Premium
Dragonfly Production and Prey Turnover
Author(s) -
Benke Arthur C.
Publication year - 1976
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1941057
Subject(s) - predation , dragonfly , littoral zone , ecology , biology , fishery , zoology , environmental science , larva
Annual production was calculated for three dominant larval odonate populations (Ladona deplanata, Epitheca spp., and Celithemis fasciata) coexisting in the littoral zone of an abandoned farm pond. Dragonfly populations and their prey were collected simultaneously with an Ekman grab at 2—wk to 1—mo intervals. Production for each dragonfly species was calculated using both the Allen curve method and the removal—summation method. Annual production for the three dominant species was ° 6 g/m 2 (dry wt), and total odonate production was estimated as 8 g/m 2 . Weekly odonate production was consistently > 0.3 g/m 2 from July through September. With a mean annual standing stock of ° 2 g/m 2 , the odonate annual turnover ratio (TR) is ° 4. Weekly TRs were highest during summer months, generally declining as individual size increased. From back calculations of the amount of food required to feed the odonates, it as estimated that a minimal value of annual prey production was 18 g/m 2 and a minimal estimate of weekly prey production in the summer months was almost 1 g/m 2 . With an observed prey standing stock of 0.6 g/m 2 , this would necessitate an annual prey TR of 30 and a weekly summer TR > 1. Since such an indirect method of calculating prey production does not account for other sources of prey mortality such as fish predation and emergence, the TRs are considered to be minimum values, perhaps only half of actual values. These relatively high TR values agree quite well with estimates based upon the amount of food required to sustain fish predators. The significance of these estimates made using indirect methods is that they are considerably higher than estimates made using more traditional direct methods. An attempt is made to resolve this discrepancy by examining sources of error associated with both approaches. Furthermore, since odonates have a standing stock frequently two to three times that of their prey and a large daily consumption capacity, I suggest that prey are saved from annihilation because they can find sufficient refuges.