Fishless? Apparently not.

Stream Spreadwings (Archilestes), such as Great Spreadwing damselflies (Archilestes grandis), …

…prefer fishless waters, where larvae swim in open like little minnows. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Location 1337). Princeton University Press. Kindle Edition.

A couple of fishless vernal pools/small permanent ponds at a remote location in Huntley Meadows Park (HMP) have proven to be ideal habitat for Great Spreadwings. One of these pools/ponds is no longer fishless, as evidenced by the following photos.

Eastern mosquitofish (Gambusia holbrooki) spotted at Huntley Meadows Park, Fairfax County, Virginia USA.

04 NOV 2015 | HMP | Eastern mosquitofish (Gambusia holbrooki)

One factor we are still learning about is the effect of fish on dragonfly larvae. There is evidence that quite a few species of odonates survive best (or only) in the absence of fish. These species are adapted to live in fishless waters just as others are adapted to live with fish. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 899-901). Princeton University Press. Kindle Edition.

Eastern mosquitofish (Gambusia holbrooki) “are voracious feeders.” Source Credit: Guidelines for the Use of Mosquitofish for Mosquito Control, Virginia Department of Game and Inland Fisheries.

Introduction of the mosquitofish (Gambusia spp.) is likewise not recommended to control mosquitos; this fish is non-native throughout much of North America, is a voracious generalist predator that eats a wide variety of aquatic invertebrates as well as tadpoles and developing salamanders, and has such a rapid reproductive rate that it can quickly take over a small space. Source Credit: Backyard Ponds – Guidelines for Creating and Managing Habitat for Dragonflies and Damselflies, Migratory Dragonfly Partnership.

Eastern mosquitofish (Gambusia holbrooki) spotted at Huntley Meadows Park, Fairfax County, Virginia USA.

04 NOV 2015 | HMP | Eastern mosquitofish (Gambusia holbrooki)

Time will tell what effect eastern mosquitofish has on the aquatic insect populations that inhabit these vernal pools/small permanent ponds, including several species of habitat-specific odonates, but it is definitely cause for concern.

Editor’s Note: Sincere thanks to John Burke for identifying the eastern mosquitofish shown in the preceding photos.

The fish in both of your photos are eastern mosquitofish (Gambusia holbrooki). The size, mouth orientation, lack of lateral line markings, and habitat are all key features. Source Credit: John Burke, Ecologist II, Watershed Planning & Assessment Branch, Stormwater Planning Division, Fairfax County Department of Public Works and Environmental Services.

Copyright © 2015 Walter Sanford. All rights reserved.

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2 Responses to “Fishless? Apparently not.”

  1. Great Spreadwing (female terminal appendages) | walter sanford's photoblog Says:

    […] good for finding Great Spreadwing damselflies (Archilestes grandis) at Huntley Meadows Park. A formerly fishless vernal pool in a remote location at the park was less than productive, yielding only two […]

  2. Voltinism | walter sanford's photoblog Says:

    […] are two vernal pools at the study site: the larger one is more like a small permanent pond that was formerly fishless; the smaller one is a true vernal pool and appears to be fishless. This individual was observed in […]

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