The effect of commercial and artisanal fishing practices on the behavioral budget of bottlenose dolphins off the coast of Montenegro, South Adriatic Sea

Abstract

The spatial–temporal distribution of cetacean species often overlaps with fishing practices in the Mediterranean, having direct and indirect consequences. This is the first long‐term study focusing on the effects of fisheries on the behavior of T. truncatus in Montenegro. Focal group scan sampling was used during surveys between September 2016 and August 2020 to create transition probability matrices using first‐order Markov chains for behavioral states in both control (absence of fishery practices) and impact chains (presence of fishery practices). Despite the low number of dolphin‐fishery interactions in Montenegro, results revealed that the behavioral budgets of T. truncatus were significantly altered both for commercial and artisanal fisheries. However, the magnitude of the threat differed between practices, with commercial fisheries altering three out of the four behaviors in the behavioral budget while artisanal fisheries altered just one. Significant behavioral changes due to disturbance can have negative consequences on the energy budget of individuals and while the Montenegrin fishing fleet is currently limited to 224 vessels, the significant effects already witnessed are concerning for Montenegrin bottlenose dolphins. To develop in‐situ mitigation strategies, there is a clear need to better understand the impact that fisheries interactions have on these individuals.

Whales and dolphins of the Adriatic Sea

“…The behaviour did not appear to be influenced by time of day, but surface feeding and socializing increased in autumn and winter, suggesting seasonal variability (Affinito et al, 2019). A longer study -2020Rudd et al, 2022) based on observations from boats and from land in the same area confirmed that travelling and diving accounted for the majority of observed behaviour, respectively 43% and 33%, while socializing accounted for 10%, surface feeding 7%, and approaches to boats 4%. Socializing was reportedly higher in summer and autumn, while surface feeding was predominant in winter (Rudd et al, 2022).…”

“…A longer study -2020Rudd et al, 2022) based on observations from boats and from land in the same area confirmed that travelling and diving accounted for the majority of observed behaviour, respectively 43% and 33%, while socializing accounted for 10%, surface feeding 7%, and approaches to boats 4%. Socializing was reportedly higher in summer and autumn, while surface feeding was predominant in winter (Rudd et al, 2022). In a different study conducted from boats, the most frequent behaviour recorded at the beginning of each sighting was diving (57%), followed by the active following of a trawler (24%), while the remaining 19% included dive-travelling, travelling and resting (Miočić-Stošić et al, 2020).…”

Initial results on the variation of whistle characteristics of bottlenose dolphins from two neighbouring regions of the Mediterranean Sea: Northern Ionian and Southern Adriatic Sea

“…It is important to understand the role of harmonics, specifically considering their high occurrence in each location during the current study. Although this study focuses on geographical differences of whistle variables between study locations, previous studies indicated that 50% of focal bottlenose dolphin groups in Montenegro were observed with the presence of subadults, with dolphins spending 70% of their time travelling, while milling and socialising behaviour only formed 10% or less of the total behavioural budget (Clarkson et al, 2020;Akkaya et al, 2021;Rudd et al, 2022). Above all, both of the locations have a significant amount of marine traffic; with approximately 4,130 vessels in the port of Taranto per year (Shipnext.com).…”

Using off-the-shelf GPS loggers to assess co-occurrence between marine mammals and small-scale fisheries: a pilot study from the Mediterranean Sea

“…Marine mammals, a sentinel group of marine megafauna, are threatened by a plethora of anthropogenic activities, such as chemical and noise pollution, resource depletion, habitat modification/loss, vessel collisions and fishing activities (Baulch & Perry, 2014; Lauriano et al ., 2014; Merchant et al ., 2014; Knowlton et al ., 2016; Alexiadou et al ., 2019; Bernaldo De Quirós et al ., 2019; Rudd et al ., 2022). In particular, interactions between fisheries and marine mammals usually stem from depredation (i.e.…”

“…Even though the central and eastern parts of the Mediterranean Sea are largely oligotrophic, they host most marine mammal species found in this region. Until recently, the research output regarding the impacts of fisheries on local marine mammal populations originating from these areas was limited (IUCN, 2012), however in more recent years a few studies have addressed marine mammal-fisheries interactions in the region (Snape et al ., 2018; Karamanlidis et al ., 2020; Rudd et al ., 2022). In addition to that, interactions between bottlenose dolphins ( Tursiops truncatus Montagu, 1821; hereafter termed bottlenose dolphins) and SSF have been reported from coastal areas of Sardinia, Italy (Díaz López, 2006; Díaz López & Bernal Shirai, 2007; Pennino et al ., 2016), the Balearic Islands, Spain (Brotons et al ., 2008; Gazo et al ., 2008) and western Greece (Gonzalvo et al ., 2015).…”