Consistent foraging areas and commuting corridors of the critically endangered Balearic shearwater Puffinus mauretanicus in the northwestern Mediterranean

Seabirds and demersal longliners in the northwestern Mediterranean: factors driving their interactions and bycatch rates

“…Belda & Sánchez 2001, Laneri et al 2010. This is because seabird species in the Mediterranean are mainly diurnal and are particularly active at dawn and dusk (Passos et al 2010, Dias et al 2012, Meier et al 2015. Concordantly, incidental catches were most frequent at dawn, although catches can also be high during daytime.…”

“…In this study, we found that seabird interactions were significantly reduced at night, with only 9% of all catches reported during this time period. This result is particularly relevant for the Critically Endangered Balearic shearwater, as this species is mostly active in daylight, specifically during the crepuscular hours (Meier et al 2015), so that catches at night are less likely. Indeed, only 3 of 64 Puffinus shearwaters caught during the onboard observations were Balearic shearwaters captured at night, all of them on the same boat in 2 consecutive days, coinciding with a full moon.…”

“…In contrast, our study reports for the first time high bycatch rates in demersal longlines of 2 globally threatened seabirds, namely the Critically Endangered Balearic shearwater and the Vulnerable Medi ter ranean shearwater (BirdLife International 2017), con firming previous suspicions (Arcos et al 2008, ICES 2013. Along with Scopoli's shearwater, these small shearwaters were the most commonly caught by demersal longliners in the Balearic Sea, particularly on the Catalan continental shelf, where important foraging grounds are located (Arcos et al 2012, Meier et al 2015. This high incidence of capture is subject to irregular catches, often involving dozens to even hundreds of individuals, thus complicating the detection and quantification of the problem.…”

“…Indeed, the lower number of bait attacks by gull species, despite being the most common birds attending longline vessels, is likely due to their lower diving capabilities, which limits their access to the baited hooks once these sink into the water. In contrast, shearwaters are strong divers that can reach the baited hooks even when these are several metres underwater, reaching depths down to 28 m (Meier et al 2015), thus increasing their bycatch risk. Likewise, in the case of the northern gannet, the species also showed a high susceptibility to being caught in longlines due to its high deep-diving ability (Ropert-Coudert et al 2009), although relatively few catches were recorded due to its relatively low occurrence behind vessels.…”

A new algorithm for the identification of dives reveals the foraging ecology of a shallow-diving seabird using accelerometer data

“…The prevalence of shallow dives in Scopoli's shearwaters was also confirmed by the depth data recorded by TDRs: 50% of dives were registered in the first 0.5 m of depth and 78% were less than 1 m deep. Similarly, in many seabird species, dives are predominantly less than 5 m deep (Paiva et al 2010a;Rollinson et al 2014;Meier et al 2015). In these species, the number of shallow dives recorded with TDR was most likely underestimated.…”