Midwater fishes collected in the vicinity of the Sub-Polar Front, Mid-North Atlantic Ocean, during ECOMAR pelagic sampling

doi:10.1016/j.dsr2.2013.08.001

Deep Sea Research Part II: Topical Studies in Oceanography

Volume 98, Part B, 15 December 2013, Pages 292-300

https://doi.org/10.1016/j.dsr2.2013.08.001 Get rights and content

Abstract

The ECOMAR project was a multidisciplinary process study conducted in the mid-North Atlantic, coincident hydrodynamically with the Sub-Polar Front (SPF; 48–54°N) and topographically with Charlie-Gibbs Fracture Zone of the Mid-Atlantic Ridge, as part of the Census of Marine Life field project MAR-ECO. Midwater trawling was conducted during the 2007 and 2009 ECOMAR expeditions at 14 stations north and south of the SPF, day and night, in four discrete depth intervals from 0 to 1000 m. A total of 56 species of midwater fishes representing 44 genera and 18 families were collected, several of which are new records for the region and/or were not previously sampled during MAR-ECO sampling. An annotated species list with depth-of-capture data is provided. Three species of the genus Cyclothone (Cyclothone braueri, Cyclothone microdon and Cyclothone pallida) and the myctophid Benthosema glaciale combined to contribute ~88% of all specimens collected. This finding differs from results of previous net-based sampling in the same area, likely due to sampling scheme differences (diel sampling, upper 800 m concentration) and gear selectivity (mesh size, trawl speed). Quantitative data from ECOMAR midwater sampling and the previous 2004 G.O. Sars MAR-ECO expedition are compared. Despite differences in gear between the major MAR-ECO expeditions, abundance estimates of some dominant species were remarkably similar. Data showed that the SPF is an asymmetrical, taxon-specific biogeographic boundary for deep-pelagic fishes in the North Atlantic; the SPF is semi-permeable to some species in one direction, while a strong boundary for species in another direction. Deeper-living fish species did not appear as affected by the SPF as a boundary.

Introduction

The pelagic, demersal and benthic deep-sea fauna in the vicinity of the northern Mid-Atlantic Ridge (MAR hereafter), from Iceland to the Azores, was intensively investigated as the focus of the Census of Marine Life project MAR-ECO (Bergstad et al., 2008). The Charlie Gibbs Fracture Zone (CGFZ) region of the MAR, and the surmounting Sub-Polar Front (SPF), located roughly halfway between Iceland and the Azores, was identified as the major topographic and oceanographic transition zone along the study transect (Vecchione et al., 2010). The upper water column north of the CGFZ, with cold surface waters, is biogeographically classified as the Subarctic Atlantic Province, while the area to the south, with warmer surface waters, is classified as the North Atlantic Current Province (UNESCO, 2009). The ECOMAR programme (Priede et al., 2013) was designed to investigate the CGFZ/SPF area, from the surface to the benthos, with the aims of evaluating mid-ocean productivity and biomass, and identifying differences in biology relative to the CGFZ/SPF (north/south) and the MAR axis (east/west). During ECOMAR cruises JC011 (2007) and JC037 (2009) the pelagic nekton/micronekton (fishes, macrocrustaceans, and pelagic mollusks) were sampled with a RMT 1+8 opening/closing rectangular midwater trawl (Letessier et al., 2011, Letessier et al., 2012). Sampling was conducted at sites north and south of the CGFZ, within the larger Sub-Polar Frontal Zone, in discrete-depth fashion from the surface to 800 m, with one trawl between 800 and 1000 m. This sampling program complements efforts of the MAR-ECO project in which dual-warp, large-mesh midwater trawls were used (Sutton et al., 2008, Wenneck et al., 2008, Klimpel et al., 2010, Heino et al., 2011, Cook et al., 2013). Here we present results of ECOMAR sampling with respect to deep-pelagic fish species composition, capture location relative to the primary gradient of the SPF, depth of capture as a function of solar cycle, and biogeography of species collected. Range extensions and new records for the MAR-ECO project are noted. Quantitative results presented here are compared in a limited fashion to those of previous MAR-ECO midwater sampling during the 2004 G.O. Sars MAR-ECO expedition. Sample size limitations preclude a comprehensive analysis of the SPF as a faunal transition zone, but biogeographic patterns displayed by the dominant components of the ichthyofaunal are presented, and qualitative aspects of the nature of the SPF transition zone are discussed.

Section snippets

Methods

Sampling was conducted at 14 stations located north and south of the CGFZ region of the MAR, both east and west of the ridge axis (i.e., northeast, northwest, southeast and southwest stations), with these stations straddling the primary water mass gradient of the Sub-Polar Front (Table 1, Fig. 1). A multiple rectangular midwater trawl (RMT1+8 M; Baker et al., 1973, Roe and Shale, 1979) consisting of one large net (mouth area of 8 m², mesh size of 4.5 mm) and one small net (mouth area of 1 m², mesh

Results

Abundances of all fishes collected during ECOMAR midwater sampling, listed by depth stratum, are presented in Table 2, Table 3, Table 4. A list of species, raw numbers collected, location, depth, known distribution, and specific annotations, if relevant, are provided below.

Summary and discussion

A minimum of 56 species were identified from 6304 specimens collected, with some taxa (e.g., Melamphaes spp.) awaiting further revision before species determination. Six species (Cyclothone alba, Diaphus roei, Eustomias monodactylus, Magnisudis atlantica, Mentodus longirostris, and Psednos andriashevi) were not collected during previous MAR-ECO sampling efforts. The specimens of P. andriashevi are the second and third known (the other being holotype), and the record of M. longirostris

Acknowledgments

We thank Professor Andrew S. Brierley for supervision and overall guidance of this work. We are grateful to Miss Susan Evans and all helpers at sea for enthusiastic sorting of catches. We thank Dr. Martin Cox and Mr. Ben Boorman for RMT fishing activities. We are grateful to the National Environment Research Council for shiptime and the School of Biology for funding toward Dr. Tom Bech Letessier's PhD. We thank MAR-ECO for funding a workshop dedicated to the analysis of the ECOMAR fish catches.

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¹: Present address: Oceanographic Center, Nova Southeastern University, 8000 North Ocean Drive, Dania Beach, FL 33004, USA.

²: Present address: Centre for Marine Futures, The UWA Oceans Institute, The University of Western Australia, UWA (M470), Stirling Highway, Crawley, WA 6009, Australia.

³: Present address: Marine Research Institute, Skúlgata 4, P.O. Box 1390, Reykjavík, Iceland.

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Midwater fishes collected in the vicinity of the Sub-Polar Front, Mid-North Atlantic Ocean, during ECOMAR pelagic sampling

Abstract

Introduction

Section snippets

Methods

Results

Summary and discussion

Acknowledgments

Deep-Sea Res. II

Deep-Sea Res. II.

Deep-Sea Res. I

J. Mar. Syst.

Deep-Sea Res. II.

Deep-Sea Res. II: Top. Stud. Oceanogr.

Photichthyidae

Sternoptychidae

The N.I.O. combination net (RMT 1+8) and further developments of rectangular midwater trawls

J. Mar. Biol. Assoc. UK

A review of the genus Psednos (Pisces, Liparidae) with description of ten new species from the north Atlantic and southwestern Indian Ocean

Bull. Mus. Comp. Zool. (Harvard)

Annotated list of the arctic marine fishes of Canada. Miscellaneous Report

Can. J. Fish. Aquat. Sci.

Bathylagidae

Bristlemouths. Family Gonostomatidae

Lanternfishes. Family Myctophidae

Melamphaidae III. Systematics and distribution of the species in the bathypelagic fish genus Scopelagadus Vaillant

Dana Rep.

Astronesthidae

Chauliodontidae

Stomiidae

Catchability of pelagic trawls for sampling deep-living nekton in the Mid-North Atlantic

ICES J. Mar. Sci.

The feeding ecology of four hatchetfishes (Sternoptychidae) in the eastern Gulf of Mexico

Bull. Mar. Sci.

Myctophidae