United States

**Abstract:**

Following the competitive exclusion principle, two closely-related species living in sympatry can only coexist if ecological niche partitioning occurs. Throughout their distribution range, Imperial Cormorant (Leucocarbo atriceps) and Rock Shag (L. magellanicus) often breed in mixed-species colonies in Patagonia, Argentina. Isotopic niche assessment of both species was performed during two breeding seasons (2010/11 and 2011/12) in three different colonies were they breed syntopically. The three colonies, Isla Gran Robredo (45°07&#39;54&#39;&#39;S, 66°03&#39;40&#39;&#39;W), Isla Leones (45°03&#39;28&#39;&#39;S, 65°35&#39;08&#39;&#39;W), and Isla Viana (45°11&#39;27&#39;&#39;S, 63°23&#39;50&#39;&#39;W), are located within the &#39;Patagonia Austral Marine Park&#39;. Whole blood samples were obtained simultaneously from breeding adults of both species during the early chick stage and used for stable isotope analysis. Isotopic niche was described by means of centroid analysis and Bayesian ellipse-based metrics. The isotopic niche overlap between species was in general small or insignificant, suggesting niche partitioning, and the isotopic niche width in the different colonies and seasons was significantly smaller in the Imperial Cormorant than in the Rock Shag. However, the isotopic niche of the Imperial Cormorant in Isla Viana during the second study season was totally included in the isotopic niche of the Rock Shag, suggesting an important niche overlap. Results showed evidence that niche partitioning processes in these cormorants is context dependent. However, further studies are needed including independent measures of prey availability and niche evaluation at additional colonies where these species breed alone and with other cormorant species, considering that the metacommunity framework predicts that the combination of species in metapopulation contexts could be sometimes achieved through pairs of species with similar resource utilization.

**Authors:**

Alejandro Gatto¹, Pablo Yorio¹

¹Centro Nacional Patagónico (CENPAT) - CONICET

3rd World Seabird Conference

Evaluating the coexistence of Imperial Cormorant and Rock Shag through isotopic niches at different colonies in central Patagonia, Argentina

Welcome Seabirders!  

Welcome to Virtual World Seabird Conference 3 - vWSC3! Whether you are in your office or lab, at home, in a coffee shop or bar poaching some wifi, or at a remote field site or research vessel – we are very excited to welcome you to the third ever World Seabird Conference. 

We would like to thank ALL of you for being so patient as WSC3 was scheduled, postponed, rescheduled, revised to virtual, and scheduled again. Throughout all those iterations there was one message that remained perfectly clear – seabirders were eager to meet and share their science. If we could not meet in person then virtual it would have to be, but a 3rd WSC was something everyone wanted. That support and commitment helped the WSU Board of Directors and Member Societies sort through all of the challenges they faced to plan and hold this conference. 

The list of those that need to be thanked is long and, while we plan on recognizing many during the live closing plenary, it is important to do so here in writing as well. 

The Australasian Seabird Group was our Local Host for our plan to meet in Hobart, Tasmania. They invested substantial time and effort to find venues and plan events that we unfortunately were not able to visit. Nonetheless we appreciate their work on behalf of WSC3 and encourage all of you to thank them when you see their members in Gathertown or elsewhere during our virtual meeting. Their willingness to host created the initial excitement for WSC3 and without that our vWSC would not have been possible.

We also wish to thank the Science Program Committee, the Virtual Committee, and the Early Career Scientist Committee for their hard work planning the logistics, events, and schedule for vWSC3. These committees also had to deal with changing parameters and short timelines that made what is always a challenging task even more challenging. The Travel Awards Committee also invested time and effort in developing procedures for awarding travel funds that ultimately would not be implemented. 

Our ability to shift from an in-person to a virtual meeting, and to do so in a way that would be financially feasible, was due to the effective efforts of The International Fundraising Committee and to our financial sponsors. The IFC raised funds to support WSC3 and then, through the good relationships they built with sponsors, ensured we could re-envision how those funds could be used to support a virtual conference that would be affordable and high-quality.

We all owe the WSU Board of Directors and the Representatives of the Member Societies a great deal of thanks. They are the ones who manage the WSU and, for the past 18 months, have had to have a series of challenging meetings and conversations, have had to make a series of difficult choices, have had to do all of that while considering the short- and long-term health of WSU and the World Seabird Conferences, and did this while also managing their own challenges at their day jobs. We are grateful for their diligence, patience, foresight, and throughout all of the meetings, their collegiality. Also – a 6-year term is quite a commitment!

There would not be a WSC3 without a successful WSC1 and WSC2. Thanks go to the Pacific Seabird Group for their support of WSC1 in Victoria, Canada, and to the African Seabird Group for their support of WSC2 in Cape Town, South Africa. In each of these endeavors and for our current conference we were fortunate to work with a dependable and trustworthy partner in Podium Conferences. Michelle Smith and Marischal de Armond have become valued members of our team and have not only helped us plan conferences but have assisted and advised the WSU Chairs and Board on issues above and beyond conference planning. 

As we embark on our vWSC3 week we extend to all of you our thanks for showing up, for being patient, and most importantly for the work you do with seabirds. We are all part of a unique, global community that shares an interest, a fascination, and a passion for birds that make a living in our world’s oceans. We have advanced the science, conservation, and management of seabirds as well the ecosystems they inhabit. We are consistently impressed and motivated by the work you do. 

The WSU formed in 2010 because we saw the need for a global organization to address challenges at a global level. Over the past 11 years WSU has grown, adapted, and evolved to become the community that this week is making vWSC3 a reality. Enjoy the week, appreciate and support the friends and colleagues you have made in the community, and if you see us in a virtual hallway please stop and say hello! 

Thank you for the opportunity to serve all of you and the WSU over the past few years,

Nicholas Carlile, Interim Chair, WSU<br>
Patrick Jodice, 2nd Chair of the WSU<br><br>

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Join us for four days of science, networking and virtual engagement with delegates from around the world!

**Abstract:**

Following the competitive exclusion principle, two closely-related species living in sympatry can only coexist if ecological niche partitioning occurs. Throughout their distribution range, Imperial Cormorant (Leucocarbo atriceps) and Rock Shag (L. magellanicus) often breed in mixed-species colonies in Patagonia, Argentina. Isotopic niche assessment of both species was performed during two breeding seasons (2010/11 and 2011/12) in three different colonies were they breed syntopically. The three colonies, Isla Gran Robredo (45°07'54''S, 66°03'40''W), Isla Leones (45°03'28''S, 65°35'08''W), and Isla Viana (45°11'27''S, 63°23'50''W), are located within the 'Patagonia Austral Marine Park'. Whole blood samples were obtained simultaneously from breeding adults of both species during the early chick stage and used for stable isotope analysis. Isotopic niche was described by means of centroid analysis and Bayesian ellipse-based metrics. The isotopic niche overlap between species was in general small or insignificant, suggesting niche partitioning, and the isotopic niche width in the different colonies and seasons was significantly smaller in the Imperial Cormorant than in the Rock Shag. However, the isotopic niche of the Imperial Cormorant in Isla Viana during the second study season was totally included in the isotopic niche of the Rock Shag, suggesting an important niche overlap. Results showed evidence that niche partitioning processes in these cormorants is context dependent. However, further studies are needed including independent measures of prey availability and niche evaluation at additional colonies where these species breed alone and with other cormorant species, considering that the metacommunity framework predicts that the combination of species in metapopulation contexts could be sometimes achieved through pairs of species with similar resource utilization.

**Authors:**

Alejandro Gatto¹, Pablo Yorio¹

¹Centro Nacional Patagónico (CENPAT) - CONICET

poster

**Abstract:**

Despite its isolation and extreme climate, Antarctica is home to a diversity of fauna and associated microorganisms, including viruses, parasites, and even antimicrobial-resistant bacteria. It has previously been proposed that perhaps the most iconic Antarctic animal, the penguin, experiences low pathogen pressure, accounting for their susceptibility to disease when exposed to foreign environments. Climate-driven and anthropogenically assisted virus emergence in Antarctica is therefore of considerable concern. At present, however, there is little understanding of the diversity and abundance of viruses currently found in Antarctica, the ecological factors that shape this diversity, nor how it relates to that seen in other geographic regions. As a means to test the hypothesis of low pathogen pressure, we determined the viromes of three species of penguins and their ticks sampled on the Antarctic peninsula: Adélie penguins (Pygoscelis adeliae), Chinstrap penguins (Pygoscelis antarctica) and Gentoo penguins (Pygoscelis papua) and the seabird tick (Ixodes uriae). Using total RNA-Sequencing (meta-transcriptomics) we identified 107 viral species, comprising penguin viruses (n=18), penguin diet and microbiome associated viruses (n=82), tick viruses (n=4) and tick transmitted arboviruses (n=2), with Adélie and Chinstrap penguins harbouring more virome diversity than Gentoo penguins. Strikingly, the level of virome diversity revealed in penguins is comparable to that see in Australian shorebirds and ducks, including the detection of many of the same viral families, and rejects the notion that penguins are subject to lower pathogen pressure. Furthermore, through the detection of previously detected viruses in penguins (Influenza A virus and Avian Avulavirus 17) we suggest that Antarctic penguins are not only spill-over hosts, but key reservoir hosts for viruses, including a number of arthropod-borne viruses (Gavier and Fennes virus). We suggest that additional sampling and continued improvement of sampling strategies will reveal an increasing diversity of viruses in Antarctic wildlife.

**Authors:**

Michelle Wille¹, Michelle Wille², Mang Shi², Daniel Gonzalez-Acuna³, Edward Holmes², Aeron Hurt¹

¹WHO Collaborating Centre for Reference and Research on Influenza, ²Marie Bashir Institute for Infectious Diseases, University of Sydney, ³Universidad de Concepcion, Facultad de Ciencias Veterinarias

Substantial viral diversity in Antarctic penguins and their ticks: no evidence for low pathogen pressure

**Abstract:**

Against a general pattern of guillemot's reduction in colonies along Murman coast (Russia, southwestern part of the Barents Sea) large-scale fluctuations in their number were observed. In 2000-2018 in four colonies the number of Common and Brunnich's guillemots has decreased by 66% and 81% respectively with maximum drop in numbers of both species was recorded in one of them, by 71 and 90%respectively. It was established that the number of Common and Brunnich's guillemots in Murman colonies largely depends on availability and size of capelin spawning stocks in winter and spring. Capelin spawning and feeding areas do not remain constant and vary from year to year depending on the Barents Sea water masses temperature. Positive anomalies in water temperature contribute to more powerful capelin accumulations occur and rapidly increase in its abundance in the southern regions of the Barents Sea and off the Kola Peninsula coast. In these years favorable feeding conditions for seabirds may exist in pre-breeding period in Eastern Murman area. Spawning stocks of capelin move eastward in warm years resulted in trophic conditions in the western regions, and possibly along the Murman coast may deteriorate. In such years comparing to years with normal temperature conditions, a restricted capelin stock can be distributed over a wider water area. Evaluating trophic conditions for the guillemots, the impact of the fishing fleet which regularly reduces capelin stocks must be considered. Their restoring occurs with the advent of high-yielding generations, caused a subsequent fishing recovery. Combination of restricted recruitment and intensive fishing can significantly destroy guillemots' food supply in the southwestern part of the Barents Sea. The degradation of guillemot's colonies is due to impact of a complex of factors, including abundance and availability of capelin stocks, capture level and temperature regime of water masses determining distribution of capelin in coastal waters.

**Authors:**

Alexey Ezhov¹, Yuri Krasnov¹, Natalia Nikolaeva²

¹Murmansk Marine Biological Institute KSC RAS, ²Lomonosov Moscow State University

Status of colonies and factors determining the development of Common (Uria aalge) and Brünnuch's (U. lomvia) guillemot's populations on Murman coast southwestern part of the Barents Sea

**Abstract:**

The Arctic is warming faster than other regions of the Earth. The little auk, or dovekie (Alle alle) as an endemic Arctic organism may be especially prone to climate change. It is a small zooplanktivorous seabird with breeding range restricted to the High Arctic. We modelled current and future distribution of a foraging little auks in one of the most important breeding areas, Svalbard, using a combination of GPS-tracking, satellite remote sensing and data-driven (conditional inference tree) and expert-knowledge (fuzzy logic) based techniques. We characterized environmental conditions (sea surface temperature, sea depth, presence/absence of marginal sea ice zone) at foraging positions of GPS-tracked individuals from three breeding colonies in Svalbard: one 'boreo-Arctic' located at the boundary of Low Arctic and High Arctic zones and two 'high-Arctic' colonies located in the largest breeding aggregations of this species in Svalbard on the west coast of Spitsbergen. The birds from one 'high-Arctic' colony, influenced by cold Arctic water, foraged in the shallow shelf zone near the colony. The birds from the remaining colonies foraged in a wider range of depths, in a higher sea surface temperature zone ('boreo-Arctic') or in the productive but distant marginal sea ice zone (second 'high-Arctic' colony). Given this flexible foraging behaviour and results of studies on their breeding performance, little auks may be temporarily resilient to moderate climate changes. However, our fuzzy logic models of future distribution under scenarios of increased sea surface temperature by 1oC and 2oC SST, predict losses of feeding habitat within the cost-effective range of foraging flights for the majority of little auk colonies in Svalbard. Over longer time scales negative consequences of global warming are inevitable. The actual response of little auks to future environmental conditions will depend on the range of their plasticity and pace of ecosystem changes.

**Authors:**

Dariusz Jakubas¹, Katarzyna Wojczulanis-Jakubas¹, Lech Iliszko¹, Hallvard Strøm², Lech Stempniewicz¹

¹University of Gdansk, ²Norwegian Polar Institute

Current and future foraging habitat niche of a High Arctic zooplanktivorous seabird, the little auk Alle alle

**Abstract:**

The yellow-legged gull (Larus michahellis) is a common seabird species around the Mediterranean coast, well adapted to exploit human-associated resources. As this species can carry a range of infectious agents, some of specific public health concern, understanding its movement ecology can provide essential information for predicting disease risk and pathogen emergence. This study aimed to characterize movement in this species using a multi-event mark-recapture modeling framework. The data included the encounter histories of 5158 birds marked at fledging between 1999 and 2004 at 14 colonies in southern France and resighted for 10 years. Our results show that young individuals have a greater mobility than older ones; 53% of juveniles are migratory during the non-breeding period and move to areas more than 50 km from the natal colony compared to only 24% in older birds that return to the breeding colony. However, the spatial extent of juvenile movements depend on colony location, with a 45% difference in the proportion of sedentary individuals between colonies 50 km apart. These differences may be explained by colony quality or population dynamics. Indeed, young birds from colonies with strong juvenile survival probabilities (~0.75) appear to be more sedentary than those from colonies with low survival probabilities (~0.36). These results indicate that young birds are likely be more important dispersers of avian disease than older birds and that this propensity may be conditioned by local breeding success, which itself may depend on the presence of parasites/pathogens.

**Authors:**

Charly Souc¹, Thomas Blanchon², Marion Vittecoq³, Rémi Choquet⁴, Karen McCoy⁵

¹MIVEGEC, University of Montpellier CNRS IRD / Tour du Valat, Research Institute for the Conservation, ²Tour du Valat, Research Institute for the Conservation of Mediterranean Wetlands, ³Tour du Valat, Research Institute for the Conservation of Mediterranean Wetlands / Centre for Resear, ⁴CEFE, University of Montpellier CNRS, ⁵MIVEGEC, University of Montpellier CNRS IRD / Centre for Research on the Ecology and Evolution of Di

Oh, the places you?ll go! Juvenile movements in the yellow-legged gull (Larus michahellis) in relation to the natal colony and its epidemiological importance

**Abstract:**

Population viability analysis (PVA) is a well-used approach for assessing how changes to vital rates will impact population dynamics, and is commonly used in environmental impact assessments to quantify potential threats to seabirds. These models typically do not account for density dependent regulation because the strength of these relationships is poorly understood. However, this omission is likely to influence the impact predicted by PVA, and thus compromise our understanding of seabird vulnerability to human activity. A small number of studies have demonstrated density dependent regulation in several species of seabird, however wider representation of the strength and direction of these relationships is lacking. In this study, we quantify the strength of density dependent regulation of breeding success in different species and populations of seabirds, addressing the likely bias in our understanding of its prevalence due to under-reporting of insignificant relationships. and examine how PVA predictions differ using five different structures for describing density dependent regulation. To do this we use long-term count and breeding success data collected from 30 populations and eight species of seabird that breed in the UK. We found evidence of positive and negative density dependent regulation that varied in strength and direction within and between species. Applying these relationship coefficients to theoretical populations of our study species using a pre-existing seabird specific PVA tool will allow us to measure the effect of differing strengths and models of density dependence on resulting rates of population change. Understanding the ways in which density dependence can be modelled in PVA and how it influences outcomes will facilitate more accurate environmental impact assessments for seabirds, and improve confidence in PVA findings.

**Authors:**

Eve Merrall¹, Jonathan Green¹, Leonie Robinson¹, Adam Butler², Matt Wood³, Mark Newell⁴, Francis Daunt⁴, Julie Black⁵, Cat Horswill⁶

¹University of Liverpool, ²Biomathematics and Statistics Scotland, ³University of Gloucestershire, ⁴UK Centre for Ecology & Hydrology, ⁵Joint Nature Conservation Committee, ⁶ZSL Institute of Zoology

Modelling density dependence in UK seabirds, in the context of population viability analysis

**Abstract:**

Changes in foraging strategies throughout the year are key determinants of seabird population dynamics. However, due to seabird post-breeding dispersal, year-round trophic ecology studies rarely focus on individuals from known colonies. Using stable isotope analysis (δ15N, δ13C) of blood and primary feathers, we tested during 2012 the trophic niche variation throughout the year in Kelp Gulls Larus dominicanus from three colonies in Patagonia, Argentina, located in areas with different availability of anthropogenic food subsidies. Isotopic niche width, measured using multivariate ellipse-based metrics, was wider at all colonies during the non-breeding season, suggesting that during this period gulls forage on a greater variety of food sources possibly related to post-breeding dispersal, seasonal changes in food resources, and/or the relaxation of central place foraging. Individuals from the colony with year-round availability of fisheries discards (Isla Vernaci) presented the lower isotopic niche width year-round compared to those from the other two colonies, one with discards only available during the breeding season (Punta Tombo) and the other with only open-air refuse dumps available all year-round (Punta León). At Isla Vernaci, an abrupt expansion in niche width occurred later in the non-breeding season, after the start of a fisheries moratorium, suggesting that Kelp Gulls remained in nearby areas and partly associated to trawl fisheries between breeding events. Preliminary diet results indicate that most studied individuals from Isla Vernaci were feeding on demersal prey, only available from fisheries discards as Kelp Gulls are surface feeders. These results suggest that the availability of discards can greatly influence Kelp Gull foraging strategies and non-breeding movements, and that changes in niche metrics can be context dependent. Future studies should complement the assessment of niche variability with studies of diet composition throughout the year.

**Authors:**

Nora Lisnizer¹, Alejandro Gatto¹, Pablo Yorio¹

¹Consejo Nacional de Investigaciones Científicas y Técnicas

Trophic niche variation throughout the year in the opportunistic Kelp Gull at different trophic scenarios in Patagonia, Argentina

**Abstract:**

Knowledge of sexual differences in diet composition is key to properly understand aspects of seabird life history, their role in marine food webs, and how human activities such as fisheries may differentially affect individuals of each sex. We assessed differences in diet composition between male and female Imperial Cormorants (<i>Leucocarbo atriceps</i>) breeding at Islas Blancas (44°46´S, 65°39´W), Argentina. Imperial cormorants show sexual size dimorphism, with males being 18% heavier than females. We obtained stomach samples through induced regurgitation from 60 adult individuals, 10 of each sex during three stages of the breeding cycle (incubation, small chicks and large chicks) in 2019. At least 11 and 28 prey taxa were recorded in stomach samples of males and females, respectively. Females consumed a greater diversity of prey species and a significantly higher number of prey items per stomach content. A two-way crossed analysis of similarities showed significant sex differences in diet composition in terms of numerical frequency along the breeding cycle. Males mainly consumed demersal species, with Argentine Red Shrimp Pleoticus muelleri (43.6%) and Argentine Hake Merluccius hubbsi (35.9%) being the main prey during incubation, and hake (>77%) the dominant prey during both chick rearing stages. Females preyed upon benthic species mostly inhabiting rocky reefs. Prey with higher representation in the diet in the three stages analyzed were the fishes Patagonotothen spp. (30.84%, 36.43% and 19.37%). Results show a clear sexual segregation in the diet of Imperial Cormorants, in agreement with studies in other dimorphic seabirds, and also suggest that sex differences reflect the spatial segregation in feeding behavior of male and female individuals. Males and females may be playing different roles in coastal food webs and may be differentially affected by coastal trawl fisheries as hake and shrimp are their main target species.

**Authors:**

Cynthia Ibarra¹, Nicolás Suárez¹, Juan Ignacio Cortés¹, Ximena Navoa², Cristian Silva³, Pablo Yorio¹

¹Centro para el Estudio de Sistemas Marinos - CONICET, ²UNPSJB- Instituto de Investigación de Hidrobiología, ³Universidad Nacional de la Patagonia San Juan Bosco

Sexual segregation in the diet of the dimorphic Imperial Cormorant breeding in northern Argentine Patagonia

**Abstract:**

While many members of the Larus genus have adapted to urban environments, the degree to which urban environments are utilized for foraging may vary greatly between species. To understand how the use of urban areas drives movement and foraging behavior in gulls, we compared differences in the habitat use and foraging ecology of herring gulls (Larus argentatus; HERG) and the lesser studied great black-backed gull (Larus marinus; GBBG). HERG are widely known to utilize urban environments, but evidence suggests that GBBG may primarily forage in marine environments. We collected data from a mixed-species breeding colony on Young's Island, NY, during the incubation period in spring 2019. We deployed GPS tags on 6 GBBG and 3 HERG with minimum and maximum deployment durations of 5 and12 days, respectively. Locations of foraging behavior were identified as areas of restricted search (ARS) using First Passage Time (FPT) analysis. We found that the proportion of foraging points within urban environments was significantly lower for GBBG than for HERG (Wilcoxon, p=0.01962). Site fidelity and the average number of foraging trips per day were also significantly lower for GBBG than HERG (Wilcoxon, p=0.03887; p=0.0181). Our results exemplify the variation in urban adaptability that exists within the Larus genus and how urban vs. non-urban habitat use may influence foraging behavior. Ongoing work is using bulk stable isotope analyses of whole blood examining ẟ13C and ẟ15N values for tagged individuals to assess differences in isotopic signatures in relation to habitat use. Together, these analyses will provide further insight in to how habitat use and the use of urban environments impacts behavior, diet, and trophic ecology.

**Authors:**

Kimberly Lato¹, Eleanor Heywood¹, Richard Veit², Lesley Thorne¹

¹Stony Brook University, ²College of Staten Island

Comparing the habitat use and foraging ecology of great black-backed and herring gulls

**Abstract:**

Fishing activities provide marine scavengers with large quantities of fisheries discards, and this anthropogenic food subsidy has become a key component in the trophic ecology of seabirds worldwide. Seabirds determine through their selective consumption which components of the discard fraction are made available to scavenger organisms in the water column and on the seabed. We evaluated the selective consumption of discards by seabirds associated with a coastal fishery targeting Argentine Red Shrimp (Pleoticus muelleri) in Patagonia, Argentina. The fishery consisting of 42 vessels discarded a mean of 682 kg per haul (n = 113). A total of 65 species were discarded, and Argentine Hake (Merluccius hubbsi) (96% FO; 260 kg/haul) and Argentine Red Shrimp (100% FO; 195 kg/haul) dominated the discard fraction of the catch. The Kelp Gull (Larus dominicanus) and Black-browed Albatross (Thalassarche melanophris) were present in all hauls and were the most abundant of the seven seabird species scavenging behind vessels (171 ± 110 and 57 ± 52 individuals per haul, respectively) representing together more than 93.5% of birds in associated assemblages. A total of 29 prey items were experimentally discarded (n = 1392), nine of which were totally ignored. Ignored invertebrates included tunicates, which constitute a large fraction of discards (>100 kg/haul). Mean sizes of fish and invertebrates consumed were 22.5 ± 8.6 and 10.4 ± 7.8 cm, respectively. Kelp Gulls selected significantly smaller prey than Black-browed Albatrosses (16.3 ± 7.9 and 29.1 ± 8.1 cm, respectively; P<0.001), showing partitioning of prey resources. Results indicate that all discarded fish species, but not all sizes, were consumed by seabirds, and some of the most abundant discarded invertebrates were ignored. Thus, only a fraction of fish and mostly invertebrates would remain available for scavenging organisms in the water column and benthic habitats.

**Authors:**

Cristian Marinao¹, Pablo Yorio²

¹Centro de Estudio de Sistemas Marinos, CESIMAR-CONICET, Argentina, ²Centro de Estudio de Sistemas Marinos, CESIMAR-CONICET, Argentina and Wildlife Conservation Society

Scavenging seabirds and selective consumption of discards in a coastal shrimp trawl fishery in Patagonia, Argentina

**Abstract:**

Interactions with fisheries have strong effects on seabird ecology, behaviour and demography. These effects may be direct or indirect, and either negative (e.g. bycatch, food depletion) or positive (e.g. food provisioning via discards and offal). Albatrosses and petrels are the most threatened group of seabirds and highly attracted to fishing vessels. Their high dispersion capacity results in interactions with fleets from several countries, including in the high seas. Strong interactions are expected where the overlap between fisheries and seabird foraging grounds is high, like in the Southwest Atlantic Ocean. Here, we described and quantified the assemblage of albatrosses and petrels attending pelagic longline (PLL) vessels off southern Brazil. Data was collected by on-board observers taken voluntarily by fishermen, totalizing 927 fishing sets (2002-2018), distributed between latitude 25º?36º S and longitude 53º?29º W. For each set, seabird censuses were conducted during hauling and environmental data was obtained. A total of 37 species of 15 genera were recorded attending PLL vessels, and abundance and species composition varied seasonally. Abundance was higher during austral Autumn/Winter, when Antarctic/Subantarctic and Tristan/Gough breeders accounted for 52% and 46% of the records, respectively, while during Spring/Summer, Antarctic/Subantarctic and Tristan/Gough breeders represented 23% and 74% of the abundance, respectively. Spectacled petrel and Atlantic Yellow-nosed Albatross were the two most frequent species in both seasons, and Spectacled petrels were also the most abundant taxa year-round, suggesting this area is important for both species during breeding and non-breeding periods. The second most abundant were Black-browed Albatross and Great Shearwater, for Autumn/Winter and Spring/Summer, respectively. The assemblage of albatrosses and petrels associated with PLL fisheries off southern Brazil is rich, varies seasonally, and is largely dominated by Mid-South Atlantic and Subantarctic breeders and North Atlantic migrants, which are subject to both positive and negative effects of this interaction.

**Authors:**

Gabriel Canani¹, Augusto Silva Costa¹, Tatiana S. Neves¹, Dimas Gianuca¹

¹Projeto Albatroz

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