Size structure of Antarctic krill inferred from samples of Pygoscelid penguin diets and those collected by the commercial krill fishery

JUÁRES M.; GRECH MARTA; CASAUX R,; NEGRETE J.; CORIA N.; SANTOS M.

MARINE BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2021 vol. 168

0025-3162

AbstractIn the Antarctic Peninsula, during the chick-rearing period Adélie (Pygoscelis adeliae) and gentoo (P. papua) penguins feedprimarily on Antarctic krill (Euphausia superba), which is also exploited by the commercial fishery. Krill length and proportionof juvenile krill consumed by these predators that breed at Stranger Point, South Shetland Islands (from 2007/2008 to2015/2016), and those collected by the krill fishery in the Mar de la Flota/Bransfield Strait (from 2009/2010 to 2015/2016)were compared to evaluate the potential of each data source as an indicator of changes in the size composition and so, inthe demographic structure of the krill population. Overall, the mean krill size taken by gentoo penguins was larger than thatingested by Adélie penguins, which consumed higher proportions of juvenile (≤ 35 mm) and one-year-old (≤ 25 mm) krill.Although the krill size caught by the fishery was statistically similar to that taken by both penguin species, there were differencesin the frequency distributions of krill size among the three databases. Furthermore, when only adult krill (> 35 mm)was considered, the three sources of krill data showed a similar inter-annual variation in the availability of adult krill cohorts.Our findings suggest that each database analysed here can potentially provide different information (although complementary)about krill size composition. In addition, inter-annual fluctuations in the smaller size classes of krill likely reflect their firstyear of recruitment and, therefore, may be used as an indicator of shifts in local krill availability