SECONDARY PRODUCTION OF CHIRONOMIDAE (DIPTERA) IN A NORTH TEMPERATE STREAM

1. Secondary production of chironomids (Diptera: Chironomidae) in a third-order northern Indiana stream was estimated using species-specific, and in most cases cohort-specific, life-history data from the field. 2. Chironomid life-history patterns were diverse, ranging from one to four generations per year in addition to asynchronous development. Cohort production intervals (CPI) for all taxa ranged from 56 to 266 days. CPI for cohorts of conspecifics differed up to 3-fold. 3. Annual secondary production was estimated using the instantaneous growth method or the size-frequency method depending on whether cohorts were distinguishable or not. Total annual chironomid production was 29 700 mg dry mass m-2, which is the highest value reported for chironomids from a north temperate stream. 4. Eighty per cent of the total chironomid production was attributed to five species: Diamesa nivoriunda (33.9%), Cricotopus bicinctus (16.6%), Pagastia sp. (10.2%), C. trifascia (9.7%) and Orthocladius obumbratus (9.6%). 5. The annual P:B ratio ranged from 4.7 to 21.9. Thus, high secondary production was due to high mean annual standing stocks and not to rapid biomass turnover.