Distribution extension of the Spectacled Petrel (Procellaria conspicillata) off the Argentine continental shelf and oceanic adjacent waters

The Spectacled Petrel Procellaria conspicillata is endemic of the Tristan da Cunha Archipelago, in the South Atlantic Ocean. However, it is scarcely detected in waters off Argentina beyond its traditional distribution along the southwest Atlantic during the breeding season. This study compiles distributional records of Spectacled Petrel for the target area (chiefly between 38°S to 46°S and 23°W to 57°W) obtained in situ, from non-systematic observations at sea, between 2015 and 2018 (totaling 4 trips); and by literature review. Nineteen new sightings of the species are presented. In 46 sightings a total of 65 individuals were recorded chiefly within waters of the Argentine continental shelf (< 200 m) (46%) and oceanic adjacent waters (54%). The bulk of the sightings (95%) were obtained during the species breeding season. In addition, we report the southernmost record of the species in oceanic waters for the southwest Atlantic (46°10′S; 57°06′W).

Spectacled Petrels are threatened mainly by the increased mortality associated with longline fishing vessels, chiefly in waters where they overlap with Brazilian fisheries fleet (Olmos 1997, Bugoni et al. 2009, Branco et al. 2014. The species is listed as "Vulnerable" by the International Union for the Conservation of Nature (IUCN) (BirdLife International 2018) due to its small breeding range and its susceptibility to stochastic events and human activities (ACAP 2018).
During the breeding season, the species feeds mainly in areas adjacent to Inaccessible Island, notably on the Walvis Chain, and moving further south on the continental shelf of South Africa up to 41 o S near the Agulhas Bank (Enticott & O'Connell 1985, Camphuysen 2001. However, recent studies conducted with satellite transmitters showed the Patagonian shelf off Argentina as a feeding site by at least some tracked individuals (Reid et al. 2014). Previous platform-of-opportunity based studies of the at-sea distribution of the Spectacled Petrel revealed that breeding individuals regularly attend waters of the southwestern sector of the Atlantic Ocean, including the Argentine continental shelf (< 200 m depth) and adjacent oceanic areas (Imberti 2002, Savigny 2002, White et al. 2002, Black et al. 2005 Quiñones & Imberti 2018).
This study updates the information on the Spectacled Petrel distribution in the Argentine continental shelf region and adjacent oceanic waters during the species' breeding season.
Sightings were accomplished opportunistically aboard different vessels performing distinct activities and routes within the Argentine continental shelf region and adjacent oceanic waters (see Table 1 for details). The range of activities and routes of these vessels include (1) tourism in southern Patagonia, the Antarctic Peninsula and the Malvinas/Falkland Islands (three trips), and (2) commercial seismic surveys in adjacent oceanic waters within the Argentine Basin (one trip). The sightings were made during the austral summer (January-February), from 2015 to 2018. For each sighting, the sea state (measured on the Beaufort scale) and wind intensity (in knots) were registered. The bulk of the sightings included single individuals (79%), flying at a minimum distance of 200 m from the stern of the ship (Figs. 1 & 2). Few sightings (n = 2) consisted of individuals recorded either floating and/ or actively feeding. Nineteen sightings encompassing up to 23 individuals were made from the vessels (Table  1), mainly between 38°S to 46°S and 23°W to 57°W. Overall (pooled) sightings occurred on the shelf-break and the continental shelf, mainly at depths ranging from 84 m to 6280 m (Fig. 1). The closest position of a Spectacled Petrel sighting from the South American continent was about 95 nautical miles (175 km) SE off Mar del Plata, Argentina. At the time of the sightings, sea state (measured on the Beaufort scale) varied between 2 and 6, and wind speed between 11.7 kt and 29 kt. On some occasions (~5% of total sightings) the species was observed in assemblages together with other seabirds, chiefly the White-chinned Petrel (P. aequinoctialis) and the Great Shearwater (Ardenna gravis) (tourism and seismic observations combined).
The compilation of previous records and the updated information presented here ( Fig. 1 & Table 1) clearly denote the use by the Spectacled Petrel, at least by some individuals, of the Argentine continental shelf and adjacent oceanic waters. They were recorded over 2000 nm (3700 km) from its breeding area and more than 1080 nm (2000 km) from the main area used by the species during the breeding season. Previous studies indicated that breeding adults concentrate their feeding activities along the mid-Atlantic ridge and along the continental shelf edge between 25-40°S, with 50% of the feeding activities occurring around 500 km from their colony (Reid et al. 2014  the species in the Patagonian shelf waters off Argentina were expected as Reid et al. (2014) also revealed the use of this area as a feeding site by at least some individuals.
Outside the breeding season, the species is found in deeper waters (> 3000 m depth) and shelf edges (1000-3000 m depth) (Bugoni et al. 2009). The main wintering area of this species occurs along the Brazilian continental shelf between São Paulo and Rio Grande do Sul states, in south-southeastern Brazil (Bugoni et al. 2009). The presence of birds recorded in Argentine waters and adjacent oceanic waters could be due to the propensity of some individuals to attend commercial fishing activities, as is the case of the Spectacled Petrels recorded by Chavez et al. (2014) and Seco-Pon et al. (2017). Still, no bycatch of the species has been recorded so far in fisheries operating within the Argentine Economic Exclusive Zone . Other confirmed records of Spectacled Petrels interacting with fisheries in the region were obtained in Uruguay ( Jiménez & Domingo 2007, Jiménez et al. 2011) and southern Brazil (Olmos 1997, Bugoni et al. 2009, Branco et al. 2014). There, the species is bycaught in longline fisheries at a rate estimated at 0.005 birds/1000 hooks and 0.008 birds/1000 hooks in pelagic longline fishing vessels operating off Uruguay and Brazil, respectively (Jiménez & Domingo 2007, Bugoni et al. 2008. The paucity of Spectacled Petrel records from Argentine waters may be due to a combination of the relatively low numbers of individuals present in the waters off Argentina during the breeding season as revealed by the literature review presented here or to the lack of personnel trained to identify them. Given that fisheries remain the main threat posed to this species (ACAP 2018), it is of great importance to increase the sampling effort to better understand the distribution and abundance of this species in the Patagonian shelf region and its interaction with human activities.