Secondary production of chironomid communities in insecticide‐treated and untreated headwater streams

SUMMARY. Production of chironomid communities of three first order, Appalachian Mountain streams was estimated and the effects of an insecticide‐induced disturbance on chironomid production was examined. Annual production of non‐Tanypodinae chironomids in the streams during the first study year (no treatment) ranged from 1366 to 3636 mg m−2, while production of Tanypodinae chironomids ranged from 48 to 116 mg m −2. Production/biomass ratios ranged between 19 and 23 for non‐Tanypodinae and from 6 to 7 for Tanypodinae chironomids. Insecticide applications resulted in significantly lower chironomid densities and biomass in the treated stream relative to the pretreatment year and reference stream. Annual production of non‐Tanypodinae (703 mg m−2) and Tanypodinae (32 mg m −2) chironomids in the treated stream decreased by 64% and 67%, respectively, compared with the pretreatment year. In contrast, production of non‐Tanypodinae (2084 mg m−2) increased by 34% and production of Tanypodinae (96 mg m−2) by 57% in the reference stream.