Recruitment indices of Norwegian spring-spawning herring for the period 1965 -1984 based on the international 0-group fish surveys

The trawl data from the International 0-group fish surveys in the Barents Sea are analyzed. The fishing powers of the participating vessels are estimated and corrected for. A relative index of year class strength is computed on a logarithmic scale applying the method described by RANDA (1982). The average yearly recruitment of Norwegian spring-spawning herring is very low in the period, and only the 1983 year class can be caracterized as a strong one. A few other year classes, 1966, 1973, 1979 and 1984 may be rated as slightly above the average if the 1983 year class is not taken into account. In the period 1975-82 an index of recruitment of herring was obtained through bioacoustic measurements in the fjords of northern Norway. In 1983 and 84 the distribution of 0-group herring changed and most of the 0-group herring was concentrated in the Barents Sea

Acoustic estimates of abundance-at-age of juvenile Norwegian spring-spawning herring (Clupea harengus L.) in the Barents Sea from 1983 to 1993

Precision and relevance of pre-recruit studies for fishery management related to fish stocks in the Barents Sea and adjacent waters. Proceeding of the sixth IMR-PINRO Symposium Bergen, 14-17 June 1994The first year-class of Norwegian spring-spawning herring to enter the Barents Sea in significant numbers since the stock collapse in the late 1960'ies was the 1983-cohort. Regular acoustic surveys have been carried out since then to assess the changes in abundance of recruiting year-classes in the area. In the following 11-year period several more cohorts of herring were distributed in the Barents Sea, and the development of the abundance of each t year-class has been followed in the same way. Altogether fifty acoustic estimates of the abundance of the first four age-groups of nine year-classes were obtained during this period. Standardised methods through the young life stages are in this context important to foresee the recruitment to the spawning stock and to make better medium term prognosis of the stock development. It is suggested that the data series presented here may be of use in shedding light on some of the processes determining the variability of year-class strength of Norwegian spring-spawning herring

Determining the extinction cross section of aggregating fish

Author Posting. © Acoustical Society of America, 1992. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 91 (1992): 1983-1989, doi:10.1121/1.403682.When fish are aggregated over a flat bottom, and fish and bottom echoes can be distinguished, it is possible to determine the fish extinction cross section by a simple application of the echo integration method. The theory for this is developed. Measurements at 38 kHz are presented for aggregations of the same 1983‐year class of herring over flat‐bottomed fjord areas in 1988, 1990, and 1991. The ratio of extinction and backscattering cross sections is found to lie in the approximate range from 1.2–2.3, depending on fish size and time of day

Acoustic abundance estimation of demersal fish in the coastal area of Møre in March 1980

At the Møre coast there are important spawning areas for cod, coalfish, haddock and herring. As a part of an interaction study of these species, i.e. the predation of the demersal species on the spawning stock and the eggs of herring, an acoustic survey for estimation of the abundance of the demersal stocks was carried out in the last week of March. During the survey hydrographic data were sampled by a CTD-sonde. Acoustic abundance of demersal fish was devided between cod and haddock as one category and coalfish as another. As biological sampling by trawling occasionally was difficult because of high density of fishermens gillnets and rough bottom, biological data also were sampled from commercial catches in the surveyed area througout March. The behaviour of the fish was favourable for acoustic abundance estimation. However, some informations about haddock, observed as a heavy predator on eggs of herring, were supposed to be lost because it often stuck close to the bottom. The highest densities of cod were observed in the Breisund and at the Buagrunn, the last area also with the best acoustic recordings of coalfish and haddock. The stock abundance estimates of cod, haddock and coalfish were respectively 32 200, 11 560 and 51 760 tonnes. The experiences from this investigation indicate the acoustic method to be prosperous in abundance estimation of demersal fish in the surveyed area during the winter season

Commitments to sustainable fisheries: Empty words or reality?

The Our Ocean conferences focus on voluntary commitments by different pledgers in support of actions towards a clean, healthy and productive ocean. We analysed the content and summarised the progress of implementation of the commitments related to sustainable fisheries at the Our Ocean conferences during 2014–2018. A total of 77 different entities provided commitments. Governments was the largest group (34) followed by NGOs (23). The majority (58%) of commitments were related to enforcement, transparency and cooperation. In particular, combating illegal, unreported and unregulated fisheries and support for the port state measures process were the focus of many of the commitments. To increase transparency and effectiveness of commitments, we suggest that more emphasis should be put on documenting and evaluating the impact of commitments. There is good progress in the implementation, and the commitments are largely reality and not empty words. We consider that the commitments have been successful in terms of generating attention and providing funding of projects that are supportive of sustainable fisheries. The diversity of pledgers is large, and an objective gap analysis on requirements for achieving sustainable fisheries regionally could provide pledgers with common ground and further increase the impact of the Our Ocean conferences.publishedVersio

Assessment of commitments on sustainable fisheries to the Our Ocean conferences : Where are we now?

Many ocean commitments have been made at the five Our Ocean conferences since 2014 under six different areas of action. The Institute of Marine Research was given the task of evaluating the 182 commitments made to the action area “Sustainable fisheries”. We analysed the content, summarised the progress of implementation and evaluated the impact of the commitments. A total of 77 entities provided commitments. Governments made up the largest group and accounted for 65% of the commitments. NGOs were the second largest group of pledgers and accounted for 20% of the commitments. There was a high degree of fulfilment of the commitments: three quarters of the commitments had a 50% or higher degree of fulfilment and 50% of the commitments have been finalised. Some recent commitments (made in 2017 and 2018) have not been initiated. Combatting of illegal, unreported and unregulated fisheries and support to the port state measures process are key issues addressed by many of the commitments. We also recognise that important components such as science, advice and laws have less support in the Our Ocean commitments and should receive more attention in the future. Regional fisheries management organizations (RFMOs) are important instruments for sustainable fisheries management and was addressed by some commitments. For RFMOs to be effective, we emphasize that they should be empowered to have legal authority to devise fisheries regulations. There are quite a few commitments in our analysis that were hard to evaluate. To increase transparency in pledging of commitments, more emphasis should be put on documenting and evaluating their impact. We consider that the Our Ocean commitments in sustainable fisheries overall have been successful in terms of generating attention to the issue and providing funding of projects that are supportive of sustainable fisheries. To achieve effective fisheries management and sustainable fisheries, it is important that all the components of the fisheries management system are in operation at the appropriate spatial scale (local, national, regional) over time. A gap analysis on requirements for achieving sustainable fisheries at the appropriate scale, is a good starting point for a systematic approach to providing commitments. We suggest that this is considered in future Our Ocean conferences.publishedVersio

Return of Norwegian spring spawning herring (Clupea harengus L.) to historical spawning grounds off southwestern Norway

From the mid-1940s to mid-1960s a northward displacement of the spawning areas of the Norwegian Spring Spawning Herring was observed. Further retraction of the population from traditional feeding and spawning grounds occurred as the stock collapsed in the late 1960s. The spawning grounds off southwestern Norway were abandoned after 1959. Ever since, spawning appears to have been restricted to a few coastal grounds and offshore banks off mid-Norway, primarily off the Møre district. At present, the abundance of the spawning stock remains comparatively low; 1.5-2 mill. tonnes as compared with 7-10 mill. tonnes in the 1950s. However, in the spawning seasons from 1989 onwards, spring spawners have again been observed at the southwestern grounds. The herring at these southern grounds in 1990 and 1991 were Norwegian Spring Spawners and utilized traditional spawning sites. The spawning time was about a month later than in the 1930s but similar to that in the 1950s. Results of acoustic surveys showed that of the total spawning stock, 1.5 - 2 % used the southwestern grounds i 1990 and 1991

Observational insights into chlorophyll distributions of subtropical South Indian Ocean eddies

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