| Summary: | Speeds and endurance of subcarangiform and anguilliform swimming fish are investigated in the burst and prolonged ranges. In subcarangiform swimming, undulations are limited to the posterior one-half to one-third of the body, while anguilliform swimming involves sinusoidal undulations of virtually the entire body length. For single species and progressively larger groups of species in each swimming mode, data from the literature are analysed by correlating expressions of fish speed and endurance, i.e. deriving fatigue curves. Two expressions for fish speed are used, the traditional BL/s, which is used most frequently in biology to normalize speed,and the dimensionless fish speed, which is used in an ecohydraulic analysis and includes the square root of body length as a scale. The results presented compare the biological and ecohydraulic expressions for fish speed and demonstrate that improved regressions are achieved with the latter approach. For subcarangiform swimmers these analyses are illustrated with data for the freshwater (rainbow trout) and anadromous (steelhead trout) forms of Oncorhynchus mykiss, separately and combined, several trout species as a Trout subgroup (6 species), several salmon added to the trout species as a Salmoninae subgroup (13 species), the Salmoninae with Coregoninae and Thymallinae added, forming the Salmonidae group (22 species in 3 subfamilies) and the Salmon and Walleye group, which adds Catostomidae (6 species), Cyprinidae (47 species), Moronidae (2 species) and Percidae (4 species) to the Salmonidae group (81 species in 5 families). Similarly, for anguilliform swimmers analyses are illustrated with data for two species individually -sea lamprey (Petromyzon marinus) and burbot (Lota lota) -or as the Eel group consisting of four species by adding more limited data on Pacific lamprey (Lampetra tridentata) and European eel (Anguilla anguilla). Regression results indicate similarities in biomechanical capabilities between single species, subgroups or larger subcarangiform or anguilliform groups. The dimensionless fish speed offers robust fatigue curves with stronger regressions when compared to the traditionally normalized fish speed for single species or groups of species. The ecohydraulic approach utilized data collected by various methods, made best use of existing limited data sets for several species and improved estimates for both the group and the single species. Furthermore, this approach generalizes fish speed versus endurance relationships and bridges data gaps by providing estimates for species in the group that lack data. This is important for scientific as well as practical purposes since just 5 of the81 subcarangiform species, 3 Oncorhynchus sp. (mykiss or steelhead, tshawytscha or chinook, and kisutch or coho), walleye (Sander vitreus), and white sucker (Catostomus commersoni), and 2 of the 4 anguilliform species, sea lamprey and burbot, have a wide range of data on endurances, speeds and fish lengths over the burst and prolonged ranges to derive well-defined individual fatigue curves.
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