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Polder Sampling of Eels, Fish in Noord-Holland

Eels Sustainability +3 more

NETHERLANDS - Together with the Water Board of the Noorderkwartier region of Noord-Holland province, IMARES Wageningen UR is conducting a polder sampling exercise in the area covered by the Water Board in May-June 2013. Over ten days, research fishing will take place in small ditches, focused, among other species, on eels.

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Eel stocks have been declining since the 1950s. In order to ensure that they do not dwindle further, an eel management plan is being developed within Europe, and thus also in the Netherlands. Part of this plan is to estimate how many eels there are in Dutch waters.

One of the ways used to establish this is to use data from fish sampling conducted for the European Water Framework Directive. This directive has been in force for water management since 2000, stipulating that the water quality of European waters must meet certain requirements from 2015.

Why take Samples in the Polder?

In recent years, samples have been taken to establish the presence of fish in waters that fall under the Water Framework Directive. Small shallow ditches were only sampled to a very limited extent. As a result, little data is available about the presence of fish in these ditches, which could also contain eel. When calculating eel stocks in the Netherlands, it is therefore necessary to obtain data about the presence of eel in small polder ditches.

How does it work?

The sampling will involve fishing small shallow polder ditches. Because the ditches are limited in size, no regular angling takes place there and therefore generally no fishing permits are issued. The sampling is used to collect data about the presence of fish, and eel in particular.

Along a section of the bank, an electrical landing net is used to fish the ditch. All the fish caught are identified by type and their lengths are measured. Subsequently, all the fish are immediately released back into the water in which they were caught.

The sampling is also used to improve the planning and the fishing techniques used. From 2014, the knowledge gained will be available for refining the sampling plan, which can also be implemented by other Water Boards.