Shearwater "6080638" from nest 670

Sad news. Via the ZEPAMAR project (SEO-Birdlife) a fisherman has reported several Scopoli's shearwaters, Calonectris diomedea, accidentally killed in longlines. Among them, a 26-year-old male, ring 6080638, that bred in the colony at Dragonera Natural Park, off the coast of Mallorca. The Animal Demography and Ecology Group (GEDA-IMEDEA) monitored the colony since 2001, gathering the phenology and breeding success of more than 300 breeding shearwaters, among them bird 6080638, from nest 670. The experienced male carried a geolocator for few years reporting precious information on the wintering ground, the feeding strategy and his breeding phenology. He was born in the same colony in 1993 and began to breed at Dragonera Natural Park in 2002. Each year he occupied nest 670 taking care of the nest, sharing the incubation of the egg with his partner and rising his chick during the summer. He was able to breed in 2012 when many shearwaters died due to the harsh winter conditions. He died in March 2020 caught on a longline. Scopoli’s shearwaters are very sensitive to accidental fishing, probably the main threat for the species. Long-term ringing schemes, as the one conducted by the GEDA, helped to obtain an estimate of the mortality due to bycatch. At this colony, between 7 and 10% of the population is estimated to die by accidental catches. A figure similar to the one of other causes of mortality, most of them, related directly or indirectly to human activities. Demographic studies suggest that the colony is going slowly toward the extinction (here and here). 

Photo: VictorParis

At present the colony acts as a population sink and the number of breeding shearwaters are maintained by immigration of individuals from other colonies (details here). Bird 6080638 has contributed for many years to this knowledge, fundamental to understand the functioning of the colony and to identify mitigation actions. Now he has joint the mortality database. Thanks to the fisherman that has reported the accidental catch, we know that 6080638 was caught in an area near the colony. An area thought to have a low risk of bycatch based on the data collected on the Balearic fishing fleet. But the mortality accidentally caused by artisanal fishing is more difficult to predict and its magnitude is still unknown. It is a large-scale problem becasue bycatches occur in both artisanal and industrial fisheries in the breeding as well as the wintering areas and they represent a serious threat also for other shearwaters, such as the Balearic shearwater, Puffinus mauretanicus.

This entry is a small tribute to 6080638 from nest 670. We will miss him. He helped us to refine our knowledge on the problem of bycatch and to move with the contribution of all, scientists, conservation institutions and fishermen toward solutions.