On the application of the echointegration method

The echo integration method used by the Institute of Marine Research is described. The model which are used to convert acoustic abundance indices into fish densities using length and species dependant conversion factors, are established and a computational example for a mixed cod and haddock recording is given. The data sampling and processing procedures onboard the survey vessel are described and discussed

Experiments with acoustic tags in Lofoten in March 1974

Introductory experiments on acoustic tagging were carried out on cod in Lofoten in March 1974. The research vessel used 'was «G. O. Sars» because of her excellent sonar equipment. Two fishes were tagged. The tags used were pure transmitters — one working on 18 kHz and the other on 120 kHz. The signals were received by means of sonars, SIMRAD SU for 18 kHz and SIMRAD SK 120 for 120 kHz. Both fishes were tracked for approximately 8 hrs. The two fishes showed some different behaviour. The first one changed swimming speed and position all the time within a limited area while the other moved slowly around within an open area

Loddeundersøkelser i Barentshavet i september-oktober 1974

During September-October 1974 observations were made on the distribution, abundance and year-class composition of capelin in the Barents Sea. Specifically it was of great importance to get an abundance estimate of the 1975 spawning population. Dense concentrations of capelin were found over a larger area than at the same time in 1973. The total population was estimated to be essentially larger than in 1973. l and 2 years old capelin showed reduced growth compared to «normal». As a result, the proportion of 2 years old capelin that is maturing, is also lower than «normal». Besides this, the abundance of 3 years old fish is found to be rather low and consequently the total spawning population will be reduced

Investigations on capelin in the Barents Sea in May-June 1974

Rapporten er også publisert som artikkel i Fiskets Gang,60(38),1974:669-673During May—June 1974 observations were made on the distribution, abundance and year-class composition of capelin in the Barents Sea. Good concentrations of capelin were found over a considerably larger area than at the same time in 1973. Both the 1972 and 1971 year-classes show reduced growth compared to what can be considered normal, but due to the large number of individuals in these two year-classes the total biomass is still at a reasonably high level. Due to selective sampling by the trawl, no conclusion should be drawn as to the strength of the 1973 year-class. A distribution map of polar cod is given

From the Weyl Anomaly to Entropy of Two-Dimensional Boundaries and Defects

We study whether the relations between the Weyl anomaly, entanglement entropy (EE), and thermal entropy of a two-dimensional (2D) conformal field theory (CFT) extend to 2D boundaries of 3D CFTs, or 2D defects of $D \geq 3$ CFTs. The Weyl anomaly of a 2D boundary or defect defines two or three central charges, respectively. One of these, $b$, obeys a c-theorem, as in 2D CFT. For a 2D defect, we show that another, $d_2$, interpreted as the defect's `conformal dimension,' must be non-negative by the Averaged Null Energy Condition (ANEC). We show that the EE of a sphere centered on a planar defect has a logarithmic contribution from the defect fixed by $b$ and $d_2$. Using this and known holographic results, we compute $b$ and $d_2$ for 1/2-BPS surface operators in the maximally supersymmetric (SUSY) 4D and 6D CFTs. The results are consistent with $b$'s c-theorem. Via free field and holographic examples we show that no universal `Cardy formula' relates the central charges to thermal entropy.Comment: 8 pages, 1 figur

Investigations on dernersal fish in the Barents Sea in winter 1978

This report describes the results from a survey on demersal fish in the Barents Sea from 30 January to 15 March 1978. The work was carried out by R.V. "G.O.Sars". Maps and tables are presented which show the hydrographic and fishing stations, echo abundance of cod, haddock and other demersal fish, frequency distributions versus length of cod and haddock, and distributions and abundance of the different year classes of cod and haddock

Investigations on demersal fish at Bear Island and West-Spitsbergen in autumn 1977

This report describes the results from a survey with R.V. "G.O.Sars" from 10 October to 5 November 1977 on demersal fish in the area off Bear Island and West-Spitsbergen. The most abundant species in the trawl catches were blue whiting, long rough dab, prawns, cod and redfish (Sebastes mentella), which respectively amounted to 31.5%, 19.2%, 15.l %, 13.4% and 9.9% of the catches. Compared with 1976 there were caught more prawns and less cod, haddock and redfish. The most numerous year class of cod were the 1973, 1975 and 1972 year classes. Haddock was very scarce. Redfish was abundant but specimens longer than 30 cm were few in the catches

The impact of offshore wind farms on the marine environment

There is an increasing need for energy. Considerable efforts are being made to develop environmentally friendly energy sources. Generating electric energy using wind turbines is one of the methods that has gained widespread, international acceptance. In Norway wind turbine farms are established as well, and more farms are planned for the coming years. Most farms are land based, but from several reasons there are increasing interests in offshore wind farms

Acoustic abundance estimation of cod and haddock in the Barents Sea in February 1976

From l to 20 February observations of cod and haddock were carried out by R.V. "G.O. Sars" in the centra1 and eastern part of the Barents Sea. The survey was part of a program with the aim of estimating the abundance of young cod and haddock by an acoustic method. The results from the survey is presented in this report together with a brief description of the method used to establish abundance estimates of young cod and haddock

Effects of sound from seismic surveys on fish reproduction, the management case from Norway

Anthropogenic noise has been recognized as a source of concern since the beginning of the 1940s and is receiving increasingly more attention. While international focus has been on the effects of noise on marine mammals, Norway has managed seismic surveys based on the potential impact on fish stocks and fisheries since the late 1980s. Norway is, therefore, one of very few countries that took fish into account at this early stage. Until 1996, spawning grounds and spawning migration, as well as areas with drifting eggs and larvae were recommended as closed for seismic surveys. Later results showed that the effects of seismic surveys on early fish development stages were negligible at the population level, resulting in the opening of areas with drifting eggs and larvae for seismic surveys. Spawning grounds, as well as concentrated migration towards these, are still closed to seismic surveys, but the refinement of areas and periods have improved over the years. Since 2018, marine mammals have been included in the advice to management. The Norwegian case provides a clear example of evidence-based management. Here, we examine how scientific advancements informed the development of Norwegian management and how management questions were incorporated into new research projects in Norway.publishedVersio