Coastal Cod Research Articles

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.

Reliability of trawl surveys on cod in Norwegian fjords

Abstract Lunde, T. M., Godø, O. R., and Rosland, R. 2008. Reliability of trawl surveys on cod in Norwegian fjords. – ICES Journal of Marine Science, 65: 937–945. According to ICES, the International Council for the Exploration of the Sea, populations of coastal cod (CC) in Norway north of 62°N have been declining since 1994. The estimates are based on analytical assessment in which the most recent estimates are tuned with survey information. We evaluate the quality of bottom-trawl surveys conducted in four North Norwegian fjords during autumn of the years 1995–2004. Surveys tended to be carried out later in autumn in the more recent years than in the earlier years. Consequently, there was a significant decrease in sun's altitude from 1995 to 2004 at the time the surveys were carried out. Further inconsistency among years dominated when comparing catch per unit effort (cpue) by year class and age over time. Often, the observed cpue at age a + 1 in year y + 1 was greater than in year y at age a. Spearman’s rank correlation of cpue vs. year also demonstrated inconsistencies in the data. The problems related to separating CC and northeast Arctic cod are discussed.

Mixed stock analysis and the power of different classes of molecular markers in discriminating coastal and oceanic Atlantic cod (Gadus morhua L.) on the Lofoten spawning grounds, Northern Norway

Atlantic cod (Gadus morhua) encompasses many different populations or stocks, which in part are managed separately. In the northeast Atlantic cod is divided into two main management units; northeast Arctic cod and coastal cod. These two groups have traditionally been separated by otolith classification. In this study, the power of different classes of genetic markers in separating the two cod groups was investigated. The variation in thirteen genetic markers, including allozymes, haemoglobin, the scDNA locus Pantophysin (Pan I) and a number of microsatellites was investigated, and mixed stock analysis and individual assignment tests were performed on samples comprising a mixture of individuals of putative coastal and oceanic type cod. The genetic analyses showed a large genetic differentiation between outer stations and stations located closer to the mainland shore. Mixed stock analysis and individual assignment tests used for estimation of stock proportions gave results similar to those obtained by otolith classification.

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.

Hypoxic avoidance behaviour in cod ( Gadus morhua L.): The effect of temperature and haemoglobin genotype

Hypoxia can influence fish growth, survival and on larger scales, population structure. These effects may be influenced by water temperature, and may vary intra-specifically with genotype. In Atlantic cod ( Gadus morhua L.), the two haemoglobin homozygotes ( Hb-I⁎11 and Hb-I⁎22) vary in oxygen affinity at different temperatures, which is thought to correspond to variation in hypoxia tolerance. We therefore tested if hypoxic avoidance behaviour in cod 1) depends on ambient temperature and 2) is modified by haemoglobin genotype. In a laminar flow choice box, we subjected juvenile cod to an initial phase of non-escapable hypoxia, and a subsequent recovery phase, where one habitat was kept at 20% O 2 saturation while the other was raised in steps to full saturation. The experiment was performed at 5 and 15 °C with Hb-I⁎11 and Hb-I⁎22 cod. Cod responded to inescapable hypoxia by reducing their overall swimming speed and then, at the initial levels of the recovery phase, avoiding the most hypoxic habitat, irrespective of temperature or genotype. Fish recovered quickly as O 2 levels increased, as evidenced by increased swimming speed and time spent in the most hypoxic habitat. The avoidance response depended strongly on temperature: the relative reduction in speed and avoidance of the most hypoxic habitat was more pronounced at 15 than at 5 °C. During the recovery phase, stressed fish initially maintained a higher swimming speed in the most hypoxic habitat. However, as O 2 increased, swimming speed in both habitats converged. This point of convergence occurred at a lower O 2 saturation at 5 °C. Fish ventilation rate in inescapable hypoxia was also higher at 15 °C. Haemoglobin genotype did not influence either ventilation rates or the nature of the hypoxic avoidance response at either temperature, but Hb-I⁎11 cod swam faster than Hb-I⁎22 cod in normoxia at 15 °C. Our results indicate that increased temperature limits the ability of cod of both haemoglobin genotypes to exploit hypoxic habitats. This may have negative future consequences for coastal cod stocks in light of increasing global temperatures and eutrophication in coastal waters.

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.

Spatial Scales of Movement in Northeast Atlantic Coastal Cod

The movement patterns of released hatchery-reared fish determine the geographical scale at which a population may be enhanced, while the movement patterns of wild fish affect the management strategies of wild populations. This article investigates (1) if movement patterns differ between hatchery reared and wild cod, and (2) if the movement patterns of coastal cod differ between regions. The results from a large mark-recapture experiment in northern Norway showed that displacement distances (DD) for both wild and hatchery-reared fish were highly skewed. The frequency distribution of DD for wild cod was well described by a log-normal distribution. While reared cod that were released at a small size (< 27 cm in length) and young age (< 1 year of age) had similar movement patterns to wild cod of similar size, reared cod that were larger and older at release dispersed rapidly after release. The frequency of long-distance migrations (DD > 50 km) for larger reared cod was similar, however, to that of wild cod. Fitting log-normal distributions to published mark-recapture data revealed that there was a latitudinal trend, with longer displacement distances in the north than in the south. Cod released in coastal bank areas and offshore island groups also had longer displacement distances than cod released at the Norwegian coast.

“Escapes” of Eggs from Farmed Cod Spawning in Net Pens: Recruitment to Wild Stocks

Escapes of farmed fish from aquaculture installations, as well as large scale stock enhancement and sea ranching activities, are regarded as risk factors for negative genetic impacts on native gene pools. These aspects have been discussed for several decades, and a number of recent experiments on Atlantic salmon have clearly demonstrated dramatically reduced overall fitness of farmed offspring compared with offspring of wild origin. The Atlantic cod (Gadus morhua L.) is now the most promising new marine species for large scale farming in Norway, and more than 500 commercial farming licenses have been issued, corresponding to a maximum annual production capacity of about 300,000 tonnes. In comparison with the environmental problems caused by escapes from the salmon farming industry, cod farming presents new challenges. As a marine species, cod are able to spawn in the net pens during the ongrowing period and thus release genetic material into the environment. Coastal cod stocks in Norwegian waters are depleted and therefore may be particularly vulnerable to genetic interaction with farmed cod. Thus, there is an urgent need for more detailed knowledge of potential hazards. A pilot experiment performed in Heimarkspollen in Austevoll (a practically landlocked fjord) demonstrated for the first time that farmed cod are capable of producing viable cod larvae that mix with larvae from wild cod. The farmed cod used in the pilot experiment were homozygotic for a rare allele (GPI-1*30), and mature fish were placed in a net pen to allow spawning and egg drift into the surrounding water to take place. Surveys of eggs found the highest densities in the vicinity of the net pen. Later larval surveys found that 20% to 25% of the larvae sampled in the area possessed the unique genetic marker and could therefore be traced to the spawning cod in the net cage. Numerous genetically marked larvae were also found outside Heimarkspollen, indicating a high degree of dispersal of eggs and larvae by tidal advection.

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.

A tool for analyzing information from data storage tags: the continuous wavelet transform (CWT)

Electronic Data Storage Tags (DSTs) have the potential of providing long term, high-resolution observation data of individual fish in the ecosystem. However, traditional time series analysis methods are limited in extracting the required information from DSTs. The continuous wavelet transform (CWT) is a tool for decomposing a time series into instantaneous frequency versus time characteristics. This allows data signals, which are restricted to specific frequencies (localized frequencies), or frequency components, which are restricted to specific time intervals (time localized) to be extracted and displayed in a highly intuitive way. The aim of this short communication is to present the CWT as a tool for extracting information from DST data. In the first case, synthetically generated data is used to demonstrate how the methodology captures different time–frequency dependent patterns in the time series data. The relevance of the methodology to real field data is demonstrated by an analysis of DST depth data from tagged Barents Sea coastal cod.

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%.

Spatial scale of genetic structuring in coastal cod Gadus morhua and geographic extent of local populations

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 343:229-237 (2007) - DOI: https://doi.org/10.3354/meps06922 Spatial scale of genetic structuring in coastal cod Gadus morhua and geographic extent of local populations Per Erik Jorde1,2,*, Halvor Knutsen1, Sigurd Heiberg Espeland2, Nils Chr. Stenseth1,2 1Institute of Marine Research, Flødevigen, 4817 His, Norway 2CEES – Centre for Ecological and Evolutionary Synthesis, University of Oslo, PO Box 1066, Blindern, 0316 Oslo, Norway *Email: p.e.jorde@bio.uio.no ABSTRACT: We estimated the spatial scale of genetically distinguishable populations of coastal Atlantic cod Gadus morhua using microsatellite DNA markers. Significant overall heterogeneity in allele frequencies was found among 5 cod samples (n = 493) along a 79 km segment of the Norwegian Skagerrak coast (FST = 0.0013; p = 0.021). Most (3 out of 4) samples separated by less than 30 km were genetically highly similar (FST < 0), whereas more distantly separated samples were typically genetically different. This genetic differentiation pattern indicates a patchy population structure with local coastal cod populations being limited in geographic extent to approx. 30 km or less. The spatial structure is thus on the scale of local fjords, suggesting a role for local topography in shaping population structure. The population structuring of coastal cod is more fine-scaled than hitherto reported, but is consistent with mark–recapture studies and data on egg distributions, and emphasises the need to focus on local populations in the management of marine fishes. KEY WORDS: Spatial scale · Coastal Atlantic cod · Gadus morhua · Local populations · Genetic differentiation · Microsatellites Full text in pdf format PreviousNextCite this article as: Jorde PE, Knutsen H, Espeland SH, Stenseth NC (2007) Spatial scale of genetic structuring in coastal cod Gadus morhua and geographic extent of local populations. Mar Ecol Prog Ser 343:229-237. https://doi.org/10.3354/meps06922 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 343. Online publication date: August 07, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

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.

Atlantic cod ( Gadus morhua L.) in inner and outer coastal zones of northern Norway display divergent genetic signature at non-neutral loci

A large majority of Atlantic cod ( Gadus morhua) found all year round in outer parts of fjords and along outer coastal areas in general in northern Norway have a genetic signature at the pantophysin ( Pan I) locus that distinguish them from Norwegian coastal cod (NCC) found further inside fjords in the same areas. The identity of these fish has been controversial and to examine if they represent a distinct coastal cod group, or are identical to the migratory North East Arctic cod (NEAC) of the Barents Sea, a comparison was conducted at 10 microsatellite loci for 15 samples comprising each of the three groups inner coastal NCC, outer coastal cod and NEAC. Spatial analysis of molecular variance revealed that the outer coastal samples cannot be discriminated from NEAC by means of microsatellite markers, supporting the similarity of the two groups at the Pan I locus. This implies that a portion of the otherwise migratory NEAC, at least in its premature stage, remains in coastal areas in close contact with the genetically quite distinct NCC group. Both the coalescent-based simulation approach and the lnRH test for selective sweeps proved two of the microsatellite loci, GMO 34 and GMO 132 to be non-neutral. Notwithstanding, these two loci, together with the acknowledged non-neutral Pan I locus, which displayed profound linkage disequilibrium to GMO 34 within NEAC, are as yet the only nuclear markers which unambiguously discriminate between NEAC and NCC. Although the relative contribution of restricted gene flow versus selection as a causative agent for the divergence between NEAC and NCC has not been assessed, we believe the magnitude of differentiation at the three loci provides rational for maintaining NEAC and NCC as separate management units.

Home range and elevated egg densities within an inshore spawning ground of coastal cod

Abstract Espeland, S. H., Gundersen, A. F., Olsen, E. M., Knutsen, H., Gjøsæter, J., and Stenseth, N. C. 2007. Home range and elevated egg densities within an inshore spawning ground of coastal cod. – ICES Journal of Marine Science, 64: 920–928. Atlantic cod (Gadus morhua) along the Norwegian Skagerrak coast are structured into genetically distinct local populations. Mechanisms contributing to this genetic structure may include spawning site fidelity of adult cod as well as retention of pelagic early life stages close to the spawning grounds. Spawning in sheltered inshore localities is likely to favour retention of eggs and larvae, the opposite situation to offshore spawning. A combined study was made of area utilization by adult cod and the distribution of cod eggs within an inshore locality of the Norwegian Skagerrak coast. The behaviour of adult cod was studied using acoustic telemetry and kernel modelling, and eggs were sampled throughout the spawning season. Generalized additive models were applied to test hypotheses about the spatial dynamics of the eggs, and the best model described a central spawning area that retained its integrity through time. Adult cod were confined to small parts of the study area and remained there throughout the spawning season. The average home range of the adult cod was 27 ha. Overall, the study demonstrated two mechanisms by which coastal (i.e. inshore) cod maintain their population structure: spawning site fidelity and the spatial dynamics of their eggs.

Three statistical approaches for genetic analysis of disease resistance to vibriosis in Atlantic cod (Gadus morhua L.)1

The objective of this study was to estimate and compare variance components and sire breeding values for disease resistance to vibriosis in Atlantic cod (Gadus morhua L.) using 3 statistical approaches. A total of 3,576 individually tagged juvenile cod from 50 full-sib families were infected with Vibrio anguillarum, which causes vibriosis, a frequently reported disease in cod aquaculture. The experimental fish were progeny of captured wild cod from populations of southern coastal cod (POP1), and northern coastal cod and northeast Arctic cod (combined as POP2 in the genetic analyses). Fish were randomly assigned to 1 of 3 test tanks, and daily mortality was recorded until the termination of the experiment at d 31 postinfection. Variance components were estimated separately for the 2 populations using a Cox regression model, univariate linear model, and a linear model that accounted for censoring. With all approaches, the additive genetic sire variance estimated from POP1 was greater than for POP2. Heritability estimates across populations varied from 0.08 to 0.17 depending on the method used. The Cox regression model and univariate linear model resulted in greater heritability estimates for POP1 (0.10 and 0.16) than for POP2 (0.08 and 0.13), whereas the contrary was true with a linear model that accounted for censoring (0.17 vs. 0.14). The predicted breeding values for the sires from the 3 approaches were highly correlated (0.97 to 0.99). This is likely due to the fact that censoring only occurred at the end of the test; i.e., observations of the most resistant fish were censored. The considerable genetic variation found in this study suggests that vibriosis resistance may be improved through selective breeding. The univariate linear model, even without censoring of the data, was robust for the estimation of breeding values using the present data. Therefore, inclusion of vibriosis resistance in the multivariate linear estimation of breeding values for the traits of economic importance in Atlantic cod seems appropriate.

Resistance to vibriosis in Atlantic cod ( Gadus morhua L.): First challenge test results

The objective of this study was to assess between-family differences in resistance to vibriosis in Atlantic cod. Twenty full-sib families, of which 13 were of Norwegian coastal cod (CC) and 7 families represented northeast Arctic cod (NEAC), were tested for survival after challenge with Vibrio anguillarum. Mortality after challenge was recorded daily, and the experiment was terminated 22 days post challenge. The overall survival at the end of the experiment was 12.3%. Significant family differences in the survival patterns were found both at the end of the test and 8 days after challenge (approximating 50% mortality). In this study, CC (14.2% survival) proved to be more resistant to vibriosis than NEAC (8.6% survival). Although further investigations are needed to quantify the amount of additive genetic variation in vibriosis resistance, this study gives an indication that challenge test results may successfully be used as selection criteria for disease resistance to classical vibriosis in Atlantic cod.

Interannual variability in abundance and length of young coastal cod in the subtidal zone

The year‐to‐year variability of total length and abundance of young cod Gadus morhua in the littoral zone of the Norwegian Skagerrak coast was dominant over spatial variability. The 0 year group cod was slightly larger in exposed areas than in protected areas. Contrary to expectations, the 0 year group cod was less abundant in the protected inner parts of the fjords. Although the natural variability was very large, exposed areas (the skerries) seemed to be the better area for the 0 year group cod, while for the 1 year group cod, no differences in abundance or growth could be identified indicating that they had adopted a mature pattern of movement, utilizing the entire fjord for feeding. Available habitat data indicated that the availability of shelter was a potential cause for the distributional pattern.

Genetic characteristics of broodstock collected from four Norwegian coastal cod (Gadus morhua) populations

Abstract The aquaculture industry in Norway is now focused on developing economically viable farming based on the Atlantic cod, Gadus morhua. Extensive research has been carried out on this species for the past two decades, much of it in connection with stock enhancement. Until now, most of the intensive cage culture has been based on wild broodstock. However, a future cod aquaculture industry must be based on a domesticated broodstock, and the initial selection of wild cod becomes an important issue. Genetic differentiation between coastal cod populations in Norway has been reported, and it is of interest to evaluate offspring from some of these populations under farmed conditions. Live mature cod were collected at four selected spawning sites along the Norwegian coast (Porsangerfjord, Tysfjord, Herøy/Helgeland, and Øygarden). The fish were transported to Parisvatnet, a cod aquaculture facility west of Bergen, where they were kept in net pens. Individual tagging and extensive sampling (blood, white muscle, and fin clips) for genetic characterization were carried out. Each potential broodstock fish was genotyped at the haemoglobin and pantophysin I loci in addition to five allozyme (LDH-3∗, GPD∗, IDH-2∗, PGM∗, PGI-1∗) and ten microsatellite loci (Gmo2, Gmo3, Gmo8, Gmo19, Gmo34, Gmo35, Gmo36, Gmo37, Gmo132, Tch11). Comparison of allele frequencies revealed significant genetic differences among some of the coastal cod samples, and offspring performance of the broodstock is now being compared under farmed conditions. The overall test revealed significant genetic differences among the coastal broodstocks, with the HbI, PanI and the microsatellite Gmo132 loci being most informative.