|Collaborative Researchers:||Diego Bernal, Ph.D. (University of Massachusetts)|
Objectives: This study was performed to document the role of the common thresher shark caudal fin during feeding.
Baited lures were slow-trolled from the PIER research vessel Malolo within the field of view of an underwater video camera. All video clips containing thresher shark feeding events were selected for frame-by-frame analysis to evaluate the specific body posture and caudal fin orientation associated with each feeding behavior. Video footage was recorded for 33 thresher shark feeding attempts, 42% of which made active attempts to strike the baited lure with their caudal fin. This work showed that all of the recorded feeding events were initiated with the upper lobe of the caudal fin (Aalbers et al., 2010).
Two distinct caudal-based feeding behaviors were documented during this study. The most prevalent feeding strategy was initiated by a rapid forward undulation of the anterior body which resulted in a posterior-traveling sinusoidal wave that consequently advanced to the uppermost tip of the caudal fin (Video clip #1 link). The second predominant feeding behavior involved a lateral strike of the caudal fin while the shark was positioned directly adjacent to the baited lure (Video clip #2 link).
This study confirms that the common thresher shark uses its elongate caudal fin to immobilize prey prior to consumption and provides insight into the evolution of this unique feeding strategy among Alopiid sharks. Additional work is necessary to more precisely understand the kinematics of the disproportionately long caudal fin during swimming and feeding. Watch additional underwater video footage of thresher shark feeding activity.
This material is based on work supported by the National Science Foundation under grants (IOS-0617384 & IOS-0617403) any opinions, findings or conclusions expressed in this material are those of the authors and do not necessarily reflect the views of NSF. Additional support was provided by the George T. Pfleger Foundation and the Bycatch Reduction and Engineering program through NOAA.