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Abstract Here, we provide the first comprehensive documentation of the north-western extreme of the blue whiting (Micromesistius poutassou, Risso 1827) distribution in Greenland waters. We compile data from hydroacoustic surveys, commercial fisheries, and bottom trawl surveys (1981–2017) and use age specific Generalized Additive Models (GAMs) to describe the historical variation in abundance and horizontal and vertical distribution. Based on those results, we infer ontogenetic progressing migration patterns of 0 to 12 years old blue whiting. We find blue whiting along the west, south and east coasts of Greenland from 59.4 °N – 71.0 °N, with the highest densities in the surveys at the shelf slope south of Dohrn Bank and the highest commercial catches at Kolbeinsey ridge off East Greenland. The spatiotemporal patterns found by statistical modelling suggest annual migrations of both juvenile and adult blue whiting into Greenland waters. Juveniles appear to enter east Greenland waters from the spawning areas further east during their first summer. During the subsequent two years, the majority of juveniles reach further to the south and west where they utilise South and West Greenland as nursey areas. When reaching adulthood they return to the spawning areas in the east, and their annual feeding migrations towards west only reach East Greenland. [ABSTRACT FROM AUTHOR]

Annual acoustic surveys of spawning southern blue whiting ( Micromesistius australis ) on the Bounty Platform, southeast of New Zealand, have been carried out using industry vessels since 2004. In most years, surveys were carried out from a single vessel, while in 2009, acoustic data were collected from three vessels. The survey approach in all years was the same—vessels with calibrated Simrad ES60/ES70 echosounders and hull-mounted 38 kHz transducers conducted aggregation-based surveys using an adaptive design. Surveys attempted to cover all areas of high southern blue whiting density. In most years there were multiple snapshots of the same aggregation. The resulting biomass was used as a relative estimate of spawning southern blue whiting abundance. There was a very large (seven-fold) increase in estimated biomass of southern blue whiting at the Bounty Platform from 2006 to 2007, which was due to the recruitment of one very strong year class (2002) into the spawning population. The estimated biomass from 2008 was also high, but biomass declined by a factor of four in 2009. The observed decline in acoustic estimates between 2008 and 2009 was too great to be explained solely by fishing and average levels of natural mortality. The very large changes in estimated abundance between years, and also between snapshots within a year, are related mainly to changes in survey temporal and spatial coverage, and illustrate an important limitation on interpretation of aggregation-based acoustic abundance estimates. In each snapshot an unknown proportion of the spawning aggregation is surveyed, and almost certainly not the entire spawning stock. Survey coverage depended on both the amount of survey time available (which is often limited by commercial constraints) and the behaviour of the fish (e.g., the extent and density of the aggregation, and the timing of spawning). It is therefore difficult to incorporate the resulting series of abundance estimates into a formal stock assessment model as a time series. Despite this, industry acoustic surveys of the Bounty Platform have led directly to management decisions and changes in catch limits. [ABSTRACT FROM AUTHOR]

Acoustic data collection trials on pelagic freezer-trawlers were realised in 2012 during several fishing trips targeting blue whiting west of the British Isles in spring, North Sea herring in summer, and horse mackerel in the English Channel and Celtic Sea in autumn. Echosounders were calibrated and time- and position-stamped data logged along the path covered by the vessels. The acoustic detections recorded during different types of trawler activity within a fishing trip (‘searching’, ‘stationary’, and ‘fishing’) were compared between target species. The highest proportion of time spent for activity ‘fishing’ was observed in the blue whiting fishery (82%), while that value was lower in the horse mackerel and herring fishery (68% and 54%). In all fisheries the quantified mean fish densities recorded were significantly higher during ‘fishing’ than during ‘searching’. Changes in recorded fish density magnitudes over time before and after trawling also showed different patterns between fisheries. The quantified peculiarities exhibited by the specific fishing trip data is discussed in light of incorporating them in monitoring programs and analysis methods that can advance ecosystem understanding. Potential future approaches for analysis methods of opportunistically recorded acoustic fishing vessel data are discussed. [ABSTRACT FROM AUTHOR]

In the Mediterranean, blue whiting, Micromesistius poutassou, constitutes a traditional fisheries resource. Over several decades, blue whiting landings in the Catalan coast (northwestern Mediterranean) have displayed cyclical variations, of c. 6 yrs, slightly decreased to five in the last two decades, as shown through wavelet analysis. These fluctuations have persisted under very different levels of fishing effort. This study evaluates the hypothesis that deep-water formation in the adjacent Gulf of Lions, and the enhanced primary productivity related to it, determines recruitment strength in blue whiting that results ultimately in the observed periodicity of the blue whiting landings. The link between landings and environmental drivers was explored using lagged cross-correlations, with 0- and 1-yr lag. The variables considered included large-scale indices [North Atlantic Oscillation (NAO) and the Atlantic Multi-decadal Oscillation (AMO)], Mediterranean climate indices [MO and Western Mediterranean Oscillation (WeMO)], and variables defining the local environmental conditions in the northwestern Mediterranean (sea-air heat flux, winter air temperature anomaly and Rhône river runoff). Significant correlations were only found between landings (1961-2011) and sea-air heat flux, which is generally taken as an indicator of processes of deep water convection, at 0 and 1-yr lag. These results suggest that the observed fluctuations in blue whiting landings respond to oceanographic processes taking place in the Gulf of Lions. [ABSTRACT FROM AUTHOR]

This paper gives an overview of sustainability and management of the straddling stock fisheries for Norwegian spring spawning herring, mackerel, and blue whiting. These stocks are harvested by coastal states and distant water fishing states (DWFS). Because multiple states access these stocks, reaching agreements on management has posed challenges, and some agreements have unravelled. For the blue whiting, the fishing industry itself played a major role in facilitating an agreement. A general lesson learned is that changes in fish migrations and stock distribution may destabilize international agreements. JEL Codes: Q22, Q34, Q57, Q58. [ABSTRACT FROM AUTHOR]

Abstract: In Europe, 88% of fish stocks are being fished beyond Maximum Sustainable Yield and 30% of stocks are outside of biological limits. The blue whiting fishery is also following a consistent trend of a declining, and the EU recently adopted a 93% quota decrease for this species. Despite the abundant literature related to genetic aspects of population structure of aquatic resources, few studies have specifically addressed the link between fisheries management and population genetics. Given potential differences in the behavior of different subpopulations, population genetics has great relevance in the correct interpretation of the evolution of stocks. Ignoring the congruence of spatial scales between the population structure of fish species and management units can result in reduced productivity and local reduction of populations. This paper adopts the framework of resilience to explore the social-ecological feedbacks between unobserved genetic diversity and human dimension of the blue whiting fishery in Galician coastal communities due to the mismanagement of the fishery in the EU. The results presented here suggest that there is considerable evidence that the currently used management unit is inconsistent with the recent growth and genetic differences observed. The results also reveal that based on the evidence currently available and in accordance with the precautionary principle, the stocks of blue whiting in Northern and Southern ICES areas should be treated as separate in the Northeast Atlantic Ocean. The results obtained indicate that unobserved genetic diversity of the fishery can lead to an equivocal reduction of fishing quotas in the Southern area. Finally, the paper also shows that the total economic losses resulting from the 93% quota decrease of the species, which includes effects on the rest of the Galician economy, is 40,081,636 Euros per year. The next Common Fishery Policy Reform offers a great opportunity to reverse the current unsustainable path of the fishery and to accept humans as a component of this marine social-ecological system. [Copyright &y& Elsevier]

Pedersen, G., Godø, O. R., Ona, E., and Macaulay, G. J. 2011. A revised target strength–length estimate for blue whiting (Micromesistius poutassou): implications for biomass estimates. – ICES Journal of Marine Science, 68: 2222–2228.Acoustic abundance estimates of blue whiting have generally been higher than estimates based on catch data. One explanation has been that the relationship between acoustic target strength (TS) and length is too low and hence overestimates the number of fish. Measurements of TS were conducted during surveys of blue whiting in March/April 2003–2007 to the west of the British Isles from several different measurement platforms, and also during August 2005 in the Norwegian Sea. Results from these experiments confirm the view that the existing TS–length relationship is too low. A new TS–length relationship is proposed that is ∼5 dB higher. Blue whiting TS is considerably higher than observed and modelled for a similar species, southern blue whiting (Micromesistius australis). [ABSTRACT FROM PUBLISHER]

In European fisheries, most stocks are overfished and many are below safe biological limits, resulting in a call from the European Commission for new long-term fisheries management plans. Here, we propose a set of intuitive harvest control rules that are economically sound, compliant with international fishery agreements, based on relevant international experiences, supportive of ecosystem-based fisheries management and compatible with the biology of the fish stocks. The rules are based on the concept of maximum sustainable yield ( MSY), with a precautionary target biomass that is 30% larger than that which produces MSY and with annual catches of 91% MSY. Allowable catches decline steeply when stocks fall below MSY levels and are set to zero when stocks fall below half of MSY levels. We show that the proposed rules could have prevented the collapse of the North Sea herring in the 1970s and that they can deal with strong cyclic variations in recruitment such as known for blue whiting. Compared to the current system, these rules would lead to higher long-term catches from larger stocks at lower cost and with less adverse environmental impact. [ABSTRACT FROM AUTHOR]

How would the formation, stability, and success of an agreement on cooperative management between neighbouring coastal states for a climate-sensitive fishery resource be affected by changes in the distribution and accessibility of the resource within the exclusive economic zones (EEZs)? In scenario 1, the blue whiting (Micromesistius poutassou) is harvestable in the EEZs of Norway, Iceland, the Faroe Islands, and the European Union (EU), as well as in the international waters of the Northeast Atlantic and the Norwegian Sea. The Barents Sea is a fringe area for the species, and there are no fisheries for blue whiting there. Hence, Russia is not regarded as a coastal state with respect to the blue whiting fishery. This severely weakens the stability of the coastal state agreement. In scenario 2, the area of distribution of the harvestable stock expands into the Russian EEZ, giving it status as a coastal state with respect to the resource and, thus, a partner in the management agreement. This secures the coastal state coalition the maximum attainable cooperative value and increases the likelihood of a stable coastal state agreement. [ABSTRACT FROM AUTHOR]

High-pressure technology is used as an alternative to heat processing because of its inactivating effect on microorganisms and enzymes. However, it can also alter the structure of other muscle proteins. The present study compares the effects of high pressure (300 MPa, 7°C, 20 min) on the proteolytic degradation and alterations in the myofibrillar proteins of sardine and blue whiting muscle. Also, muscle homogenates and enzyme extracts were pressurized in order to evaluate the high-pressure effects on unprotected proteolytic enzymes outside the whole muscle structure. Peak proteolytic activity was found to occur at 55°C in both species. The peak activity pH was pH 3 for the sardine and pH 8 for the blue whiting; the main enzyme families being aspartic proteases in the former and alkaline serine proteases in the latter. Pressurization lowered activity levels at the peak activity pH and temperature in the fish muscle (by 30.8% in the sardine and by 9.5% in the blue whiting) and also slightly in the enzyme extracts (by 16.8% in the sardine and by 19.4% in the blue whiting). The electrophoretic profiles disclosed higher protein degradation in the pressurized muscle. Overall, the observed changes in proteolytic activity can be attributed not only to the effect of high pressure on the enzymes, but also and mainly, to the effect on other muscle proteins. [ABSTRACT FROM AUTHOR]

Johnsen, E., and Godø, O. R. 2007. Diel variations in acoustic recordings of blue whiting (Micromesistius poutassou). – ICES Journal of Marine Science, 64: 1202–1209. Annual landings of blue whiting (Micromesistius poutassou) in the northeast Atlantic have exceeded 2 million metric tonnes in recent years, and overexploitation is an increasing concern in terms of the sustainability of the fishery. The most important fisheries-independent dataset used for tuning the analytical stock assessment comes from the Norwegian surveys of blue whiting west off the British Isles. The survey is carried out in March/April during peak spawning, and improving its quality will have a direct positive effect on stock assessment. Here, we analyse diel effects on the abundance and vertical distribution as recorded by acoustics in 1995 and 1996 and from 1998 to 2002, and evaluate the potential effects on the survey estimates. On average, the acoustic density of blue whiting was ∼20% higher by day than by night. However, the diel bias varied considerably among years, and surprisingly, the acoustic density in shallow water (<350 m) was in general highest at night, when the blue whiting were distributed higher in the water column and more dispersed. The span in the vertical depth range increased considerably with bottom depth in water shallower than 550 m. In deeper water, where blue whiting had little or no bottom association, the day–night differences in vertical distribution were smaller and not affected by bottom depth. The inconsistency of the diel effect from year to year negatively affects the time-series used during annual stock assessments. [ABSTRACT FROM PUBLISHER]

Abstract: Age based assessment forms the basis of management advice for the heavily exploited combined stock of blue whiting (Micromesistius poutassou) in the Northeast Atlantic. However, little historic attention has been given to the reliability of age estimates gathered from several nations involved in this assessment. Using recognised graphical and statistical approaches, bias and precision was investigated for experienced age-readers of blue whiting. Significant linear bias was found to exist between age-readers, with ages differing, on average, by 1 year for important year classes. Indications are that spawning checks and split rings affect the interpretation of annuli for some age-readers. An experience gradient became evident during the analysis; more experienced age-readers had greater levels of precision. Within reader precision was found to be higher than between reader precision; however, within reader bias was also evident with two out of three age-readers systematically revising ages downwards when re-ageing otoliths. Results indicate that differences exist on a limited international level for the age determination of blue whiting. This issue now needs to be addressed by the scientific community. [Copyright &y& Elsevier]

The blue whiting is the most important demersal species caught by the Spanish trawler fleet in the southern Bay of Biscay. Lesser spotted dogfish are not a commercial by-catch, and are discarded immediately after sorting. During 1994 the contents of 1094 dogfish stomachs were analysed. The results show that lesser spotted dogfish with a total length of >17 cm eat blue whiting throughout the year. The length range of blue whiting found in lesser spotted dogfish stomachs was similar to the length range discarded by the fishery. Blue whiting account for 20% of the stomach volume in lesser spotted dogfish 30–50 cm long. From the state of digestion of blue whiting prey, and the comparative analysis of the size distributions of blue whiting in lesser spotted dogfish stomachs and in the fishery, it appears that many of these blue whiting are discards, consumed when already dead or damaged. The impact of this supplementary food on lesser spotted dogfish abundance is discussed. [ABSTRACT FROM PUBLISHER]