Kick Sampling: How to Unlock the Secrets of River Insects

Kick sampling is one of the quickest ways to understand what’s really happening beneath the surface of a river. In just a few minutes, you can uncover the aquatic insects that trout and grayling feed on every day — and instantly make smarter fly choices.

30 minutes of insect sampling will turbo-charge your catch!!

Kick Sampling Key Takeaways:

• Kick sampling helps reveal the insects trout and grayling are actively feeding on.
• Even a quick stone-washing sample can dramatically improve fly selection.
• The more time you spend understanding aquatic insects, the better you’ll become at reading water, predicting hatches, and catching fish.
• Sampling different habitats — riffles, gravel, weed beds, and slower water — gives a more complete picture of river life. 

Why insect entomology matters to fly anglers:

For fly anglers, this hidden underwater world holds the key to consistent success. Mayfly nymphs, caddis larvae, stoneflies, shrimp, and countless other river invertebrates form the foundation of a river’s food chain.

Learning how to identify them not only improves your trout and grayling fishing, but also gives you a deeper understanding of river health and seasonal fish behaviour. Therefore, knowing the type of insects that inhabit the river you’re fishing helps you select the appropriate artificial flies (dry, wet, or nymph), to increase your chances of catching trout and grayling. 

Scientific monitoring programmes also use kick sampling because freshwater invertebrates are reliable indicators of water quality and ecosystem condition.

In this guide, I’ll show you two simple approaches to kick sampling:

• A quick “on-the-go” method for choosing flies while fishing.
• A more detailed survey technique for studying river biodiversity and insect life.

Whether you’re exploring a new beat, improving your entomology knowledge, or simply becoming more connected to the rivers you fish, insect sampling is a skill every fly angler should learn.

Procedure and Essential Equipment for Kick Sampling

The sampling equipment you need depends on what you’re trying to achieve, and I break this down into two objectives:

• A quick assessment to guide fly selection while out fishing.
• Detailed study to understand the diversity of aquatic life in the river.

1. Kick Sampling On-the-Go (Stone Washing): 

When I’m faced with fishing a new river or beat, I normally take the time to determine what aquatic insects are present, which guides my fly selection when flies are not hatching. This can simply be done by lifting a few stones out of shallow riffles above pools to see what insects are crawling on their underside.

A quick assessment of the aquatic insects while out fishing can be achieved with a few bits of kit that easily fit into your fly bag or a large coat pocket:

• A clear plastic takeaway box,
• 5ml white plastic medicine spoon,
• Plastic pipette,
• Smartphone (macro camera setting),
• Digital microscope (optional)

On free-stone rivers, you can avoid the need for carrying a kick net in which you sample the river.

Stone Washing Sampling Procedure

I use the quick method to understand the fly life present in shallow riffles above large pools. The beauty of this approach is that it can be done with minimal disturbance to the riverbed.

1. Select a spot in the riffle that contains hand-sized submerged pebbles.
2. Quickly, lift the pebble from the river and while holding over the plastic tray wash the stone with a handful of river water, collecting the washing in the tray.
3. Most of the nymphs on the pebble will be washed into the tray.
4. Using the pipette transfer the nymphs to the 5ml medicine spoon.
5. Take a picture of the insect with your smart-phone
6. Repeat until you’ve taken pictures of a representative sample of the collected insects

Examples of the aquatic insects that I have found using the stone washing method and photographed with my iPhone include…

Pros & Cons of the Stone Washing Method.

2. Detailed Kick Sampling Aquatic Insect Survey

The stone-washing method is confined to sampling shallow riffles and gives details on the insects that live there. However, in order to provide a more complete analysis of the insects living in the river, a more detailed kick sampling survey is needed, which is more involved and needs more equipment.

Equipment Needed:

• A fine mesh kick sampling net
• Wading gear (waders and boots)
• 5 litre collecting bucket 
• A shallow sorting & specimen trays
• Sampling Pipettes & small tweezers
• Magnifying glass,
• Digital microscope compatible with a Smartphone
• Recoding charts

Procedure:

1. Find a suitable spot in the river. Riverbeds with moderate to sluggish flow and boulders or gravel are suitable.
2. Stand in the river and hold the kick net facing downstream. Gently kick the gravel, rock and silt upstream of the net.
3. After about a minute of kicking, gently lift the net and put the collected sample in your tray or bucket. You want to collect the insects that are lurking within the silt, so don’t disrupt it too much.
4. Sort and examine the collected material with a pipette or tweezers. Examine the water for aquatic insects, larvae, nymphs, and other macroinvertebrates. To get a better view, use a magnifying lens.
5. Record the insects you find, noting their size, colour, and any distinguishing features. Ideally, take photos with the digital microscope for species identification at home.

All the images of aquatic insects seen above were captured with a modern smartphone, but if you want to view the insects in greater detail, a portable digital microscope is worth the investment.

The images below show an Olive Upright nymph at various phases of development. From a juvenile nymph on the left to an adult nymph with completely developed wing buds on the right.

Pros & Cons of the Detailed Kick Sampling Method.

Putting your insect knowledge into action

Once you’ve gathered and identified insect specimens, you can apply this knowledge to improve your fly fishing success in a number of ways:

• Fly Selection – This enables you to choose fly patterns that closely imitate the insects you’ve identified. Matching the size, colour, and behaviour of the natural insects increases your chances of fooling fish.
• Timing Your Fishing Trips – Plan your outings to coincide with insect hatches. Knowing when certain insects are most active will help you be in the right place at the right time.
• Reading the Water – Use your insect knowledge to identify feeding zones and likely fish-holding areas. Trout and grayling often position themselves strategically to intercept drifting insects.
• Record and Learn – Keep a fishing journal to track your bug-sampling findings and fishing results. Over time, you’ll build a valuable database of insect activity and its impact on your fishing success.

Safety & Best Practice for Kick Sampling:

• avoid excessive riverbed disturbance,
• don’t sample in fish spawning areas,
• return specimens alive,
• and don’t sampling during dangerous flows.

Conclusion

Kick sampling is a powerful tool in the fly angler’s arsenal, offering a deeper connection to the river and its inhabitants. By understanding aquatic insects and their role in the ecosystem, you gain a deeper appreciation for the intricate balance of nature. More importantly, you unlock the potential to become a more successful and skilled angler.

So, the next time you’re on the riverbank, take a moment to peek beneath the surface. Explore the fascinating world of aquatic insects, and let their secrets guide you towards unforgettable fly fishing experiences.

Happy fishing!