Norwegian Coastal Cod Research Articles

Extreme male-skewed sex ratios on spawning grounds for Atlantic cod Gadus morhua with typical coastal cod signatures of the Pan I (pantophysin) locus

Large offshore and small inshore populations of Atlantic cod Gadus morhua L. display differences in migratory patterns and settling regimes, but little is known about possible differences in spawning behaviour. Cod presumably of the Norwegian coastal cod type were therefore sampled during 7 spawning seasons (2002�2013) in Malangen, northern Norway. A spawning site in neighbouring Balsfjord was sampled during 5 consecutive spawning seasons (2002�2006). Length, weight, sex and maturity stage were recorded for each individual fish (n = 995). To verify their population assignment, frequencies of the 2 different Pan I (pantophysin) alleles were measured in 6 sampling years in Malangen and 3 in Balsfjord (n = 728). During all sur- vey years there was an extreme skewed sex ratio at the spawning sites. In 6 of 7 seasons in Malan- gen, 8-9 of 10 fish were males, and in Balsfjord 9 of 10 fish were males on average, indicating some form of lekking behaviour among the spawning fish. Average size of the fish varied among years and also between sexes in individual years, although not consistently. The smallest proportion of mature fish was seen in Malangen in the year with the earliest sampling date (23 February). This was also the sample with the least skewed sex ratio (6.5 of 10 fish were males). The frequency of the Pan I A allele of the Malangen cod was highly stable among years at close to 90%, showing that this spawning ground is exclusively used by coastal cod. In Balsfjord, frequencies of the Pan I A allele were lower (67�78%). This fjord is suggested to be more penetrable for the migratory NE Arctic cod with their high frequencies of the Pan I B allele, making it a less exclusively coastal cod residence. In both fjords, length of mature males but not females varied among the Pan I genotypes.

Ocean acidification may aggravate social-ecological trade-offs in coastal fisheries.

Ocean Acidification (OA) will influence marine ecosystems by changing species abundance and composition. Major effects are described for calcifying organisms, which are significantly impacted by decreasing pH values. Direct effects on commercially important fish are less well studied. The early life stages of fish populations often lack internal regulatory mechanisms to withstand the effects of abnormal pH. Negative effects can be expected on growth, survival, and recruitment success. Here we study Norwegian coastal cod, one of the few stocks where such a negative effect was experimentally quantified, and develop a framework for coupling experimental data on OA effects to ecological-economic fisheries models. In this paper, we scale the observed physiological responses to the population level by using the experimentally determined mortality rates as part of the stock-recruitment relationship. We then use an ecological-economic optimization model, to explore the potential effect of rising CO2 concentration on ecological (stock size), economic (profits), consumer-related (harvest) and social (employment) indicators, with scenarios ranging from present day conditions up to extreme acidification. Under the assumptions of our model, yields and profits could largely be maintained under moderate OA by adapting future fishing mortality (and related effort) to changes owing to altered pH. This adaptation comes at the costs of reduced stock size and employment, however. Explicitly visualizing these ecological, economic and social tradeoffs will help in defining realistic future objectives. Our results can be generalized to any stressor (or stressor combination), which is decreasing recruitment success. The main findings of an aggravation of trade-offs will remain valid. This seems to be of special relevance for coastal stocks with limited options for migration to avoid unfavorable future conditions and subsequently for coastal fisheries, which are often small scale local fisheries with limited operational ranges.

Linking tagging technology and molecular genetics to gain insight in the spatial dynamics of two stocks of cod in Northeast Atlantic waters

The Northeast Arctic cod (Gadus morhua L.: NEAC) remains the most abundant cod stock in the North Atlantic, while the catches of the partially co-occurring Norwegian coastal cod (NCC) stocks have dramatically decreased in recent years. To ensure effective management of the two stocks, it is necessary to know if the population genetic structure is associated with any pattern in the spatial dynamics or whether it is affected by any distinct environmental factors. By combining information from electronic data storage tags (DST) and molecular genetics methods with statistical tools, we have been able to associate spatial dynamics and distinct environmental factors to the two cod stocks. In general, adult NEAC migrate between deep, warm overwintering grounds and shallow summer feeding grounds where water temperatures maybe low. In contrast, NCC do not undertake large-scale seasonal migrations, show little seasonal variation in depth distribution, and experience the opposite seasonal change in temperature compared with NEAC. However, within the NCC group, some individuals did conduct longer horizontal movements than others. Even though the distances calculated in this study represent the shortest distance between release and recapture positions, they are far higher than previously reported by NCC. Distinctive depth profiles indicate that this migrant NCC have moved out of the area, passing the deep trenches outside Lofoten while more stationary NCC occupies shallower depths throughout the year. The temperature profiles also indicate that migrant and stationary NCC has occupied different areas during the year. We demonstrate that the combination of information from DSTs and molecular genetics offers a deeper understanding of individual cod behaviour, provides an insight in the spatial dynamics of the species, and ultimately, improves the scientific basis for management of a complex mixed fishery of Atlantic cod.

Modelling dispersal of eggs and quantifying connectivity among Norwegian coastal cod subpopulations

Abstract The Norwegian coast is populated by two cod populations: Northeast Arctic cod and Norwegian Coastal cod. In this paper, we use a further division based on life history: oceanic cod, coastal cod, and fjord cod. A numerical ocean model was implemented for the northern Norwegian coast where all these populations have spawning areas. The model results were used to simulate connectivity and retention of cod eggs from the different subpopulations. The model reproduced the observed variability and mesoscale activity in the Norwegian Coastal Current. Eggs released at an oceanic spawning area were transported northwards along the coastline. Coastal cod eggs had intermediate connectivity with each other and fjord cod eggs had high local retention. Although the high retention of eggs in fjord areas is mainly caused by a subsurface distribution of eggs, the intermediate retention of eggs from coastal spawning areas is caused by small-scale eddies in-between many small islands. The high-resolution ocean model made it possible to reveal these specific dispersal patterns. The high retention of early life stages in fjords combined with strong homing to spawning areas indicates that fjord subpopulations may be described as a metapopulation.

Settling-depth vs. genotype and size vs. genotype correlations at the Pan I locus in 0-group Atlantic cod Gadus morhua

We sampled 0-group juvenile Atlantic cod Gadus morhua L. within fjords and off- shore in northern Norway from 1994 to 2008 using different gears for the 3 sampling depths: shore seine (0�3 m), pelagic trawl (various depths), and bottom trawl (>80 m). Frequencies of alleles at the Pan I locus (4218 fish analysed) showed highly significant differences among samples col- lected in the different habitats. The Pan I A allele showed a mean frequency of ~80% in the shore seine samples, 12% in the bottom trawl samples, and between 5 and 57% in the pelagic samples. These differences are thought to reflect the co-occurrence of different populations of cod in the area with different settling regimes. Shallow-water settlers are thought to represent the stationary Norwegian coastal cod (NCC), the deep-water settlers represent the migratory Arcto-Norwegian cod (ANC), and the non-settled individuals represent a variable mixture of the 2 populations. For designated samples, we analyzed 16 microsatellites (non-neutral and neutral) that supported a genetic divergence between shallow-water and deep-water settlers. Correlations between length and Pan I genotypes within selected samples showed that the Pan I BB homozygotes (typical of ANC) were significantly longer than the Pan I AA homozygotes (typical of NCC). This could reflect differences in spawning time and growth conditions between ANC and NCC, just as well as one genotype being superior to the others in terms of growth performance. Finally, we argue that the Pan I difference between 0-group NCC and ANC is not caused by contemporary selection but reflects adaptation on an ecological post-glacial time scale.

Population connectivity among migratory and stationary cod Gadus morhua in the Northeast Atlantic—A review of 80 years of study

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 435:269-283 (2011) - DOI: https://doi.org/10.3354/meps09232 REVIEW Population connectivity among migratory and stationary cod Gadus morhua in the Northeast Atlantic—A review of 80 years of study Jarle Tryti Nordeide1,*, Steinar D. Johansen1,2, Tor Erik Jørgensen1, Bård Ove Karlsen1,2, Truls Moum1 1Marine Genomics Research Group, Faculty of Biosciences and Aquaculture, University of Nordland, 8049 Bodø, Norway 2Department of Medical Biology, Faculty of Health Sciences, University of Tromsø, 9037 Tromsø, Norway *Email: jarle.nordeide@uin.no ABSTRACT: The population structure of Atlantic cod Gadus morhua L. in the Barents Sea and in fjords and coastal waters in Norway and northwestern Russia has been a controversial subject since the 1930s. Eight decades of scientific inquiry have compared migratory NE Arctic (NA) and stationary Norwegian and Russian coastal cod (NC). At one extreme the existence of 2 non-interbreeding groups is advocated, whereas others find support for low genetic differentiation due to substantial gene flow, with geographical distance being the limiting factor. We review studies of a wide range of phenotypic (e.g. growth, maturation, counts of vertebrae) and polymorphic genetic markers (e.g. allozymes, mtDNA, microsatellites, single nucleotide polymorphisms). Regardless of whether or not the observed differences have a genetic basis, 70% of the 54 reviewed papers conclude that NA and NC differ with respect to the characters studied. However, few papers remain after exclusion of those relying on characteristics or markers that are generally agreed to be subject to selection and therefore less suited to assessing population connectivity. The lack of studies examining the potential influence of environments on growth of annual zones in otoliths is surprising, since otoliths are used to categorize specimens in managing the NA and NC and in scientific papers. We conclude that it is still an open question whether NA and NC effectively make up 1 large population or >1 non-interbreeding ‘groups’. As next-generation sequencing technology transforms ‘population genetics’ into ‘population genomics’, we will move towards a better understanding of differentiation among fish populations. KEY WORDS: Cod · Population genetics · Gadus morhua · NE Atlantic · Selection · Non-neutral loci Full text in pdf format PreviousNextCite this article as: Nordeide JT, Johansen SD, Jørgensen TE, Karlsen BO, Moum T (2011) Population connectivity among migratory and stationary cod Gadus morhua in the Northeast Atlantic—A review of 80 years of study. Mar Ecol Prog Ser 435:269-283. https://doi.org/10.3354/meps09232 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 435. Online publication date: August 22, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Probability-based surveying using self-sampling to estimate catch and effort in Norway's coastal tourist fishery

Abstract Vølstad, J. H., Korsbrekke, K., Nedreaas, K. H., Nilsen, M., Nilsson, G. N., Pennington, M., Subbey, S., and Wienerroither, R. 2011. Probability-based surveying using self-sampling to estimate catch and effort in Norway's coastal tourist fishery. – ICES Journal of Marine Science, 68: 1785–1791. Recreational fishing as a tourist activity has become an increasingly important part of the Norwegian travel industry and may contribute significantly to the fishing mortality on Norwegian coastal cod (Gadus morhua). Quantifying catches in the tourist fishery is made difficult by Norway's intricate and long coastline, and the lack of a fishing licence system, a registry of businesses catering for fishing tourists, and a registry of charter boats. A probability-based survey was used to estimate annual catch and effort by boat for anglers associated with 445 tourist-fishing businesses during 2009. From a stratified random sample of businesses, fishing tourists were recruited systematically over time to record their daily catch and effort in diaries. Cod dominated the reported landed catch (harvest) north of 62°N, and saithe and mackerel dominated south of 62°N. The estimated total landed catch of all species taken by tourist fishers in the business sector during 2009 was 3335 t (relative standard error, RSE = 17%), of which 1613 t (RSE = 22%) were cod. It is concluded that surveys based on self-sampling can yield accurate estimates of catch and effort accounted for by the business sector of the Norwegian tourist fishery and that the tourist catch of coastal cod is insignificant compared with the commercial and recreational catch by local residents.

High-latitude climate variability and its effect on fisheries resources as revealed by fossil cod otoliths

Abstract Geffen, A. J., Høie, H., Folkvord, A., Hufthammer, A. K., Andersson, C., Ninnemann, U., Pedersen, R. B., and Nedreaas, K. 2011. High-latitude climate variability and its effect on fisheries resources as revealed by fossil cod otoliths. – ICES Journal of Marine Science, 68: 1081–1089. Cod (Gadus morhua) otoliths from archaeological sites in northern Norway were analysed to reconstruct the temperature regime and determine the age structure, growth, and population identity of the fish harvested. Otoliths were selected from late- and post-medieval sites (700–300 years ago) to evaluate historical changes in the geographic region that matches the present-day stocks of Northeast Arctic cod (NEAC) and Norwegian coastal cod (NCC). Seasonal temperature cycles were reconstructed from stable isotope (δ18O) measurements along transects representing fish ages 1.5–3 years old. Reconstructions of the size, age, and growth characteristics of individual fish were based on otolith growth increments. The geographical source and stock identity of the individuals were estimated based on otolith elemental composition and otolith growth features. Both NCC and NEAC fish were represented at Måsøy and Vanna. The results indicate that fishing at Vanna exploited NEAC during their spawning migration, compared with fishing at Måsøy, which was restricted to more coastal fish. Fish growth patterns appeared to be affected by changes in the temperature regimes as estimated from otolith δ18O and back-calculated fish length-at-age, with evident differences between pre- and post-1600 periods.

Bromine patterns in Norwegian coastal Cod otoliths—a possible marker for distinguishing stocks?

Bromine was found to accumulate in otoliths of Norwegian coastal Cod Gadus morhua that were reared under known conditions. Despite the fact that the Cod were moved from one rearing environment to another, causing marked changes in some otolith elemental concentrations, bromine appeared to accumulate continuously along certain growth axes as revealed by 2-D elemental mapping. In contrast, North Sea and Baltic Sea Cod showed little to no patterning in Br. We suggest that Br uptake in otoliths may be under physiological and genetic control, and as such, may prove useful as a stock identification tool.

Spatiotemporal distribution of coastal and oceanic Atlantic cod Gadus morhua sub-groups after escape from a farm

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 1:11-19 (2010) - DOI: https://doi.org/10.3354/aei00003 Spatiotemporal distribution of coastal and oceanic Atlantic cod Gadus morhua sub-groups after escape from a farm Ingebrigt Uglem1,*, Pål Arne Bjørn2, Hiromichi Mitamura3, Rune Nilsen2 1Norwegian Institute of Nature Research, Tungasletta 2, 7485 Trondheim, Norway 2Nofima Marin, Muninbakken 9-13, PO Box 6122, 9291 Tromsø, Norway 3Graduate School of Informatics, Kyoto University, Kyoto 606-8501, Japan *Email: ingebrigt.uglem@nina.no ABSTRACT: Little is known about how escaped farmed Atlantic cod Gadus morhua L. affect the environment, but the potential for negative ecological consequences might be significant. In this study, the movements of adult farmed north-east Arctic cod (NEAC) and Norwegian coastal cod (NCC) were mapped after a simulated escape from an aquaculture farm to evaluate if post-escape movements and potential for recapture differs between these 2 genotypes. There was no major difference between NEAC and NCC equipped with acoustic transmitters with respect to spatiotemporal distribution or swimming depth during a 10 wk period after simulated escape incidents. The tagged cod immediately descended to average depths <20 m, and subsequently were most frequently observed along the shore. A substantial proportion of the farmed cod released at the cod farm left within the first week, while cod released at a nearby mussel farm were attracted to the cod farm. Beyond Week 2, the fish detected at the cod farm consisted of approximately similar proportions of fish released at either the mussel or cod farm. One third of the tagged cod was recaptured in local small-scale commercial and recreational fisheries during the first 3 wk after release. Thus, our results indicate that organised recapture fishery is a realistic option for reducing possible ecological and genetic impacts of escaped farmed cod. Such fishery must, however, be initiated as soon as possible after an escape incident and there is a need for development of a methodology for rapid detection and efficient recapture of escapees. KEY WORDS: Atlantic cod · Gadus morhua · Aquaculture · Fish escape · Recapture Full text in pdf format PreviousNextCite this article as: Uglem I, Bjørn PA, Mitamura H, Nilsen R (2010) Spatiotemporal distribution of coastal and oceanic Atlantic cod Gadus morhua sub-groups after escape from a farm. Aquacult Environ Interact 1:11-19. https://doi.org/10.3354/aei00003 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 1, No. 1. Online publication date: April 29, 2010 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2010 Inter-Research.

Heritability of resistance to viral nervous necrosis in Atlantic cod ( Gadus morhua L .)

Nodavirus are the causative agents of viral nervous necrosis (VNN), and has been shown to cause mortality in numerous fish species worldwide, among them is the Atlantic cod ( Gadus morhua L .). In this study, heritability of VNN resistance in Atlantic cod was estimated through challenge testing of 50 large full sib families (∼ 94 fish per family) comprising two genetically distinct groups of Atlantic cod (Norwegian coastal cod and northeast Arctic cod) and their F1 crossbreds. The overall survival (dead/alive) at end of test was 30%, but coastal cod had considerably higher survival (56%) than northeast Arctic cod (10%), while the F 1 cross was intermediate (31%). Furthermore, enormous variation in family survival was observed within each group (17 to 82% for coastal cod, 0 to 42% for northeast Arctic cod and 0 to 92% for the F 1 cross). As a consequence, the estimated within-strain heritability of survival under challenge testing was extremely high (0.75 ± 0.11 on the underlying scale and 0.43 ± 0.07 on the observable scale). Common environmental effects of full-sib families were not significant in addition to additive genetic effects, but the data structure was not optimal for distinguishing these effects.

13C NMR as a tool for authentication of different gadoid fish species with emphasis on phospholipid profiles

The aim of this study was to evaluate if phospholipid profiles obtained by 13C nuclear magnetic resonance (NMR) spectroscopy is characteristic enough to separate species of lean gadoid fish. 13C NMR data were obtained from muscle lipids of five categories of lean gadoid fish, namely, north-east arctic cod and Norwegian coastal cod ( Gadus morhua), haddock ( Melanogrammus aeglifinus), saithe ( Pollachius virens), and pollack ( P. pollachius). A total of 27 fish caught at the same location on the Norwegian coast in the traditional fishing season (March/April) in 2006 were analysed. The sn-2 position specificity of 22:6n-3 (docosahexaenoic acid, DHA) in phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) for the different species/stocks were investigated, and the full 13C NMR spectra applied in multivariate analysis. Stereospecific distribution calculations showed significant differences among species in the distribution of 22:6n-3 in PC and PE, and the pollack group displayed the lowest values for 22:6n-3 in sn-2 position, both in PC and PE. This first screening showed that by using the 13C NMR fingerprint of muscle lipids, linear discriminant analysis gave a correct classification rate of 78% according to the five categories of lean gadoid fish, while successful classification (100%) was achieved with Bayesian belief networks (BBN) predictions.

A common garden experiment with larval Northeast Arctic and Norwegian coastal cod cohorts in replicated mesocosms

Abstract A replicated mesocosm experiment was carried out to evaluate differential effects of feeding conditions for larval Northeast Arctic (NA) cod and Norwegian coastal (NC) cod. The two populations were (1) reared together with a 6-day older NA cohort (mixed) in high (HC) and low prey concentration (LC; 2000 and 200 prey/L initially), and (2) reared separately in HC treatments (non-mixed) to be able to evaluate both the effect of feeding conditions and possible effects of size interaction within mesocosms. The larvae were fed natural zooplankton, and the two stocks were identified in the mixed mesocosms by otolith marking. NA larvae hatched at a larger size, had higher growth rates, and survived better than NC larvae in both mixed and non-mixed mesocosms in the HC treatment. The second cohort clearly survived better in the non-mixed than in the mixed mesocosms, indicating the presence of an interaction effect before cannibalism could occur. We found a significant higher weight-at-length between NC and NA larvae (

Escape-related behaviour of Atlantic cod,Gadus morhuaL., in a simulated farm situation

Cultured fish escaping from farms represent an economic loss as well as a potential problem for wild fish populations. This study investigated the escape-related behaviour of farmed Norwegian coastal and northeast Arctic cod (NEAC), Gadus morhua L. Six groups of fish were observed during three replicate trials in a large tank that was split into two equal parts by a net wall. The fish could move freely through an opening in the net during the trials. Three groups were not fed during the trials. The first escape occurred shortly after producing the net opening (11±10.5 min; mean±standard deviation). Norwegian coastal cod were more prone to escape than the NEAC. A starvation period of 9 days increased the number of fish on the escape side of the tank. Net biting and net inspection by the fish were frequently observed, irrespective of whether the fish were fed or not. The same fish were repeatedly found on the escape side of the tank, but the propensity for recurrent escape behaviour was not related to genotype, feeding status or size. The results suggest that other factors, such as individual variation in boldness or exploration behaviour, could affect the willingness to escape.

Buoyancy and vertical distribution of Norwegian coastal cod (Gadus morhua) eggs from different areas along the coast

Abstract Stenevik, E. K., Sundby, S., and Agnalt, A. L. 2008. Buoyancy and vertical distribution of Norwegian coastal cod (Gadus morhua) eggs from different areas along the coast. – ICES Journal of Marine Science, 65: 1198–1202. There are significant genetic differences in coastal cod (Gadus morhua) along the Norwegian coast, and in order to maintain these differences, there must be mechanisms that ensure local retention of eggs and larvae in the spawning areas. The buoyancy of eggs from four different areas along the Norwegian coast was measured using a density gradient column, and the results from modelling experiments showed that in three of the groups (Tysfjord, Helgeland, and Øygarden), the buoyancy in combination with local hydrography would place the eggs in subsurface waters where retention is greater than in surface waters.

Feeding of mature cod (Gadus morhua) on the spawning grounds in Lofoten

Abstract Michalsen, K., Johannesen, E., and Bogstad, B. 2008. Feeding of mature cod (Gadus morhua) on the spawning grounds in Lofoten. – ICES Journal of Marine Science, 65: 571–580. Many authors state that cod (Gadus morhua) do not feed during the spawning period. However, this more or less established fact has rarely been investigated in the field. Here, the content of stomachs from Northeast Arctic cod (NEAC) and Norwegian coastal cod (NCC) sampled from the spawning ground in Lofoten were examined over a 10-year period (1996–2006). The occurrence of food in the stomachs of spawning cod, stomach fullness, diet composition, and variation in these variables between NEAC and NCC, year, and sex were analysed and compared. The analysis shows that cod do feed, even when they are in a spawning state. NCC had a lower proportion of empty stomachs and the stomachs were fuller than those from NEAC. Females had a lower proportion of empty stomachs than males and their stomachs were in general fuller. Herring (Clupea harengus) dominated the diet of cod. However, cod consumption of herring on the spawning grounds seems to be a minor source of mortality on herring. Although spawning cod do feed, the proportion of empty stomachs was higher and stomach fullness was lower than in stomachs of NEAC from the Barents Sea.

Identification and characterisation of novel SNP markers in Atlantic cod: Evidence for directional selection

BackgroundThe Atlantic cod (Gadus morhua) is a groundfish of great economic value in fisheries and an emerging species in aquaculture. Genetic markers are needed to identify wild stocks in order to ensure sustainable management, and for marker-assisted selection and pedigree determination in aquaculture. Here, we report on the development and evaluation of a large number of Single Nucleotide Polymorphism (SNP) markers from the alignment of Expressed Sequence Tag (EST) sequences in Atlantic cod. We also present basic population parameters of the SNPs in samples of North-East Arctic cod and Norwegian coastal cod obtained from three different localities, and test for SNPs that may have been targeted by natural selection.ResultsA total of 17,056 EST sequences were used to find 724 putative SNPs, from which 318 segregating SNPs were isolated. The SNPs were tested on Atlantic cod from four different sites, comprising both North-East Arctic cod (NEAC) and Norwegian coastal cod (NCC). The average heterozygosity of the SNPs was 0.25 and the average minor allele frequency was 0.18. FST values were highly variable, with the majority of SNPs displaying very little differentiation while others had FST values as high as 0.83. The FST values of 29 SNPs were found to be larger than expected under a strictly neutral model, suggesting that these loci are, or have been, influenced by natural selection. For the majority of these outlier SNPs, allele frequencies in a northern sample of NCC were intermediate between allele frequencies in a southern sample of NCC and a sample of NEAC, indicating a cline in allele frequencies similar to that found at the Pantophysin I locus.ConclusionThe SNP markers presented here are powerful tools for future genetics work related to management and aquaculture. In particular, some SNPs exhibiting high levels of population divergence have potential to significantly enhance studies on the population structure of Atlantic cod.

Explaining noncompliance in the Norwegian coastal cod fishery: an application of the multinomial logit

Establishing motive is central to the analysis of criminal behaviour. This article analyses the range of motives for noncompliant behaviour among coastal cod fishermen. A multinomial logit model is employed to analyse the reasons that underlie various motives. The four motives compared in this study are economic, technological and social and motives caused by bureaucracy and legitimacy problems. The economic motive is found to be most important for coastal fishermen. However, the cross-sectional data indicate that motives vary with fishing gear, vessel length and fishermen's age. The results indicate that identifying motives for noncompliant behaviour is not straightforward but is important for reducing the extent of infringements of the regulations. Fishermen who use gill net, seine and long line, for example, are more often motivated to noncompliance by technical problems and bureaucracy than hand-jig fishers. The study suggests that in order to prevent noncompliance behaviour, the authorities’ management policy should be designed to address the problems encountered by different categories of fishers. For example, offences that are committed because of technical problems should be resolved by increasing the involvement of fishermen in the process of drawing up regulations, whereas offences motivated by economic factors should be reduced by increasing inspections.

Separation of Norwegian coastal cod and Northeast Arctic cod by outer otolith shape analysis

For stock assessment purposes, Atlantic cod ( Gadus morhua) from the coastal and offshore regions off northern Norway is usually allocated to Norwegian coastal cod (NCC) or Northeast Arctic cod (NEAC) by internal morphological features of their otoliths. As this classification is subject to individual interpretation by otolith age readers, this study investigated an alternative objective approach for the separation of the two cod groups, using otolith shape analysis. Several hundred otolith samples from coastal fjord areas along northern Norway and from the Barents Sea were analysed by univariate shape descriptors and elliptical Fourier analysis (EFA). When combining uni- and multivariate descriptors and applying the otolith reader typing as reference, the classification score was 89% for NCC and 90% for NEAC. These results indicate that the internal morphology of the otoliths, evaluated by the age readers, is translated to a great extent to their outer morphology and that otoliths can be allocated to NCC and NEAC by their shapes with high certainty. When genetic typing data ( Pan I marker) were used as reference, the classification scores were reduced to 83% for NCC and 76% for NEAC when combining uni- and multivariate descriptors and excluding heterozygotes. This implies that differences in otolith morphology cannot directly be linked to genetic structure. Differences in environmental conditions, however, seem to have a considerable influence on how otolith growth increments and consequently otolith shapes are formed. As the various fjord systems in Norway provide local habitats and as differences within the NCC with regard to genetic structure and life-history parameters had been found in earlier studies, variation of NCC otolith shapes between three coastal regions was also examined. The region classification scores for reader-typed NCC varied between 60% and 81%.

Comparing microsatellite variation in north‐east Atlantic cod (Gadus morhua L.) to genetic structuring as revealed by the pantophysin (Pan I) locus

Variation at seven microsatellite loci was compared with variation observed at Pan I, a single copy nuclear DNA gene coding for pantophysin, in 14 samples of Atlantic cod (Gadus morhua) stretching from Spitsbergen to the North Sea. Population structuring indicated by the two types of markers was concordant and in agreement with the traditional grouping of cod in the study area into three main populations: north‐east Arctic cod (NEAC), Norwegian coastal cod (NCC) and North Sea cod (NSC). Microsatellites, however, revealed genetic heterogeneity not only within NCC, as did Pan I, but also within NEAC and NSC, which appeared to be homogenous when analysed for Pan I. Moreover, microsatellites displayed lower levels of differentiation than Pan I between NEAC and two other groups. Differences in the magnitude of differentiation for the two types of markers may be attributable to higher levels of polymorphism and alleged selective neutrality of microsatellites. Isolation by distance was clearly apparent for microsatellites but was less evident for Pan I, indicating that environmentally induced selection appears to shape the patterns of genetic differentiation for this marker. Even though the population structure of north‐east Atlantic cod, as revealed by microsatellites and Pan I, appears to be maintained largely by restricted gene flow, selection acting on a recent historical time scale probably contributes to the observed geographic pattern of Pan I frequencies.