Seabird predation on Arctic cod during summer in the Canadian Arctic

Abstract

Seabirds feed heavily on Arctic cod Boreogadus saida during the summer in the Canadian Arctic but little is known of the interactions among birds while foraging and the factors that drive feeding behaviour. The objective of this study was to describe the relationship between seabirds and Arctic cod in a productive feeding area distant from breeding colonies. Transect surveys were completed using standardized count protocols to determine the density of seabirds in Allen Bay, Cornwallis Island, Nunavut. Shore-based observation sites determined seabird foraging behaviour associated with the presence of schools and environmental variables. The density of birds (156 birds km −2 ) was high compared to that of other locations in the Canadian Arctic. Several bird species were more active early in the morning and with winds from the south, possibly due to an increase in Arctic cod feeding on zooplankton at the surface. Northern fulmars Fulmarus glacialis and black-legged kittiwakes Rissa tridactyla captured Arctic cod directly from the water; however, they lost nearly 25% of captures to glaucous gulls Larus hyperboreus and parasitic jaegers Stercorarius parasiticus. These kleptoparasitic seabirds benefited the most in Allen Bay obtaining as much as 8 times more Arctic cod than species capturing cod directly. Northern fulmars captured 3 times more Arctic cod from schools, and black-legged kittiwakes captured similar proportions of schooling and non-schooling cod. We conclude that non-schooling Arctic cod are as important as schooling cod as an energy source for seabirds in nearshore areas, such as Allen Bay, during the summer.KEY WORDS: Boreogadus saida · Schooling · Kleptoparasitism · Foraging · Black-legged kittiwake · Northern fulmar · Glaucous gullResale or republication not permitted without written consent of the publisher because often less energy is expended compared to capturing prey directly (Stempniewicz & Iliszko 2010). Nevertheless, little attention has been given to this foraging method in the Canadian High Arctic.The main prey item for marine seabirds in the Canadian High Arctic is Arctic cod Boreogadus saida as it is an abundant, ubiquitous, and high energy forage fish (Bradstreet et al. 1986). Consuming 12 to 32 individuals is energetically equivalent to ~34 500 calanoid copepods (Bradstreet & Cross 1982). As such, cod is a keystone species linking lower and higher trophic levels (Welch et al. 1992). Large feeding aggregations including hundreds of whales and seals and thousands of seabirds have been described in relation to cod schools, with the suggestion that such an event could lead to the consumption of 20 t of cod daily (Welch et al. 1993). Arctic cod are spatially and temporally unpredictable and we believe that schooling and non-schooling cod are important components of the Arctic marine food web.This study describes the relationship between seabirds and Arctic cod in Allen Bay, Cornwallis Island, Nunavut, known for its abundance of cod and predatory interactions during the summer (Welch...

Foraging ecology of ringed seals (Pusa hispida), beluga whales (Delphinapterus leucas) and narwhals (Monodon monoceros) in the Canadian High Arctic determined by stomach content and stable isotope analysis

“…However, smaller and sparsely dispersed non-schooling Arctic cod appear to be a significant source of food, particularly for ringed seals. During several months of observations in Allen Bay (Matley et al 2012), ringed seals did not forage on schools of Arctic cod near the surface, yet belugas and harp seals often did*an observation also noted by Bradstreet et al (1986). Interestingly, the mean length of net-captured Arctic cod from schools in Allen Bay was 187.0 mm (Crawford & Jorgenson 1996), while non-schooling adults in Resolute Bay were 163.5 mm (Hop et al 1997).…”

“…This is not surprising considering that Arctic cod aggregated in abundant schools in Allen Bay during the sampling period (see Matley et al 2012) and are known to be heavily exploited by predators in this area (Hobson & Welch 1992;Hop et al 1997). This research also showed differences in ringed seal feeding patterns among individuals and compared to the toothed whales based on multiple sampling techniques.…”

Hotspots in cold seas: The composition, distribution, and abundance of marine birds in the North American Arctic

“…Sea ice distribution is another factor known to influence the abundance and distribution of seabirds [ Hunt , ; Stirling , ]. Ice algae found under the sea ice forms the foundation of the Arctic food web [ Horner , ], linking the organisms found on the undersurface of sea ice [ Horner , ] to the higher trophic level organisms such as amphipods and Arctic cod [ Bradstreet and Cross , ; Gradinger and Bluhm , ], which are prey for many species of Arctic seabirds [ Bradstreet , ; Bradstreet and Cross , ; Welch et al ., ; Matley et al ., ]. Diving piscivores, such as thick‐billed murres, are often associated with offshore ice edges and coastal landfast ice edges [ Bradstreet , ], which are also critical in the breeding distribution and timing of this species in the high Arctic [ Laidre et al ., ].…”

Good Days, Bad Days: Wind as a Driver of Foraging Success in a Flightless Seabird, the Southern Rockhopper Penguin

“…Local wind conditions are known to affect the presence of prey species (e.g. [23] ) and the ability of seabirds to capture prey [24] . Scientists are now realizing that a change in wind regimes can have important consequences for seabird foraging conditions and consequently their life history [25] .…”