerances: Implications for population dynamics in large regulated rivers. Freshwater Science

2016

• Kennedy et al. 2016. Flow Management for Hydropower Extirpates Aquatic Insects, Undermining River Food Webs. BioScience
• Macroinvertebrate Oviposition (egg-laying) Habitat Preferences on the Green River below Flaming Gorge Dam
• Novel Hydrologic Regimes Disrupt Insect Life History Strategies: Effects of Hydropeaking on Insect Oviposition
• Controls on the Structure and Function of Tailwater Macroinvertebrate Assemblages, USU progress report November 2016
• Oviposition Habitat Selectivity of Tailwater Macroinvertebrates: A Methodological Approach from the Colorado River Basin
• A life history bottleneck for aquatic insects arising from load following
• How dams can go with the flow: Small changes to water flow regimes from dams can help to restore river ecosystems. By N. LeRoy Poff and John C. Schmidt

• Caddis hatch below Parker Dam. There are several species of EPT below Parker and Davis Dam in spite of daily fluctuations that exceed 6 feet per day.

At least three genera of caddisflies and one genus of mayfly were collected in drift and benthic samples downstream of Davis and Parker Dams. These are species of a net-spinning caddisfly in the family Hydropsychidae (Smicridea), a case-building caddisfly in the family Leptoceridae (Nectopsyche), microcaddisflies in the family Hydroptilidae, and a swimming mayfly in the family Baetidae (Baetis). Hydroptilidae are found in light trap samples downstream of Lees Ferry in Grand Canyon, and are common in Arizona streans and rivers (Blinn and Ruiter, 2009). They are nonetheless very small (as indicated by its common name): at under 5 mm in total length (Merritt and others, 2008), generally smaller even than midge (Chironomidae) larvae, and therefore not a valuable prey item for fish. The genus Smicridea spins silk nets for capturing floating particles or organic matter suspended in the water column. For this reason, its family, in general, is common in tailwaters, where they can achieve great densities (Nakano and Strayer, 2014). In fact, Smicridea specifically is a documented pest species in the Parker Dam tailwater and in the Central Arizona Project canals carrying water to the Phoenix metropolitan area (D. Ruiter, personal communication). Baetis mayflies are one of the more common genera in aquatic ecosystems (Merritt and others, 2008); like midges, they are virtually ubiquitous in freshwater habitats. Relatively less information is currently available about the Nectopsyche caddisflies found in these sites, pending further literature research. (2016 GCMRC trip summary to WAPA)