MEPS 569:173-185 (2017)  -  DOI: https://doi.org/10.3354/meps12093

Southern Ocean mesopelagic fish communities in the Scotia Sea are sustained by mass immigration

Ryan A. Saunders1,*, Martin A. Collins2,3, Gabriele Stowasser1, Geraint A. Tarling1

1British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK
2Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK
3Centre for Environment Fisheries and Aquaculture Sciences, Pakefield Road, Lowestoft NR33 0HT, UK
*Corresponding author:

ABSTRACT: The biomass of mesopelagic fish in the Southern Ocean is one of the largest of any ocean region and is dominated (both in terms of diversity and biomass) by myctophids (lanternfish). Despite their high ecological importance both in this region and globally, our understanding of the life cycles and distribution of myctophids remains limited. We examined length-frequency data from trawl nets collected across a major sector of the Southern Ocean (the Scotia-Weddell sector) in different seasons to determine patterns of recruitment and growth. There was an absence of larval myctophids, of any species, in net catches, while larger, older individuals became increasingly dominant with increasing latitude. Very few specimens were found to contain mature gonads, indicating that individuals do not reach reproductive condition in this region. Most myctophid species that occurred within the survey regions neither recruited locally nor were self-supporting. Myctophids are prey to a large number of higher predators (penguins, seals and cetaceans) in the Scotia Sea, and are a major predator of zooplankton and krill. We show that this vital part of the Southern Ocean food-web is dependent on mass immigration from lower latitudes in the region. By implication, the sensitivities of this system depend not only on local conditions but also on levels of connectivity to other oceanic regions.


KEY WORDS: Myctophidae · Expatriate · Food-webs · Population dynamics · Recruitment


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Cite this article as: Saunders RA, Collins MA, Stowasser G, Tarling GA (2017) Southern Ocean mesopelagic fish communities in the Scotia Sea are sustained by mass immigration. Mar Ecol Prog Ser 569:173-185. https://doi.org/10.3354/meps12093

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