Effects of incomplete sampling on macroinvertebrate secondary production estimates in a forested headwater stream

Estimates of secondary production depend on the efficiency of sampling methods in capturing abundances and body lengths of the entire macroinvertebrate community. The efficiency of common sampling methods in fulfilling these criteria is poorly understood. We compared the effects of a Surber sampler (250 mu m mesh size) and a Freeze corer in capturing abundance, biomass, and secondary production of macroinvertebrates in a forested headwater stream. We then examined how the use of nets with different mesh sizes could affect estimates of secondary production. Macroinvertebrate abundance was three times lower, and biomass was three times higher with the Surber than with the Freeze corer. Neither method captured the entire length distribution, and incomplete sampling of body lengths and abundance resulted in underestimating total secondary production by 48% (Surber) and 49% (Freeze corer). We estimated that reducing the mesh size from 250 to 100 mu m would reduce the underestimation of production from similar to 48 to similar to 12% due to the inclusion of smaller individuals. Our results improve the efficiency of common sampling methods, allowing a reliable quantification of the role of macroinvertebrates in stream ecosystem functioning.

Automated summary

Estimates of secondary production are affected by sampling methods' efficiency in capturing macroinvertebrate community abundances and body lengths. The efficiency of common methods is poorly understood. Comparisons between a Surber sampler and a Freeze corer in a forested stream showed differences in macroinvertebrate abundance and biomass. The incomplete sampling of body lengths and abundance underestimated total secondary production by 48% (Surber) and 49% (Freeze corer). Reducing mesh size from 250 to 100 μm could decrease underestimation to about 12%. These results enhance the efficiency of sampling methods and provide reliable quantification of macroinvertebrate role in stream ecosystems.