
TY  - JOUR
A1  - Marchant, R. 
A1  - Hehir, G. 
T1  - How efficient is extraction of stream insect larvae from quantitative benthic samples?
JF  - Marine and Freshwater Research
JO  - Mar. Freshwater Res.
Y1  - 2000
VL  - 51
IS  - 8
SP  - 825
EP  - 826
KW  - glossosomatids
UR  - https://doi.org/10.1071/MF00072 
N2  - The efficiency of extraction of Agapetus larvae (Glossosomatidae : Trichoptera) from quantitative benthic samples was estimated by the use of two approaches: an indirect estimate based on the probability of missing a specimen in two scans of a sample (the two-count method) and a direct estimate derived by re-picking samples. Both approaches gave similar estimates for the probability of missing a specimen of a given size and both showed that this probability increased as size decreased; losses ranged from 6% to 30%. The two-count method thus provides a reliable way to compensate for these losses. Such corrections made little difference to conclusions concerning Agapetus population density, larval growth or secondary production derived from a previous study. However, when no corrections are applied, mortality estimates may be inaccurate if early instars are picked with less efficiency than later ones. 
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