Distributions of krill and Antarctic silverfish and correlations with environmental variables in the western Ross Sea, Antarctica

Abstract

Antarctic krill Euphausia superba, crystal krill E. crystallorophias, and Antarctic silverfish Pleuragramma antarctica are key mid-trophic level species in the Ross Sea, connecting primary production to the upper trophic levels. Distributions of these species were constructed from observations made in the western Ross Sea from 1988 to 2004. Distributions of environmental conditions were obtained from a 5-km resolution circulation model (temperature, mixed layer depth, surface speed) and satellite-derived observations (chlorophyll, sea ice cover). A hierarchy of statistical methods determined correlations and relationships between species and environmental conditions. Each species occupies a localized habitat defined by different environmental characteristics. Antarctic krill are concentrated along the northwestern shelf break in a habitat characterized by deep (>1000 m) bottom depth, warm temperature (1 to 1.25°C), decreased sea ice, and proximity to the shelf break. Crystal krill and Antarctic silverfish are concentrated in Terra Nova Bay. Common characteristics of the habitat for these species are southwesterly location, coastal proximity, and cold temperature (−1.75 to −2°C). The habitat characteristics obtained for the 3 species provide a basis for projecting potential distribution changes in response to environmental change and for delineating regions of the Ross Sea for focused management and selection of marine protected areas that support ecosystem-level conservation plans.

Gone fishing: Adélie penguin site-specific foraging tactics and breeding performance

“…The fact that more fish were caught off InIs may also be due to favourable conditions for rapid growth of P. antarctica larvae near polynya, in line with autumnal phytoplankton blooms (Vacchi et al 2012). Indeed, Terra Nova Bay seems to be particularly rich in silverfish at various growth stages (Davis et al 2017, O'Driscoll et al 2018. Concerning the slight difference in breeding chronology between the two colonies, the colder weather and blizzard we recorded at InIs during early incubation could have delayed hatching.…”

Spatial structuring and life history connectivity of Antarctic silverfish along the southern continental shelf of the Weddell Sea

“…Much of the evidence for the role of hydrography in connectivity between silverfish populations has been derived from indirect observation using monodisciplinary approaches (Hubold 1984, Kellermann 1986, 1996, Agostini et al 2015, Brooks et al 2018). Yet multi-disciplinary studies can allow cross-corroboration and comparison between complementary techniques (Begg et al 1999, Sturrock et al 2012, while understanding of the physical context can help to directly address the role of physical-biological interactions in structuring silverfish populations (Ashford et al 2017, Davis et al 2017, Brooks et al 2018). This allows for connectivity hypotheses to be tested between neighboring populations in which the inter-play between local hydrographic features and life history is important (Ashford et al 2017).…”

Post-fledging survival of Adélie penguins at multiple colonies: chicks raised on fish do well

“…Silverfish can reach 14 yr of age, but the modal age in the Ross Sea is 6 to 9 yr (Sutton & Horn 2011). Silverfish may be well mixed in the western Ross Sea, without much evidence of an effect of a strong subadult year class sustaining the stock for extended periods (Davis et al 2017, Brooks et al 2018. Thus, it is unlikely that different subpopulations occur in the southern Ross Sea and in McMurdo Sound, and that the penguins from Cape Crozier depleted one infrequent strong year class of fish.…”