The Importance of Krill Predation in the Southern Ocean

Abstract

Antarctic krill is a major prey species for a diverse array of Southern Ocean predators. The amount of krill that predators consume, and how this changes over space and time, is a key issue in understanding both regional and circumpolar aspects of the Southern Ocean foodweb. We assess current knowledge of consumption by the various predator groups, and the ecological processes through which krill and its predators influence each other. Knowledge has improved greatly over recent decades and has revealed a high level of complexity in the processes that govern krill consumption. We focus on the Antarctic Peninsula and Scotia Sea region where both krill and its consumers occur in significant concentrations and where an updated estimate of krill consumption by the main vertebrate groups is 55 million tonnes per year. Research has mainly focused on mammalian and avian predators of post-larval krill, particularly penguins. Potentially important consumer groups like fish, cephalopods and carnivorous zooplankton remain poorly understood, as does consumption of the early life stages of krill. As a consequence of these knowledge gaps and the variability that arises from complexity, a reliable seasonally, spatially or taxonomically resolved description of krill consumption remains elusive. One of the key motivations for attempting to estimate krill consumption is to understand how changes in krill availability impact predator populations.Such understanding is an important requirement for ecosystem based management of the Antarctic krill fishery. We therefore propose that integrated study areas in strategic fishing locations should be developed to directly assess the response of krill predators to changes in krill availability.

The importance of Antarctic krill in biogeochemical cycles

“…These approaches have been attempted individually with varying success [108][109][110] , but are yet to be assimilated and used together to estimate E. superba biomass. Primary production can provide an upper limit on krill population biomass 110 , but foodweb models are needed to fill gaps where data are sparse and variable for krill predators 111 .…”

KRILLBASE: a circumpolar database of Antarctic krill and salp numerical densities, 1926–2016

“…They have broadly similar size, but have fundamentally different life cycles, habitat preferences, and nutritional composition and thus have contrasting roles in the food web. Krill is a major food item for a suite of vertebrate and invertebrate predator species (Murphy et al, 2007;Trathan and Hill, 2016). Salps appear in the diets of various invertebrates, fish and birds but do not seem to be as important as krill to most of the air-breathing predator group (Pakhomov et al, 2002).…”

“…This 4 means that CCAMLR is responsible for managing the impacts of the fishery on the health, resilience and integrity of the wider ecosystem. However, there is little information about many relevant aspects of krill ecology and population dynamics (Siegel and Watkins 2016), including stock identity (Jarman and Deagle, 2016), and predator-prey relationships (Trathan and Hill, 2016). Reducing these uncertainties might be necessary for CCAMLR to achieve its conservation objectives (Constable, 2011).…”

Antarctic Futures: An Assessment of Climate-Driven Changes in Ecosystem Structure, Function, and Service Provisioning in the Southern Ocean

“…Antarctic krill (E. superba) is a particularly successful cold-water species in terms of biomass and distribution and one for which conceptual models of its life cycle are well developed (e.g., Quetin & Ross 2009). It occurs mainly in large swarms and is a major food source for various marine mammals, birds, seals, and fish (e.g., Trathan & Hill 2016). It plays a potentially important role in biogeochemical cycling (e.g., Belcher et al 2019) and is the main target of Antarctic fisheries.…”