DOI: 10.5285/5798742d-dd5f-480b-8298-2c2b449cbab3
title: Length, weight and abundance data of fish species captured in RMT-25 net surveys in the Scotia Sea, Southern Ocean in 2006, 2008, and 2009

description: This dataset compiles fish length and weight measurements from the RMT-25 net hauls carried out on Discovery 2010 cruises (JR161, JR177, JR200) in the Scotia Sea, Southern Ocean in spring 2006, summer 2008, and autumn 2009. The dataset comprises of the station net hauls only. Research cruises were led by British Antarctic Survey aboard the RRS James Clark Ross. Net hauls were conducted along a transect from the Antarctic Polar Front to the sea ice zone in the Scotia Sea. Hauls included in this dataset are depth stratified (1000-700 m, 700-400 m, 400-200 m, 200m to surface). Individual fish lengths, and weights were measured on board. Where weights were not measured, length-weight regressions have been used to estimate fish weight. This data set accompanies the paper by Belcher et al. in Marine Ecology Progress Series, titled, Respiration rates and active carbon flux of mesopelagic fishes (Family Myctophidae) in the Scotia Sea, Southern Ocean.
description: 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). This dataset comprises of station net tows only. 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 ~0.001 degC. 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.
description: 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.