A comprehensive entomologic biodiversity

Without aquatic and terrestrial insects, there would be no fly fishing for wild trout! It’s a self-evident truth any fly angler or naturalist can understand at once.

The waters of my region have the privilege of being sufficiently protected to be able to support clear and clean waters, compatible with a comprehensive entomologic biodiversity.
The rivers of the Monts d’Arrée and Trégor region still present, and for others present again, a strong global biological index. This simply means that there remain sufficient bio-indicators, most of which are pollution-sensitive representative species like ephemeroptera, plecoptera and trichoptera.

The rivers and river stretches I have on my list are particularly rich in trichopera (caddisflies), ephemeroptera and plecoptera, sometimes in teeming numbers like you would find maybe in far flung virgin places Down Under. This is a result of exemplary water management done by river keepers, angling associations and environmental protection associations (see Links) that still keep a vigilant focus on cooperating for the watersheds to be kept from all sorts of aggression they are subject to. And still, the battle is not won; a great biodiversity treasure trove today can be a desert tomorrow as agricultural runoff remains the largest menace for those clean waters and their inhabitants.

Without aquatic and terrestrial insects, there would be no fly fishing for wild trout! It’s a self-evident truth any fly angler or naturalist can understand at once.

This entomologic wealth, most impressive when seen by anglers having the privilege to be on the water during insect hatches ranks among the greatest shows nature can produce: the bridal flight of mayflies. This abundance of aquatic life gives a new sense to the term fly fishing: duns, spinners and spent mayflies magically pull rising fish to the surface and produce those takes we anglers all dream about, dry fly fishing in its classic form.

One distinctive feature of rivers and streams in Brittany is the fact that they run through natural meadowlands or through forested areas that produce large numbers of terrestrial insects which, when blown onto the water, have an important impact on a wild trout’s menu.

The documentation found below is but a modest compilation of the principal aquatic and terrestrial insect species (or rather insect groups). It also includes other invertebrates with an impact of a trout’s diet, such as crustaceans.

You will find the periods of emergence, their frequency as well as the size of the hatch(es). Those anglers familiar with the correspondence between those invertebrates and their imitations in their different stages of evolution under and above the surface (larval, nymph, pupal stages, emergers, stillborn, duns, spinners, spent) will find matters easier to comprehend and to put into practice, even though things can be complicated, too… But isn’t this something we fly anglers are striving for? Much too easy can sometimes ruin the experience…

I hope you will find yourself one of those magical moments when all things fall into place and masses of spinners of different species hover over the water, with trout relentlessly rising and all but ignoring your offering. It then will turn into a game of chess played between the angler and the river. Oftentimes, the “mystery of the brown” cannot be solved… unless you have the assistance of a local…









Insects of Brittany | Photo gallery