1. |
Compression index |
CI = BH/BW |
High values indicate laterally compressed fish, which inhabit sites with low water velocity (Watson & Balon, 1984Watson, D. J. & E. Balon. 1984. Ecomorphological analysis of taxocenes in rainforest streams of northern Borneo. Journal of Fish Biology, 25: 371-384.). |
2. |
Index of ventral flattening |
IVF = MH/BH |
Low values are typical of fish living in water with high velocity, allowing them to maintain position without swimming (Hora, 1930Hora, S. L. 1930. Ecology, bionomics and evolution of the torrential fauna, with special reference to the organs of attachment. Philosophical Transactions of the Royal Society of London, 28: 171-282.). |
3. |
Relative body height |
RBH = BH/SL |
This index is inversely related to water velocity and directly related to the ability to perform vertical displacements (Gatz, 1979Gatz Junior, A. J. 1979. Ecological morphology of freshwater stream fishes. Tulanne Studies in Zoology Botany, 21: 91-124.). |
4. |
Relative eye position |
REP = EH/HeH |
This index is related to the detection of food, provides information on the use of vision during predatory activities (Pouilly et al., 2003Pouilly, M., F. Lino, J. G. Bretenoux & C. Rosales. 2003. Dietary morphological relationships in a fish assemblage of the Bolivian Amazonian floodplain. Journal of Fish Biology, 62: 1137-1158.) and indicates the preferred position in the water column (Gatz, 1979Gatz Junior, A. J. 1979. Ecological morphology of freshwater stream fishes. Tulanne Studies in Zoology Botany, 21: 91-124.). |
5. |
Relative eye area |
REA = EA/(SL)2
|
This index is related to the detection of food and provides information on the use of vision during predatory activities (Pouilly et al., 2003Pouilly, M., F. Lino, J. G. Bretenoux & C. Rosales. 2003. Dietary morphological relationships in a fish assemblage of the Bolivian Amazonian floodplain. Journal of Fish Biology, 62: 1137-1158.). |
6. |
Relative head length |
RHeL = HeL/SL |
Directly related to prey size, and high values suggest predatory species with relatively large prey (Gatz, 1979Gatz Junior, A. J. 1979. Ecological morphology of freshwater stream fishes. Tulanne Studies in Zoology Botany, 21: 91-124.). |
7. |
Relative length of the caudal peduncle |
RLCdP = LCdP/SL |
Relatively long peduncles indicate fish that inhabit turbulent waters and have a good swimming ability (Gatz, 1979Gatz Junior, A. J. 1979. Ecological morphology of freshwater stream fishes. Tulanne Studies in Zoology Botany, 21: 91-124.; Watson & Balon, 1984Watson, D. J. & E. Balon. 1984. Ecomorphological analysis of taxocenes in rainforest streams of northern Borneo. Journal of Fish Biology, 25: 371-384.). |
8. |
Relative height of the caudal peduncle |
RHCdP = HCdP/BH |
Low values indicate greater maneuverability (Winemiller, 1991Winemiller, K. O. 1991. Ecomorphological diversification in lowland freshwater fish assemblages from five biotic regions. Ecological Monographs, 61: 343-365.). |
9. |
Relative width of the caudal peduncle |
RWCdP = WCdP/BW |
High values indicate better long-distance swimmers (Winemiller, 1991Winemiller, K. O. 1991. Ecomorphological diversification in lowland freshwater fish assemblages from five biotic regions. Ecological Monographs, 61: 343-365.). |
10. |
Compression index of the caudal peduncle |
CICdP = HCdP/WCdP |
This index is inversely related to the amplitude of swimming motions, with high values indicating compressed peduncles typical of less active swimmers (Gatz, 1979Gatz Junior, A. J. 1979. Ecological morphology of freshwater stream fishes. Tulanne Studies in Zoology Botany, 21: 91-124.). |
11. |
Relative area of the dorsal fin |
RADsF = ADsF/BA |
Dorsal fins with a large area are better able to stabilize during deviations (Gosline, 1971Gosline, W. A. 1971. Functional morphology and classification of teleostean fishes. Honolulu, University of Hawaii.). |
12. |
Relative area of the caudal fin |
RACdF = ACdF/BA |
High values indicate fins able to produce rapid impulses, which are typical of the swimming of many benthonic fishes (Watson & Balon, 1984Watson, D. J. & E. Balon. 1984. Ecomorphological analysis of taxocenes in rainforest streams of northern Borneo. Journal of Fish Biology, 25: 371-384.). |
13. |
Aspect ratio of the caudal fin |
ARCdF = (HCdF)2/ACdF |
This index is directly proportional to the amount of swimming performed by the fish (Gatz, 1979Gatz Junior, A. J. 1979. Ecological morphology of freshwater stream fishes. Tulanne Studies in Zoology Botany, 21: 91-124.). |
14. |
Relative area of the anal fin |
RAAnF = AAnF/(SL)2
|
Large relative areas indicate high maneuverability and ability for stabilizing motions (Breda et al., 2005). |
15. |
Aspect ratio of the anal fin |
ARAnF = (LAnF)2/AAnF |
Anal fins with a high aspect ratio indicate good ability for rapid movements of progression and regression (Breda et al., 2005) |
16. |
Relative length of the pelvic fin |
RLPlF = LPlF/SL |
Related to habitat preference, with a longer index in rocky habitats and a shorter one in nektonic species (Gatz, 1979Gatz Junior, A. J. 1979. Ecological morphology of freshwater stream fishes. Tulanne Studies in Zoology Botany, 21: 91-124.). |
17. |
Relative area of the pelvic fin |
RAPlF = APlF/BA |
Benthonic fishes have relatively large areas (Gatz, 1979Gatz Junior, A. J. 1979. Ecological morphology of freshwater stream fishes. Tulanne Studies in Zoology Botany, 21: 91-124.). |
18. |
Aspect ratio of the pelvic fin |
ARPlF = LPlF/WPlF |
Low values are found in fish that use the pelvic fins for braking and swimming forward, and greater values are found in fish that use these fins to retreat and maintain their position in the water column (Gatz, 1979Gatz Junior, A. J. 1979. Ecological morphology of freshwater stream fishes. Tulanne Studies in Zoology Botany, 21: 91-124.). |
19. |
Relative length of the pectoral fin |
RLPtF = LPtF/SL |
High values indicate fish that inhabit slow waters and perform many maneuvers (Gatz, 1979Gatz Junior, A. J. 1979. Ecological morphology of freshwater stream fishes. Tulanne Studies in Zoology Botany, 21: 91-124.). |
20. |
Relative area of the pectoral fin |
RAPtF = APtF/BA |
High values indicate slow swimmers, which use these fins to maneuver, and fish inhabiting rapid waters, which use them as water deflection surfaces to keep their body close to the substrate (Watson & Balon, 1984Watson, D. J. & E. Balon. 1984. Ecomorphological analysis of taxocenes in rainforest streams of northern Borneo. Journal of Fish Biology, 25: 371-384.). |
21. |
Aspect ratio of the pectoral fin |
ARPtF = LPtF/WPtF |
High values indicate long fins and suggest fish with good swimming ability (Watson & Balon, 1984Watson, D. J. & E. Balon. 1984. Ecomorphological analysis of taxocenes in rainforest streams of northern Borneo. Journal of Fish Biology, 25: 371-384.). |