CANAPE: Follow the Fish

02 December 2019 - Published by Harry Mach
The quiet waters of Friesland offer a chance to get away from the chaos of modern city life, however now even the fish have email addresses.

We have previously reported on the water monitoring work we are doing in the Friesland Lake of De Leijen, building up a picture of the spatial water quality in the lake. Now we are working with the local angling community to understand better, how bream behave in this water system.

 Map showing tracking receiver grid in lake de Leijen

The receiver grid in lake de Leijen

Over the summer, we have put in place a VEMCO receiver network on De Leijen, covering the entire lake in a grid. This will allow for a comparison of the data on fish movements with the data gathered on a range of water quality indicators, including turbidity, salinity and nutrient levels.

This water quality data was collected over the last two years by towing a novel water quality-monitoring device around the lake. Normally researchers position water quality monitoring sondes at a fixed location, which is useful for monitoring general criteria (as is done for work at Hickling Broad, UK) but does not allow a dynamic picture of the lake to be built up. However, through this method VHL University of Applied Sciences have been able to develop a dynamic image of water quality.

Map showing different levels of turbidity around lake de Leijen

Turbidity measurements around Lake De Leijen

Each bream caught is tagged. With a VEMCO, Pit or yellow Floy Tag depending on the size of the bream. These 3 tagging methods give us different spatial data.

We have 25 VEMCO acoustic tagged bream which give us very precise spatial data.  150 bream are outfitted with a PIT tracker, and has a small yellow tag with an email address included. Upon that we have another 250 bream which only haven a yellow tag. The tags  are inscribed with an e-mail address and a following number and will not only allow people to email in their sightings of the fish, but will also discourage people from eating the fish. This is quite important, as fillet du PIT tracker is not only not appetising, but also expensive for us as well. The process is carefully managed to avoid pain or harm to the fish. The fish are also weighed and measured.

Tags in boxes

PIT and Floy tags waiting to be attached to the fish.

White box with black tags in foreground, cardboard box with yellow tags in background

Coupled with the water quality data, this will allow an understanding of how the Bream in the lakes interact with different areas of water quality, and inform strategies to improve the biodiversity and resilience of the lake system.

Scientists will not be able to gather this data alone, so they are working with the local angling community to support the data collection. All the tracked fish are marked with a tag and an email address, to allow anglers to report their sightings back to VHL University of Applied Sciences.