Quantifying the habitat and zoogeomorphic capabilities of spawning European barbel Barbus barbus, a lithophilous cyprinid

Gutmann Roberts, Catherine, Basic, Tea and Pledger, Andrew (2019) Quantifying the habitat and zoogeomorphic capabilities of spawning European barbel Barbus barbus, a lithophilous cyprinid.

The availability of suitable gravels is critical for the spawning success of lithophilous fishes, including redd builders. Redd construction during spawning can alter bed topography, sedimentary structures and sediment grain-size distributions, indicating the potential importance of spawning as a zoogeomorphic activity. Here, interactions between redd building fish and their spawning environment were investigated using European barbel Barbus barbus with a comparative approach across three English rivers: Teme (western), Great Ouse (eastern) and Idle (central). Surface sediments of spawning habitats were coarser in the Teme than in the other rivers but other sediment characteristics including sub-surface fine sediment (<2 mm) content was similar across the three rivers (≈ 20% content). Water velocities were also similar at spawning sites despite differences in channel width and water depth. Spawning redds were characterised by a pit and tailspill, with minor differences in surface grain size characteristics between these and the surrounding riverbed. Estimates of the fraction of particles that could be moved by spawning barbel exceeded 97% in all rivers. There was variation in the estimated reproductive potential between rivers (3098 to 11142 eggs m–2) but not in predictions of egg mortality. These results demonstrate that relatively minor differences in substratum characteristics between rivers are potentially having disproportionate impacts on barbel spawning success and that spawning non-salmonid fishes are capable zoogeomorphic agents.