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Atlantic Cod (atlantic + cod)
Terms modified by Atlantic Cod Selected AbstractsIMPACT OF FREEZING TEMPERATURE ON QUALITY OF FARMED ATLANTIC COD (GADUS MORHUA L.)JOURNAL OF TEXTURE STUDIES, Issue 4 2007TURID MØRKØRE ABSTRACT This study evaluates the impact of freezing temperature (,10,,25,,40,,55 or,70C) on thaw exudates, liquid leakage during freeze-chilling, appearance, gaping and mechanical properties of farmed Atlantic cod fillets. Freezing temperature significantly influenced each of the characteristics studied. High temperatures (,10 and,25C) gave increased thaw exudates, and freezing at,10C gave the highest liquid leakage during freeze-chilling. Fillets frozen at,10C had the lowest gaping and the whitest appearance. The results indicated the highest degree of toughening upon freezing at,10 or,55C, whereas the degree of toughening appeared to be similar and lower for fillets frozen at,25,,40 or,70C. The impact of freezing temperatures on the quality of farmed cod therefore appeared to be complex, but no overall beneficial effects were found by decreasing the freezing temperature below,40C. PRACTICAL APPLICATIONS For the fish processing industry, it is important to define optimal freezing and frozen storage regimes that are cost efficient and at the same time preserve the fresh fillet quality. Farmed cod differ from their wild counterparts by having lower water content, lower muscle pH and thicker fillets. Hence, industrial guidelines for wild cod may not be transferable to farmed cod. This study showed no beneficial effects by decreasing the freezing temperature below ,40C. Freezing and frozen storage are usually separated commercially. Results from the present study give valuable contribution to future studies aiming at defining optimal combination of freezing and frozen storage temperatures for farmed Atlantic cod. [source] Alternate oils in fish feedsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 3 2007Jana Pickova Abstract Nearly half of the fish consumed as food worldwide are raised on fish farms rather than caught in the wild, as shown by FAO statistics. The increasing aquaculture of predatory carnivorous fish demands new sources of feed constituents, particularly oils at the moment. Common terrestrial plant oils contain only traces of the long-chain polyunsaturated fatty acids. In connection with fish feed, especially the lack of n -3 "marine fatty acids" is obvious. Recommendations on the required amounts of the fatty acids DHA (22:6n -3) and EPA (20:5n -3) exist from 1994. When plant oil-based diets are fed during the growing phase and replaced by a fish oil-based diet during a period prior to slaughter, most of the beneficial lipid composition of fish in terms of human dietary recommendations is restored. Little attention has been focused on the fish welfare in connection to substitution of dietary oil sources, and studies are still scarce. New fish diets will rely heavily on the use of alternate ingredients such as plant oils also for carnivorous cold-temperate water fish species. In the future, an addition of synthetic or GMO-produced "marine" fatty acids is a possible scenario. The aim of this review is to highlight some plant oils used in fish feeds, with special emphasis on compounds other than fatty acids. We also include some results from an ongoing study, where the effect of dietary soy oil on gonad maturation in Atlantic cod (Gadus morhua) is indicated. [source] ORIGINAL ARTICLE: Propensity of marine reserves to reduce the evolutionary effects of fishing in a migratory speciesEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 3 2009Erin S. Dunlop Abstract Evolutionary effects of fishing can have unwanted consequences diminishing a fishery's value and sustainability. Reserves, or no-take areas, have been proposed as a management tool for reducing fisheries-induced selection, but their effectiveness for migratory species has remained unexplored. Here we develop an eco-genetic model to predict the effects of marine reserves on fisheries-induced evolution under migration. To represent a stock that undergoes an annual migration between feeding and spawning grounds, we draw model parameters from Atlantic cod (Gadus morhua) in the northern part of its range. Our analysis leads to the following conclusions: (i) a reserve in a stock's feeding grounds, protecting immature and mature fish alike, reduces fisheries-induced evolution, even though protected and unprotected population components mix on the spawning grounds; (ii) in contrast, a reserve in a stock's spawning grounds, protecting only mature fish, has little mitigating effects on fisheries-induced evolution and can sometimes even exacerbate its magnitude; (iii) evolutionary changes that are already underway may be difficult to reverse with a reserve; (iv) directly after a reserve is created or enlarged, most reserve scenarios result in yield losses; and (v) timescale is very important: short-term yield losses immediately after a reserve's creation can give way to long-term gains. [source] Trophic role of Atlantic cod in the ecosystemFISH AND FISHERIES, Issue 1 2009Jason S. Link Abstract As the world's oceans continue to undergo drastic changes, understanding the role of key species therein will become increasingly important. To explore the role of Atlantic cod (Gadus morhua Gadidae) in the ecosystem, we reviewed biological interactions between cod and its prey, predators and competitors within six ecosystems taken from a broad geographic range: three are cod-capelin (Mallotus villosus Osmeridae) systems towards cod's northern Atlantic limit (Barents Sea, Iceland and Newfoundland,Labrador), two are more diverse systems towards the southern end of the range (North Sea and Georges Bank,Gulf of Maine), and one is a species-poor system with an unusual physical and biotic environment (Baltic Sea). We attempt a synthesis of the role of cod in these six ecosystems and speculate on how it might change in response to a variety of influences, particularly climate change, in a fashion that may apply to a wide range of species. We find cod prey, predators and competitors functionally similar in all six ecosystems. Conversely, we estimate different magnitudes for the role of cod in an ecosystem, with consequently different effects on cod, their prey and predator populations. Fishing has generally diminished the ecological role of cod. What remains unclear is how additional climate variability will alter cod stocks, and thus its role in the ecosystem. [source] Paradigm shifts in marine fisheries genetics: ugly hypotheses slain by beautiful factsFISH AND FISHERIES, Issue 4 2008Lorenz Hauser Abstract By providing new approaches to the investigation of demographic and evolutionary dynamics of wild populations, molecular genetics has led to fundamental changes in our understanding of marine ecology. In particular, genetic approaches have revolutionized our understanding in three areas: (i) most importantly, they have contributed to the discovery of extensive genetic population structure in many marine species, overturning the notion of large, essentially homogenous marine populations limiting local adaptation and speciation. (ii) Concomitant differences in ecologically important traits now indicate extensive adaptive differentiation and biocomplexity, potentially increasing the resilience to exploitation and disturbance. Evidence for rapid adaptive change in many populations underlies recent concerns about fisheries-induced evolution affecting life-history traits. (iii) A compilation of recent published research shows estimated effective population sizes that are 2,6 orders of magnitude smaller than census sizes, suggesting more complex recruitment dynamics in marine species than previously assumed. Studies on Atlantic cod are used to illustrate these paradigm shifts. In our synthesis, we emphasize the implications of these discoveries for marine ecology and evolution as well as the management and conservation of exploited marine fish populations. An important implication of genetic structuring and the potential for adaptive divergence is that locally adapted populations are unlikely to be replaced through immigration, with potentially detrimental consequences for the resilience to environmental change , a key consideration for sustainable fisheries management. [source] Testing hypotheses about fecundity, body size and maternal condition in fishesFISH AND FISHERIES, Issue 2 2004Marten A. Koops Abstract Recent research suggests that maternal condition positively influences the number of eggs spawned in fishes. These studies commonly choose a priori to use body length rather than weight as an explanatory variable of offspring production, even though weight is usually the better predictor of fecundity. We are concerned that consistent exclusion of body weight as a predictor of egg production inflates the variance in fecundity attributable to maternal condition. By analysing data on three populations of Atlantic cod (Gadus morhua, Gadidae) and 10 populations of brook trout (Salvelinus fontinalis, Salmonidae), we illustrate the need for a statistically defensible method of model selection to distinguish the effects of maternal condition on egg production from the effects of body size alone. Forward stepwise regression and null model analyses reveal how length-based regressions can significantly over-estimate correlations between condition and fecundity, leading us to conclude that the effect of condition on egg productivity may not be as ubiquitous or as biologically important as previously thought. Our work underscores the need for greater statistical clarity in analyses of the effects of maternal condition on reproductive productivity in fishes. [source] The enhancement of cod stocksFISH AND FISHERIES, Issue 2 2000T. Svåsand Atlantic cod have been a primary target for marine stock enhancement since the 1880s. In the early part of this period, hatched larvae were released in Norway, the USA and Canada. The last larval releases were conducted in Norway in 1971, and a century of cod larvae releases were halted without any clear evidence of benefit. Since the early 1980s, the focus has been on production of larger, more viable juvenile cod. Emphasis has been given to the design of tag,release programmes involving large-scale releases and ecosystem analysis in selected ecosystems. Most of this research has been carried out in Norway, where more than one million tagged juvenile cod have been released. Smaller stocking experiments have also been performed in Denmark, Sweden, the Faroe Islands and the USA. This paper reviews the major findings from these programmes. We include summaries and evaluations of rearing techniques for juvenile cod, methods of tagging and recapture, experimental fishing, migration, mortality and growth rates in the different habitats, genetic analysis, and ecosystem studies that have tried to describe the variation in the cod carrying capacity of selected release areas. Despite relatively large variation in environmental conditions, in cod production and in fishing mortality along the Norwegian coast, results indicate that, under the conditions experienced during the 1980s and 1990s, releases of juvenile cod did not significantly increase cod production and catches. The biological limitations and future prospects of Atlantic cod stock enhancement are addressed. [source] Geolocation of Atlantic cod (Gadus morhua) movements in the Gulf of Maine using tidal informationFISHERIES OCEANOGRAPHY, Issue 4 2007J. P. GRÖGER Abstract Information derived from archival tags (digital storage tags, DSTs) were used to backtrack the migration of 11 tagged Atlantic cod (Gadus morhua) during 2001 in Massachusetts Bay, the Gulf of Maine, and Georges Bank. The DST tags continuously recorded time, temperature and depth. To geolocate fish positions during its time at large, we first extracted the tidal signal from the pressure recordings on the DST tags, and then compared the resulting data to data predicted with a Massachusetts Bay tidal model that provided us with geographical coordinates at a given date and time. Using least-squares criteria within an estimated geographical region of confidence that was constrained by biological and statistical information (e.g. swimming speed, known release and recapture location, and bottom depth) we were able to geolocate the fish. The resultant geolocated migration tracks indicate a large degree of movement of Atlantic cod in the region and an elevated importance of the Great South Channel (GSC) migration corridor between Massachusetts Bay and the western Georges Bank and Nantucket Shoals region. This observation contrasts strongly with inferences of limited movements by Atlantic cod based on conventional tag recapture methods (mean of 1200 km traveled versus 44 km traveled as measured by conventional tagging and geolocation, respectively). This study demonstrates that geolocation methodologies applied to archival tag studies hold great promise of becoming an important new tool for fisheries managers to quantify the movements of fishes. It also points out the need for greater collaboration between fisheries scientists and oceanographers, and particularly for the development of improved tidal models to cover stock regions more accurately and with higher precision. [source] Changes in spawning stock structure strengthen the link between climate and recruitment in a heavily fished cod (Gadus morhua) stockFISHERIES OCEANOGRAPHY, Issue 3 2006GEIR OTTERSEN Abstract Atlantic cod (Gadus morhua) is one of the commercially most important fish species in the North Atlantic and plays a central role in several ecosystems. Fishing pressure has been heavy over a prolonged period and the recent decades have shown dramatic decline in abundance of many stocks. The Arcto-Norwegian (or North-east Arctic) cod stock in the Barents Sea is now the largest stock of Atlantic cod. Recruitment to this stock has varied extensively during the last 60 yr. There is evidence for fluctuations in climate, particularly sea temperature, being a main cause for this variability, higher temperatures being favourable for survival throughout the critical early life stages. Our studies of time series present compelling evidence for a strengthening of the climate,cod recruitment link during the last decades. We suggest this is an effect of the age and length composition of the spawning stock having changed distinctly. The age of the average spawner has decreased by more than 3 yr from between 10 and 11 in the late 1940s to 7,8 in the 1990s, average length from just above 90 cm to around 80 cm. The number of age classes contributing to the spawning stock has also decreased, while the number of length groups present increased slightly. Significant decrease in age of spawners has frequently been described for other heavily fished stocks worldwide. We therefore find it likely that the proposed mechanism of increased influence of climate on recruitment through changes in the spawning stock age and size composition is of a general nature and might be found in other systems. [source] Accuracy and precision of the continuous underway fish egg sampler (CUFES) and bongo nets: a comparison of three species of temperate fishFISHERIES OCEANOGRAPHY, Issue 6 2005P. PEPIN Abstract We examine the accuracy and precision of the continuous underway fish egg sampler (CUFES) relative to bongo nets based on the catch ratio of Atlantic cod (Gadus morhua), American plaice (Hippoglossoides platessoides), and cunner (Tautogolabrus adspersus). We derived expectation of catch ratios based on the application of a one-dimensional model of the vertical distribution of fish eggs applied to cod and on prior data on egg vertical distribution. Samples were collected in May and August 2001, two periods when the vertical structure of the water column differed substantially. Stationary CUFES collections did not yield significant differences in accuracy or precision relative to the underway CUFES. In May, when there was relatively little stratification, the CUFES-to-bongo catch ratio of cod and plaice eggs was well within expectations based on model predictions. In August, the CUFES-to-bongo catch ratios of cod and cunner were higher than expected. Generally, there was a greater proportion of early stage eggs in bongo than in CUFES samples, with the strongest differences in American plaice. The replicate variance of the CUFES was ,25 times greater than that of the bongo nets, probably because of the large volumes sampled by bongo nets relative to the CUFES. Given that the CUFES provides greater accuracy in mapping but lower precision than bongo nets, multiple sampling gears may be the most effective method for surveying fish eggs of pelagic and demersal species. [source] The influence of temperature on advective loss of Atlantic cod (Gadus morhua) eggs from the inshore environmentFISHERIES OCEANOGRAPHY, Issue 4 2001Ian R. Bradbury We use a simple model of temperature-dependent egg development and mortality to develop several hypotheses concerning the effect of temperature on the occurrence of eggs of Atlantic cod, Gadus morhua, in Placentia Bay, Newfoundland. Predictions from this exploratory model were tested through a series of synoptic ichthyoplankton surveys throughout spawning and postspawning periods during 1997 and 1998. Although several egg mortality relationships were explored through the simulation, a constant mortality rate best represented the pattern observed in the two years of data. Peaks in late stage egg densities occurred in August of both 1997 and 1998 and were apparently decoupled from egg production peaks in April. We observed a decrease in mortality and the distance dispersed during egg development with increases in water temperature. We suggest that the effects of predation are small relative to the advective effects within this system, and that the interaction between advection and temperature-dependent vital rates of eggs may have dramatic consequences for coastal retention of propagules produced by inshore spawning events. [source] A link between sound producing musculature and mating success in Atlantic codJOURNAL OF FISH BIOLOGY, Issue 3 2008S. Rowe Individual variability in the mating success of male Atlantic cod Gadus morhua was quantified within an aggregation (n= 59) breeding undisturbed in a large (684 m3) mesocosm tank. Observational and morphometric data were examined to assess the degree to which this mating variation could be explained by aspects of morphology, condition and spawning behaviour. The number of ventral mounts initiated (i.e. mating success) was highly variable; most mounts were initiated by a very small percentage of available males. The significant correlate of male mating success was mass of the sound producing musculature, i.e. drumming muscles. Neither body size, condition, pelvic and median fin morphology nor aggression influenced the number of ventral mounts initiated by a male. The present study suggests a possible link between sound production and mating success in Atlantic cod. [source] The relationship between caudal differential pressure and activity of Atlantic cod: a potential method to predict oxygen consumption of free-swimming fishJOURNAL OF FISH BIOLOGY, Issue 4 2007M. F. Steinhausen This study reports the first results on telemetry of caudal differential pressure during spontaneous swimming activity in cod Gadus morhua and demonstrates that tail-beat pressure may be used as a predictor of activity and swimming costs of free-swimming cod. Tail-beat pressure was monitored using a differential pressure sensor on the caudal peduncle of cod and spontaneous swimming activity was quantified using a customized video-computer tracking programme. Tail-beat pressure was found to correlate with (1) swimming speed (U) and oxygen consumption during forced swimming and (2) mean U during spontaneous activity. Based on the relationship between and the integrated pressure performed by the tail during forced swimming, it should be possible to predict during spontaneous activity. To gain precise measures of activity and thus predictions of for free-swimming fish, however, individual calibrations are necessary. [source] Role of habitat in mediating mortality during the post-settlement transition phase of temperate marine fishesJOURNAL OF FISH BIOLOGY, Issue 3 2007F Juanes The transition phase describes a distinct post-settlement stage associated with the recruitment to benthic habitats by pelagic life stages. The habitat shift is often accompanied by feeding shifts and metamorphosis from larval to juvenile phases. Density-dependent settlement, growth and mortality are often the major factors controlling recruitment success of this phase. Habitat use also becomes more pronounced after settlement. The role of habitat-mediated post-settlement mortality is elucidated by focusing on the early life history of Atlantic cod (Gadus morhua) and cunner (Tautogolabrus adspersus) in the north-west Atlantic. In these species, settlement can occur over all bottom types, but habitat-specific differences in post-settlement mortality rates combined with size and priority at settlement effects on growth and survival determine recruitment and eventual year-class strength. These results and those from other temperate marine fish species along with work on tropical reef species emphasize the generality of habitat-based density-dependent mortality during the transition phase and its potential for population regulation. These results have implications for fisheries management and can be used to outline a procedure to assist managers in identifying and managing essential transitional habitats including the potential role of marine protected areas in habitat conservation. [source] The development of haddock and Atlantic cod sperm cryopreservation techniques and the effect of sperm age on cryopreservation successJOURNAL OF FISH BIOLOGY, Issue 2 2004R. M. Rideout Three cryoprotectants [dimethyl sulphoxide (DMSO), propylene glycol (PG) and glycerol], two diluents (sucrose- and saline-based), two sperm collection times, two freezing rates and three times between thaw and activation (0, 30 and 60 min) were tested in order to develop a protocol for the cryopreservation of sperm of haddock Melanogrammus aeglefinus and Atlantic cod Gadus morhua. The faster freezing rate resulted in extremely low post-thaw motility in comparison to the slower freezing rate, which was successful for sperm from both gadids. In both cases, the use of PG resulted in significantly higher post-thaw sperm motility-recovery indices than with DMSO or glycerol, which did not differ significantly from one another. Diluent had no effect on post-thaw sperm motility for Atlantic cod or haddock. Sperm collected at the end of the spawning season tended to have reduced post-thaw motility compared to that collected 2 weeks after the start of spawning. A 30 min delay between thaw and activation of haddock and Atlantic cod sperm resulted in a significant decrease in sperm motility. When PG was used as cryoprotectant, sperm motility continued to decrease between 30 and 60 min post-thaw. With DMSO or glycerol as cryoprotectant, motilities were already very low after 30 min post-thaw and did not decrease any further after 60 min. Cryoprotectant, diluent and time between thaw and activation had no effect on mean or maximum sperm swimming speeds for either Atlantic cod or haddock sperm. Fertilization success for haddock eggs, like sperm motility, was higher with PG-frozen sperm than DMSO- or glycerol-frozen sperm. These results constitute the first reported successful cryopreservation of haddock sperm and improve on previous methods used to cryopreserve sperm from Atlantic cod. [source] Temperature-dependent changes in energy metabolism, intracellular pH and blood oxygen tension in the Atlantic codJOURNAL OF FISH BIOLOGY, Issue 6 2003F. J. Sartoris The effect of acute increase in temperature on oxygen partial pressure (Po2) was measured in the gill arches of Atlantic cod Gadus morhua between 10 and 19° C by use of oxygen microoptodes. Oxygen saturation of the gill blood under control conditions varied between 90 and 15% reflecting a variable percentage of arterial or venous blood in accordance with the position of each optode in the gill arch. The data obtained suggested that arterial Po2 remained more or less constant and arterial oxygen uptake did not become limiting during warming. A progressive drop in venous Po2, however, was observed at >10° C indicating that excessive oxygen uptake from the blood is not fully compensated for by circulatory performance, until finally, Po2 levels fully collapse. In a second set of experiments energy and acid,base status of white muscle of Atlantic cod in vivo was measured by magnetic resonance (31P-NMR) spectroscopy in unanaesthetized and unimmobilized fish in the temperature range between 13 and 21° C. A decrease in white muscle intracellular pH (pHi) with temperature occurred between 10 and 16° C (,pH per ° C = ,0·025 per ° C). In white muscle temperature changes had no influence on high-energy phosphates such as phosphocreatine (PCr) or ATP except during exposure to high critical temperatures (>16° C), indicating that white muscle energy status appears to be relatively insensitive to thermal stress if compared to the thermal sensitivity of the whole animal. The data were consistent with the hypothesis of an oxygen limitation of thermal tolerance in animals, which is set by limited capacity of oxygen supply mechanisms. In the case of Atlantic cod circulatory rather than ventilatory performance may be the first process to cause oxygen deficiency during heat stress. [source] Development of feeding structures in larval fish with different life histories: winter flounder and Atlantic codJOURNAL OF FISH BIOLOGY, Issue 4 2001I. Hunt von Herbing The size at which feeding structures developed and shifts in head proportions occurred, differed between Atlantic cod Gadus morhua and winter flounder Pseudopleuronectes americanus. The sequence and timing of the development of feeding structures may not be dependent on size, but may occur because they are necessary to meet specific requirements offish larvae feeding in the plankton. In early larval stages development of feeding structures was similar in number and type and was necessary for first-feeding in both species. In later stages, significant differences between species occurred in the timing of the development of feeding structures. In cod differentiation of new structures and changes in head proportions occurred at about two-thirds of the way through larval life, which coincided with an increase in growth. In flounder changes in feeding morphology did not occur during the symmetrical larval stage, but occurred only after metamorphosis to the asymmetrical demersal juvenile stage. Differences between cod and flounder in the size at which feeding structures develop may reflect life history adaptations expressed in the duration of the pelagic larval stage, as well as differences in juvenile habitat and feeding ecology. [source] Seasonal changes of thyroid hormones in field-collected Atlantic cod in relation to condition indices, water temperature and photoperiodJOURNAL OF FISH BIOLOGY, Issue 3 2000L. A. Comeau Serum T4 and T3 in wild Atlantic cod Gadus morhua ranged from 1 to 12 ng ml,1 and from 2 to 27 ng ml,1 respectively over a 3-year period. In general, the concentrations increased from summer (T3) or early autumn (T4) to maxima in mid-winter and declined abruptly during spring. The T4/T3 monthly means were lowest in summer and highest in winter. The seasonal patterns of thyroid hormones were weakly correlated with changes in water temperature. However, both T4 and T3 co-varied simultaneously with photoperiod. In addition, T3 was correlated with the hepatosomatic index and condition factor during summer and autumn. It is suggested that the seasonal changes in the release of T4 from the thyroid were photoperioddriven, and that the course of T3 was regulated by the metabolic state of the fish during the somatic growth period. [source] Tissue tropism of nervous necrosis virus (NNV) in Atlantic cod, Gadus morhua L., after intraperitoneal challenge with a virus isolate from diseased Atlantic halibut, Hippoglossus hippoglossus (L.)JOURNAL OF FISH DISEASES, Issue 8 2009K Korsnes Abstract Atlantic cod, Gadus morhua, averaging 100 g, were experimentally challenged by intraperitoneal injection of nervous necrosis virus (NNV) originating from Atlantic halibut. Cod tissues, including blood, gill, pectoral fin, barbel, ventricle, atrium, spleen, liver, lateral line (including muscle tissue), eye (retina) and brain, were sampled at day 25 and 130 and investigated by real-time RT-PCR for the presence of NNV. Relative quantifications at day 130 were calculated using the 2,,,Ct method. Immunosuppression by injection of prednisolone-acetate was introduced for a 30-day period, and tissue sampled at day 180 and relative quantification estimated. No mortality or clinical signs of disease were observed in the challenged group. The challenge resulted in detection of NNV in blood, spleen, kidney, liver, heart atrium and heart ventricle at day 25, and by the end of the experiment NNV showed a clear increase in brain and retina, suggesting these to be the primary tissues for viral replication. There was no increase in the relative amount of NNV in blood, atrium, ventricle, spleen, liver and kidney. Corticosteroid implants resulted in a weak increase in virus RNA in spleen, kidney, liver and brain. These findings suggest that Atlantic cod is susceptible to infection with NNV from halibut. The observed tissue tropism patterns suggest an initial viraemic phase, followed by neurotrophy. Head-kidney is the best tissue identified for possible NNV detection by non-lethal biopsy, but detection was not possible in all injected fish. [source] IMPACT OF FREEZING TEMPERATURE ON QUALITY OF FARMED ATLANTIC COD (GADUS MORHUA L.)JOURNAL OF TEXTURE STUDIES, Issue 4 2007TURID MØRKØRE ABSTRACT This study evaluates the impact of freezing temperature (,10,,25,,40,,55 or,70C) on thaw exudates, liquid leakage during freeze-chilling, appearance, gaping and mechanical properties of farmed Atlantic cod fillets. Freezing temperature significantly influenced each of the characteristics studied. High temperatures (,10 and,25C) gave increased thaw exudates, and freezing at,10C gave the highest liquid leakage during freeze-chilling. Fillets frozen at,10C had the lowest gaping and the whitest appearance. The results indicated the highest degree of toughening upon freezing at,10 or,55C, whereas the degree of toughening appeared to be similar and lower for fillets frozen at,25,,40 or,70C. The impact of freezing temperatures on the quality of farmed cod therefore appeared to be complex, but no overall beneficial effects were found by decreasing the freezing temperature below,40C. PRACTICAL APPLICATIONS For the fish processing industry, it is important to define optimal freezing and frozen storage regimes that are cost efficient and at the same time preserve the fresh fillet quality. Farmed cod differ from their wild counterparts by having lower water content, lower muscle pH and thicker fillets. Hence, industrial guidelines for wild cod may not be transferable to farmed cod. This study showed no beneficial effects by decreasing the freezing temperature below ,40C. Freezing and frozen storage are usually separated commercially. Results from the present study give valuable contribution to future studies aiming at defining optimal combination of freezing and frozen storage temperatures for farmed Atlantic cod. [source] Production, Quality, and Low Temperature Incubation of Eggs of Atlantic Cod Gadus morhua and Haddock Melanogrammus aeglefinus in CaptivityJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2000Lawrence J. Buckley Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus broodstock maintained under altered regimens of temperature and photoperiod spawned up to 8 mo per year. The cod broodstock produced viable embryos from October through June. The haddock broodstock produced viable embryos from December through May. Egg diameters were largest during the middle of the spawning season when water temperature was at a minimum, resulting in an inverse relationship between egg diameter and water temperature in both species. Egg quality was high, as evaluated by buoyancy, fertilization rate, regularity of early cleavage, and percent viable hatch. Low temperature incubation of cod and haddock eggs extended the embryonic period. Cod embryos tolerated a wider range of temperatures than haddock. High mortality (1 90%) was observed before hatching in haddock embryos incubated at 1 C. Atlantic cod embryos hatched at temperatures as low as ,1 C, extending the embryonic period to 59 d. At 8 C Atlantic cod and haddock embryos hatched in 11,12 d. To determine if extending the embryo incubation time by using low temperatures had a detrimental effect, embryos were incubated through hatch at either 1 C or 6 C, and the larvae from both groups reared at 6 C. Growth and early survival of larvae were comparable in both treatments. [source] Characterization of 18 new microsatellite loci in Atlantic cod (Gadus morhua L.)MOLECULAR ECOLOGY RESOURCES, Issue 6 2008SIGURLAUG SKIRNISDOTTIR Abstract Eighteen new microsatellite loci consisting of 10 di-, 5 tri-, 2 tetra- and 1 heptanucleotide repeats are introduced for the Atlantic cod (Gadus morhua L.). All loci were co-amplified in two polymerase chain reactions (plus two previously published microsatellites) and all products were typed clearly. The number of alleles per locus ranged from six (PGmo130) to 45 (PGmo76) and the observed heterozygosity ranged from 0.356 (PGmo130) to 0.957 (PGmo95). All loci except one followed Hardy,Weinberg expectations. Genetic linkage disequilibrium analysis between all pairs of loci did not yield any significant values. [source] Isolation and characterization of microsatellite loci in the deep-sea marine fish, the roundnose grenadier (Coryphaenoides rupestris)MOLECULAR ECOLOGY RESOURCES, Issue 5 2008HALVOR KNUTSEN Abstract We developed polymerase chain reaction primers for eight dinucleotide microsatellite loci in the marine deep sea fish, roundnose grenadier (Coryphaenoides rupestris). All markers were obtained from a partial genomic DNA library, and characterized in 90 unrelated individuals from one putative population sampled on the Mid-Atlantic Ridge. The number of alleles ranged from two to 61 with an average of 21 per locus. The observed heterozygosity levels ranged from 0.301 to 0.987 with an average of 0.672. Several of the markers amplified multiple alleles from either the Atlantic cod (Gadus morhua) or the deep-sea fish roughhead grenadier (Macrourus berglax). [source] Development of 25 gene-associated microsatellite markers of Atlantic cod (Gadus morhua L.)MOLECULAR ECOLOGY RESOURCES, Issue 4 2006JØRGEN STENVIK Abstract Microsatellites were identified by screening 2294 GenBank entries available for Atlantic cod (Gadus morhua L.), mainly representing expressed sequence tags and cDNA sequences. Ninety-two novel microsatellite loci (tetra-, tri- and dinucleotides) were characterized on 96 individuals. This strategy yielded 25 gene-associated polymorphic microsatellite markers (11 tri- and 14 dinucleotides) with two to 20 alleles and an average heterozygosity of 0.48 in the population studied (range 0.02,0.89). One marker exhibited significant homozygote excess, and one of the primer pairs amplified two linked markers. The gene identity was determined at nine of the loci, confirming the associated microsatellites as type I markers. [source] Nine new polymorphic microsatellite loci for the amplification of archived otolith DNA of Atlantic cod, Gadus morhua L.MOLECULAR ECOLOGY RESOURCES, Issue 2 2006KLARA BJÖRG JAKOBSDÓTTIR Abstract Nine out of 22 microsatellite primers tested were successfully amplified on three samples of cod Gadus morhua L. (two contemporary and one archived otolith samples). All loci were polymorphic (5,23 alleles/locus). The average observed heterozygosity across loci and samples was 0.625, ranging from 0.294 to 0.895 at each locus. All loci were under Hardy,Weinberg equilibrium, except PGmo56 that showed significant excess of heterozygotes in all studied samples. The isolated loci were suitable for degraded DNA and therefore useful for conducting a long-term temporal study with DNA obtained from archived otoliths of cod. [source] Genotyping of pantophysin I (Pan I) of Atlantic cod (Gadus morhua L.) by allele-specific PCRMOLECULAR ECOLOGY RESOURCES, Issue 1 2006JØRGEN STENVIK Abstract The two main allelic variants of the Atlantic cod (Gadus morhua L.) pantophysin I (Pan I) locus have different frequencies within different cod stocks. The Dra I polymorphism which distinguishes the two alleles can thus be used for discrimination of coastal and offshore cod populations. We present a new method for Pan I genotyping using fluorescent allele-specific duplex polymerase chain reaction (PCR). This method is more rapid, reliable and cost-effective than the previously published method and it is not affected by DNA source and quality. This improvement is important for studies demanding high throughput and accuracy of Pan I genotyping [source] Genetic diversity within and among Atlantic cod (Gadus morhua) farmed in marine cages: a proof-of-concept study for the identification of escapeesANIMAL GENETICS, Issue 5 2010K. A. Glover Summary This study presents a molecular genetic characterization of Atlantic cod reared in commercial marine farms. Samples consisted of approximately 47 fish collected from nine cages located on four farms throughout Norway. In addition, 28 farmed escapees were recaptured in the sea (443 fish in total). Nine microsatellite loci and the Pan I gene were analysed, revealing a total of 181 alleles. Each sample contained 43,63% of total allelic variation. Comparing variation with published data for wild cod indicates that lower genetic variation exists within single cages than in wild populations. Significant linkage disequilibrium was observed amongst pairs of loci in all samples, suggesting a low number of contributing parental fish. Global FST was 0.049, and the highest pairwise FST value (pooled loci) was 0.085. For single loci, the Pan I gene was the most diagnostic, displaying a global FST of 0.203. Simulations amongst the samples collected on farms revealed an overall correct self-assignment percentage of 75%, demonstrating a high probability of identifying individuals to their farm of origin. Identification of the 28 escapees revealed a single cage as the most likely source of origin for half of the escapees, whilst the remaining fish were assigned to a mixture of samples, suggesting more than one source of escapees. [source] A SNP/microsatellite genetic linkage map of the Atlantic cod (Gadus morhua)ANIMAL GENETICS, Issue 6 2009T. Moen Summary A first genetic linkage map of the Atlantic cod (Gadus morhua) was produced, based on segregation data from 12 full-sib families of Norwegian origin. The map contained 174 single nucleotide polymorphism markers and 33 microsatellites, distributed on 25 linkage groups and had a length of 1225 cM. A significant difference in recombination rates between sexes was found, the average ratio of female:male recombination rates being 1.78 ± 1.62 (SD). [source] A method to determine protein digestibility of microdiets for larval and early juvenile fishAQUACULTURE NUTRITION, Issue 6 2009J.M. HANSEN Abstract A method to evaluate protein quality using in vivo methods was developed for larval fish. FluoSpheres® fluorescent microspheres (10 ,m) were incorporated into two test diets, our standard zein microdiet (ZMD) and a microdiet with identical ingredients except for the replacement of high quality fish meal with the same product cooked for 24 h at 80 °C (ZMD-CF). Several trials were performed to design a reliable method to test digestibility using FluoSpheres® as a marker. The developed in vivo technique was tested on 35 days posthatch (dph) larval Atlantic cod (Gadus morhua L.) and two tropical fish species in the early juvenile stage. The method took into account loss of total protein to the faecal pellet and water column. Apparent digestibility of protein in larval cod fed ZMD was significantly higher than that of larvae fed ZMD-CF (P < 0.05). A growth study to validate differences between the two diets showed significant differences in growth and survival of larvae fed ZMD versus ZMD-CF (P < 0.05). Further validation of our results was indicated through the use of a pH-stat method using enzymes extracted from 35 dph larval cod guts. This novel technique will be advantageous for researchers to evaluate feed ingredients for larval marine fish and is adaptable to many different areas of larval fish nutrition. [source] Effects of protein hydrolysate in weaning diets for Atlantic cod (Gadus morhua L.) and Atlantic halibut (Hippoglossus hippoglossus L.)AQUACULTURE NUTRITION, Issue 2 2009A. KVÅLE Abstract The study aims to test whether predigested dietary protein enhances the utilization of formulated diets at weaning, and also whether it stimulates intestinal maturation. In this study, Atlantic cod [Gadus morhua L.; 41 days posthatch (dph)] and Atlantic halibut [Hippoglossus hippoglossus L.; 63 days postfirst feeding (dpff)] were weaned onto diets with graded levels of protein hydrolysate. By increasing the inclusion of dietary protein as hydrolysate from 0 to 400 g kg,1, cod increased the rate of survival from 7 ± 1% to 18 ± 2% (82 dph; regression, P = 4*10,7). In halibut, the survival rate decreased from 57 ± 9% to 22 ± 7% as the inclusion of protein in the form of hydrolysate increased from 0 to 450 g kg,1 (119 dpff; regression, P = 8*10,5). Growth was not affected in any of the species. Results in specific activities of the intestinal enzymes leucine aminopeptidase (LAP) and alkaline phospatase (AP) supported the results in survival in halibut and partly also in cod, by showing increased activities in groups with increased survival (anova, P < 0.05). The lower optimal level of hydrolysed protein in halibut than in cod is suggested mainly because of a slower feeding practice in halibut, which allows more extensive nutrient leaching before ingestion. [source] | ||||||||||||||||