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

Baker, A. de C.; Clarke, M. R.; Harris, Matthew L.

doi:10.1017/s0025315400056708

Cited by 239 publications

(68 citation statements)

References 4 publications

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“…The nets were towed in leads in the pack-ice and in the southern coastal polynya (from the Russian: stretch of open water in an ice-covered area). All zooplankton abundance data are based on 32 standardized R M T 1 + 8 hauls (mesh size 320 and 4500 Ixm; mouth opening 1 and 8 m2; Baker et al 1973) from the upper 300 m in February/March 1983 (Table 1). Twenty-two stations were located on the shelf while ten stations were from oceanic waters (Fig.…”

Section: Methodsmentioning

confidence: 99%

Zooplankton biomass in the ice-covered Weddell Sea, Antarctica

et al. 1991

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Abstract. Zooplankton was sampled by a RectangularMidwater Trawl (RMT 1 + 8) in Weddell Sea surface waters (0 to 300 m) between 66 and 78°S during austral summer (February-March 1983). Sixty-nine taxa including different developmental stages were considered and divided into 16 size classes between < 1 and > 39.5 mm length. Biomass was determined by taxon and size class for three different meso-and macroplankton communities in the oceanic region, on the northeastern shelf and on the southern shelf of the Weddell Sea. The highest biomass of 11.2 mg DWm -3 (3.4 g DWm -2) was found in the northeastern shelf community (70 to 74°S), where juvenile and adult Euphausia crystallorophias accounted for 3 . 7 m g D W m -3 (1.1gDWm-2). Although not quantitatively sampled, early copepodite stages (CI to CIII) of Calanoides acutus and Calanus propinquus ranked second with 2.7 mg DWm -3 (0.8 g DWm-2). Biomass in the northeastern shelf community was concentrated in the size ranges 1 to 4 mm and 19.5 to 39.5 mm. The oceanic community of the central Weddell Sea was dominated by copepods smaller than 5 mm, which made up half of the total oceanic biomass. The tunicate Salpa thompsoni (7.0 to 8.5 mm) was the dominant single species with 1.6 mg DWm -3 (0.5 g D w m -a ) .Euphausiids, mainly juvenile and adult krill Euphausia superba, comprised 1.2 mg DWm -3 (0.4 g DWm-2).Total standing stock in the oceanic community was 9.4 mg DWm -3 (2.8 g DWm-2). Lowest biomass values were found in the southern shelf community (south of 75°S) with 4 . 0 m g D W m -3 ( l . 2 g D W m -2 ) , concentrated in the 1 to 4 mm and 14.5 to 34.5 mm size classes.Abundant species were the pteropod Limacina helicina

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Section: Methodsmentioning

confidence: 99%

Zooplankton biomass in the ice-covered Weddell Sea, Antarctica

et al. 1991

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“…This is essentially a twin net consisting of an 8-m 2 trawl of 4.5-ram mesh size and a 1-m 2 plankton net of 0.303-mm mesh size. The opening and closing of the two nets were controlled by a net monitor which acoustically telemetered in-situ measurements of the depth of the net, temperature, speed and distance fished (Baker et al, 1973).…”

Section: Methodsmentioning

confidence: 99%

Vertical distribution and feeding patterns of midwater fish in the central equatorial Atlantic

Kinzer

Schulz

1985

Marine Biology

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Fishes and zooplankton were obtained (March-April 1979 and partly in August 1974) from 45 hauls taken during the day and at night in the central equatorial Atlantic between Latitude 3 ~ and 2 ~ from the surface to 1 250-m depth, using the RMT 1+8, a combined opening-closing plankton and micronekton trawl. The vertical distribution of 30 myctophid species is described.All species migrate in a diel pattern, Ceratoscopelus warmingii and Lampanyctus photonotus down to at least 1 250 m. During daytime most species aggregated at 400-to 700-m depth, therefore only partly occupying the depth of the Deep Scattering Layer (400 to 500 m at 15 kHz). The feeding patterns of seven of the most abundant species were compared, with a total of 1 905 stomach contents being analysed. All seven species are regarded as opportunistic predators, which feed predominantly during the night on calanoid copepods. A total of 66 species of calanoid copepods were identified among the prey items, with smaller species definitely being in the minority.Stomachs of C. warmingii (700 to 1 250 m depth) and Lepidophanes guentheri (500 to 900 m depth) from daytime samples contained copepod species restricted to the upper 150 m of the water column, including Undinula vulgaris, Nannocalanus minor, and Euchaeta marina, thereby confirming an extended vertical migration of predators. Differences in diet and preferences between species in their total food spectrum are described.

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“…8 plankton net (Baker et al 1973), an opening and closing net system in which two nets are combined in one framework, was used to collect krill samples from the upper 200 m of the water column. The mesh size of the larger 8 m 2 net and the smaller 1 m 2 net was 4.5 and 0.33 mm, respectively.…”

Section: Krill Surveymentioning

confidence: 99%

Horizontal niche partitioning of humpback and fin whales around the West Antarctic Peninsula: evidence from a concurrent whale and krill survey

et al. 2016

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A dedicated aerial cetacean survey was conducted concurrently to a standardised net trawl survey for krill in order to investigate distribution patterns of large whales and different krill species and to investigate relationships of these. Distance sampling data were used to produce density surface models for humpback (Megaptera novaeangliae) and fin whales (Balaenoptera physalus) around the West Antarctic Peninsula (WAP). Abundance for both species was estimated over two strata in the Bransfield Strait and Drake Passage. Distinct distribution patterns suggest horizontal niche partitioning of the two whale species around the WAP, with fin whales aggregating at the shelf edge of the South Shetland Islands in the Drake Passage and humpback whales in the Bransfield Strait. Krill biomass estimated from the concurrent krill survey was used along with CTD data from the same expedition, bathymetric parameters and satellite data on chlorophyll-a and ice concentration to model krill distribution. Comparisons of the predicted distributions of both whale species with the predicted distributions of Euphausia superba, Euphausia crystallorophias and Thysanoessa macrura suggest a complex relationship rather than a straightforward correlation between krill and whales. However, results indicate that fin whales were feeding in an area dominated by T. macrura, while humpback whales were found in areas of higher E. superba biomass. Our results provide abundance estimates for humpback whales and, for the first time, fin whales in the WAP and contribute important information on feeding ecology and habitat use of these two species in the Southern Ocean.

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

Cited by 239 publications

References 4 publications

Zooplankton biomass in the ice-covered Weddell Sea, Antarctica

Zooplankton biomass in the ice-covered Weddell Sea, Antarctica

Vertical distribution and feeding patterns of midwater fish in the central equatorial Atlantic

Horizontal niche partitioning of humpback and fin whales around the West Antarctic Peninsula: evidence from a concurrent whale and krill survey

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