Most fishes live in cluttered habitats characterized by structures such as surfaces, struts (e.g. large woody debris) and protuberances (e.g. boulders). These habitats are typically productive and support a rich fauna of benthic fishes (Moyle and Cech, 1996). Many benthic fishes are flattened in the...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.555.8910 http://jeb.biologists.org/content/205/14/2125.full.pdf |
| Summary: | Most fishes live in cluttered habitats characterized by structures such as surfaces, struts (e.g. large woody debris) and protuberances (e.g. boulders). These habitats are typically productive and support a rich fauna of benthic fishes (Moyle and Cech, 1996). Many benthic fishes are flattened in the plane of the substratum and negatively buoyant, especially when there are currents for which these features facilitate station-holding (Arnold and Weihs, 1978). The most flattened groups are found among the pleuronectiform flatfishes, batoid rays and more ray-like selachians. These fishes also have large body spans, probably to help maintain body volume in spite of body flattening. The swimming kinematics of highly flattened benthic fishes differs from that of their more fusiform relatives. The amplitude of body motions tends to be large over a greater portion of the propulsor, with plaice being more anguilliform and rays giving their name to swimming with large-amplitude undulations of the pectoral fins in the rajiform mode (Breder, 1926; Rosenberger, 2001). Human-engineered vehicles and animals moving close to a solid surface can reduce thrust requirements and increase efficiency as a result of interactions between the wake and the surface (ground effect) (Reid, 1932; Blake, 1979, 1983a,b; Lighthill, 1979; Webb, 1993). This hydrodynamic ground effect does not affect fast-start performance (Webb, 1981), but continuous swimmers do benefit (Blake, 1979; Webb, 1993). The ground effect for axial undulatory swimming fish decreases rapidly with height, being reduced by up to 95 % at a gap/span ratio of 1, and becoming very small, essentially negligible, at a value of 2 (Webb, 1993). For rigid bodies, ground effects reach zero at a gap/span ratio of 3 (Reid, 1932; Blake, 1979, 1983b; Lighthill, 1979). To assess the effects of a nearby surface on the swimming of benthic fishes, observations were made on plaice (Pleuronectes platessa) and cod (Gadus morhua) swimming at various heights above the bottom. This study focuses on ... |
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