Sampling demersal zooplankton: A comparison of field collections using three different emergence traps

Comparisons of demersal zooplankton collected in three structurally different emergence traps indicated that density and diversity estimates are affected by design features and sampling procedures. The smallest mesh netting (63 μm) in the walls of Hobson-Chess traps contained larger catches than traps with 202- or 333-μm mesh. Samples from Porter-Porter traps tethered 1 and 10 cm above the bottom had statistically more zooplankton than all other traps set on the substratum. A consistently greater total number of demersal zooplankton was captured in the Alldredge-King traps when all three trap types sampled at the same time and area. The abundance and rank order of all but the most numerous animals ( = harpacticoid copepods) differed between the traps. Alldredge-King traps caught more of the larger organisms (= polychaetes, cumaceans, and gammaridean amphipods), whereas, the Porter-Porter and Hobson-Chess traps contained larger densities of smaller zooplankton ( = copepod nauplii and gastropod veligers).