Recovery of macroinvertebrates by screening in the field


Dukerschein, J. T., R. Gent, and J. Sauer.  1996.  Recovery of macroinvertebrates by
screening in the field:  A comparison between coarse (1.18 mm)- and fine (0.60 mm)-mesh sieves.
Journal of Freshwater Ecology 11(1):61 65.  Reprinted by U.S. Geological
Survey, Environmental Management Technical Center, Onalaska, Wisconsin, June 1997. 
LTRMP 97-R009.  5 pp. (NTIS #PB97-180129)


ABSTRACT

We evaluated the potential loss of target benthic macroinvertebrates from coarse-mesh
field wash down of samples through a 1.18-mm mesh sieve nested on a 0.60-mm mesh
sieve.  Visible target organisms (midges, mayflies, and fingernail clams) in the 1.18-mm
mesh sieve were removed from the sample and enumerated in the field.  The entire
contents of both sieves were preserved for subsequent laboratory enumeration under 4 
magnification.  Percent recoveries from each treatment were based on total intact
organisms found in all sieves.  Percent recovery for fingernail clams found in the field
(31%) was lower than for mayflies (79%) and midges (88%).  Laboratory enumeration of
organisms retained by the 1.18-mm sieve yielded additional fingernail clams (to total
74% recovered in the field and lab), mayflies (to total 89%), and midges (to total 91%). 
If the 1.18-mm sieve is used alone in the field, it is adequate to monitor mayflies, midges
>1 cm, and adult fingernail clams ò5.0 mm shell length.


KEYWORDS

Chironomids, fingernail clams, macroinvertebrates, mayflies, Pelecypoda, sieve size,
Upper Mississippi River System