Monitoring fishing mortality: Compliance in Norwegian offshore fisheries

Sustainable management of wild fish stocks by means of catch quotas requires reliable data on fishing mortality. Norwegian authorities have attempted to ensure the reliability of this data through catch report procedures and a ban on dumping. The reliability of data on fishing mortality depends on the fishers’ compliance with these regulations. This article outlines the main factors that govern compliance and non-compliance in the Norwegian pelagic fisheries. Data was generated during fieldwork in the offshore pelagic fishing fleet.     

Food webs and carbon flux in the Barents Sea

Within the framework of the physical forcing, we describe and quantify the key ecosystem components and basic food web structure of the Barents Sea. Emphasis is given to the energy flow through the ecosystem from an end-to-end perspective, i.e. from bacteria, through phytoplankton and zooplankton to fish, mammals and birds. Primary production in the Barents is on average 93 g C m⁻² y⁻¹, but interannually highly variable (±19%), responding to climate variability and change (e.g. variations in Atlantic Water inflow, the position of the ice edge and low-pressure pathways). The traditional focus upon large phytoplankton cells in polar regions seems less adequate in the Barents, as the cell carbon in the pelagic is most often dominated by small cells that are entangled in an efficient microbial loop that appears to be well coupled to the grazing food web. Primary production in the ice-covered waters of the Barents is clearly dominated by planktonic algae and the supply of ice biota by local production or advection is small. The pelagic–benthic coupling is strong, in particular in the marginal ice zone. In total 80% of the harvestable production is channelled through the deep-water communities and benthos. 19% of the harvestable production is grazed by the dominating copepods Calanus finmarchicus and C. glacialis in Atlantic or Arctic Water, respectively. These two species, in addition to capelin (Mallotus villosus) and herring (Clupea harengus), are the keystone organisms in the Barents that create the basis for the rich assemblage of higher trophic level organisms, facilitating one of the worlds largest fisheries (capelin, cod, shrimps, seals and whales). Less than 1% of the harvestable production is channelled through the most dominating higher trophic levels such as cod, harp seals, minke whales and sea birds. Atlantic cod, seals, whales, birds and man compete for harvestable energy with similar shares. Climate variability and change, differences in recruitment, variable resource availability, harvesting restrictions and management schemes will influence the resource exploitation between these competitors, that basically depend upon the efficient energy transfer from primary production to highly successful, lipid-rich zooplankton and pelagic fishes.     

Indication of thiols in black sea deep water

Potentiometric titrations of deep Black Sea water give reasonably precise values of sulphide in the concentration range 30–300 μmol l⁻¹ and a strong indication of thiols in the concentration range 10–30 μmol l⁻¹. Organic analysis of Black Sea water should therefore include the search for compounds containing SH groups. A simple stoichiometric model indicates that sulphur-containing proteins might be the main source of thiols after hydrolysis and deamination. The alkalinity and total sulphide are simply related by A_t = 3287 ± 30 + (3.84 ± 0.10) [H₂ S]_t μmol kg⁻¹. The slope of 3.84 instead of the stoichiometric slope of 2.31 indicates a lack of reduced sulphate in the form of hydrogen sulphide.     

Intercomparison of different methods for the determination of trace metals in seawater

During a cruise on the North Sea and the North East Atlantic, about 90 samples were obtained from various depths. Concentrations of cadmium, copper, lead, nickel and zinc were determined by atomic absorption spectroscopy after separation/concentration using two different extraction methods. One, using APDC and MIBK, was applied directly on board while the other, using a mixture of dithiocarbamates and freon, was applied after storage under acid conditions. About half of the samples were also analysed for cadmium, copper and lead using ASV. The results of these determinations are intercompared. Consistent results were obtained for cadmium with the two extraction methods and for lead with the freon extraction method and ASV. In the other cases discrepancies were found.     

Iron in the water column of the Weddell Sea

Total, dissolved and suspended iron has been determined in the water column of the Weddell Sea area during the austral summer 1988–1989. Some data are also presented for dissolved manganese, suspended manganese and suspended aluminium. The average value for dissolved iron was found to be 1.2 nM, with somewhat higher values at the Filchner Ice Shelf. The total iron was found to be considerably higher, with a range between 1 and 6 nM in the central Weddell Sea and 1 and 25 nM at the shelves. Transport of iron from the shelves into the Weddell Sea basin is demonstrated. This is observed both for total and dissolved iron.     

Trophic structure of zooplankton in the Fram Strait in spring and autumn 2003

The trophic structure of zooplankton was investigated in Fram Strait (north western Svalbard) in spring and autumn of 2003. Depth-stratified zooplankton samples were collected at 12 stations on the shelf (200 m), across the shelf-slope (500 m) and over deep water (>750 m), using a Multiple Plankton Sampler equipped with 0.180-mm mesh size nets.Higher zooplankton abundance and estimated biomass were found in the shelf area. Abundance and biomass were two times higher in August, when sea-surface temperature was higher than in May. Herbivores dominated numerically in May, and omnivores in August, suggesting a seasonal sequence of domination by different trophic groups. Cirripedia nauplii and Fritillaria borealis prevailed in spring, whereas copepod nauplii and Calanus finmarchicus were numerically the most important herbivores in autumn. Small copepods, Oithona similis and Triconia borealis, were the most numerous omnivorous species in both seasons, but their abundances increased in autumn. Chaetognatha (mainly Eukrohnia hamata) accounted for the highest abundance and biomass among predatory taxa at all deep-water stations and during both seasons. Regarding vertical distribution, herbivores dominated numerically in the surface layer (0–20 m), and omnivores were concentrated somewhat deeper (20–50 m) during both seasons. Maximum abundance of predators was found in the surface layer (0–20 m) in spring, and generally in the 20–50 m layer in autumn. This paper presents the first comprehensive summary of the zooplankton trophic structure in the Fram Strait area. Our goals are to improve understanding of energy transfer through this ecosystem, and of potential climate-induced changes in Arctic marine food webs.     

The application of computer-assisted photogrammetric methods in the structural analysis of part of the North Greenland Fold Belt

The development of computer support in photogrammetric measurements has facilitated quick calculations of structural geological elements such as strike and dip, fold axes and axial planes. Computer-assisted photogrammetric methods have been applied in a structural analysis of 3000 km² in central Peary Land, North Greenland. Detailed studies have been carried out in an area covered by a single stereo model representing part of the southernmost margin of the North Greenland Fold Belt. On the basis of the aerial photos, a map with both lithological boundaries and structural measurements may be drawn. In little known areas with complex structural relationships field work is necessary to control the interpretation. In the present study refolded thrust fault structures were investigated. Preparatory photogrammetric studies allow the limited time available for field work to be effectively utilised, and accurate geological maps to be produced relatively quickly.     

The Uppsala urban meteorology project

An extensive urban meteorology project in Uppsala, Sweden, is described. The city itself is considered suitable as a kind of model city, being almost circular, having sharp urban/rural boundaries and being situated in a relatively flat area. The project incorporates numerous measurements. A main station with a 100-m mast is situated at the NE urban/rural border. Its instrumentation consists of a slow-response (profile) system and a turbulence system. The profile instrumentation is described in detail. In addition to the main station, the project comprises: measurements from two 14-m masts, one on the top of a centrally located building, the other mobile; pilot balloon ascents; tethered balloon soundings, car-borne temperature traverses etc. Some preliminary results are presented: analyses of wind profiles from the mast and three-dimensional heat island studies.