Comparison of sampling efficiency of the chironomid larvae by different types of bottom mud sampler

Sampling efficiency of two chironomids, Chironomus plumosus and Tokunagayusurika akamusi, was tested with five bottom mud samplers, of which three were a grab type and two were a core type. The capacity of these samplers was as follows : (A) a standard Ekman-Birge grab, 17cm×225cm2; (B) a modified Ekman-Binge grab, 22cm×225cm2; (C) a tall box type grab. 40cm×213cm2; (D) a cylindrical core sampler, 70cm×12cm2; and (E) a square core sampler 70cm×28cm2. Since the chironomids distributed at various depths in the mud, the samplers capable of taking mud from the deeper layers were more efficient. The most efficient sampler was the tall box type grab, followed by the square core sampler. The cylindrical core sampler was not necessarily efficient in collecting these chironomid larvae, though mud was taken from the deeper layers, suggesting that the core diameter was a critical in collection of the chironomid larvae.