Showing papers on "Gadus published in 1985"
TL;DR: There was a highly significant correlation between genetic and geographic distance for the samples from the Atlantic suggesting that a substantial gene flow has occurred between these stocks with geographic distance being an inhibiting factor.
Abstract: The amount of genetic differentiation between stocks of Atlantic cod (Gadus morhua) was estimated from electrophoretically detectable protein loci expressed in skeletal muscle and liver. Variant al...
219 citations
TL;DR: The ability of larvae to capture artemia nauplii was related to the size of their mouth gape, itself a function of larval size, which may help them survive the shift to exogenous feeding better than those from small eggs.
Abstract: The size of Atlantic cod eggs declines during the spawning season, and the potential effects of this on larval development were studied. Eggs from 12 females were artificially fertilized and incubated in separate aquaria. Egg diameter was correlated significantly (P < 0.05) with egg dry weight. The standard length of unfed larvae continued to increase a few days beyond yolk exhaustion, whereas the increase in muscle tissue (myotome height) reached its maximum at the time of yolk exhaustion. Egg dry weight was significantly correlated with larva dry weight, standard length, myotome height, and the size of the mouth gape. The ability of larvae to capture artemia nauplii was related to the size of their mouth gape, itself a function of larval size. Atlantic cod larvae from large eggs may survive the shift to exogenous feeding better than those from small eggs. Late-spawned Atlantic cod larvae may have a lower survival potential than those spawned earlier in the season.
153 citations
126 citations
TL;DR: Four isozymes of cytochrome P-450 were purified to varying degrees of homogeneity from liver microsomes of cod, a marine teleost fish, and showed differences in the rate and optimal pH for conversion of this substrate, and in optical properties.
114 citations
TL;DR: The population declined during summer probably due to cannibalism and predation from birds, and a first attempt to augment the fishery for Atlantic cod was made in the Austevoll region.
Abstract: In March-April 1983, 2.5 × 106 yolk-sac Atlantic cod larvae were released in a dammed estuarine pond. One month later, more than half a million metamorphosed. The larvae and metamorphosed juveniles depleted the natural food supply by mid-May, but the fish accepted small pellets containing 30% krill meal dispensed from automatic feeders. From mid-June, young Atlantic cod primarily ate the pellets, supplemented with minor amounts of wild calanoid and harpacticoid copepods. The population declined during summer probably due to cannibalism and predation from birds. No outbreaks of disease were observed, and infestation with parasites (nematodes) was less than 20%. Altogether, 75,000 juvenile Atlantic cod were captured alive from late May to October. By October, about 20,000 15-cm-long juveniles were tagged and released in the Austevoll region in a first attempt to augment the fishery for Atlantic cod.
81 citations
TL;DR: The stomach contents of 5,408 herring caught during North Sea trawl surveys in February 1980, 1982, and 1983 were analysed with a view of estimating predation mortalities exerted by the herring stock on plaice and cod eggs, based on the spatial distribution of size categories of herring and the numbers at age estimated from virtual population analysis.
Abstract: The stomach contents of 5,408 herring caught during North Sea trawl surveys in February 1980, 1982, and 1983 were analysed with a view of estimating predation mortalities exerted by the herring stock on plaice and cod eggs, based on the spatial distribution of size categories of herring and the numbers at age estimated from virtual population analysis. Predation on plaice and cod eggs was generally confined to the southern North Sea and only the younger age groups of herring (ages 2 and 3) consumed substantial numbers of fish eggs. Occasionally fish larvae (herring and plaice) were encountered. The estimated fraction consumed of the initial numbers of eggs produced varied from 0.7 to 1.9% for plaice and from 0.04 to 0.19% for cod. These estimates are necessarily crude and can only give a rough indication of the true predation mortalities. Although some effect of herring stock size on the level of recruitment of plaice might be expected, it is unlikely that the generally observed increase in recru...
77 citations
TL;DR: Fibres from icefish and cod failed to relax completely following activations at temperatures above approximately 12°C, suggesting the formation of a population of Ca-insensitive cross bridges, which appears largely to involve differences in the ability of cross bridges to generate force.
Abstract: Single fast fibres were isolated from the myotomal muscles of icefish (Chaenocephalus aceratus Lonnberg, Antarctica), North Sea Cod (Gadus morhua L.) and Pacific Blue Marlin (Makaira nigricans Wakiya, Hawaii). Fibres were chemically skinned with the non-ionic detergent Brij-58. Maximum tensions (Po, kN m-2) developed at the characteristic body temperature of each species are 231 for icefish (-1 degree C), 187 for cod (8 degrees C) and 156 for marlin (20 degrees C). At 0 degree C Po is 7 times higher for fibres from the icefish than from the marlin. Fibres from icefish and cod failed to relax completely following activations at temperatures above approximately 12 degrees C. The resultant post-contraction force is associated with a proportional increase in stiffness, suggesting the formation of a population of Ca-insensitive cross bridges. At 10 degrees C there is little interspecific variation in unloaded contraction velocity (Vmax) among the three species. Vmax (muscle lengths s-1) at normal body temperatures are 0.9 for icefish (-1 degree C), 1.0 for cod (8 degrees C) and 3.4 for marlin (20 degrees C). The force-velocity (P-V) relationship becomes progressively more curved with increasing temperature for all three species. Maximum power output for the fast muscle fibres from the Antarctic species at -1 degree C is around 60% of that of the tropical fish at 20 degrees C. Evolutionary temperature compensation of muscle power output appears largely to involve differences in the ability of cross bridges to generate force.
55 citations
TL;DR: Cod chitinase and chitobiase are endogenous and constitutive enzymes and had similar numbers of bacteria within the gastro-intestinal compartments as feeding fish.
Abstract: The levels of chitinolytic enzymes and chitinolytic bacteria in the digestive tract of feeding and fasting cod were compared. Enzyme activities within a given tissue were of a similar order irrespective of the presence of chitinolytic bacteria and/or chitin. Cod chitinase and chitobiase are therefore endogenous and constitutive enzymes. Fasting cod had similar numbers of bacteria within the gastro-intestinal compartments as feeding fish. Representative bacterial isolates from fasting fish were characterized.
53 citations
TL;DR: Conventional indices based upon relations of dry weight or body height at the anus to length were most sensitive to environmental conditions, and there was no apparent advantage in performing a multivariate analysis based upon a larger series of measurements.
Abstract: In our study of the condition of larval cod (Gadus morhua) collected off southwest Nova Scotia in winter-spring, 1983, we (1) examined relationships between larval condition and ambient environmental conditions, and (2) compared the use of simple morphometric indices of larval condition and of multivariate statistics to obtain information relevant to larval condition. Twelve indices of relative condition were obtained, based upon seven measurements made on each larva, and a principal component (PC) analysis was performed on these condition indices. Most condition indices and the first PC were significantly correlated with numbers of nauplii and of zooplankters per m3 in the water column, which are direct measures of food available to the larvae, but not to less direct measures of environmental quality for the larvae, such as plankton displacement volume or chlorophyll concentration. Conventional indices based upon relations of dry weight or body height at the anus to length were most sensitive to environmental conditions. There was no apparent advantage in performing a multivariate analysis based upon a larger series of measurements.
44 citations
TL;DR: The time trend in the DDT contamination of the marine environment in a Norwegian fjord where DDT has been used extensively in local fruitgrowing, has been studied for 10 years and the decrease in ∑-DDT illustrates the effectiveness of the 1970 ban on its use in Norway.
Abstract: The time trend in the DDT contamination of the marine environment in a Norwegian fjord where DDT has been used extensively in local fruitgrowing, has been studied for 10 years following the DDT ban. Residues of ∑-DDT (p,p′-DDT + 1.11p,p′-DDE + 1.11p,p′-TDE (DDD). The factor 1.11 is added to correct for the lower molecular weight) in 225 liver samples of seven sedentary fish species showed a downward trend during the period 1972 to 1982. The decrease in ∑-DDT illustrates the effectiveness of the 1970 ban on its use in Norway. The highest 1982 mean level of ∑-DDT was found in the liver of cod (Gadus morhua) (1237 μg/kg, wet weight, range 191–3845 μg/kg) and was about 1/3 of the corresponding 1972 residue level. The decrease of ∑-DDT was less rapid in the liver of the cod and the haddock (Melanogrammus aeglefinus) (half-life time 5.0 years with a 95% confidence limit of 2.3 years) than in the fish species sea scorpion (Myoxocephalus scorpius), cat fish (Anarhichas lupus), ballan wrasse (Labrus berggylta) and lemon sole (Microstomus kitt) (half-life time 2.6 years with a 95% confidence limit of 0.8 years). Cod and haddock have a substantially higher fat content in the liver compared to the other fish species. A half-life time of 3–5 years for biologically available DDT residues is suggested to apply generally to Nordic marine environments. Unmetabolized DDT constitute a smaller proportion of ∑-DDT in 1982 than in the previous years. However, a great variation between species and individuals was found. PCB contamination in the fish was low, and reflect a Norwegian baseline contamination. The highest 1982 mean level of PCB residues was found in cod liver (454 μg/kg, wet weight, range 175–1073 μg/kg) which was about 1/3 of the 1972 value. The levels of ∑-DDT and PCBs were correlated to fish weight in the cod. These two types of residues were mutually correlated over all weights. No correlation was found between the fat content of the liver and the residue level of organochlorine chemicals within the species. Only low levels of contamination by hexachlorobenzene (HCB), α-, γ-HCH and ∑-chlordane were found in 1982. The highest levels were found in cod liver (HCB 6–26; γ-HCH 6–16; α-HCH 4–140;∑-chlordane = oxychlordane + transnonachlor 38–220 μg/kg, wet weight). The levels of organochlorines in fish from a Norwegian fjord were generally low and not believed to have any toxicological implications.
41 citations
TL;DR: A hypothesis of a three-part density-dependent mechanism controlling fecundity is postulated for Atlantic cod reared in the laboratory over 10 months, for each of two consecutive years, 1978–1980.
TL;DR: The susceptibility of four species of marine fish to leech-transmitted Trypanosoma murmanensis was assessed by comparing condition factor, organ somatic indices, parasitological, hematological, and histological findings with corresponding uninfected animals.
Abstract: The susceptibility of four species of marine fish (Gadus morhua, Pseudopleuronectes americanus, Myoxocephalus scorpius, and Myoxocephalus octodecemspinosus) to leech-transmitted Trypanosoma murmane...
01 Mar 1985
TL;DR: Genotypes atLDH-3 andPGI-1 are not selectively neutral, and allele frequency differences at these two loci between groups of cod in nature should not be interpreted as markers of reproductive isolation.
Abstract: Genotypes atLDH-3 (lactate dehydrogenase) andPGI-1 (phosphoglucoisomerase) in 263 0-group specimens of Atlantic cod(Gadus morhua) caught in Trondheimsfjorden, Norway, in fall 1983 showed significantly different survival rates during 72 days in captivity. The heterozygote was nominally superior at both loci, and there was a significant accumulation of double heterozygotes among the survivors. Apparently,LDH-3 andPGI-1 are not selectively neutral, and allele frequency differences at these two loci between groups of cod in nature should not be interpreted as markers of reproductive isolation. The results are related to current concepts of cod population structure.
TL;DR: The present study was designed to determine the possible interaction of methylmercury and selenium in different tissues of cod by means of feeding diets supplemented with nontoxic levels of the elements.
Abstract: A protecting role of selenite against the toxic effects of different mercury compounds is well documented. The organ distribution and retention of inorganic mercury as well as of methylmercury seem to be influenced by a high selenium status. Mercury is characteristically present in the aquatic environment and follows the food chain. Several authors have shown a correlation between high concentrations of mercury and selenium in aquatic organisms. Virtually nothing is known about the interaction of methylmercury and selenium in feeding experiments on fish. Therefore the present study was designed to determine the possible interaction of methylmercury and selenium in different tissues of cod (Gadus morhua) by means of feeding diets supplemented with nontoxic levels of the elements.
01 Mar 1985
TL;DR: The results appear to support recent reports on considerable selection effects at HbI, and stress the unreliability of allele frequencies at this locus for use in studies of the genetic population structure of cod.
Abstract: A total of 262 specimens (0-, and 1-group) of Atlantic cod(Gadus morhua) representing 4 different yearclasses were caught in Trondheimsfjorden, Norway, during 1977–1984. They were genotyped by agar gel electrophoresis for the polymorphic haemoglobin locusHbI (Sick, 1961). The analyses revealed a highly significant (P=0.0003) heterogeneity ofHbI allele frequencies between yearclasses. The difference in the frequency of theHbI-1 allele between the first (1977) and the last (1983) yearclass amounted to 0.18 (±0.07). The results appear to support recent reports on considerable selection effects atHbI, and stress the unreliability of allele frequencies at this locus for use in studies of the genetic population structure of cod.
TL;DR: Breeding tubercles in Gadus are described for the first time and it is probable that the tubercles may serve to maintain contact during the reproductive period.
Abstract: Breeding tubercles in Gadus are described for the first time. Each of the three known species of Gadus displays specific peculiarities: in G. ogac, tubercles are numerous, long, and club-shaped; in...
TL;DR: Investigation of the effects of the water-soluble fraction of North Sea crude oil of cod eggs and larvae showed that oxygen consumption of the larvae at the time of final yolk absorption is strongly suppressed by oil exposure at concentrations down to 50 ppb.
TL;DR: Trawling effort was standardized by horsepower class for Canadian trawlers landing Pacific Cod and its two principal shelf cohabitants during April–September 1960–81 from the three major offshore regions: southwest Vancouver Island, Queen Charlotte Sound, and Hecate Strait.
Abstract: Trawling effort was standardized by horsepower class for Canadian trawlers landing Pacific Cod (Gadus macrocephalus) and its two principal shelf cohabitants during April–September 1960–81 from the ...
TL;DR: The effects of viral ERYthrocytic necrosis (VEN) on clinical blood parameters and erythrocyte metabolism were investigated in Atlantic cod and Atlantic herring and no effects on plasma electrolyte or protein concentrations in either species were detected.
Abstract: The effects of viral erythrocytic necrosis (VEN) on clinical blood parameters and erythrocyte metabolism were investigated in Atlantic cod (Gadus morphua) and Atlantic herring (Clupea harengus h.). VEN-infected cod and herring exhibited lower hematocrits (HCT) and erythrocyte counts (E) in comparison to uninfected fish. In addition, VEN-infected cod, but not herring, had significantly lower hemoglobin concentrations (HB). No effects on plasma electrolyte or protein concentrations in either species were detected. Several metabolic changes were noted in VEN-infected erythrocytes. Infected cod erythrocytes had significantly lower lactate dehydrogenase (LDH) and glucose-6-phosphate dehydrogenase (G-6-PD) activities than erythrocytes from uninfected fish. No alterations in citrate synthetase (CS) activity were observed. No effects on LDH, G-6-PD, or CS activity were detected in VEN-infected herring. In VEN-infected cod erythrocytes the ATP levels were decreased approximately 50% compared to uninfected fish. In contrast, VEN infection in herring was associated with an elevation of ATP levels by approximately 33%.
TL;DR: Eleven mysids occurring in the stomachs of cod taken in winter, spring, and autumn of 1982 and 1983 in the shelf area south and west of Iceland have been examined.
Abstract: The mysids occurring in the stomachs of cod (Gadus morhua Linnaeus, 1758) taken in winter, spring, and autumn of 1982 and 1983 in the shelf area south and west of Iceland have been examined. Eleven species but only 55 individuals were found in the 1448 stomachs containing food, which were analysed. Mysis mixta Lilljeborg, 1852, which occurred at one station, amounted to 42% of the mysids found in the cod stomachs. The other species were, in declining numbers of abundance, Meterythrops robusta S.I. Smith, 1879; Mysideis insignis (G.O. Sars, 1864); Amblyops abbreviata (G.O. Sars, 1869); Parerythrops obesa (G.O Sars, 1864); Stilomysis grandis (Goes, 1863); Boreomysis nobilis G.O. Sars, 1885 Gnathophausia zoea Willemoes-Suhm, 1875; Boreomysis microps G.O. Sars, 1883 Mysidopsis didelphys (Norman, 1863), and Schistomysis ornata (G.O. Sars, 1864). Of the last four species only one individual was found. M. mixta, M. robusta, S. grandis, and B. nobilis have previously been found in cod stomachs sampled in...
Journal Article•
TL;DR: A volumetric analysis was made of the subdivisions of the Cod brain and it was found to have a large cerebellum, large medulla oblongata and a tendency to macrosmy, but a small telencephalon and tectum opticum (tendency to micropty).
Abstract: The Cod, Gadus morhua, is a North Atlantic fish of the family Gadidae which occurs at depths of 80 to 600 m (usually 150 to 200 m). It often occurs in shoals and tends to be migratory. It has a typical teleost brain except for the gadid feature of long olfactory tracts. Gadid fishes have a low level of encephalization (RIDET, 1982). The index of encephalization of the Cod is near the mean for the family. This index changes with season due to the change in body weight; it is lowest during the spawning season (which takes place in spring). Five subspecies of Gadus morhua are recognized. A comparison was made of the index of encephalization of the subspecies which is restricted to the White Sea, Gadus morhua maris albi, Derjugin 1920 and Gadus m. morhua, Linne 1758. The index of the White Sea form was significantly higher, thus supporting its recognition as subspecies. A volumetric analysis was made of the subdivisions of the Cod brain. It was found to have a large cerebellum, large medulla oblongata and a tendency to macrosmy, but a small telencephalon and tectum opticum (tendency to micropty). This is what would be expected from the environment and habits of this fish.
TL;DR: Exposure to the water-soluble fraction of Ekofisk and Statfjord B crude oils at concentrations of 50–150 ppb does not significantly affect the surface membrane permeability or body fluid solute concentrations during the egg stage, and the tested concentration range covers even heavily industrialised estuaries.
TL;DR: The regiospecificity of phenanthrene metabolism in vitro is studied in vitro both with microsomes from differently pretreated cod and with isolated cytochrome P-450 isozymes from BNF-induced cod to investigate the immunochemical properties of the variously treated cod liver microsome.
TL;DR: It is concluded that cod and haddock eggs can be distinguished using the high resolution gas chromatography method and selected peaks were used to create a matrix for multivariate analysis.
Abstract: Single cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) eggs were acid hydrolized All the fatty acids were liberated and converted to methyl ester in a one-step reaction The nonpolar hex
TL;DR: It is concluded that the adrenergic nerves of the swimbladder gas gland of the cod preferentially accumulate noradrenaline, a situation similar to that in mammals.
Abstract: The neuronal and extraneuronal accumulation of radiolabelledl-adrenaline andl-noradrenaline was studied in the gas gland of the swimbladder of the Atlantic cod,Gadus morhua. Both amines are taken up into the tissue compartments, and a preference for noradrenaline for both uptake processes was demonstrated. A relatively high neuronal accumulation compared to earlier results (cod spleen; Ungell and Nilsson 1984) was seen and this is probably due to the more dense innervation of the swimbladder gas gland. A higher extraneuronal accumulation may be due to the presence of arterial smooth muscle.
TL;DR: The result indicates that 50 percent maturity was reached at about 60cm for male and 62cm for female cod from the eastern Bering Sea.
Abstract: In order to estimate the size at maturity of Pacific cod Gadus macrocephalus, daily changes in the gonadosomatic index (GSI) were examined for both male and female cod by size class during the six-month period from July to December. Gonads used for the present study were taken from 1, 899 individuals of cod sampled during Japan-U. S. cooperative groundfish surveys conducted in the Bering Sea in 1981 and 1982. Based on the data in November and December when GSI in both sexes showed a rapid increase, the percentage of maturing population by fork length was obtained. The result indicates that 50 percent maturity was reached at about 60cm for male and 62cm for female cod from the eastern Bering Sea.
01 Jan 1985