Interactions of large pelagic sharks (Elasmobranchii) with capture-based tuna aquaculture and salmon farming in the Mediterranean Sea

Interactions between large pelagic sharks and marine aquaculture remain poorly documented in the Mediterranean Sea. We report six cage-entry events involving blue sharks, Prionace glauca (Linnaeus, 1758), and shortfin makos, Isurus oxyrinchus Rafinesque, 1810, associated with capture-based Atlantic bluefin tuna aquaculture and Atlantic salmon farming between 2018 and 2026. Records were compiled from direct observations, information provided by personnel involved in fishing and aquaculture operations, and original photographic and video material. Four cage-entry events occurred through breaches in the cage netting, while two blue sharks were captured incidentally with tuna in purse seines and subsequently transferred into transport cages. Three sharks were released alive and three died after becoming entangled in cage netting. Evidence of feeding was recorded in five of the six cage-entry events. The records demonstrate two distinct pathways of shark entry into aquaculture cages: entry through breaches in cage netting and incidental transfer from purse seines into tuna transport cages. Although the opportunistic nature of the observations precludes estimation of interaction frequency, the documented mortalities highlight the importance of systematic reporting, rapid-release procedures, and mitigation measures aimed at reducing shark entry and entanglement.