Monitoring Abundance and Distribution of Northern Gannets Morus bassanus in Western Iberian Waters in Autumn by Aerial Surveys

AUTHOR CONTRIBUTIONS - Study conception HA and CE; Investigation HA, PCR, jBS, MF, ATP, JMC, JV and CE; Methodology HA, PCR, JBS, JV and CE; Resources HA, JBS, JV and CE; Data curation HA, PCR, JBS, JV; Writing initial draft HA; Writing critical review and commentary of revision HA, PCR, jBS, MF, ATP, JMC and CE; Supervision PCR, JV and CE; Project Administration JV and CE.Several North Atlantic breeding seabirds, such as the Northern Gannet Morus bassanus, use Western Iberian Waters for wintering and migration. In this study, we aimed at producing absolute population estimates of post-breeding Gannets and evaluating the importance of the study area within the species’ migration range. We performed six aerial surveys in September and/or October each year between 2010 and 2015, covering 74,840km2 in total. Using line transect methodology, 3,672 Gannet sightings were recorded along 10,496.3 nautical miles (nm). Immature individuals and adults comprised approximately 87% of all sightings. Using Distance sampling, overall abundance was estimated at 89,930 birds, ranging from 58,010 individuals in 2014 to 128,140 in 2015. the highest densities per sector areas were recorded in the North and Centre sectors whereas the lowest densities were registered in the Galicia sector, the Spanish region within the study area. Gannets were mostly present in shallow shelf waters of the continental shelf, particularly between 3 and 20 nautical miles offshore. Habitat suitability models for Gannets in the study area were tested using several eco-geographical variables and chlorophyll concentrations were found to contribute most to explaining annual Gannet occurrence probabilities. A global interannual spatial analysis demonstrated the core areas for conservation of the Northern Gannet in Western Iberian Waters. Moreover, our results demonstrate that Western Iberian waters are used by almost 10% of the global Northern Gannet population, corroborating the existence of seabird hotspots during the non-breeding period, along migration corridors and at their wintering grounds.info:eu-repo/semantics/publishedVersio

Deep ocean drivers better explain habitat preferences of sperm whales Physeter macrocephalus than beaked whales in the Bay of Biscay

Species Distribution Models are commonly used with surface dynamic environmental variables as proxies for prey distribution to characterise marine top predator habitats. For oceanic species that spend lot of time at depth, surface variables might not be relevant to predict deep-dwelling prey distributions. We hypothesised that descriptors of deep-water layers would better predict the deep-diving cetacean distributions than surface variables. We combined static variables and dynamic variables integrated over different depth classes of the water column into Generalised Additive Models to predict the distribution of sperm whales Physeter macrocephalus and beaked whales Ziphiidae in the Bay of Biscay, eastern North Atlantic. We identified which variables best predicted their distribution. Although the highest densities of both taxa were predicted near the continental slope and canyons, the most important variables for beaked whales appeared to be static variables and surface to subsurface dynamic variables, while for sperm whales only surface and deep-water variables were selected. This could suggest differences in foraging strategies and in the prey targeted between the two taxa. Increasing the use of variables describing the deep-water layers would provide a better understanding of the oceanic species distribution and better assist in the planning of human activities in these habitats.Versión del edito

Assessment of harbour porpoise bycatch along the Portuguese and Galician Coast: insights from strandings over two decades

The Iberian harbour porpoise population is small and fisheries bycatch has been described as one of its most important threats. Data on harbour porpoise strandings collected by the Portuguese and Galician stranding networks between 2000 and 2020 are indicative of a recent mortality increase in the western Iberian coast (particularly in northern Portugal). Overall, in Portugal and Galicia, individuals stranded due to confirmed fishery interaction represented 46.98% of all analysed porpoises, and individuals stranded due to probable fishery interaction represented another 10.99% of all analysed porpoises. Considering the Portuguese annual abundance estimates available between 2011 and 2015, it was possible to calculate that an annual average of 207 individuals was removed from the population in Portuguese waters alone, which largely surpasses the potential biological removal (PBR) estimates (22 porpoises, CI: 12–43) for the same period. These results are conservative and bycatch values from strandings are likely underestimated. A structured action plan accounting for new activities at sea is needed to limit the Iberian porpoise population decline. Meanwhile, there is an urgent need for a fishing effort reorganization to directly decrease porpoise mortality.LA/P/0094/2020; LA/P/0101/2020info:eu-repo/semantics/publishedVersio

Quantifying and understanding cetacean bycatch

ICES Annual Science Conference 2023, 11–14 September 2023, Bilbao, SpainFishery bycatch mortality is generally considered to be the main threat to cetaceans in European Atlantic waters. The marine waters in the Northwest of the Iberian Peninsula are among the richest in fishery resources in Europe and, consequently, they are also very important for fisheries. Analysis of cause of death and life history data from strandings in Galicia suggested that the bycatch is a major threat in common dolphins (Delphinus delphis) and harbour porpoises (Phocoena phocoena). The mortality rate in the Iberian population of the harbour porpoise could be well above safe limits. MERMACIFRA (“Monitoring, Assessment and Reduction of Accidental Mortality of Cetaceans due to Interactions with the Spanish Fleet - Review and Action”) is a national Project funded by the Fishery Ministry of Spain, the main objective of which is to monitor, assess and reduce bycatch of cetacean species in Spanish Atlantic waters. This includes acquisition of information on bycaught animals from strandings and on-board monitoring, to quantify bycatch mortality and to build a “profile” of bycaught animals in terms of their sex, size, age, reproductive status and health status. The project collaborates with the Galician stranding network, which attends stranded cetaceans on the Galician coast. Between 1990 and 2020, 3,404 strandings of common dolphins (on average 114 per year) and 344 strandings of harbour porpoises (on average 11 per year) were reported. It was observed that, over the last decade, the number of strandings with bycatch evidence has tended to increase. For 2021, considering only those carcasses examined which preservation state were from fresh to slight (n = 52 for common dolphin, and n = 13 for harbour porpoise), it was obtained that 54% of common dolphins (n = 28) and 23% of harbour porpoises (n = 3) had evidence of fishery interaction. During 2022-2023, we received two notifications from fishers regarding bycaught dolphins. In the first, two common dolphins were collected and studied in the north of Galicia. In the second case, two bycaught common dolphins were thrown overboard by the crew. These data are useful to better understand the reasons for bycatch as well as the resulting mortality. MERMACIFRA also aim to assess methods to reduce bycatch in nets and purse seine fisheries (e.g., using net modifications and observers on-board). Pilots using three types of acoustic deterrent devices indicates different efficacy depending on the species and fisheryN

Descifrando la dieta de las principales especies de cetáceos odontocetos en aguas de Galicia: 30 años de estudio

XIII Congreso de la Sociedad Española de Cetáceos (SEC), Eivissa, 27 – 30 octubre 2022N

From Galician waters to cetacean stomachs, a feeding story told by preys

34th European Cetacean Society Conference, O Grove, 16-20 April 2023Cetaceans play an important role in maintaining the health and stability of marine ecosystems. To understand the trophic relationships of these top predators in waters off the Northwest Iberian Peninsula, and to determine their possible competition with fisheries, the stomach contents of 751 common dolphins (Delphinus delphis), 60 striped dolphins (Stenella coeruleoalba), 124 bottlenose dolphins (Tursiops truncatus), and 72 harbour porpoises (Phocoena phocoena) stranded on the Galician coast between 1990-2018 (almost 30 years) were analysed. Results indicated that their diets are mainly piscivorous (after identified 90 different taxa: 68 fish and 22 cephalopods), being the blue whiting (Micromesistius poutassou) and the European hake (Merluccius merluccius) the most important preys (in occurrence, number, and biomass) throughout all the years studied and for the four cetacean species. The long time series available allowed to detect interannual variation in the diet of both common dolphins and harbour porpoises by means of Generalised Additive Models (GAMs), observing an increase in the presence of European hake and a decrease of sardines (Sardina pilchardus) in the stomachs through time. Seasonal variation in the diets of the common and striped dolphins were also observed, with a higher consumption of blue whiting during the summer (May-September). Significant differences were found in the diet of the two bottlenose dolphin ecotypes present in Galicia, the coastal ecotype contains a higher percentage of demersal preys in the stomachs, while the oceanic ecotype contains more pelagic preys, confirming the habitat separation between the two. Results also confirmed an ontogenic variability in the diet of harbour porpoises, with juvenile animals showing a higher presence of coastal preys in the diet (e.g., pouting – Trisopterus luscus). There is an overlap between the diet of these four cetacean species and the fisheries‟ target species in the area, indicating competition for some resourcesN

The prelude to industrial whaling:Identifying the targets of ancient European whaling using zooarchaeology and collagen mass-peptide fingerprinting

Taxonomic identification of whale bones found during archaeological excavations is problematic due to their typically fragmented state. This difficulty limits understanding of both the past spatio-temporal distributions of whale populations and of possible early whaling activities. To overcome this challenge, we performed zooarchaeology by mass spectrometry on an unprecedented 719 archaeological and palaeontological specimens of probable whale bone from Atlantic European contexts, predominantly dating from ca 3500 BCE to the eighteenth century CE. The results show high numbers of Balaenidae (many probably North Atlantic right whale (Eubalaena glacialis)) and grey whale (Eschrichtius robustus) specimens, two taxa no longer present in the eastern North Atlantic. This discovery matches expectations regarding the past utilization of North Atlantic right whales, but was unanticipated for grey whales, which have hitherto rarely been identified in the European zooarchaeological record. Many of these specimens derive from contexts associated with mediaeval cultures frequently linked to whaling: the Basques, northern Spaniards, Normans, Flemish, Frisians, Anglo-Saxons and Scandinavians. This association raises the likelihood that early whaling impacted these taxa, contributing to their extirpation and extinction. Much lower numbers of other large cetacean taxa were identified, suggesting that what are now the most depleted whales were once those most frequently used.</p

Large‐scale modelling of deep‐diving cetacean habitats

Versión del editor5,14

Capturado y registrado: potencial de las redes de varamientos para el estudio de las capturas accidentales de cetáceos

XII Congreso de la Sociedad Española de Cetáceos, 4 al 7 de octubre de 2021, onlineN