Large rivers pose a number of challenges for quantifying the
distribution and abundance of biota such as macroinvertebrates and fish.
Sampling is typically hampered by the physical difficulties and dangers
associated with accessing deep and fast-flowing water, and the
complexity and scale of habitats that occur within them. Moreover, the
large size of these rivers presents challenges in capturing the range of
variation present when assessing biodiversity and species
distributions. No single sampling method will achieve all goals as each
one has advantages and disadvantages (see table for macroinvertebrates),
so a combination of methods is often best.
LERNZ researchers have conducted an international review of approaches
to sampling macroinvertebrates in large rivers, and have tested various
Air-lift sampler - operates using compressed air and can access benthic habitats from 2-5 m deep
- Coir samplers - provides a standard structure typical of root mat habitats; can be deployed over a range of depths.
samplers - also referred to as Hester-Dendy samplers, these samplers
can be made from perspex or wood. They provide flat surfaces and spaces
between plates for colonisation
- Sweep netting - can be used to sample shore-zone habitats including macrophytes, wood, tree roots, and sand-gravel beaches.
addition we have compared various methods for sampling shore-zone fish
communities in contrasting habitats (beach, willow, riprap). LERNZ also
has an electric fishing boat for sampling fish in non-wadeable habitats
(link to Invasive Fish theme - Control and monitoring methods - Electric
- Collier K.J.; Hamer, M.P.; Moore S.C.
2014. Littoral and benthic macroinvertebrate community responses to
contrasting stressors in a large New Zealand river. New Zealand Journal
of Marine and Freshwater Research in press.
J.; Pingram, M.; Collier, K.J. 2012. Review of functional and
macroinvertebrate sampling methods for non-wadeable rivers. Cawthron
report no. 2222, Cawthron Institute, Nelson.
K.J.; Hamer, M. 2011. Artificial substrate monitoring of
macroinvertebrates in the Waikato River: 25 years on. Waikato Regional
Council technical report 2011/25. Waikato Regional Council, Hamilton.
K.J.; Hamer, M.; Chadderton, W.L. 2009. A new artificial substrate for
sampling deep river macroinvertebrates. New Zealand Natural Sciences 34: