Birds of a Feather Eat Plastic Together: High Levels of Plastic Ingestion in Great Shearwater Adults and Juveniles Across Their Annual Migratory Cycle

Limited work to date has examined plastic ingestion in highly migratory seabirds like Great Shearwaters (Ardenna gravis) across their entire migratory range. We examined 217 Great Shearwaters obtained from 2008–2019 at multiple locations spanning their yearly migration cycle across the Northwest and South Atlantic to assess accumulation of ingested plastic as well as trends over time and between locations. A total of 2328 plastic fragments were documented in the ventriculus portion of the gastrointestinal tract, with an average of 9 plastic fragments per bird. The mass, count, and frequency of plastic occurrence (FO) varied by location, with higher plastic burdens but lower FO in South Atlantic adults and chicks from the breeding colonies. No fragments of the same size or morphology were found in the primary forage fish prey, the Sand Lance (Ammodytes spp., n = 202) that supports Great Shearwaters in Massachusetts Bay, United States, suggesting the birds directly ingest the bulk of their plastic loads rather than accumulating via trophic transfer. Fourier-transform infrared spectroscopy indicated that low- and high-density polyethylene were the most common polymers ingested, within all years and locations. Individuals from the South Atlantic contained a higher proportion of larger plastic items and fragments compared to analogous life stages in the NW Atlantic, possibly due to increased use of remote, pelagic areas subject to reduced inputs of smaller, more diverse, and potentially less buoyant plastics found adjacent to coastal margins. Different signatures of polymer type, size, and category between similar life stages at different locations suggests rapid turnover of ingested plastics commensurate with migratory stage and location, though more empirical evidence is needed to ground-truth this hypothesis. This work is the first to comprehensively measure the accumulation of ingested plastics by Great Shearwaters over the last decade and across multiple locations spanning their yearly trans-equatorial migration cycle and underscores their utility as sentinels of plastic pollution in Atlantic ecosystems.

ЛЕТНЕЕ ПИТАНИЕ СИВУЧА В ВОДАХ ДАЛЬНЕГО ВОСТОКА РОССИИ В 2004–2008 ГОДАХ

The diet of Steller sea lion Eumetopias jubatus was studied based on undigested food parts found in feces collected in the summer season on 20 rookeries in the Russian Far East. A total of 915 samples were analyzed between 2004 and 2008, in which 65 food items were identified. The frequency of occurrence of 11 diet items was greater than 5%, including Atka mackerel Pleurogrammus monopterygius (64.8%), Pollock Theragra chalcogramma (44.3%), Pacific salmon Salmonidae (20.5%), Irish lord Hemilepidotus sp. (20.4%), Pacific sand lance Ammodytes hexapterus (15.8%), Pacific herring Clupea pallasi (9.5%), Squid and Octopus Cephalopoda (8.4%), Pacific cod Gadus macrocephalus (5, 9%), Pacific sandfish Trichodon trichodon (5.9%), Flatfishes Pleuronectidae (5.8%), Threespine stickleback Gasterosteus aculaeatus (4.9%). Three regions with different diets were identified – the Sea of Okhotsk, the Kuril Islands, and Kamchatka with the Commander Islands. In the Sea of Okhotsk, Pollock and Herring (83.6% by frequency of occurrence) dominated among undigested food remains in feces. The diet at the Kuril Islands rookeries was variable within the region. The general pattern was a low diversity of diet at each Kuril Island sites and predominance of 1-3 food items, probably the most accessible near the sites (Pollock, Squid and Octopus, Atka mackerel, Pacific salmon). The diet pattern in Kamchatka and the Commander Islands in the summer season was characterized by a high diet diversity. In contrast to other regions, the diet includes in high proportion small non-commercial species – Sand lance, Irish lord, Pacific sandfish, Flatfishes, Threespine stickleback and others. The regional patterns of sea lion diets show the spatial distribution and areas of abundant biomass of the main food items. The diet patterns of sea lions from rookeries differed from haulouts in having a higher content of abundant food items. Long-term changes in diet structure were not statistically significant.

Environmental drivers of the abundance and distribution of forage fishes on the Northeast US shelf, with a particular emphasis on northern sand lance

Small pelagic fishes, also termed forage fishes, represent a critical link between secondary production and myriad top predators in marine ecosystems, including the Northeast US shelf. In this dissertation, I analyze the drivers of forage fish distribution throughout the Northeast US shelf and the drivers of the abundance of the ecologically important northern sand lance. Chapter 2 examines the basic ecology of northern sand lance and uses these insights to identify mechanistic drivers of their abundance. I then explore different scenarios of these drivers to project sand lance abundance through the end of the 21st century, which appears precarious for adult sand lance unless current trajectories change. Chapter 3 analyzes the environmental drivers of the distribution of the six dominant, offshore forage fish species (northern sand lance, Atlantic herring, alewife, blueback herring, Atlantic mackerel, and Atlantic butterfish) on the Northeast US shelf to elucidate the role of environmental covariates in shelf occupancy by these taxa. The results of this chapter indicate shelf occupancy of butterfish and Atlantic mackerel are increasing through time while occupancy of sand lance is decreasing with time. The occurrence of most of these species is also moving deeper and northward with time. Chapter 4 assesses the source-sink dynamics of three sand lance hotspots through Lagrangian particle tracking models simulating larval sand lance transport. Connectivity varies among these hotspots with Georges Bank and Stellwagen Bank having notable retention while the Great South Channel relies on larvae from other hotspots. Retention on Stellwagen Bank and Georges Bank are linked to strong wind events during the larval period of sand lance. Collectively, this dissertation improves our understanding of the dynamics driving variability in the Northeast US shelf forage fish complex, particularly for northern sand lance.

Identifying and monitoring of forage fish spawning beaches in British Columbia’s Salish Sea for conservation of forage fish

Pacific sand lance ( Ammodytes personatus) and surf smelt ( Hypomesus pretiosus) are ecologically important forage fish in the marine food webs within the Salish Sea, including British Columbia (BC). Although important, little information exists around the spatiotemporal distribution of these fishes’ beach spawning habitat in the BC Salish Sea. In 2017, the Mount Arrowsmith Biosphere Region Research Institute initiated spawning beach surveys within the Mount Arrowsmith Biosphere Region (MABR). Surveys have geographically expanded along the eastern Vancouver Island coastline between Bowser and Cowichan Bay, BC, including Gabriola Island and Thetis Island. Pacific sand lance embryos have been detected at 17 beaches, with six beaches located within the MABR. Pacific sand lance spawning events have been detected between November and mid-February, with the bulk of embryos detected in November and December. To date, surf smelt embryos have not been detected at the 56 different beaches. These data begin to fill existing data gaps surrounding Pacific sand lance and surf smelt in BC. Furthermore, longer-term data submissions to the Strait of Georgia Data Centre, an open-access database, will provide the necessary data needed to advocate for improved regulatory protections for these ecologically important fish and their spawning habitat.