Methodology:

Diet samples were taken each year from approximately 30-40 Adelie penguins, over a four-week period during creche. Birds were captured when returning to feed their chicks and samples were obtained using the stomach lavage method (Wilson 1984; Williams 1991, CCAMLR CEMP Standard Method A8A). The contents were subsequently drained through two sieves (3.35 and 250 micrometres) and wet meal mass was recorded. Samples were then categorised into crustacean, fish and cephalopod components and weighed by category. Prey items were also further categorised by species, when possible. Fish otoliths and krill carapaces were separated and measured. Otolith characteristics were used to identify the fish species consumed.

Individual krill specimens all suffered varying degrees of damage prior to identification due to the process of consumption and partial digestion. The sex and age group of individual krill was determined by measuring the removed carapace length (RCL) using times 6 magnification under a binocular microscope and identifying specific diagnostics. Measurements were to the nearest eyepiece unit. Maturity stages were determined using the measured removed carapace length (RCL) per the code index from Morris et al. 1988, and are included as a csv file (signy_krill_maturity_stages_code.csv) with the data.

For a full explanation of the methodology used see Hill HJ. 1990; Polar Biol, 10(4):317-20; Reid K. 1998; Polar Biol, 19(2):145-147, CCAMLR CEMP Standard Method A8A.

For reference to the code index in Morris et al. 1988, see Morris, D.J., J.L. Watkins, C. Ricketts, F. Buchholz and J. Priddle. 1988. An assessment of the merits of length and weight measurements of Antarctic krill Euphausia superba. British Antarctic Survey Bulletin, 79: 27-50.

For otolith measurements, the microscope was first set to an appropriate magnification - allowing otoliths to fit onto one measurement scale. The magnification was then checked using the stage micrometer and adjusted when necessary. Otolith lengths were then measured using the measuring scale in the microscope eye piece. Depending on the species of fish the length measurement was taken in slightly different places.

Data quality:

N/A