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Morhua
Kinds of Morhua Terms modified by Morhua Selected AbstractsAlternate 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] MEASURING PROBABILISTIC REACTION NORMS FOR AGE AND SIZE AT MATURATIONEVOLUTION, Issue 4 2002Mikko Heino Abstract We present a new probabilistic concept of reaction norms for age and size at maturation that is applicable when observations are carried out at discrete time intervals. This approach can also be used to estimate reaction norms for age and size at metamorphosis or at other ontogenetic transitions. Such estimations are critical for understanding phenotypic plasticity and life-history changes in variable environments, assessing genetic changes in the presence of phenotypic plasticity, and calibrating size- and age-structured population models. We show that previous approaches to this problem, based on regressing size against age at maturation, give results that are systematically biased when compared to the probabilistic reaction norms. The bias can be substantial and is likely to lead to qualitatively incorrect conclusions; it is caused by failing to account for the probabilistic nature of the maturation process. We explain why, instead, robust estimations of maturation reaction norms should be based on logistic regression or on other statistical models that treat the probability of maturing as a dependent variable. We demonstrate the utility of our approach with two examples. First, the analysis of data generated for a known reaction norm highlights some crucial limitations of previous approaches. Second, application to the northeast arctic cod (Gadus morhua) illustrates how our approach can be used to shed new light on existing real-world data. [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] ORIGINAL ARTICLE: Implications of fisheries-induced evolution for stock rebuilding and recoveryEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 3 2009Katja Enberg Abstract Worldwide depletion of fish stocks has led fisheries managers to become increasingly concerned about rebuilding and recovery planning. To succeed, factors affecting recovery dynamics need to be understood, including the role of fisheries-induced evolution. Here we investigate a stock's response to fishing followed by a harvest moratorium by analyzing an individual-based evolutionary model parameterized for Atlantic cod Gadus morhua from its northern range, representative of long-lived, late-maturing species. The model allows evolution of life-history processes including maturation, reproduction, and growth. It also incorporates environmental variability, phenotypic plasticity, and density-dependent feedbacks. Fisheries-induced evolution affects recovery in several ways. The first decades of recovery were dominated by demographic and density-dependent processes. Biomass rebuilding was only lightly influenced by fisheries-induced evolution, whereas other stock characteristics such as maturation age, spawning stock biomass, and recruitment were substantially affected, recovering to new demographic equilibria below their preharvest levels. This is because genetic traits took thousands of years to evolve back to preharvest levels, indicating that natural selection driving recovery of these traits is weaker than fisheries-induced selection was. Our results strengthen the case for proactive management of fisheries-induced evolution, as the restoration of genetic traits altered by fishing is slow and may even be impractical. [source] Genetic population structure of marine fish: mismatch between biological and fisheries management unitsFISH AND FISHERIES, Issue 4 2009Henning Reiss Abstract An essential prerequisite of a sustainable fisheries management is the matching of biologically relevant processes and management action. In fisheries management and assessment, fish stocks are the fundamental biological unit, but the reasoning for the operational management unit is often indistinct and mismatches between the biology and the management action frequently occur. Despite the plethora of population genetic data on marine fishes, to date little or no use is made of the information, despite the fact that the detection of genetic differentiation may indicate reproductively distinct populations. Here, we discuss key aspects of genetic population differentiation in the context of their importance for fisheries management. Furthermore, we evaluate the population structure of all 32 managed marine fish species in the north-east Atlantic and relate this structure to current management units and practice. Although a large number of studies on genetic population structure have been published in the last decades, data are still rare for most exploited species. The mismatch between genetic population structure and the current management units found for six species (Gadus morhua, Melanogrammus aeglefinus, Merlangius merlangus, Micromesistius poutassou, Merluccius merluccius and Clupea harengus), emphasizes the need for a revision of these units and questions the appropriateness of current management measures. The implementation of complex and dynamic population structures into novel and less static management procedures should be a primary task for future fisheries management approaches. [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] A new approach to prioritizing marine fish and shellfish populations for conservationFISH AND FISHERIES, Issue 4 2001Einar Eg Nielsen Abstract There has been increasing awareness of the vulnerability of marine organisms to population extirpation and species extinction. While very few documented cases of species extinction exist in the marine environment, it is anticipated that managers will face the dilemma of prioritizing populations of marine fish and shellfish for protection in the near future. Current prioritization procedures have been developed from salmonid models with the intent of applying them to all marine organisms, and in some cases to freshwater and terrestrial taxa. In this review we provide evidence for the relevance of such a process for marine species and further suggest five broad categories of marine organisms that have distinctive traits influencing their genetic structure. The current prioritization models have been adapted to account for each of these species groups. Emphasis is placed on ,Classical Marine Species' which represent the opposite end of the continuum from the salmon model, displaying high within-population genetic variance. From this category, three cod (Gadus morhua) stocks were selected to evaluate a revised scheme developed specifically for ,Classical Marine Species' that includes performance measures such as (i) reduction in number of spawning populations; (ii) reduction of Ne : Nc (ratio of effective to census population size); (iii) changes in life-history traits; (iv) critical density for spawning success; and (v) patchy vs. continuous distribution pattern. When the salmonid scheme was applied, the cod examples were allocated low values, indicating that they were not under threat. However, when the revised scheme was applied, all three cod stocks were allocated high values, indicating that the revised scheme was more reflective of the particular life-history traits of this category of organisms. [source] Process-based model for direct and indirect effects of hydrographic conditions on Central Baltic cod (Gadus morhua) egg mortalityFISHERIES OCEANOGRAPHY, Issue 2 2008K. H. ANDERSEN Abstract A process-oriented model for the mortality of eggs of cod Gadus morhua in the Central Baltic Sea is developed, based on a synthesis of existing knowledge of the effects of salinity, oxygen and predation by sprat Sprattus sprattus. The models show the importance of the vertical and temporal overlap between eggs and predations. Effects related to the changing buoyancy of the eggs due to age and size of the mother fish, batch number and stock structure are not of major importance for the egg survival of this stock. It is demonstrated that under the present high sprat predation pressure, the observed delay in spawning time has increased egg survival. [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 oxygen saturation on the distributional overlap of predator (cod, Gadus morhua) and prey (herring, Clupea harengus) in the Bornholm Basin of the Baltic SeaFISHERIES OCEANOGRAPHY, Issue 1 2002Stefan Neuenfeldt Environmental heterogeneity can create boundary conditions for the co-occurrence of marine predators and their prey. If one or both are spatially constrained by their tolerance to environmental variables, then spatial differences in the availability of possible habitats define the volume of distributional overlap. Cod (Gadus morhua L.) and its prey, herring (Clupea harengus L.), in the vertically stratified Bornholm Basin of the Baltic Sea are presented as an example. A non-linear model was used to estimate oxygen avoidance thresholds for both species. Herring avoided oxygen saturation levels below 50%, while cod tolerated oxygen saturation down to 16%. The threshold of 50% oxygen saturation, below which cod could not encounter its prey, herring, was applied to a time series of vertical oxygen profiles from the centre of the Bornholm Basin to estimate the size of the overlap volume during the winter period from 1958 to 1999. Dependent on the oxygenation of the deep-water, the overlap volume varied between 57 km3 and 250 km3. [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] Patterns in the spawning of cod (Gadus morhua L.), sole (Solea solea L.) and plaice (Pleuronectes platessa L.) in the Irish Sea as determined by generalized additive modellingFISHERIES OCEANOGRAPHY, Issue 1 2000Eleven ichthyoplankton cruises were undertaken covering most of the Irish Sea during the period February to June, 1995. To identify spawning localities and investigate temporal trends in egg production, the data on stage 1 A egg distributions of cod (Gadus morhua), plaice (Pleuronectes platessa) and sole (Solea solea) have been modelled using generalized additive models (GAMs). A two-stage approach was adopted where presence/absence was firstly modelled as a binary process and a GAM surface subsequently fitted to egg production (conditional on presence). We demonstrate that this approach can be used to model egg production both in space and in time. The spawning sites for cod, plaice and sole in the Irish Sea were defined in terms of the probability of egg occurrence. For cod, we demonstrate that by integrating under predicted egg production surfaces, a cumulative production curve can be generated and used to define percentiles of production and thus delimit the extent of the spawning season. However, for plaice and sole, the surveys did not fully cover the spawning season and the limitations that this imposes on GAM modelling of these data are discussed. Comparison of the spawning sites in 1995 with historical data suggests that the locations of cod, plaice and sole egg production in the Irish Sea have probably remained relatively constant over the last 30 years. [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] Lack of glucose and hsp70 responses in haddock Melanogrammus aeglefinus (L.) subjected to handling and heat shockJOURNAL OF FISH BIOLOGY, Issue 1 2008L. O. B. Afonso Juvenile haddock Melanogrammus aeglefinus (c. 39 g) were exposed to either a handling stressor (1 min out of water) or heat shock (increase from 10 to 15° C for 1 h), and plasma cortisol, plasma glucose and gill hsp70 levels were determined before, and at 1, 3, 6, 12, 24 and 48 h post-stress. The pattern of cortisol increase was similar following both stressors, with levels increasing by 25-fold at 1 h post-stress, but returning to pre-stress levels (2,5 ng ml,1) by 3 h. In contrast, neither handling nor heat shock caused an increase in plasma glucose levels. Although gill hsp70 was detected, presumably constitutive levels, in both control and heat shocked groups, there were not significant changes in gill hsp70 levels after exposure to heat shock. The lack of glucose and hsp70 responses to these typical stressors is consistent with previous studies on Atlantic cod Gadus morhua, and suggests that the stress physiology of Gadidae differs from the ,typical' teleost. [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] Is reduced body growth of cod exposed to the gill parasite Lernaeocera branchialis a cost of resistance?JOURNAL OF FISH BIOLOGY, Issue 5 2006D. A. Lysne Three hundred and sixty-nine cod Gadus morhua were individually marked and caged for 19 months. During this period, each cod was inspected several times for Lernaeocera branchialis. Growth in four groups of cod, identified by their infection history, were compared. During the caging, 79% of the cod remained uninfected, 8ˇ5% were infected, but lost the parasite, 8% were infected with one parasite and 4ˇ5% were infected with more than one parasite. The infected fish either harboured the parasite at caging or were infected during the study period. The highest rate of increase, both in body mass and in standard length (LS), was recorded in the group of male fish infected with one parasite throughout the experimental period. Conversely, those males free from infection showed significantly lower growth. The observed differences in growth could not be explained by changes in variables related to reproductive strategies. The alternative explanation for these results is that resistance to L. branchialis was associated with costs in terms of reduced growth of body mass and LS. [source] Estimating the timing of growth rings in Atlantic cod otoliths using stable oxygen isotopesJOURNAL OF FISH BIOLOGY, Issue 3 2006H. Hřie A technique involving micro-scale sampling of otolith carbonate and analyses of stable oxygen isotope composition was used to relate the zone appearance of the otolith to the seasonal temperature cycle. Otolith opacity could then be related to the timing of zone formation. Otoliths from two groups of Atlantic cod Gadus morhua held under known temperature conditions over a period of 4 and 6 years were examined. The otolith translucency followed the same pattern as the estimated temperature (from otolith ,18O values) in the yearly increments three and four, meaning that the translucent zones were deposited at the seasonal highest temperature in late summer and early autumn. The relative light intensities of otolith yearly increments five and six of older fish (deposited in the same years), however, were not significantly correlated to the estimated temperatures since increased otolith translucency also occurred at low temperatures. This might have been caused by stress in connection with gonad development or starvation during the spawning period. The results showed that this method of coupling otolith opacity and stable oxygen isotope composition can be used to estimate the timing of zone formations in otoliths. [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] Ecological relevance of temporal stability in regional fish catchesJOURNAL OF FISH BIOLOGY, Issue 5 2003H. Hinz The concept of habitat selection based on ,Ideal Free Distribution' theory suggests that areas of high suitability may attract larger quantities of fishes than less suitable or unsuitable areas. Catch data were used from groundfish surveys to identify areas of consistently high densities of whiting Merlangius merlangus, cod Gadus morhua and haddock Melanogrammus aeglefinus in the Irish Sea and plaice Pleuronectes platessa, sole Solea solea, lemon sole Microstomus kitt in the English Channel over a period of 10 and 9 years respectively. A method was introduced to delineate areas of the seabed that held consistently high numbers of fishes objectively from large datasets. These areas may constitute important habitat characteristics which may merit further scientific investigations in respect to ,Essential Fish Habitats'(EFH). In addition, the number of stations with consistently high abundances of fishes and the number of stations where no fishes were caught gave an indication of the site specificity of the fish species analysed. For the gadoids, whiting was found to be less site specific than cod and haddock, while for the flatfishes, plaice and sole were less site specific than lemon sole. The findings are discussed in the context of previously published studies on dietary specializm. The site specificity of demersal fishes has implications for the siting process for marine protected areas as fish species with a strong habitat affinity can be expected to benefit more from such management schemes. [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 = ,0ˇ025 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] Micro- and macroscopic characteristics to stage gonadal maturation of female Baltic codJOURNAL OF FISH BIOLOGY, Issue 2 2003J. Tomkiewicz A set of histological characteristics to judge ovarian development was established and used to elaborate morphological criteria of 10 maturity stages of Baltic cod Gadus morhua sampled throughout the annual cycle to represent different macroscopic maturity stages. The applied characteristics confirmed most stages of the macroscopic scale, but the separation of late immature and resting mature females remained imprecise. Atretic vitellogenic oocytes or encapsulated residual eggs identified the resting condition morphologically, but not all ovaries with visible signs of previous spawning showed such features. One ovarian stage that was previously classified as ,ripening' was changed to ,spawning', owing to the prevalence of hydrated eggs and empty follicles. Ovaries with malfunctions were defined by a separate stage. Macroscopic criteria were revised by comparing the gross anatomy of ovaries with their histology. Female length and gonado-somatic index supported stage definitions, but substantial variation in Fulton's condition factor and the hepato-somatic index rendered these of little use for this purpose. The time of sampling influenced staging accuracy. A female spawner probability function based on the proportion of ripening and ripe specimens in early spring seems to be the most appropriate method to estimate spawner biomass and reproductive potential. [source] Oxygen and salinity characteristics of predator,prey distributional overlaps shown by predatory Baltic cod during spawningJOURNAL OF FISH BIOLOGY, Issue 1 2003S. Neuenfeldt In the distributional overlap volume of Baltic cod Gadus morhua and its prey, studied in the Bornholm Basin in the southern Baltic Sea, only a fraction of the sprat Sprattus sprattus population vertically overlapped with the Baltic cod population. Sprat occurred in the intermediate water, in the halocline and in the bottom water, while herring Clupea harengus and Baltic cod occurred exclusively in the halocline and in the bottom water. Only parts of the sprat population were hence accessible for Baltic cod, and only a fraction of the sprat had access to the Baltic cod eggs below the halocline. Baltic cod,clupeid overlap volumes appeared to be determined by salinity stratification and oxygenation of the bottom water. Hydrography time series were used to estimate average habitat volumes and overlap from July to September in 1958,1999. In the 1999 survey spawning Baltic cod had greater ratios of empty stomachs and lower average rations than non-spawning Baltic cod. The average ration for Baltic cod caught within 11ˇ,4 m from the bottom (demersal) did not differ from the average ration of Baltic cod caught in shallower waters (pelagic), because spawning and non-spawning Baltic cod in both strata were caught at equal rates. The diet of the Baltic cod caught demersally contained more benthic invertebrates, especially Saduria entomon, but Baltic cod caught pelagically also had fresh benthic food in their stomachs, indicating vertical migration of individual fish. [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] Phenotypic, serological and genetic characterization of Pseudomonas anguilliseptica strains isolated from cod, Gadus morhua L., in northern EuropeJOURNAL OF FISH DISEASES, Issue 11 2007S Balboa Abstract The biochemical, serological and genetic characteristics of six strains of Pseudomonas anguilliseptica isolated from cod, Gadus morhua, in Scotland were compared to well characterized isolates of this same bacterial species but of different origin. Biochemical and physiological analyses showed that this group of isolates was highly homogeneous, their characteristics matching previous descriptions of the pathogen. Similar results were obtained for the six cod isolates in the serological assays, all of them belonging to the serotype O1. Marked homogeneity was observed also in the genetic study, analysed by means of RAPD, ERIC-PCR and REP-PCR procedures, showing that they were similar to isolates from gilthead seabream, Sparus aurata, black spot seabream, Pagellus bogaraveo, and turbot, Psetta maxima. Virulence assays demonstrated that the cod isolates were highly pathogenic for turbot and sole, Solea senegalensis, with LD50 between 7.6 × 104 and 5 × 107 bacterial cells per fish. [source] EFFECT OF VARIOUS ANTIOXIDANTS ON THE OXIDATIVE STABILITY OF ACID AND ALKALI SOLUBILIZED MUSCLE PROTEIN ISOLATESJOURNAL OF FOOD BIOCHEMISTRY, Issue 2 2009SIVAKUMAR RAGHAVAN ABSTRACT Protein isolates prepared from cod (Gadus morhua) myofibrillar proteins using acid or alkali solubilization are susceptible to oxidative rancidity. Oxidation could be delayed by the exogenous addition of antioxidants. The objective of this research was to compare the efficacy of antioxidants such as ,-tocopherol, butylated hydroxyanisole (BHA) and propyl gallate, to inhibit oxidation in acid- and alkali- solubilized cod protein isolates. Oxidation was catalyzed using cod hemolysate. Oxidation of lipids was monitored by the measurement of thiobarbituric acid reactive substances and painty odor. Results showed that protein isolates prepared using the acid process was significantly (P < 0.05) more susceptible to lipid oxidation than alkali-solubilized protein isolates. Regardless of pH treatments, the efficacy of various antioxidants decreased in the order propyl gallate > BHA > ,-tocopherol. PRACTICAL APPLICATIONS Research has shown that seafood available for human consumption is rapidly getting depleted and that many fish species may become extinct in the next half-century or so. Acid and alkali solubilization methods are recent but well-known techniques used for preparing protein isolates from under-utilized aquatic species and the by-products of seafood industry. Although numerous researchers have studied the use of acid and alkali processes on several sources of seafood, almost no research has been done on the use of antioxidants to protect protein isolates from lipid oxidation. In our research, we have studied the effect of various antioxidants on the oxidative stability of acid- and alkali-solubilized fish myofibrillar proteins. The results from this work will enable the seafood industry to properly identify the process and the type of antioxidants required for making muscle food products with increased oxidative stability. [source] | ||||||||||||||||