Spawning habitat enhancement in the European bullhead (Cottus gobio), an endangered freshwater fish in degraded lowland rivers
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Published source details
Knaepkens G., Bruyndoncx L., Coeck J. & Eens M. (2004) Spawning habitat enhancement in the European bullhead (Cottus gobio), an endangered freshwater fish in degraded lowland rivers. Biodiversity and Conservation, 13, 2443-2452.
Published source details Knaepkens G., Bruyndoncx L., Coeck J. & Eens M. (2004) Spawning habitat enhancement in the European bullhead (Cottus gobio), an endangered freshwater fish in degraded lowland rivers. Biodiversity and Conservation, 13, 2443-2452.
Summary
Due to river regulation and pollution, habitat of the European bullhead Cottus gobio (a small endangered freshwater fish) has been degraded. One factor attributed to declines is an apparent lack of suitable spawning sites e.g. cavities underneath stones which are required for 'nesting' and egg-laying.
Addition of artificial structures to degraded stretches of streams (where for example cobble stones have been removed) may be beneficial. This study evaluated the use of ceramic tiles as artificial spawning substrates in canalised and (remaining) meandering parts of two anthropogenically perturbated lowland rivers in Flanders (Belgium).
Study sites: The study was conducted in the Zwanebeek (average width 2 m) and the Laarse Beek average width 3 m), two lowland rivers in Flanders, northern Belgium.
Addition of ceramic tiles: Ceramic tiles (29 cm x 21.5 cm x 5 cm thick) were added to provide potential European bullhead spawning sites just before the spawning season, in January 2000.
In the Zwanebeek, tiles were added to eight randomly selected stream stretches (312 tiles in total). In the Laarse Beek, they were added to four randomly chosen sites located in a meander, and four situated in a canalised section (416 tiles in total). Within each site, were added 13 rows of three (Zwanebeek) or four (Laarse Beek) tiles equally spread over the width of the river, adjacent rows approximately 2 m apart.
Monitoring: All tiles were inspected once for the presence of egg-clusters during the spawning season (April 2000). Depth of the tiles in the water column and the water velocity (using a portable flowmeter) near the tiles were recorded.
Zwanebeek: At all eight sites in the Zwanebeek, bullhead egg-clusters were found attached to the tiles. Of the tiles initially placed on the bottom of the river, 89% were relocated, 32 (12%) of which had egg-clusters (26 tiles had one egg-cluster, 5 had two egg-clusters and 1 had three egg-clusters) at the time of inspection. The tiles were located at a variety of water depths and water velocities but neither had an apparent effect on the presence or absence of egg-clusters.
Laarse Beek: In the Laarse Beek, there was no apparent preference for the meander or canalized lengths of the river for egg-laying. Egg-clusters were found attached to tiles in all study sections. The proportion of tiles recovered was 87% in the canalised sections and 72% in the meander. One hundred tiles had egg-clusters (69 had one egg-cluster, 25 had two egg-clusters, 3 had three egg-clusters, 2 had four egg-clusters and 1 tile had five egg-clusters) equivalent to a 30% use of the recovered tiles as spawning substrate at the time of inspection.
The tiles with egg-clusters were located at a variety of water depths and water velocities. There was a significant interaction between depth of the tiles and the trajectory (i.e. meander or canalised) in which tiles were placed; in the meander, the probability that eggs are found on tiles was significantly positively correlated with the depth of the tiles in the river; in the canalised sections, depth had no detectable effect on the presence of eggs.
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