Life cycle and production ofCladopelma virescens (Mg.) (Diptera: Chironomidae) in Lake Banyoles (NE Spain)

Abstract

Life cycles and annual production of the chironomidCladopelma virescens are studied at two different depths in the sublittoral (5m) and the profundal (12m) zones of the karstic Lake Banyoles (NE Spain). Two generations were completed by this chironomid in the two sampling stations studied. Production was estimated with two different methods: increment-summation (IS) and size-frequency (SF). In the IS method the smoothed survivorship curves were estimated because of the absence of the smaller instars in the samples. The mean annual production varied from 44 to 70 mg m−2y−1 in the deeper station and from 215 to 270 mg m−2y−1 in the shallower, depending on whether the size-frequency or increment summation method was used. Annual P/B varied between 5.07 and 5.67, and 6.14 and 4.11 respectively. Due to the many assumptions to be made with the IS method, we suggest the SF method in this case, because the values given by the two methods are of the same order of magnitude.