Distribution of mesopelagic fish in the Scotia Sea from RMT25 and pelagic trawls deployed from RRS James Clark Ross and RRS John Biscoe

Study Extent

Data were obtained from RMT 25 nets deployed from the surface to 1000 m during five research cruises undertaken in the Scotia sea region, including around South Georgia. Cruise JB11 (Piatkowski et al., 1994) was undertaken during January 1991, JR100 was April 2004, with JR161, JR177 & JR200 (Collins et al., 2012) undertaken during austral spring (Nov 2006), summer (Jan 2008) and autumn (March 2009) respectively. During JR100 additional samples were collected with an International Young Gadoid Pelagic Trawl (IYGPT).

Sampling

The RMT25 (see Piatkowski et al., 1994) consists of two nets that are opened and closed on command to sample discrete depth layers. The net was monitored in real-time using a custom-built net monitoring system that logged depth and ambient temperature. Each net had a theoretical mouth opening of 25 m2, with a cod-end mesh of 5 mm and was towed obliquely at 2.5 knots for 30 - 60 min in each depth horizon. The net was fitted with a protected cod-end to keep captured animals in good condition. Nets sampled discrete layers from the surface to 1000 m. Full station details and sampling methods are included in Piatkowski et al. (1994) and Collins et al. (2008, 2012). Net haul catches were sorted to the lowest taxonomic level using published guides (Gon and Heemstra, 1990; Hulley, 1981), and our own reference collection and experience. Species names follow the World Register of Marine Species, but we have used Lampanyctus rather than Nannobrachium for Lampanyctus achirus. Total catch weights were obtained for each fish species using a motion compensated balance. All fish were measured (standard length (SL) and/or total length (TL) to the nearest mm. Each fish can be uniquely identified from a combination of Event - Net - ID. Most of the fish were sampled for stomach contents analysis (Shreeve et al., 2009; Saunders et al., 2015), otoliths and tissue samples were taken for biochemical analyses (Stowasser et al., 2009, 2012) and genetic studies (Van de Putte et al., 2012). Some fish were preserved whole and have been lodged with the Natural History Museum in London.

Quality Control

The data are largely consistent with the information published in Collins et al. (2008, 2012) and Piatkowski et al. (1994), but a few points to note: 1. Piatkowski et al. (1994) only included data from Station 1 and Station 2. Data from six additional nets from SW of South Georgia are included here. 2. Collins et al. (2012) only included stratified (non-target) nets, but the data includes fish caught in targeted hauls. 3. There is some uncertainty regarding the specific identification of fish of the genus Bathylagus. Collins et al. (2008) reported B. antarcticus, B. tenuis and B. gracilis, but preliminary molecular analysis (unpublished) suggests that there are four species. It is likely that the fish caught in the southern Scotia Sea are B. antarcticus, but others should be considered Bathylagus sp.

Method steps

1. Cruise Reports: British Antarctic Survey, 1998. JB11: RRS John Biscoe South Georgia Marine Biology (OBP11), January 1991-February 1991. https://www.bodc.ac.uk/resources/inventories/cruise_inventory/report/6523/. British Antarctic Survey, 2004. RRS James Clark Ross Cruise JR100 March 8th-April 5th 2004. https://www.bodc.ac.uk/resources/inventories/cruise_inventory/report/6794/. British Antarctic Survey, 2006. Discovery 2010 Spring Cruise (JR161): A study of pelagic marine food web interactions and condition factors of zooplankton across the Scotia Sea. October 24th - December 3rd 2006. https://www.bodc.ac.uk/resources/inventories/cruise_inventory/report/8262/. British Antarctic Survey, 2008. Discovery 2010 - Summer Cruise (JR177). Life cycles and trophic interactions of the Scotia Sea pelagic community: from ice-edge to Polar Front. December 31st to February 16th 2008. https://www.bodc.ac.uk/resources/inventories/cruise_inventory/report/8276/. British Antarctic Survey, 2009. Discovery 2010 - Autumn Cruise (JR200). Life cycles and trophic interactions of the Scotia Sea pelagic community: from the South Orkneys to the Polar Front. 11th March to 18th April, 2009. https://www.bodc.ac.uk/resources/inventories/cruise_inventory/report/9357/. Parts of this dataset have been published to support specific publications. Data on myctophids have also been submitted to Myctobase.
2. Articles that have utilised the data: Shreeve RS, Collins MA, Tarling GA, Main CE, Ward, P & Johnston NM, 2009. Feeding ecology of myctophid fishes in the northern Scotia Sea. Marine Ecology Progress Series 386, 221-236. https://doi.org/10.3354/meps08064. Turner JR, White EM, Collins MA, Partridge JC & Douglas RH, 2009. Vision in lanternfish (Myctophidae): Adaptations for viewing bioluminescence in the deep-sea. Deep-Sea Research Part I: Oceanographic Research Papers, 56(6), 1003 - 1017. https://doi.org/10.1016/j.dsr.2009.01.007. Stowasser, Pond DW & Collins MA, 2009. Using fatty acid analysis to elucidate the feeding habits of Southern Ocean mesopelagic fish. Marine Biology 156, 2289-2302. https://doi.org/10.1007/s00227-009-1256-4. Waluda CM, Collins MA, Black AD, Staniland IJ, Trathan PN, 2010. Linking predator and prey behaviour: contrasts between Antarctic fur seals and macaroni penguins at South Georgia. Marine Biology 157:99-112. https://doi.org/10.1007/s00227-009-1299-6. Ward P, Atkinson A, Venables HJ, Tarling GA, Whitehouse MJ, Fielding S, Collins MA, Korb R, Black A, Stowasser G, Schmidt K, Thorpe SE, Enderlein P, 2012. Food web structure and bioregions in the Scotia Sea: a seasonal synthesis. Deep-Sea Research II 59-60, 253-266. https://doi.org/10.1016/j.dsr2.2011.08.005. Stowasser G, Atkinson A, McGill, RA, Phillips RA., Collins MA & Pond, DW, 2012. Food web dynamics in the Scotia Sea in summer: A stable isotope study. Deep-Sea Research II 59-60, 208-221. https://doi.org/10.1016/j.dsr2.2011.08.004. Van de Putte A, Van Houdt JKJ, Maes GE, Hellermans B, Collins MA, Volckaert FAM, 2012. High genetic diversity and connectivity in a common mesopelagic fish of the Southern Ocean: The myctophid Electrona antarctica. Deep Sea Research II 59-60, 199-207. https://doi.org/10.1016/j.dsr2.2011.05.011. Saunders RA, Collins MA, Ward P, Tarling GA, Shreeve RA. 2014. The trophodynamics of Southern Ocean Electrona (Myctophidae) in the Scotia Sea. Polar Biology 37, 789-807. https://doi.org/10.1007/s00300-014-1480-3. Saunders RA, Collins MA, Ward P, Stowasser G, Shreeve RA & Tarling GA, 2014. Distribution, population structure and trophodynamics of Southern Ocean Gymnoscopelus (Myctophidae) in the Scotia Sea. Polar Biology 38, 287-308. https://doi.org/10.1007/s00300-014-1584-9. Saunders RA, Collins MA, Ward P, Stowasser G, Hill SI, Shreeve RA & Tarling GA, 2015. Predatory impact of the myctophid fish community on zooplankton in the Scotia Sea (Southern Ocean). Marine Ecology Progress Series 541, 45-64. https://doi.org/10.3354/meps11527. Saunders RA, Collins MA, Ward P, Stowasser G, Shreeve RA & Tarling GA, 2015. Trophodynamics of Protomyctophum (Myctophidae) in the Scotia Sea (Southern Ocean). Journal of Fish Biology 87, 1031-1058. https://doi.org/10.1111/jfb.12776. Lourenço S, Saunders RA, Collins MA, Shreeve R, Assis CA, Belchier M, Watkins JL & Xavier JC. 2017. Life cycle, distribution and trophodynamics of the lanternfish Krefftichthys anderssoni (Lönnberg, 1905) in the Scotia Sea. Polar Biology 40, 1229-1245. https://doi.org/10.1007/s00300-016-2046-3. Saunders RA, Collins MA, Stowasser G & Tarling GA. 2017. Southern Ocean mesopelagic fish communities in the Scotia Sea are sustained by mass immigration. Marine Ecology Progress Series, 569, 173-185. https://doi.org/10.3354/meps12093. Saunders RA, Collins MA, Shreeve R, Ward P, Stowasser G, Hill SL & Tarling GA. 2018. Seasonal variation in the predatory impact of myctophids on zooplankton in the Scotia Sea (Southern Ocean). Progress in Oceanography, 168, 123-144. https://doi.org/10.1016/j.pocean.2018.09.017. Saunders RA & Tarling GA (2018). Southern Ocean mesopelagic fish comply with Bergmann''s rule. The American Naturalist 191, 343-351. https://doi.org/10.1086/695767. Dornan T, Fielding, S, Saunders RA & Genner MJ. 2019. Swimbladder morphology masks Southern Ocean mesopelagic fish biomass. Proceedings of the Royal Society B: Biological Sciences 286, 20190353. https://doi.org/10.1098/rspb.2019.0353. Belcher A, Saunders RA & Tarling, GA, 2019. Respiration rates and active carbon flux of mesopelagic fishes (Family Myctophidae) in the Scotia Sea, Southern Ocean. Marine Ecology Progress Series 610, 149-162. https://doi.org/10.3354/meps12861. Saunders RA, Hill SL, Tarling GA & Murphy EJ, 2019. Myctophid Fish (Family Myctophidae) Are Central Consumers in the Food Web of the Scotia Sea (Southern Ocean). Frontiers in Marine Science 6, 530. https://doi.org/10.3389/fmars.2019.00530. Saunders RA, Lourenço S, Vieira R, Collins MA, Assis CA & Xavier JC, 2020. Age and growth of Brauer's lanternfish Gymnoscopelus braueri and rhombic lanternfish Krefftichthys anderssoni (Family Myctophidae) in the Scotia Sea, Southern Ocean. Journal of Fish Biology 96, 364-377. https://doi.org/10.1111/jfb.14206. Saunders RA, Lourenço S, Vieira R, Collins MA & Xavier JC, 2021. Length-weight and otolith size to standard length relationships in 12 species of Southern Ocean Myctophidae: A tool for predator diet studies. Journal of Ichthyology. https://doi.org/10.1111/jai.14126.

1. Bathylagus
   rank: genus
2. Myctophidae
   rank: family

Southern Ocean, Scotia Sea