Tails of the Sea: Morphological Scaling and Ontogeny of Shark Caudal Fins

Abstract

Sharks are critical to ocean ecosystems and have been studied in many ecological and biomechanical capacities. One area of study that is relatively lacking is analysis of caudal fin shape with respect to ecological changes throughout ontogeny. Caudal fins are the sharks’ main propulsion structures and as such can dictate a certain amount of their behavior such as what prey they go after, what habitats they occupy, and how they grow over time. Many sharks begin in a nursery environment, such as mangroves, which can protect against predation before becoming large enough to occupy their adult habitats. This study aimed to focus on how the caudal fin may be changing as the shark grows both within a species and amongst a variety of species. After analyzing nine species across five orders it was found that certain linear tail measurements are changing allometrically but many are growing isometrically. Those that are allometric may be adjusting their caudal lobe ratios to better fit their adult environments after leaving their juvenile nursery habitats. Further studies should focus on quantifying the fluid dynamics behind these shape changes to better understand the role the caudal fin is playing in their lifespan.