THE MYTH OF THE FISHLESS POND
by Bob Honig
Argia 13(4):14-15 (5 January 2002)
[Argia is the newsletter of the Dragonfly Society of the Americas]
Recent books and articles have recommended that homeowners who want dragonflies keep their backyard ponds fish free, lest all the odonate larvae end up as fish lunch. Certainly, in what may be considered the traditional backyard pond, with a lot of open water and only scattered vegetation where insect larvae may find cover, fish may devour essentially all the larval odonates. Keeping this kind of pond fish-free to promote odonate success seems a sound approach.
But not all ponds are created equal. If there is sufficient cover (i.e., vegetation), dragonfly and damselfly larvae can successfully mature and emerge as adults. This is exactly what happens in nature, which certainly isn't fish-free -- so why not in backyard ponds as well? Perfect examples of this are two ponds (roughly 6x10 feet and 14x15 feet) that my wife and I installed in our yard: we have plenty of fish (Gambusia and Sailfin Mollies), in fact maybe a bit of an overpopulation; and we have plenty of dense vegetation so that the dragonfly and damselfly larvae can find refuge -- in fact the later, larger larval stages probably feed on the small fish. As a result, every year we have many dragonflies that visit the pond and whose larvae successfully mature to emerge as adults; and we don't have to use artificial means to control mosquitoes. (There are limits, I would imagine: if we introduced larger, more voracious fish, such as Bluegill or Koi, coexistence may become a thing of the past.)
In the roughly 5 years since our first pond was up and running, we have observed 23 species of Odonates. Each year since, adults of at least 3 species -- Anax junius, Erythemis simplicicollis, and Pachydiplax longipennis -- emerge in abundance. Adults of Orthemis ferruginea, Tramea carolina, and one or more damselfly species also have successfully emerged. Males of Libellula needhami and Erythrodiplax umbrata have staked out territories in our back yard, but we haven't seen the females ovipositing. In the first few years, before the fish populations were booming, many Pantala flavescens emerged as well; but its preferred larval habitats are temporary waters, without vegetation -- a preference that would make it easy prey in waters with abundant fish (in fact we haven't seen this species ovipositing in our ponds during the past two years).
Entire species list :
1. *** Anax junius (Green Darner)
2. *** Erythemis simplicicollis (E. Pondhawk)
3. Erythemis vesiculosa (Great Pondhawk)
4. Erythrodiplax umbrata (Band-winged Dragonlet)
5. Erythrodiplax minuscula (Little Blue Dragonlet)
6. *** Libellula croceipennis (Neon Skimmer)
7. Libellula incesta (Slaty Skimmer)
8. Libellula luctuosa (Widow Skimmer)
9. Libellula lydia (Common Whitetail)
10. * Libellula needhami (Needham's Skimmer)
11. Libellula vibrans (Great Blue Skimmer)
12. Miathyria marcella (Hyacinth Glider)
13. *** Orthemis ferruginea (Roseate Skimmer)
14. *** Pantala flavescens (Wandering Glider, formerly Globetrotter)
15. Pantala hymenaea (Spot-winged Glider)
16. *** Pachydiplax longipennis (Blue Dasher, formerly Blue Pirate)
17. ** Sympetrum corruptum (Variegated Meadowhawk)
18. *** Tramea carolina (Carolina Saddlebags, formerly Violet-masked Glider)
19. Tramea onusta (Black Saddlebags)
20. Ischnura hastata (Citrine Forktail)
21. Ischnura posita (Fragile Forktail)
22. Ischnura ramburii (Rambur's Forktail)
23. Telebasis sp. (Firetail sp.)
24. UPDATE [addition since submittal of article]: Epiaeschna heros (Swamp Darner)
*** = Known to have successfully completed larval stage in and emerged from our ponds. Also we have found exuviae of unknown damselfly sp. or spp. but not yet identified them.
** = Observed ovipositing in our ponds.
* = Suspected to have oviposited -- males observed perched and defending territory for several summers.
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