A suction pump sampler for invertebrate drift detects exceptionally high concentrations of small invertebrates that drift nets miss

Invertebrate drift is a key process in riverine ecosystems controlling aquatic invertebrate distribution and availability to fish as prey. However, accurately quantifying drifting invertebrates of all sizes is difficult because the fine-mesh nets required to capture the smallest specimens clog easil...

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Bibliographic Details
Published in:Hydrobiologia 2022-05, Vol.849 (9), p.2077-2089
Main Authors: Neuswanger, Jason R., Schoen, Erik R., Wipfli, Mark S., Volk, Carol J., Savereide, James W.
Format: Article
Language:English
Subjects:
Aquatic ecosystems
Aquatic invertebrates
Aquatic organisms
Biomedical and Life Sciences
Creeks & streams
Drift
Drift net fishing
Driftnets
Ecology
Efficiency
Filtration
Finite element method
Fish
Fishes
Foraging
Freshwater & Marine Ecology
Gillnets
High flow
Invertebrates
Juveniles
Life Sciences
Nets
Post offices
Prey
Primary Research Paper
River water
Rivers
Suction
Zoology
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Summary:Invertebrate drift is a key process in riverine ecosystems controlling aquatic invertebrate distribution and availability to fish as prey. However, accurately quantifying drifting invertebrates of all sizes is difficult because the fine-mesh nets required to capture the smallest specimens clog easily, which reduces filtration efficiency and measurement accuracy. To address this problem, we developed a gas-powered pump system that delivers 20 m 3 /hour of river water through nested 80- and 750-μm-mesh nets suspended in the air. We compared 17 pumped samples with those obtained by adjacent, conventional deployment of a 250-μm drift net in a clear-water Alaskan river during both low and high flows. Our drift pump system sampled a geometric mean drift concentration of 467 invertebrates m −3 (maximum 5637 m −3 ) – eleven times the mean concentration of 42 m −3 estimated using the drift net. Invertebrates ≤ 3 mm long, primarily chironomids, comprised the entire difference between methods. Investigators for whom the drift of 0.5–3 mm invertebrates might be relevant (e.g., those applying foraging models for juvenile drift-feeding fishes) should consider using a pump or similar aerial filtration method to quantify small invertebrate drift, lest they underestimate it by an order of magnitude.
ISSN:0018-8158
1573-5117
DOI:10.1007/s10750-022-04849-1