Fish are one of the biotic quality elements applied in the EU Water Framework Directive for the assessment of the ecological status of inland waters (rivers, lakes, transitional waters)

The ecological classification of water bodies using fish has been repeatedly applied in the past and is particularly effective in cases of anthropogenic degradation in hydrology, connectivity, morphology, especially in rivers.

As regards methodology, the fish sampling is performed by the staff of  IMBRIW by using primarily electrofishing sampling methods which are the most widespread and standardized fish-capture techniques in running waters.  IMBRIW employs two main types of electrofishing devices (one large device for deep rivers and back-pack electofishing devices for smaller streams). Usually fish sampling is carried out by teams consisted of four field workers.

Typically, one person is responsible for completing the protocol field forms, another person is responsible for the operation of the circuit of the power source, and finally two people are responsible for collecting the fish. Moreover, the large electrofishing generator can be placed on board a boat and thus deeper river segments can be sampled. This method is used in large rivers, usually lowland type, which are not wadable because of their depth. The individuals operating with this method are usually four to five, with a person to be solely responsible for the navigation of the boat.

Within the ichthyological monitoring scheme fish sampling is conducted in all sampling sites of the network twice a year, in spring and summer (high and low flow, respectively).

The length of the sampling section of the river is at least 100m, to cover adequately all habitats in a “representative” reach; while frequently, in large rivers, this length can be up at 200 m. The strategy of the fish sampling follows a “scan” line meandering path, along the wetted channel of the river. HCMR promotes a rapid assessment procedure in fish collecting. Fish are directly identified to the species level and categorized in length classes. After recording the data in the fish field forms the fish are returned alive into the river.

At each location, apart from the ichthyologist data, data concerning the technical details of the sampling, types of habitats sampled, prevailing pressures and other topographical, hydrological and morphological characteristics of the sampling are recorded in a separate field form.

A draft version of the Inland Waters Fish Monitoring Operations Manual is available for down-load:

Inland Waters Fish Monitoring Operations Manual (Version 1.0)

Click on the following links for the fish protocols used by IMBRIW and an example of a field seminar organized by IMBRIW:

HCMR Rapid fish sampling field form
HCMR Size class fish list field form
IMBRIW’s first electrofishing seminar in Greece held in June 2012 in Kleitoria, Peloponnese
Freshwater Fishes and Lampreys of Greece. An Annotated checklist (Monographs on Marine Sciences No.8)