Jellyfish blooms in the Northern Adriatic Sea: Fishermen's perceptions and economic impacts on fisheries

Extensive blooms of gelatinous macrozooplankton species (“Jellyfish”) have appeared in recent decades in Northern Adriatic (NA) waters. Anecdotal evidence suggests that these blooms have had a considerable impact on fishing operations, as this region is one of the most heavily exploited Mediterranean fishing grounds. In order to gain a better understanding of the possible economic losses for the Italian NA fishing industry due to jellyfish impacts, we conducted a survey of fishermen in the city of Chioggia, which is the main fishing port for the NA basin. The study focused on fishermen's perceptions about jellyfish blooms in the NA Sea and also investigated whether and how blooms compromised fishing operations. Survey results confirm that blooms have negatively affected fishing operations in the last few decades. We estimate that economic losses due to reduction in fish catches could amount to as much as € 8.2 million per year for the Italian NA trawling fleet. Other costs on this fleet include additional fuel costs due to displacement of fishing operations, which could represent an increase in costs of over € 460,000 per year. Moreover, during a jellyfish bloom episode it can happen that time has to be spent by fishermen to repair nets damaged by jellyfish caught in them, leading to an estimated cost for the trawling fleet and small scale fisheries of over 89,000 man-hours per year. This study not only confirms that jellyfish blooms have a considerable impact on fishing operations but also shows how costly blooms can be for the NA fisheries.