Methodology:

Detailed surveys for mesopelagic fish were conducted in the Scotia Sea as part of the British Antarctic Survey's Discovery 2010 programme, as described in Collins et al. (2012). An opening and closing 25 m2 rectangular mid-water trawl net (RMT25, minimum 4 mm mesh; Piatkowski et al. 1994) was deployed along a transect spanning the entire Scotia Sea between the Antarctic Polar Front (APF) and the sea ice zone (SIZ) during three cruises; November 2006 (cruise JR161, Austral spring), January 2008 (cruise JR177, Austral summer), and March 2009 (cruise JR200, Austral autumn). Stratified net hauls were carried out at six stations that encompassed the main water masses and frontal zones of the region; Polar Front (PF), Southern Scotia Sea (SSS), Mid Scotia Sea (MSS), Western Scotia Sea (WSS), Northern Scotia Sea (NSS), and Georgia Basin (GB), at depths of: 0-200, 200-400, 400-700, and 700-1000 m. The depth and ambient temperature of the nets were logged using a custom-built net monitoring system. The temperature sensor (SBE-3) was factory calibrated prior to the surveys and was accurate to about 0.001 °C. Net hauls were repeated during the day and night in spring and summer, but at night only during autumn. All fish caught were sorted onboard, identified to the lowest taxonomic level, measured to the nearest mm using standard length (SL) and the wet mass (WM) measured to the nearest 0.01 g using a motion compensated balance.

Data collection:

Opening and closing 25 m2 rectangular mid-water trawl net (RMT25, minimum 4 mm mesh),

Temperature sensor (SBE-3), Depth Sensor.

Data quality:

The data are as accurate as possible. Abundance data were only obtained from valid net hauls where the RMT25 device operated properly during deployment. Length measurements were obtained from all undamaged specimens during fieldwork. Concurrent length and weight measurements were obtained for randomly selected subsamples of undamaged specimens, so weight measurements are not available for every specimen measured in the series. All length-weight data were scrutinised for obvious erroneous values as result of measurement or typographic errors prior to compilation of this data set.