Collecting Invertebrates
Collecting aquatic invertebrates is a fun and interesting activity that can reveal useful information about the health of a river. The presence or absence of certain types of invertebrates can indicate the effects of pollution.
Collection Sites
Various invertebrates are adapted for life in areas with different river bottoms and water that may be shallow or deep, fast or slow. Since most observers don't have time to thoroughly sample all these habitats in one trip, a good idea is to focus areas that feature:
- gravel or rocks
- shallow water
- moderate flow velocity
Consistency
No one likes wading into mud and becoming stuck, and most people avoid wading into fast water that is deeper than their boots. It's obvious from these limitations that the most common choice for sampling sites will not accurately represent all of the habitats found along the length of a river. But, since different habitats have different invertebrates, it is easier to compare results if the same type of habitat is sampled each time. So, good advice would be to sample each time in shallow, moderately flowing water with gravel or rock bottom in order to provide consistency to a monitoring program.
Equipment
Aquatic invertebrates should be captured by observers wearing rubber boots, hip waders or chest waders, especially if there is a concern over cold water, broken glass or sewage contamination.
Safety should always be the first priority during river monitoring. Observers should wear personal floatation devices (P.F.D.'s) and be under qualified supervision.
Observers collect invertebrates using equipment such as fine-meshed sweep nets, kick nets, Neill cylinders or deepwater artificial samplers (wire cages filled with rocks).
- Nets have the advantage of being easy to carry, easy to use and inexpensive to build, however, they don't capture all the invertebrates present at a sample site.
- Neill cylinders are expensive to buy and they capture an overwhelming number of invertebrates that can take many hours to sort and identify with a microscope back in a lab.
Using a Kick Net
Useful invertebrate information can be obtained with a simple kick net, especially if proper procedures are followed.
|
