The first report of adult blue shark surviving severe head impalement by a swordfish, with an overview of similar incidents

Abstract

The blue shark (Prionace glauca) and swordfish (Xiphias gladius) are two large apex predators sharing the same pelagic environment and exhibiting partial dietary overlap, which collectively lead to interactions that might include conflicts. This paper presents the first verified case of a blue shark surviving an impalement by a swordfish, marking the first incident of its kind in the Adriatic Sea. On February 17, 2023, an adult blue shark captured in Vlorë (southern Albania) was found with an 18.6 cm fragment of swordfish bill embedded in its suborbital shelf of the neurocranium, extending through the stapedial fenestra. Despite this injury, no major internal damage was observed and the shark exhibited active feeding behaviour. The paper further provides a detailed overview of all known incidents of blue shark impalements by swordfish to date. The findings presented herein highlight the need for further observations to understand the nature of these conflicts and the interactions between swordfish and sharks.