Some observations on the feeding ecology of Norwegian spring spawning herring (Clupea harengus) along the coast of Norway

The feeding ecology of Norwegian spring spawning herring Clupea harengus was studied with samples collected from cruises in February -March 1991, May 1992, and February and April 1993. A wide variety of zooplankton organisms were observed in the diet of herring, with crustaceans dominating except in samples from May 1992 when larvaceans (Oikopleura sp.) dominated. Fish were occasionally preyed. In addition to larvaceans, copepods (Calanus finmarchicus and C. hyperboreus ) and amphipods (Parathemisto spp.) were important food items in the diet of herring captured in May 1992. Krill (Thysanoessa inermis and Meganyctiphanes norvegica) were the major prey of herring from the Møre coast in February-March 1991 and in February 1993. Plankton samples taken with MOCNESS from the same area also showed krill to be dominant. Sixty to seventy per cent of the stomachs examined from these two cruises were empty indicating low feeding activity during the spawning season

Foraging success in planktivorous fish increases with topographic blockage of prey distributions

Banks and shelves are productive zones of the ocean, and often home to large fish stocks. Can shallower bottom topographies improve foraging opportunities for pelagic fish by blocking zooplankton from hiding in deep, darker water? We use mechanistic principles of visual prey search and an extensive dataset of zooplankton depth distributions to model foraging success in planktivorous fish across a large marine ecosystem. Our results show that zooplankton distribute deeper with deeper bathymetry, and that fish find exponentially less food with increasing bottom depths. Over shallow banks, zooplankton are forced into higher light exposure, providing higher prey encounter rates for fish despite lower abundance of prey. Stomach data analyses from a key planktivore support these predictions and suggest that fish foraging on copepods are more successful over shallower grounds. Our study demonstrates that prey availability for planktivorous fish is not proportional to zooplankton abundance, while the bottom depth is an important factor in fish foraging success and zooplankton mortality rates.publishedVersio

Spatial patterns and key drivers of zooplankton in the north central Indian Ocean

Zooplankton is a vital component in the pelagic marine ecosystems, linking lower to higher trophic levels. A survey was conducted with R/V Dr. Fridtjof Nansen in Sri Lankan waters in summer 2018 to explore zooplankton dynamics in relation to abiotic and biotic variables. A distinct pattern in physical and biological properties characterized Sri Lankan waters into two ecosystems: (1) low production, high temperature, and low salinity in the east, and (2) high production, low temperature, and high salinity in the west. The highest mean abundance (1931 ind. m−3) and biomass (1.79 g dry wt. m−2) of zooplankton were significantly associated with cooler, high saline, and more productive waters in the North West and South West. In general, zooplankton were significantly more abundant in the west (1841 ind. m−3) than the east (707 ind. m−3). The most abundant copepod families were Paracalanidae (20.4%) and Tachidiidae (10.2%). The copepod Paracalanus parvus was the most dominant species. Our study reveals that temperature is a key driver explaining 67% of the variance in zooplankton biomass in this region. This study provides novel baseline results on spatial patterns of zooplankton abundance, biomass, and species composition from an understudied region of the north central Indian Ocean.publishedVersio

Initial collateral measurements of some properties of Calanus finmarchicus

In general, acoustic quantification of zooplankton such as Calanus finmarchicus requires the use of models, among other reasons, to aid in the interpretations of data collected on animals whose scattering properties change with development stage, season, and other environmentally linked factors. In conjunction with a project to determine acoustic scattering signatures of zooplankton and fish, a study is being performed to measure physical, morphometric, and biochemical properties of selected euphausiid species and Calanus finmarchicus. An important feature of this study is the performance of a suite of measurements on animals collected at the same time and place. The measurement methods being used to study Calanus are presented here together with results from the initial field experiment. The criticism of interested parties is solicited

Productivity in the Barents Sea - Response to recent climate variability

The temporal and spatial dynamics of primary and secondary biomass/production in the Barents Sea since the late 1990s are examined using remote sensing data, observations and a coupled physical-biological model. Field observations of mesozooplankton biomass, and chlorophyll a data from transects (different seasons) and large-scale surveys (autumn) were used for validation of the remote sensing products and modeling results. The validation showed that satellite data are well suited to study temporal and spatial dynamics of chlorophyll a in the Barents Sea and that the model is an essential tool for secondary production estimates. Temperature, open water area, chlorophyll a, and zooplankton biomass show large interannual variations in the Barents Sea. The climatic variability is strongest in the northern and eastern parts. The moderate increase in net primary production evident in this study is likely an ecosystem response to changes in climate during the same period. Increased open water area and duration of open water season, which are related to elevated temperatures, appear to be the key drivers of the changes in annual net primary production that has occurred in the northern and eastern areas of this ecosystem. The temporal and spatial variability in zooplankton biomass appears to be controlled largely by predation pressure. In the southeastern Barents Sea, statistically significant linkages were observed between chlorophyll a and zooplankton biomass, as well as between net primary production and fish biomass, indicating bottom-up trophic interactions in this region

Diversity and seasonal development of large zooplankton along physical gradients in the Arctic Barents Sea

Due to ongoing climate change, a new Arctic Ocean ecosystem is emerging. Within the framework of the Nansen Legacy project, we investigated the community composition of the large zooplankton and its seasonal development along a latitudinal gradient in the northern Barents Sea. Total biomass was maximal in summer and early winter, and minimal in spring, with copepods contributing considerably in all seasons. Euphausiids represented a minor fraction of the biomass, whereas chaetognaths and other gelatinous zooplankton contributed substantially to the sampled zooplankton at all stations, particularly in winter. Amphipod biomass was high in early winter, but otherwise low. Temperature in the water column interior and bottom-depth had the highest explanatory power for the community composition of the large zooplankton, both revealing the same distinct Atlantic and Arctic domains along the studied section. The continental shelf of the northern Barents Sea had an Arctic signature and was in terms of biomass characterized by a dominance of cold-water species, such as Themisto libellula, and Calanus glacialis. The copepod Calanus hyperboreus was the dominant over the continental slope. Locations at the southern and northern end of the studied section were influenced by Atlantic Water (at intermediate depth at the northern stations), and contained a mixture of temperate species, deep-water species, and sympagic amphipods in northern ice-covered waters. In the northern Barents Sea, a seasonal change was observed in the biomass fractions of different zooplankton feeding guilds, with dominance of herbivores in summer and carnivores in winter. This suggests switching between bottom-up and top-down control through the year. On the continental slope, species that are typically considered omnivores seemed to increase in importance. The role of seasonally changing food preferences to bridge periods outside of the main primary production season is discussed in light of ecosystem resilience to the expected changes in the Arctic Ocean.publishedVersio

Døde og strandete krepsdyr - Nitti tilfeller rapportert til Havforskningsinstituttet i perioden 2014-2020

Havforskningsinstituttet begynte med en systematisk registrering av innrapporterte funn av strandet krill i 2014. Antall tilfeller var få fra 2014 til 2017, men økte kraftig i 2018 og har siden holdt seg på dette nivået. Det er vanskelig å vite om dette skyldes at krill har drevet i land oftere de siste tre årene enn tidligere, eller om flere nå melder ifra om funn. Antallet innrapporterte tilfeller økte akkurat da bruken av kjemiske avlusingsmidler i landet som helhet minket kraftig, mens antallet innrapporterte tilfeller var relativt lavt i de årene der bruken av avlusingsmidler var høyest. Hyppigheten av strandet krill kan også ha en sammenheng med mengden krill i sjøen. Mars, august, september og oktober skiller seg klart ut som månedene med flest funn. De aller fleste funnene er fra Rogaland og gamle Hordaland fylke. De eneste områdene i landet hvor det ikke er rapportert om funn av strandet krill, er Finnmark og Skagerakkysten.publishedVersio

First results from the L3+C experiment at CERN

The L3+C experiment combines the high-precision spectrometer of the L3 detector at LEP, CERN, with a small air shower array. The momenta of cosmic ray induced muons can be measured from 20 to 2000 GeV/c. During the 1999 data taking period 5 billion muon events were recorded in the spectrometer. From April until mid Summer 2000 an additional 3 billion muon events have been recorded as well as 25 million air shower events. Here the first results on the muon momentum spectrum and charge ratio will be presented

Deliverable 1.1 review document on the management of marine areas with particular regard on concepts, objectives, frameworks and tools to implement, monitor, and evaluate spatially managed areas

The main objectives if this document were to review the existing information on spatial management of marine areas, identifying the relevant policy objectives, to identify parameters linked to the success or failure of the various Spatially Managed marine Areas (SMAs) regimes, to report on methods and tools used in monitoring and evaluation of the state of SMAs, and to identify gaps and weaknesses in the existing frameworks in relation to the implementation, monitoring, evaluation and management of SMAs. The document is naturally divided in two sections: Section 1 reviews the concepts, objectives, drivers, policy and management framework, and extraneous factors related to the design, implementation and evaluation of SMAs; Section 2 reviews the tools and methods to monitor and evaluate seabed habitats and marine populations.peer-reviewe