Cottidae

Abstract: The ability of an organism to acquire O2 from its environment is key to survival and can play an important role in dictating a species' ecological distribution. This study is the first, to our knowledge, to show a tight, phylogenetically independent correlation between hypoxia tolerance, traits involved in dictating O2 extraction capacity and the distribution of a group of closely related fish species, sculpins from the family Cottidae, along the nearshore marine environment. Sculpins with higher hypoxia tolerance, measured as low critical O2 tensions (Pcrit), inhabit the O2 variable intertidal zones, while species with lower hypoxia tolerance inhabit the more O2 stable subtidal zone or freshwater. Hypoxia tolerance is phylogenetically independently associated with an enhanced O2 extraction capacity, with three principal components accounting for 75 per cent of the variation in Pcrit: routine O2 consumption rate; mass-specific gill surface area; and whole blood haemoglobin (Hb)–O2-binding affinity (P50). Variation in whole blood Hb–O2 P50 is strongly correlated with the intrinsic O2-binding properties of the purified Hb while the differences in the concentration of the allosteric Hb modulators, ATP and GTP, provide a Hb system with substantial plasticity for survival in a highly O2 variable environment.

Abstract: The supposition that prey animals assess and behave flexibly in response to different degrees of predation threat is known as the threat-sensitive predator avoidance hypothesis. We completed a seri...

Abstract: SUMMARY 1. We used direct observation and mark-recapture techniques to quantify movements by mottled sculpins (Cottus bairdi) in a 1 km segment of Shope Fork in western North Carolina. Our objectives were to: (i) quantify the overall rate of sculpin movement, (ii) assess variation in movement among years, individuals, and sculpin size classes, (iii) relate movement to variation in stream flow and population size structure, and (iv) quantify relationships between movement and individual growth rates. 2. Movements were very restricted: median and mean movement distances for all sculpin size classes over a 45 day period were 1.3 and 4.4 m respectively. Nevertheless, there was a high degree of intrapopulation and temporal variation in sculpin movement. Movement of juveniles increased with discharge and with the density of large adults. Movement by small and large adults was not influenced by stream flow, but large adults where more mobile when their own density was high. Finally, there were differences in the growth rates of mobile and sedentary sculpins. Mobile juveniles grew faster than sedentary individuals under conditions of low flow and high density of large adults, whereas adults exhibited the opposite pattern. 3. Our results support the hypothesis that juvenile movement and growth is influenced by both intraspecific interactions with adults and stream flow. In contrast, adult movement appears to be influenced by competitive interactions among residents for suitable space. The relationship between movement and growth may provide a negative feedback mechanism regulating mottled sculpin populations in this system.

Abstract: Density and biomass of fishes, from shallow rocky and soft bottom habitats on the Swedish west coast, showed large seasonal variation with low values in winter and spring and with peaks in June Season was also the most important factor determining the fish assemblage structure Within season, however, there was a clear separation in assemblage structure between rocky-and soft-bottom habitats There were significantly higher total fish abundances and biomasses during night compared with day catches On soft bottoms density and biomass of fishes decreased with increasing depth, but no such pattern was seen in rocky habitats indicating that the distribution of fishes was related to vegetation cover Altogether, 53 fish species were recorded of which 30 were common to both habitats Species richness was similar on rocky and soft bottoms Of the 10 most abundant species found in rocky habitats four belonged to the Labridae and three to the Gadidae The fish assemblage on soft bottoms were of a more mixed nature with representatives among the 10 dominants from six families (Clupeidae, Cottidae, Gadidae, Gobiidae, Labridae and Pleuronectidae) When ranking the 10 dominant fish species on rocky bottoms according to biomass c 50% of the mass was Labridae, 19% Gadidae and 13% Cottidae In soft bottom habitats, fish biomass was mainly distributed between six families Pleuronectidae and Gadidae were dominant and each made up 25% of the biomass, whereas Labridae only contributed 4% of the fish mass It is concluded that the fish assemblage in rocky habitats is dominated by permanent non-commercial species (63% of biomass), whereas soft bottoms mainly function as nurseries for juvenile fishes and as feeding grounds for seasonal migrants of commercial species (80% of biomass)