Characterisation of large zooplankton sampled with two different gears during midwinter in Rijpfjorden, Svalbard

During a midwinter cruise north of 80°N to Rijpfjorden, Svalbard, the composition and vertical distribution of the zooplankton community were studied using two different samplers 1) a vertically hauled multiple plankton sampler (MPS; mouth area 0.25 m2, mesh size 200 μm) and 2) a horizontally towed Methot Isaacs Kidd trawl (MIK; mouth area 3.14 m2, mesh size 1500 μm). Our results revealed substantially higher species diversity (49 taxa) than if a single sampler (MPS: 38 taxa, MIK: 28) had been used. The youngest stage present (CIII) of Calanus spp. (including C. finmarchicus and C. glacialis) was sampled exclusively by the MPS, and the frequency of CIV copepodites in MPS was double that than in MIK samples. In contrast, catches of the CV-CVI copepodites of Calanus spp. were substantially higher in the MIK samples (3-fold and 5-fold higher for adult males and females, respectively). The MIK sampling clearly showed that the highest abundances of all three Thysanoessa spp. were in the upper layers, although there was a tendency for the larger-sized euphausiids to occur deeper. Consistent patterns for the vertical distributions of the large zooplankters (e.g. ctenophores, euphausiids) collected by the MPS and MIK samplers provided more complete data on their abundances and sizes than obtained by the single net. Possible mechanisms contributing to the observed patterns of distribution, e.g. high abundances of both Calanus spp. and their predators (ctenophores and chaetognaths) in the upper water layers during midwinter are discussed.

Distribution and abundance of Pleuronectiformes larvae off Southeastern Brazil

The objective of this study was the description of the composition, abundance and density in horizontal and vertical distribution of Pleuronectiformes larvae on the southeastern Brazilian continental shelf. The samples were collected with bongo nets and a Multi Plankton Sampler (MPS), both in summer and winter 2002. A total of 352 flatfishes larvae were collected in summer and 343 in winter, representing three families and a total of 13 taxa: Paralichthyidae (Citharichthys cornutus, C. spilopterus, Citharichthys sp., Cyclopsetta chittendeni, Syacium spp., Etropus spp. and Paralichthys spp.), Bothidae (Bothus ocellatus and Monolene antillarum) and Cynoglossidae (Symphurus trewavasae, S. jenynsi, S. plagusia and S. ginsburgi). The most abundant taxa were Etropus spp., Syacium spp. and Bothus ocellatus. Etropus spp. occurred mainly as far out as the 200 m isobath and Syacium spp. from 100 m. B. ocellatus was present mainly in the oceanic zone between Ubatuba and Rio de Janeiro as from the 200 m isobath. The greatest average densities of these species occurred in the strata from 0 to 20 m depth in summer and between 20 and 40 m in winter.