© 2005 International Council for the Exploration of the Sea
Diets of herring, mackerel, and blue whiting in the Norwegian Sea in relation to Calanus finmarchicus distribution and temperature conditions
PINRO 6 Knipovich Street, 183763 Murmansk, Russia
*Correspondence to I. Prokopchuk: tel: +7 8152472464; fax: +7 8152473331. e-mail: irene_pr{at}pinro.ru.
Diets of Norwegian spring-spawning herring, mackerel, and blue whiting in the Norwegian Sea are investigated in relation to the distribution of plankton and hydrographic conditions. Fish stomachs and zooplankton samples were collected during summer (June and July) cruises in 2001 and 2002. Calanus finmarchicus was the principal prey of mackerel, accounting for 53–98% of total stomach content by weight. The diet composition of herring varied depending on feeding area and availability of food under various environmental conditions. C. finmarchicus was important prey for herring only in July 2001 (about 77% by weight) in the central part of the sea and in June 2002 (about 82% by weight) near the Lofotens. In July 2002 appendicularians (Oikopleura spp.), amphipods (mainly Parathemisto abissorum), and euphausiids were important in the diet of herring, and at some stations cannibalism was observed. The main prey of blue whiting were amphipods (10–34% by weight), appendicularians (11–34%), and euphausiids (8–47%), as they usually feed deep in the water column, though C. finmarchicus was important, particularly in June 2002, when blue whiting were caught in the upper layers of the sea. Higher water temperatures indirectly affect pelagic fish through accelerated development of their prey and favourable conditions for migration farther north.
Keywords: blue whiting, Calanus finmarchicus, diet, environmental conditions, herring, mackerel, Norwegian Sea
Received 1 July 2004; accepted 20 August 2005.
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Introduction |
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 Top Introduction Material and methodsResultsDiscussionConclusionReferences |
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Copepods dominate the zooplankton community of the Norwegian Sea, with Calanus finmarchicus (Gunnerus) being the most important species with regard to both abundance and biomass (Wiborg, 1955; Gruzov, 1963; Marshall and Orr, 1972; Aksnes and Blindheim, 1996; Gislason and Astthorsson, 1996; Hirche et al., 2001). C. finmarchicus is prey for such pelagic fish as Norwegian spring-spawning herring (Clupea harengus Linné), Atlantic mackerel (Scomberus scomberus Linné), and blue whiting (Micromesistus poutassou Norman). All three species undergo summer feeding migrations into the Norwegian Sea, with herring and mackerel feeding near the sea surface, and blue whiting generally feeding deeper in the water column. Herring have been hypothesized to adapt their feeding migrations according to the temporal development of C. finmarchicus (Østvedt, 1965; Corten, 2000; Kaartvedt, 2000), but it has also been suggested that herring distributions influence the timing and duration of the C. finmarchicus migrations, as well as their annual descent and ascent, and the number of generations per year (Kaartvedt, 1996, 2000).
Hydrographic conditions are thought to influence the initiation of feeding of pelagic fish species and their feeding duration, intensity, and area preferences. Temperature impacts fish directly by changing digestion rates, and indirectly by influencing prey development rates and distribution. Also, extremely high temperature anomalies can decrease zooplankton productivity, which leads to poor feeding conditions for fish (Wyszynski, 1989).
The purpose of this study is to identify the diet of herring, mackerel, and blue whiting in the Norwegian Sea, and to estimate the effects on diet of temperature conditions and prey availability, with special focus on C. finmarchicus.
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Material and methods |
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Data were collected during Russian surveys in the Norwegian Sea in June–July of 2001 and 2002. Hydrographic data were obtained using a CTD along standard sections and at trawl stations. Temperature anomalies were identified by comparing with the long-term (1951–2000) mean (Sentyabov et al., 2003).
Zooplankton data, collected by vertical hauls from 50 m to the sea surface using a Juday net (entrance diameter of 37 cm, mesh size of 180 µm), were taken simultaneously with hydrographic observations. Plankton samples were preserved in a 4% formaldehyde–seawater solution for later analysis. The total numbers of samples analysed were 159 in 2001 and 142 in 2002. Species composition of plankton and stage structure of C. finmarchicus were analysed at sea. Relative abundance indices of plankton organisms and different copepodid stages of C. finmarchicus were estimated (1 – single individuals in the sample, 2 – dozens, 3 – hundreds, 4 – thousands). The total biomass of plankton was also determined (wet weight ±0.1 g).
Herring, mackerel, and blue whiting were sampled simultaneously with pelagic trawls in the Norwegian Sea. Sampling of fish by trawl was generally once per day, but herring were sampled twice on 14 June 2001 and blue whiting twice on 6 July 2002. The trawl had a vertical opening of 45 m and the vessel speed was approximately 4.3 knots. The trawling time varied from 30 to 75 min and the trawling depth from 0 to 310 m. Occasionally, several depths were trawled at the same site. The number of fish stomachs removed for diet analysis per trawl ranged from 19 to 30. In total, 172 herring stomachs, 181 mackerel stomachs, and 478 blue whiting stomachs were analysed. The stomachs were preserved in 10% formaldehyde–seawater solution immediately following removal from the fish. At the PINRO laboratory, stomach contents were analysed using a binocular microscope. The consumed organisms were identified to species level if possible, then counted, measured, and weighed with an accuracy of 0.1 mg. C. finmarchicus were staged and the abundance of each stage was estimated. In order to characterize the fish diet, mean stomach fullness, average fat content, and the percentage of prey species in the bolus (by weight) were calculated. Mean stomach fullness was determined visually using the following scale: 0 – empty; 1 – very little content; 2 – some content; 3 – full, but not bloated; 4 – bloated; 5 – everted.
The stage structure and abundances of C. finmarchicus in the plankton samples taken at the same locations as the trawl stations during July 2002 were identified and counted, respectively, for comparison with the fish stomach data. At all other times, only the relative abundance index was determined for the plankton samples.
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Results |
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Hydrographic conditions
In 2001, temperatures in the Norwegian Sea in both the warm Norwegian Atlantic Current (NwAC) waters and the more offshore admixture of NwAC and East Icelandic Current (EIC) waters, hereafter called Mixed Waters, were close to their long-term means. Average temperatures of the upper 50 m layer in the NwAC were 8–9°C (Figure 1). In 2002, water temperatures in the Norwegian Sea were abnormally high, attaining more than 10°C in the NwAC (Figure 1), 1.5–2.0°C higher than the average throughout the region (Figure 2).
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Plankton
Copepods were the most abundant prey with C. finmarchicus, the dominant species, making up to 60–95% of the total number of zooplankton organisms. The spatial patterns of C. finmarchicus of different stages varied between 2001 and 2002. In 2001, C. finmarchicus nauplii were concentrated in the central Norwegian Sea (Figure 3A). Copepodid stages CI–III occurred in considerable quantities throughout much of the area (Figure 3B), while stages CIV–V were distributed mostly in the south and between 68°N and 70°N (Figure 3C). In 2002, highest concentrations of C. finmarchicus nauplii were in the south and off Lofoten (68–70°N 5–15°E; Figure 3E). The highest concentrations of stages CI–III were observed near the zero meridian and in the northeast, while stages CIV–V were most abundant in the northwest and southeast (Figure 3F, G). The relative abundance of C. finmarchicus CIV–V in 2002 was somewhat higher than in 2001. This was also true for C. finmarchicus females (Figure 3D, H).
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In 2001, zooplankton biomass concentrations
500 mg m–3 were observed over a large area, whereas in 2002 they were more limited to the northwest and southeast (Figure 4). Mean plankton biomass in 2001 and 2002 was 765 mg m–3 and 832 mg m–3, respectively. Plankton biomass in both years was dominated by C. finmarchicus stages CIV–V and to a lesser extent by mature individuals.
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The diet of pelagic fish
Herring
Food was found in 93% of the 172 herring stomachs analysed. Mean stomach fullness varied from 1.2 to 3.7 and the herring diet differed depending on area, month, and year (Table 1). C. finmarchicus, C. hyperboreus, and Pareuchaeta norvegica were identified among the various copepods in the herring stomachs. C. finmarchicus constituted
78% of the total prey by weight in the central Norwegian Sea in July 2001 and 82% in June 2002 near the Lofotens (Figure 5). Note that the following percentages are also by weight unless otherwise indicated. The amount of C. hyperboreus and P. norvegica in the diet was insignificant (
0.3%).
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In July 2001, herring fed mostly on C. finmarchicus stage CV (
45%) and females (stage CVI; 33%) (Figure 6A). In June 2002, C. finmarchicus CIV–V dominated the stomach contents (31% and 55%, respectively), but in July it was copepodid stages CIII–IV (55% and 23%; Figure 6B). While C. finmarchicus females were found in herring stomachs in both years, they were relatively more abundant in 2001 (33%) than in 2002 (3%; Figure 6A, B). Based on the 2002 data when stage abundances from both the stomach and plankton data were available, herring strongly select larger C. finmarchicus (Figure 6C).
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Appendicularians Oikopleura sp. (
21–41%), amphipods (9–28%), and euphausiids (6–59%) were also important prey for herring in July 2002 (Figure 5). Amphipods were Parathemisto abyssorum and P. libellula, of which the first species contributed an important proportion to the diet of herring but the second was found only very rarely and in insignificant proportions. Among euphausiids, two species were identified in the herring stomachs, Meganyctiphanes norvegica and Thysanoessa longicaudata, but the latter were rare. In July 2002, cannibalism was observed, with herring juveniles constituting 100% of total stomach content in one sample (Figure 5). Sebastes spp. dominated (80.9%) herring stomachs at another trawl site (Figure 5).
Mackerel
Of the 181 mackerel stomachs analysed, only one was empty. The mean stomach fullness was quite high (2.6), indicative of active feeding (Table 1). The average number of C. finmarchicus per mackerel stomach in 2001 was 6000 individuals during June but <1000 in July, while in 2002 the average number was 5000 individuals during June and 30 000 in July, (Figure 7). C. finmarchicus was the principal prey species accounting for 52–98% by weight of the stomach contents in 2001 and more in 2002 (Figure 8).
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In June 2001, in the southern Norwegian Sea near the Faroe Islands, the diet of mackerel also consisted of small copepods (Pseudocalanus elongatus, Oithona similis, Temora longicornis, Acartia clausi, juveniles of Metridia spp.), Cladocera (Evadne nordmanni and Podon leucarti) (
21%), and euphausiids (31%) (Figure 8). In 2002, mackerel fed almost exclusively on C. finmarchicus (Figure 8). Stages CIV–V and CII–III of C. finmarchicus occurred in the diet of mackerel in the middle and at the end of June 2001 (Figure 6D). In July 2001, the diet of mackerel consisted mainly of C. finmarchicus CIV–V and females (CVIf, Figure 6D). In June 2002, stages CV and females formed the highest percentage of the mackerel diet, while in July C. finmarchicus CIII–IV dominated (Figure 6E). In both June and July 2002, the percentage of older stages of C. finmarchicus was higher in the mackerel diet than in the plankton samples (Figure 6F, G).
The average fat content of mackerel in 2001 increased from 0.8 in June to 2.1 in July, but the mean stomach fullness decreased from 3.0 to 2.5, respectively. In 2002, the general proportion of C. finmarchicus in the mackerel diet increased from June to July, as respectively did the mean stomach fullness (from 2.3 to 2.8) and the fat content (from 1.9 to 2.2).
Blue whiting
Of the 478 blue whiting stomachs analysed, 92% contained food. The largest number of fish with empty stomachs was registered in 2001, increasing from June (8%) to July (25%) (Table 1). The mean stomach fullness varied from 2.1 to 2.5, respectively.
In June 2001, blue whiting fed mostly on C. finmarchicus (41%), euphausiids (25%), and juveniles of Parathemisto spp. (20%), but in July, appendicularians Oikopleura spp. (45%) were the most important diet component (Figure 9A). Large cold-water C. hyperboreus made up to 67% of the total food weight at one station in the northwestern Norwegian Sea in July, although generally its importance in the diet was insignificant (Figure 9A).
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In June 2002, C. finmarchicus constituted 97% of the stomach contents of the blue whiting caught in the upper 10 m layer. At depths of 200–240 m, blue whiting fed on adult euphausiids (46%), Parathemisto spp. (34%), and deepwater copepods of the genus Pareuchaeta (10%) (Figure 9B). In July C. finmarchicus constituted only
17% of the blue whiting diet, with juveniles of Parathemisto spp. (47%) and adults of euphausiids (35%) the principal prey species (Figure 9B). Only C. finmarchicus stage CV and females occurred in blue whiting stomachs (Figure 6H) although earlier stages were observed (Figure 6I). In 2001, the average number of C. finmarchicus per blue whiting stomach in June was nearly five times larger than in July.
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Discussion |
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TopIntroductionMaterial and methodsResultsDiscussionConclusionReferences |
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The period from the end of the 1990s to the beginning of the 2000s was characterized by continuous intensification of the advection of warm Atlantic waters into the Norwegian Sea and increasing water temperatures, with a maximum in 2002 (Figure 2). Summer temperatures in the central Norwegian Sea in 2001 and 2002 differed (Holst et al., 2001; ICES, 2002b), with the Atlantic water temperature in the upper 50 m in the central regions being 1°C higher in 2002 than in 2001, and in the east higher by more than 2°C (Figure 1).
The high abundances of nauplii and early copepodid stages of C. finmarchicus in both 2001 and 2002 suggest that the population was actively reproducing. Mature individuals were also numerous. Spawning times and the development rate of C. finmarchicus varied spatially in response to differences in hydrographic conditions. For example, spawning in the warmer southeast Norwegian Sea was over by June even though it was only just beginning in the colder waters in the northwest. Higher than normal temperatures during 2002 are thought to have led to the higher abundances of both nauplii and copepodid stages CIV–V. The higher abundance of older copepodid stages of C. finmarchicus during the survey 2002 is thought to be due to early spring spawning coupled with a faster developmental rate, which together resulted in better survival, perhaps due to reduced stage durations and hence lower predation. A second generation may also have contributed to the higher number of nauplii.
Different stage compositions of C. finmarchicus in plankton samples compared with that in the stomachs of herring, mackerel, and blue whiting suggests prey selectivity (Figure 6C, F, I). For instance, herring fed mainly on large over-wintered C. finmarchicus, consistent with earlier studies (Pavshtiks, 1956; Shaposhnikova, 1964; Melle et al., 1994; Dalpadado et al., 2000; Gislason and Astthorsson, 2002). Dalpadado et al. (1996, 2000), who also found that herring stomachs contained larger C. finmarchicus, assumed that the absence of small copepodites in the herring diet was caused by faster digestion. However, the absence of early copepodid stages of C. finmarchicus in the herring stomachs even during early stages of digestion in our study indicates that herring probably did not feed on these small individuals.
Shaposhnikova (1964) states that most of the herring population leaves the spawning grounds to feed, migrating gradually northwards from one prespawning C. finmarchicus concentration to another. This behaviour may explain the high percentage of larger C. finmarchicus in the diet of herring compared with mackerel, and gives herring a competitive advantage over mackerel and blue whiting through its earlier arrival in the feeding areas.
Higher water temperatures resulted in a very strong year class of herring in 2002, and their larvae and 0-group were distributed over vast areas of the Norwegian Sea. The large year class is believed to have contributed to the cannibalism. Herring are active predators that feed on their own larvae (Dalpadado et al., 2000), and when the C. finmarchicus population is reduced, consumption of herring juveniles will increase (Rudakova, 1966). Holst (1992) found that cannibalism can act as a major factor regulating the abundance of herring year classes in some coastal areas in north Norway, where the distribution of the 0-group overlaps with that of adult herring.
Mackerel typically feed on copepods, euphausiids, pteropods, arrow-worms, and fish during summer (Vinogradov, 1982; Mehl and Westgård, 1983). In our studies, C. finmarchicus was the principal prey species for mackerel. While there was feeding selectivity for older stages of C. finmarchicus in the mackerel diet, the stage structure was more similar to the distribution pattern observed in the plankton samples than for either herring or blue whiting (Figure 6C, F, I). In contrast to our results, Vinogradov (1981), in comparing the diet of pelagic fish species with the composition of prey species in the zooplankton, found that in most cases they were similar, but that the composition varied according to area and season. Differences in the composition of C. finmarchicus copepodid stages in plankton samples and in the mackerel stomachs may be caused by the feeding selectivity of mackerel and the patchiness of C. finmarchicus as well (Boldovskiy, 1941).
The decrease in the number of individuals in the mackerel stomachs from June to July 2001 was due to fewer early copepodid stages of C. finmarchicus in July. The general proportion by weight of C. finmarchicus in the mackerel diet in 2002 increased greatly from June to July. The increase in the fat content and a decrease in the mean stomach fullness suggest that mackerel feeding activity might decline with a higher condition level, as observed in 2001. In 2002 mackerel condition level was not high and, therefore, the fish continued feeding intensively.
C. finmarchicus is of less importance for blue whiting than herring and mackerel. Generally inhabiting deeper waters, blue whiting feed mostly on Euphausiacea, Hyperiidae, Appendicularia, Chaetognatha, and juvenile fish (Zilanov, 1964). Nevertheless, blue whiting can actively feed on C. finmarchicus especially if they are in large concentrations and feeding near the surface. Blue whiting feed on large C. finmarchicus only. There were more C. finmarchicus consumed in 2002 than in 2001, perhaps due to increased time in the surface layer during 2002. The maximum intensity of blue whiting feeding most often occurs in June and depends on the plankton organisms' development rate, which in turn is connected to hydrographic conditions (Plechanova and Soboleva, 1986; Plekhanova, 1990). Gerasimova and Plekhanova (1994) distinguished the areas where blue whiting feed on copepods in May–June. When feeding schools migrate farther north, copepods in the diet are replaced by hyperiids (in the west and northwest) and euphausiids (in the east).
The initiation of feeding migration of pelagic fish species and its duration is influenced by hydrographic conditions. The increased advection of warm Atlantic water by the Norwegian Current and high positive temperature anomalies in 2002 caused an early spring onset of C. finmarchicus development. As a consequence, the second generation of C. finmarchicus appeared earlier, and the number of young copepodid stages was high, resulting in poorer feeding conditions for herring, which prefer larger C. finmarchicus. In order for fish to find suitable food, e.g. large prespawning specimens of C. finmarchicus, they have to migrate farther north, outside the survey area. The regional difference in the seasonal development of the phytoplankton is reflected in the spawning time and the development of C. finmarchicus. The increased temperatures speed up the onset of the phytoplankton bloom and the development rates of C. finmarchicus, so fish can find appropriate food even in northern areas, where prespawning concentrations of C. finmarchicus form according to the rate of warming of the water.
In 2002 with abnormally warm conditions, mackerel were caught farther north than in previous years (ICES, 2003a, 2004). In June 2001, herring were rare, and in July only one trawl had sufficient herring for diet analysis. The sample was taken in the area of low concentration of herring, because most herring migrated far north (Holst et al., 2001). Low plankton biomass and the enormous year class of 1-group blue whiting in the southern and central Norwegian Sea favoured the extreme herring migration to the north in 2001 (Holst et al., 2001). In 2002, herring were distributed farther north than in the whole period of the recovery of the herring stock after its major stock collapse in the late 1960s (ICES, 2002a, 2003b; Morozova and Sentyabov, 2003). Analysing the different factors influencing the migration pattern of fish will be the aim of future investigations.
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Conclusion |
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TopIntroductionMaterial and methodsResultsDiscussionConclusionReferences |
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Herring, mackerel, and blue whiting undertake feeding migrations to the Norwegian Sea. Predation by these fish species on C. finmarchicus varied by month (June to July) and by year (2001–2002) depending on fish behaviour, their feeding preferences, and environmental conditions. Herring migrate gradually northwards from one prespawning C. finmarchicus concentration to another, and their early start gives them a competitive feeding advantage over the later migrating mackerel and blue whiting. Herring mostly select large and mature C. finmarchicus, so may affect the reproductive potential of C. finmarchicus. Mackerel feed in the upper layers of the ocean. The stage structure of C. finmarchicus in the mackerel diet was more similar to the distribution pattern of C. finmarchicus stages, but still showed some selectivity for older stages. Blue whiting reside in deeper water and C. finmarchicus are less important in their diet than in that of herring and mackerel. Blue whiting mainly feed on euphausiids, hyperiids, and other prey. However, blue whiting consumption on the deep over-wintering stock of C. finmarchicus may influence zooplankton population abundance in the following year. Higher water temperatures indirectly affect pelagic fish through accelerated development of their prey, and favourable conditions for migration farther north.
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Acknowledgements |
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We thank Olga Gerasimova for help in processing the fish stomachs and useful advice.
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References |
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Aksnes D. and Blindheim J. (1996) Circulation patterns in the North Atlantic and possible impact on population dynamics of Calanus finmarchicus. Ophelia 44:7–28.[Web of Science]
Boldovskiy G.B. (1941) The food and diet of herring of the Barents Sea. Trudy PINRO 7:219–286 (in Russian).
Corten A. (2000) A possible adaptation of herring feeding migrations to a change in timing of the Calanus finmarchicus season in the eastern North Sea. ICES Journal of Marine Science 57:1261–1270.[CrossRef][Web of Science]
Dalpadado P., Ellertsen B., Melle W., Dommasnes A. (2000) Food and feeding conditions of Norwegian spring-spawning herring (Clupea harengus) through its feeding migrations. ICES Journal of Marine Science 57:843–857.
Dalpadado P., Melle W., Ellertsen B., Dommasnes A. (1996) Food and feeding conditions of Clupea harengus in the Norwegian Sea. ICES CM 1996/L:20. 33 pp.
Gerasimova O. V. and Plekhanova N. V. (1994) Distribution of forage zooplankton and spatial structure of the trophic relations between blue whiting and mackerel in the Norwegian Sea. Report of PINRO Research in 1993, Murmansk: 129–143 (in Russian).
Gislason A. and Astthorsson O.S. (1996) Seasonal development of Calanus finmarchicus along an inshore–offshore gradient southwest of Iceland. Ophelia 44:71–84.[Web of Science]
Gislason A. and Astthorsson O.S. (2002) The food of Norwegian spring-spawning herring in the western Norwegian Sea in relation to the annual cycle of zooplankton. Sarsia 87:236–247.[CrossRef][Web of Science]
Gruzov L. N. (1963) The main patterns of seasonal development of zooplankton in different areas of the Norwegian Sea. AtlantNIRO, Kaliningrad. 5–30 (in Russian).
Hirche H-J., Brey T., Niehoff B. (2001) A high frequency time series at Ocean Ship Station M (Norwegian Sea): population dynamics of Calanus finmarchicus. Marine Ecology Progress Series 219:205–219.[Web of Science]
Holst J. C. (1992) Cannibalism as a factor regulating year class strength in the Norwegian spring-spawning herring stock. ICES CM 1992/H:14. 10 pp.
Holst J. C., Couperus B., Gudmundsdottir A., Hammer C., Jacobsen J. A., Krysov A., Melle W., Kaartvedt S. (2001) Report on surveys of the distribution, abundance and migrations of the Norwegian spring-spawning herring, other pelagic fish and the environment of the Norwegian Sea and adjacent waters in late winter, spring and summer of 2001. ICES CM 2001/D:07. 55 pp.
ICES. (2002a) Report of the northern pelagic and blue whiting fisheries working group. ICES CM 2002/ACFM:19. 304 pp.
ICES. (2002b) Report of the planning group on surveys on pelagic fish in the Norwegian Sea 2002. ICES CM 2002/D:07. 68 pp.
ICES. (2003a) Report of the working group on the assessment of mackerel, horse mackerel, sardine, and anchovy. ICES CM 2003/ACFM:07. 482 pp.
ICES. (2003b) Report of the northern pelagic and blue whiting fisheries working group. ICES CM/ACFM:23. 246 pp.
ICES. (2004) Report of the working group on the assessment of mackerel, horse mackerel, sardine and anchovy. ICES CM 2004/ACFM:08. 493 pp.
Kaartvedt S. (1996) Habitat preference during overwintering and timing of seasonal vertical migration of Calanus finmarchicus. Ophelia 44:145–156.[Web of Science]
Kaartvedt S. (2000) Life history of Calanus finmarchicus in the Norwegian Sea in relation to planktivorous fish. ICES Journal of Marine Science 57:1819–1824.
Marshall S.M. and Orr A.P. (1972) The Biology of a Marine Copepod, Calanus finmarchicus Gunnerus(Oliver and Boyd, Edinburgh) 195 pp.
Mehl S. and Westgård T. (1983) The diet and consumption of mackerel in the North Sea. ICES CM 1983/H:34. 30 pp.
Melle W., Røttingen I., Skjoldal H-R. (1994) Feeding and migration of Norwegian spring spawning herring in the Norwegian Sea. ICES Document CM 1994/R: 9. 25 pp.
Morozova G. and Sentyabov E. (2003) The Atlas of Herring Fishery in the Norwegian Sea in 1995–2001(PINRO Press, Murmansk) 127 pp. (in Russian).
Østvedt O.J. (1965) The migration of Norwegian herring to Icelandic waters and the environmental conditions in May–June, 1961–1964. Reports of Norwegian Fishery and Marine Investigations 13:29–47.
Pavshtiks E.A. (1956) Seasonal changes of plankton and feeding migrations of herring. Trudy PINRO 9:93–123 (in Russian).
Plekhanova N. V. (1990) The conditions of blue whiting feeding in the Norwegian Sea in the spring–summer period 1980–1987. Biology and Fisheries of the Norwegian Spring Spawning Herring and Blue Whiting in the Northeast Atlantic. Proceedings of the 4th Soviet–Norwegian Symposium pp. 400–419.
Plechanova N. V. and Soboleva M. S. (1986) Feeding conditions and nutrition features of the Norwegian Sea blue whiting in summer 1981/1982. ICES CM 1986/H:34. 12 pp.
Rudakova V.A. (1966) The conditions and main feeding pattern of Atlanto-Scandian herring (Clupea harengus harengus L.) in the Norwegian Sea (1951–1962). Trudy PINRO 17:5–53 (in Russian).
Sentyabov E., Borovkov V., Plekhanova N., Krysov A. (2003) Hydrographic conditions in the Norwegian Sea in the 1990s and their influence on plankton status and Atlanto-Scandian herring migrations. ICES Marine Science Symposia 219:443–446.
Shaposhnikova G.H. (1964) The pattern of fish distribution depending on feeding and diet. Diet of Marine Commercial Fish(Nauka, Moscow) pp. 3–94 (in Russian).
Vinogradov V.I. (1981) Daily rhythms and diet of abundant pelagic fish species in shallow waters of the Nantucket Island (New England) in summer. The Biology of the Sea 3:22–27 (in Russian).
Vinogradov V.I. (1982) Seasonal and annual dynamics of the diet and feeding intensity of Atlantic Mackerel (Scomber scombrus) on plankton prey species in the Northwest Atlantic in 1971–1974. Trudy AtlantNIRO 45–51 (in Russian).
Wiborg K.F. (1955) Zooplankton in relation to hydrography in the Norwegian Sea. Report on Norwegian Fishery Marine Investigations 11:1–66.
Wyszynski M. (1989) The influence of thermal conditions on the biology of herring (Clupea harengus membras L.) in the central Baltic. Rapports et Procès-verbaux des Réunions du Conseil International pour l'Exploration de la Mer 190:173–177.
Zilanov V. K. (1964) On food competition of blue whiting and herring in the Norwegian Sea. The Materials of Fisheries Research in the Northern Basin 4:45–48 (in Russian).
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