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Cod Gadus Morhua (cod + gadus_morhua)

Distribution by Scientific Domains

Earth and Environmental Science	93%

Kinds of Cod Gadus Morhua

atlantic cod gadus morhua

Selected Abstracts

Production, Quality, and Low Temperature Incubation of Eggs of Atlantic Cod Gadus morhua and Haddock Melanogrammus aeglefinus in Captivity

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2000
Lawrence 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]

ORIGINAL ARTICLE: Implications of fisheries-induced evolution for stock rebuilding and recovery

EVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 3 2009
Katja 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]

Process-based model for direct and indirect effects of hydrographic conditions on Central Baltic cod (Gadus morhua) egg mortality

FISHERIES OCEANOGRAPHY, Issue 2 2008
K. 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]

A link between sound producing musculature and mating success in Atlantic cod

JOURNAL OF FISH BIOLOGY, Issue 3 2008
S. 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 shock

JOURNAL OF FISH BIOLOGY, Issue 1 2008
L. 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 fish

JOURNAL OF FISH BIOLOGY, Issue 4 2007
M. 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]

Is reduced body growth of cod exposed to the gill parasite Lernaeocera branchialis a cost of resistance?

JOURNAL OF FISH BIOLOGY, Issue 5 2006
D. 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, 8·5% were infected, but lost the parasite, 8% were infected with one parasite and 4·5% 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 isotopes

JOURNAL OF FISH BIOLOGY, Issue 3 2006
H. Høie
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 success

JOURNAL OF FISH BIOLOGY, Issue 2 2004
R. 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 catches

JOURNAL OF FISH BIOLOGY, Issue 5 2003
H. 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 cod

JOURNAL OF FISH BIOLOGY, Issue 6 2003
F. 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]

Micro- and macroscopic characteristics to stage gonadal maturation of female Baltic cod

JOURNAL OF FISH BIOLOGY, Issue 2 2003
J. 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 spawning

JOURNAL OF FISH BIOLOGY, Issue 1 2003
S. 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 11·,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 cod

JOURNAL OF FISH BIOLOGY, Issue 4 2001
I. 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 photoperiod

JOURNAL OF FISH BIOLOGY, Issue 3 2000
L. 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]