Analysis of water samples

You'll remember we just took the water quality samples and obviously with clean dry containers so we don't contaminate the samples.  We did this so that we can get the samples fresh before any accidental stirring up of the water such as when we start to "trawl" or net for fish life.

We analyse the water samples for various water quality properties, such as pH and clarity.  Hayley Cambourn demonstrates the measurement of clarity as the property, turbidity, in the first pictures below.

Sampling of fish life

There are two ways we can use to sample the the number and type of fish. Both depend upon stealth so as not to frighten the fish and therefore miss them!  Each has its own advantages and disadvantages so we use both ways.

Active fish trapping requires the use of special fish nets. There are various designs of fishing nets that are handled manually by "brave souls" who don't mind getting their feet wet (or use wellington boots!). These nets are often rectangular in shape and the handlers trawl for fish by sweeping them through likely pools of water. The quality of sampling may depend upon our skill. There is one disadvantage in that the process tends to stir up the bottom and increase the turbidity of the water, thereby causing the fish to scatter and become harder to sample. 
We always "trawl" upstream from the lowest point so that we don't ruin the water for representative sampling. We generally don't do any such sampling unless the water quality samples have been taken AND all static trap sampling has been completed in the area.

Hayley Cambourn shows how turbidity measurements are taken.

Here is a close-up of the big tube containing the water sample

A large fish net is used for "snap sampling" of streams. James prepares to sample.

Chris checks the catch. You can get fairly wet at times if you don't wear your gum-boots!

James, Daniel and Chris using a new strategy

We use special traps for static trapping of fish. This type of sampling is less disruptive but relies upon our selection of the correct bait to attract the wide range of types of  fish that might be present. Typically, we use prawns because they can be purchased and attract most fish. You'll see there is a pocket of the trap in which we tuck away the bait.  Michael, Daniel, James and Chris watch John set the trap. We'll need more than the one trap for the relatively large section of creek we'll be surveying.

John Beumer adds the prawns to the trap pouch (real ones, no cat food for us!).

The boys watch and prepare their static traps.

You throw the trap on a line into a likely spot for the fish

Here's a suitable jar for us to hold our water sample to see the fish.

Hannah and Elise check their fish against the details given in their Identification Chart.

The Chart allows step by step identification of all the main types of fish

Identification of our fish

Once we catch our fish in either type of trap we carefully transfer the fish into our clean glass or plastic jars containing adequate fresh water from the stream. Now we can take our time and observe the various features of each fish.

We look at the body shape and size, the number and types of fins and tail, and the nature and distribution of any colour over the body of fish. We record all these details on our observation data sheets and then compare them against a special identification flow chart. This chart gives step by step instructions leading by a process of acceptance and elimination of choices to a decision as to the type of fish being examined.  

You may download a PDF copy of this chart and the "Standard procedures for conducting a community fish monitoring program", specially compiled by Brisbane Waterwatch for these Fish Snapshots from the Downloads page.

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