Ontogenetic Microhabitat Shifts in the Bullhead,Cottus gobio L.,in a Fast Flowing Stream

Abstract

We investigated differences in microhabitat preference curves for bullheads, Cottus gobio L., of different size-classes during low flow periods, and evaluated the influence of such differences on habitat use through Weighted Usable Area (WUA) predictions in relation to river flow in a piedmont stream in Southwest France. Water depth, current velocity, and substratum composition were used to calculate proportional use values for each size-class (SC), and to quantify size-specific microhabitat preferences. Bullhead used non-cohesive and coarse mineral particles (pebbles, cobbles, boulders), but there was a spatial segregation of individuals from different size classes (SC1-SC4). Smaller bullhead (SC1, total length < 60 mm) took refuge under cobbles, significantly preferred shallower areas, and were less prone to select high current velocities than larger bullhead (SC 2 to 4, >60 mm), the latter occurring below (or under) the largest particles, where current velocity is weakened and sand accumulates. SC1 bullhead had a more restricted range for each habitat descriptors, and were thus likely to require a more specific habitat type than other bullhead. The maximum WUA values and the related preferred discharges (0.15-0.75 m 3 s -1) depended on the considered size-class. Our results suggest that ontogenetic niche shifts may play a role in the structure and dynamics of populations, by adjusting species' requirements to the spatial and temporal dynamics of environmental conditions, including abiotic and biotic conditions.

Population trends and current status of the endangered Pyrenean sculpin Cottus hispaniolensis in the Spanish part of the Garonne drainage

“…2); and the proportion of pools, runs and riffles, stream regulation, and brown trout density was not significantly related to sculpin density and occurrence. Our results are similar to those showed by Legalle et al (2005aLegalle et al ( , 2005b for sculpin populations in the French part of the Garonne drainage, where fish selected areas of coarse substrate where water velocity is weakened and sand accumulates.…”

“…This type of habitat disturbance reduce the natural streams sinuosity (Brookes, 1994) and may alter the preferred microhabitat of Pyrenean sculpin, i.e. shallow littoral areas (5-20 cm depth) and moderate current velocities (<40 cm s À1 ) with coarse substrate (Legalle et al, 2005a). Although our data did not show significant effects of flow regulation on sculpin density or occurrence, more research is needed since damming and flow regulation may adversely affect physical and hydraulic habitats, and therefore could reduce abundance and richness of fish and macroinvertebrate assemblages (Poff and Zimmerman, 2010).…”

Mesohabitat use by bullhead (Cottus gobio)

“…These show that habitat use and preference by bullhead differ between sites and studies. For example, depth preferences have been found to vary from 0.05 m (Legalle et al, 2004) to 0.40 m (Roussel & Bardonnet, 1996); velocities range from 0.10 m s -1 (Carter et al, 2004) to 1 m s -1 (Knaepkens et al, 2002). Most studies agree that bullhead prefer gravel, cobble, pebble and boulder beds.…”

The influence of calcium concentration on the distribution of the river bullheadCottus gobioL. (Teleostes, Cottidae)

“…Although our study was conducted at macrohabitat level, an interesting result emerged at microhabitat scale: the inverse relationship between altitude and sex ratio in the population may be associated to C. gobio's preferences in terms of substrate and water velocity as suggested by recent studies (Legalle et al 2005a;Van Liefferinge et al 2005). Different habitat use in relation to size class and vital phase and the differences in sex ratio may be the result of the changing of these microhabitat features between the source and the valley (respectively, large particle size and high velocity vs. small particle size and low velocity), since the female of this species smaller that the male (Smyly 1957).…”