Nonlethally assessing elasmobranch ontogenetic shifts in energetics

Wheeler, Carolyn R., Irschick, Duncan J., Mandelman, John W., and Rummer, Jodie L. (2023) Nonlethally assessing elasmobranch ontogenetic shifts in energetics. Journal of Fish Biology, 103 (2). pp. 235-246.

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Body condition is an important proxy for the overall health and energetic status of fishes. The classically used Fulton's condition factor requires length and mass measurements, but mass can be difficult to obtain in large species. Girth measurements can replace mass for wild pelagic sharks. However, girth-calculated condition has not been validated against Fulton's condition factor intraspecifically, across ontogeny or reproduction, or in a controlled setting. We used the epaulette shark (Hemiscyllium ocellatum), because they are amenable to captive reproduction, to track fine-scale body condition changes across life stages, oviparous reproduction and between condition indices. We measured four girths, total length and mass of 16 captive epaulette sharks across 1 year and tracked female reproduction daily. We also collected length and mass data from an additional 72 wild-caught sharks and 155 sharks from five previous studies and two public aquaria to examine the relationship between length and mass for this species. Even though data were derived from a variety of sources, a predictable length–mass relationship (R2 = 0.990) was achievable, indicating that combining data from a variety of sources could help overcome knowledge gaps regarding basic life history characteristics. We also found that condition factor decreased during early life stages, then increased again into adulthood, with predictable changes across the female reproductive cycle. Finally, we determined that both Fulton's and girth condition analyses were comparable. Outcomes from this study uniquely provide body condition changes across the complete life history, including fine-scale female reproductive stages, and validate the use of girths as a nonlethal whole-organism energetic assessment for fishes.

Item ID: 78994
Item Type: Article (Research - C1)
ISSN: 1095-8649
Keywords: chondrichthyes, condition factor, isometric scaling, life history, morphometrics, reproduction
Copyright Information: © 2023 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Funders: ARC Centre of Excellence for Coral Reef Studies
Research Data:
Date Deposited: 06 Nov 2023 23:21
FoR Codes: 31 BIOLOGICAL SCIENCES > 3109 Zoology > 310903 Animal developmental and reproductive biology @ 50%
31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 50%
SEO Codes: 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280102 Expanding knowledge in the biological sciences @ 100%
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