Secondary production of Brachycentrus numerosus using ladder sampler colonization data

Estimation of secondary production for aquatic invertebrates inhabiting medium and large rivers can be problematic.  Regular monthly collections are necessary throughout the year for most species to obtain an accurate estimate, especially for species with synchronous development.  Collection can be extremely difficult during some seasons as water flow varies.  During high water, current velocities increase and collection of substrates on the riverbed can be near impossible.  We used a ladder sampler fitted with wood substrates to overcome this problem and to estimate secondary production using cohort techniques for Brachycentrus numerosus, a synchronous univoltine species, on snags.  Production values ranged from 192-756 mg m^-2 y^-1.  Cohort production to biomass ratio was 7.69-7.78 y^-1.