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A River Keeper’s Year: Spring

The second in a series of guest blogs by Dr John Urquhart.

We are, I suppose, river keepers, of sorts; my wife April, my other best friend Kerry, and me.

March: A month of anticipation for the season ahead. If we are going to stock the river with farmed fish, now is the time to do it. Opinions about this practice diverge. Opponents say that we are introducing competitors with the native trout for the food available; but the food is abundant.

Farmed fish are bred to be sterile, so they do not contaminate the gene pool, and they provide our membership with some fish to catch – although we insist that all fish are returned to the water. Indeed, we take great care of them. We learned from our carp fishing friends to carry with us a “Fish first aid” substance which is part antiseptic, part plastic skin and part a haemostat, so it will stop any bleeding. If a fish has been struck by an otter or cormorant, and has an injury, an application of this heals it, and the fish swims away vigorously. And we know it works, for we see fish in our river who have healed injuries.

Applying healing spray to a trout

Applying fish first aid to a trout with an otter injury.

April 1st is the opening day of the fishing season. The 25th of the month is St Mark’s Day, and around this time we see the appearance of the Hawthorn fly, also named after the saint as Bibio marci, St Mark’s fly, and great sport can be expected. These are terrestrial insects (unlike the aquatic insects that tend to draw our attention) and quite unmistakeable as they are among the clumsiest insects in flight, trailing their legs beneath them and being blown by the gentlest of breezes onto the water, where the trout devour them enthusiastically.

Bibio marci, hawthorn fly or St Mark’s fly. Probably the clumsiest in flight.

Another insect making an appearance around this time is the caddis, which is also known as sedge, especially in the USA (but frequently confused with the alder fly; they are different species.) This lives in the water as a nymph for up to a year before hatching as an adult insect and has a cunning way to protect itself; it builds itself a tube of silk which it forms into a case with the addition of tiny pebbles and fragments of twigs.

A caddis nymph in his case: photo from the Riverfly partnership

Caddisflies are also quite clumsy in flight – although not as clumsy as the hawthorn fly – and will crash into the water when attempting to lay their eggs, become stuck in the surface tension and make an easy meal for the trout. We tie successful imitations of these insects, too, often using deer hair, which is hollow, and floats perfectly and “Cul de Canard” feathers – waterproof, and from an unmentionable part of the canard. That’s a duck.

And its imitation; from Barbless Flies

Adult caddis

 

 

 

 

 

 

 

 

Throughout the year we take great interest in the condition of the water in the river. There are three areas where we can deploy “citizen science” to assess the health of the river. By collecting data over time, using scientifically respected and repeatable means, changes over time and between locations can be identified.

There is a project known as Riverfly, which uses a process called kick sampling where the river bed is disturbed in a precise way and the debris collected in a fine net. The invertebrates collected are then identified and counted and used as a surrogate for the health of the river; the more insects, the better.

Kick sampling

We also measure the oxygen in the river on a regular basis. The colder the water, the better oxygen (or indeed any gas) is dissolved – if you leave a bottle of tonic on the parcel shelf of your car, in the sun, and unwisely remove the cap, you will have had a practical demonstration of this; if you had put it in the fridge first, you wouldn’t be wearing it now. So, when the temperature rises, and the oxygen falls, we suspend fishing because a fish hooked and released is less likely to survive under these conditions.

Finally, we are part of a project run by the Angling Trust under the “Anglers against pollution” banner, where we test the river every month for phosphates (from agricultural runoff), nitrates, ammonia (sewage) and particulates.

As a friend observed after a conversation about the work we do, “You love your river, don’t you.” Wine may have been taken. The friend was right, though.

In the next part of the series, I will discuss the summer and the work ahead of the volunteer river keeper in those months.

You can read John’s Autumn/Winter diary of river keeping here: A River Keeper’s Year: Autumn and Winter

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