Length-weight relationships and coefficient of condition of Euphausia superba and Thysanoessa macrura (Crustacea: Euphausiacea) in southwest Indian Ocean during summer |
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Authors: | J Färber-Lorda |
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Institution: | (1) Centro de Investigación Cientifica y de Educación Superior de Ensenada, B. C. Kilometro 107, Carretera Tijuana-Ensenada, Ensenada, Baja California, Mexico |
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Abstract: | Samples of antarctic euphausiids, Euphausia superba and Thysanoessa macrura were obtained during the MD 25 FIBEX expedition of the R. V. Marion Dufresne , in February 1981, to the southwest Indian Ocean. Individual and mean coefficients of condition (K
m) were calculated from variations in weight as a function of total length and of carapace length. In E. superba, no significant differences were found as a function of sex or development stage in either total length and weight or carapace length and weight. In T. macrura, a significant allometric difference emerged in the wet weight of juveniles, males and females as a function of total length, and in wet weight as a function of carapace length between adults and subadults. In both E. superba and T. macrura, wet weight as a function of total length differed significantly among stations, and also between species, with a greater weight increase for T. macrura in summer. The coefficients of condition calculated for all wet weight-total length relationships showed that the morphologically different Group II males were heavier than Group I males and mature females. K
m in T. macrura was higher for females than for juveniles or males, indicating a greater weight gain by the females. These differences probably reflect real differences in physiology and may affect the distribution of these two species. |
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