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Correlations of Swimming Patterns with Spinal Deformities in the Sand Tiger Shark, Carcharias taurus

  • Author(s): Tate, Erin E.
  • Anderson, Paul A.
  • Huber, Daniel R.
  • Berzins, Ilze K.
  • et al.
Creative Commons 'BY' version 3.0 license
Abstract

Spinal deformities among captive sand tiger sharks, Carcharias taurus, are unfortunately common, and abnormal swimming behavior due to constrained aquarium space has been hypothesized to contribute to the development of this condition. Public aquaria across the United States were surveyed for number, condition (healthy vs. affected), and total length of resident C. taurus specimens and for dimensions of their aquaria. They were also asked to record 10 minute video segments of individual C. taurus swimming in lateral view. Total length of sharks, regardless of condition, averaged 225 ± 5 (mean ± SE) cm. Aquarium shapes varied widely, but aquaria held median volumes of 1.03 X 106 L, and were a median of 4.6 m in depth and 20.7 m in greatest horizontal distance. The greatest horizontal distance of aquaria was negatively correlated with disease prevalence of resident populations in a logarithmic fashion (r = 0.72). Behaviorally, sharks were assessed for total time and percentage of time spent swimming in a specific direction (clockwise, counter-clockwise, or linear), in a glide, and tail-beat duration. Regardless of condition, C. taurus spent a median of 98.9% of time swimming and 0.62% of time gliding. Healthy sharks spent a median of 0.67% gliding versus a median of 0% for afflicted sharks (p= 0.036), suggesting an increased swim-to-glide ratio among the latter group. All sharks swam asymmetrically in either a clockwise or counter-clockwise direction for a median of 99.7% of observed time. Affected specimens had tail beat durations of 3.37 ± 0.23 s vs. 2.72 ± 0.10 s for healthy sharks (p = 0.005). The increase in swim-to-glide ratios and inordinate time spent swimming asymmetrically for all affected sharks support the hypothesis that swimming patterns induced by captive exhibits may contribute to spinal deformities in C. taurus due to more stress placed on the spine. Large, complex aquarium designs are recommended in the planning of new exhibits to discourage stereotypical swimming behavior and also to provide sufficient length for sharks to complete natural swimming repertoires. Comprehensive behavioral enrichment activities that encourage complex movement are also recommended as well as considerations such as even weight distribution of the animal during capture, sourcing of appropriately aged sharks, and nutritional supplementation.

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