Abstract
ABSTRACT We analyzed growth and reproduction of captive-born smallnose fanskates Sympterygia bonapartii. Egg cases were obtained from oviposition of two females caught in the wild and held at Temaikèn Aquarium. Following hatching, growth was analyzed in 13 females and 21 males until sexual maturity. Pattern of oviposition activity and reproductive performance were evaluated in six of the captive-reared females. Four models were fitted to growth data, among which the logistic function was the one attaining the best fit. The highest growth rate for both sexes was recorded during the first year of life, whereas growth was significantly higher in females than in males during the second year. Size at first oviposition was 61.7 ± 3.5 cm TL, similar to wild specimens. However, captive-reared females reached maturity before two years of age, i.e. much earlier than wild skates, implying a significant phenotypic plasticity in this species. The similarity in size at maturity and the difference in age at maturity between captive and wild specimens indicate that there is a decoupling of both parameters mediated through growth rates. Captive-born skates reproduced successfully and yielded viable offspring, indicating that the environment at Temaikèn Aquarium is suitable for S. bonapartii to attain its full life cycle.
Highlights
The life history of elasmobranch fishes can be characterized as being typical of equilibrium strategists (Frisk et al, 2001; Charnov, 2002)
The husbandry conditions at Temaikèn Aquarium were adequate for S. bonapartii to complete its life cycle, from birth to reproduction
The temperature of the skate habitat at Temaikèn Aquarium was within the range of sea water temperature off north Argentina (8.2-23 oC; Lucas et al, 2005)
Summary
The life history of elasmobranch fishes can be characterized as being typical of equilibrium strategists (Frisk et al, 2001; Charnov, 2002). They depend on a relatively stable environment and high offspring survival, producing young that are relatively large and precocious. Physical changes to the egg case and internal chamber are triggered by the embryo, providing the critical physical requirements necessary for successful growth and development (Koob, Cox, 1990; Berestovskii, 1994; Hamlett, Koob, 1999; Wyffels, 2009)
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