This footage demonstrates how Atlantic sailfish (Istiophorus albicans) use their bill to hunt schooling prey (sardines in this case). The first and last video segments shows a large group of sailfish (approx 40 fish) interacting with a school of several hundred sardines. The second segment shows a « slash » (a broad sweeping movement with the bill in which the sailfish hits a number of potential prey) in high speed (slow motion). The third segment shows a number of different of steps involved in a sailfish attacking a prey school in real time (including a « tap » which is representative of a highly targeted movement of the bill towards a single prey individual).
We identified 10 main states of sailfish predation behaviour: (i) prey herding, (ii) chasing, (iii) approach, (iv) imminent attack (bill inside or in close proximity to school), (v) attack (including both slash and tap), (vi) prey contact (when the bill makes physical contact with one or more sardines), (vii) prey handling (redirection of prey towards mouth using bill), (viii) capture/ingestion, (ix) reapproach (in an instance when capture/ingestion was unsuccessful) or alternatively, (x) departure. This process can be repeated until every individual in the prey school is caught and consumed.
This research on how sailfish use their bill was recently published in the Proceedings of the Royal Society, April 2014.
Title: How sailfish use their bills to capture schooling prey
Proc. R. Soc. B 20140444. http://dx.doi.org/10.1098/rspb.2014.0444
The istiophorid family of billfishes is characterized by an extended rostrum or ‘bill’. While various functions (e.g. foraging and hydrodynamic benefits) have been proposed for this structure, until now no study has directly investigated the mechanisms by which billfishes use their rostrum to feed on prey. Here,we present the first unequivocal evidence of how the bill is used by Atlantic sailfish (Istiophorus albicans) to attack schooling sardines in the open ocean. Using high-speed video-analysis, we show that (i) sailfish manage to insert their bill into sardine schools without eliciting an evasive response and (ii) subsequently use their bill to either tap on individual prey targets or to slash through the school with powerful lateral motions characterized by one of the highest accelerations ever recorded in an aquatic vertebrate. Our results demonstrate that the combination of stealth and rapid motion make the sailfish bill an extremely effective feeding adaptation for capturing schooling prey.
We own the copyright to this video. Please do not copy any portion of this footage without prior written consent. (The sailfish team; for more information contact A. Wilson above)