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Growth and survival of Kemp's ridley sea turtle, Lepidochelys kempi, in captivity
  • Published Date:
Filetype[PDF - 3.26 MB]

  • Corporate Authors:
    Southeast Fisheries Center (U.S.), Galveston Laboratory, ; Southeast Fisheries Center (U.S.) ;
  • Series:
    NOAA technical memorandum NMFS-SEFC ; 186
  • Document Type:
  • Description:
    Six year-classes (1978-1983) of Kemp's ridley sea turtle, Lepidochelys kempi, were reared at the National Marine Fisheries Service, Southeast Fisheries Center, Galveston Laboratory in Galveston, Texas. This paper describes the growth in weight per individual, the increase in biomass, and the survival of aggregates of turtles during their first year of life in captivity. It also lays a statistical foundation for future experiments on factors affecting growth and survival of Kemp's ridley in captivity. The exponential phases of first-year growth in weight per individual (for all year-classes, 1978-1983) and increase in biomass (only for year-classes 1981-1983) of aggregates of turtles were transformed to straight-line relationships represented by the rectilinear regressions of the natural logarithm of weight or biomass on the square root of age or square root of lapsed time (when age was unknown). The slopes of the straight lines, as indices of the rates of increase in weight (growth rate) and biomass, were used to detect differences among year-classes or sub-divisions (e.g., "imprint-groups" and clutches) within year-classes. The most rapid growth was exhibited by the 1980 year-class and the slowest growth by the 1983 year-class. Within the 1981-1983 year-classes, there were significant differences among clutches in growth rate and rate of increase in biomass, but these differences were confounded with other sources of variation. There was greater similarity in growth rates than in rates of biomass increase among year-classes and among clutches within year- classes. There was a curved relationship (concave downward) between the indices of biomass increase and of growth. At lower levels of both indices, the growth rate index exceeded the index of biomass increase. The two indices converged (became more alike) as they increased. Survival and growth rate index increased up to point, then survival declined with further increase in the growth rate index. Such results suggest that carrying capacity of the raceways for turtle biomass is a limiting factor and that compensatory mortality occurs as the size of the turtles increases. A minimum sample size of 25 turtles per clutch is adequate for detecting differences between means of logarithmically transformed weights, either for comparisons among different clutches at the same time or for comparisons within the same clutch at different times. Growth in weight with carapace length followed the "cube law." Carapace width and length were linearly related, with the former being only slightly shorter than the latter. Growth in weight of ten turtles from the 1978 year-class, held in captivity for 5 years at Sea-Arama Marineworld in Galveston after having been reared at the Galveston Laboratory, followed a sigmoid pattern described by a fitted Gompertz growth function. The upper asymptotic weight was 29.2 kg, much smaller than the size (34-49 kg) recorded for nesting adults.

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