Showing papers on "Atlantic cod published in 1988"
TL;DR: Atlantic cod, Gadus morhua, were maintained on different ration levels or starved to produce a variety of growth rates to determine the in vivo rates of protein synthesis and degradation.
Abstract: Atlantic cod, Gadus morhua, were maintained on different ration levels or starved to produce a variety of growth rates. The in vivo rates of protein synthesis and degradation were determined for th...
264 citations
01 Jan 1988
TL;DR: This manual documents age determination techniques used by staff at the Woods Hole Laboratory, National Marine Fisheries Service, together with criteria used to interpret growth patterns and assign ages.
Abstract: The successful application of techniques to enhance detection of age marks in biological specimens is of vital importance in fisheries research. This manual documents age determination techniques used by staff at the Woods Hole Laboratory, National Marine Fisheries Service. General information on procedures for preparing anatomical structures is described, together with criteria used to interpret growth patterns and assign ages. Annotated
photographs of age structures are provided to illustrate
criteria. Detailed procedures are given for the following species: Atlantic herring (Clupea harengus), haddock (Melanogrammus aeglefinus), Atlantic cod (Gadus morhua), pollock (Pollachius virens), silver hake (Merluccius bilinearis), red hake (Urophycis chuss), black sea bass (Centropristis striata), weakfish (Cynoscion regalis), Atlantic mackerel (Scomber scombrus), butterfish (Peprilus triacanthus), redfish (Sebastes fasciatus), summer
flounder (Paralichthys dentatus), winter flounder (Pseudopleuronectes americanus), witch flounder (Glyptocephalus cynoglossus), American plaice (Hippoglossoides platessoides), yellowtail
flounder (Limanda ferruginea), surf clam (Spisula solidissima), and ocean quahog (Arctica islandica). (PDF file contains 142 pages.)
99 citations
TL;DR: Coastal upwellings and downwellings forced by alongshore winds on the north shore of the Gulf of St. Lawrence were associated with variability in onshore movements and inshore daily catches of Atlantic cod.
Abstract: Coastal upwellings and downwellings forced by alongshore winds on the north shore of the Gulf of St. Lawrence were associated with variability in onshore movements and inshore daily catches of Atlantic cod (Gadus morhua). Mean cod densities in the zone offshore from the trap sites, determined by hydroacoustic integration scaled by an in situ dual beam determined mean backscatter, ranged from 2.6 to 82.7 fish/105 m3. Cod were located where sea temperatures ranged from −0.5 to 8.5 °C. Catches were nil where temperatures were outside this range. Cod were located at depths which correlated with the strength of alongshore currents (r = −0.55). A path analysis model with predictors alongshore wind stress and current, sea temperature, and cod density accounted for 76% of the variance in catch. Cod abundance in the offshore zone accounted for the most variance independent of other factors (27%). Sea temperature and currents accounted for 15 and 13%, respectively. Peaks in catch (to 1500 kg/d) coincided with maxim...
66 citations
TL;DR: Die1 changes in the vertical distribution of age-0 (post-laival) Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus were examined in isothermal and stratified waters of Georges Bank in June 1985 and found that changes in depth were more extensive for cod than haddocks.
Abstract: Die1 changes in the vertical distribution of age-0 (post-laival) Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus were examined in isothermal and stratified waters of Georges Bank in June 1985. Discrete depth collections every 4 h ~ndicated that changes in depth were more extensive for cod than haddock. At both sites, cod were predominately near bottom during the day and in midwater at night, although at the stratified site this upward migration may have been limited by the thermocline. Age-0 haddock at the stratified site occurred about the thermocline with little die1 change of depth. At the mixed site, haddock were distributed predominately near bottom but were caught throughout the water column during the periods before noon and midnight. Small cod and haddock (<30 mm standard length for cod, <40 mm for haddock) were distributed at shallower depths and undertook less extensive migrations than larger fish. Relationships of temperature, salinity, light, tidal current speed and preferred zooplankton prey to the changes in depth distributions were examined. Vertical migrations of cod were related to the die1 light cycle at both sites. At the mixed site, the number of haddock caught was inversely related to the mean tidal current speed during the sampling period. Preferred prey, especially the mysid Neomysis americana, may have moved into midwater w ~ t h haddock during slackened currents, remaining near bottom with cod at other times in daylight. Zooplankton biomass and physiological condition (as Fulton's K) of cod and haddock were significantly greater at the mixed site. Electivity indices indicated that N. americana, which occurred at high densities, was the preferred prey of both fish species at this site. At the stratified site, cod and its preferred prey Tisbe sp. were both distributed in deep water, while haddock and its preferred prey Limacina sp. CO-occurred in near-surface waters. The similar distributions of cod and haddock when prey were plentiful, and separate distributions when prey were scarce, may have served to reduce interspecific competition. Adequate prediction of haddock vertical distributions for survey purposes may require knowledge of thermal structure, distribution of prey, and tidal current speed.
62 citations
TL;DR: In this article, the mean contents on a product base found for CB 153, the most abundant one, were 990 ± 250 μ g/kg in cod liver from the southern North Sea, 300 ± 120 g/ kg in the central North Sea and 120 ± 32 µg/k in the northern North Sea.
60 citations
TL;DR: An allozyme investigation of 41 protein‐coding loci in two morphologically similar fishes, Atlantic and Pacific cod, indicates that Pacific cod experienced a severe population bottleneck that led to the loss of gene diversity and gene expression.
Abstract: An allozyme investigation of 41 protein-coding loci in two morphologically similar fishes, Atlantic and Pacific cod, indicates that Pacific cod experienced a severe population bottleneck that led to the loss of gene diversity and gene expression. Pacific cod possesses a significantly lesser amount of gene diversity (H = 0.032) than Atlantic cod (H = 0.125) and lacks gene expression for Me-3. Allele-frequency distributions differ between species as predicted by neutral theory: Atlantic cod has a U-shaped distribution, which is expected for populations in drift-mutation equilibrium, whereas Pacific cod has a J-shaped distribution with an excess of low-frequency alleles. This excess may be explained by the appearance of new alleles through mutation which have not yet reached intermediate frequencies through drift. The population bottleneck in Pacific cod was most likely associated with founder populations that dispersed into the Pacific Ocean after the Bering Strait opened. Under the molecular-clock hypothesis a Nei genetic distance of 0.415 (based on 41 loci) suggests that Pacific cod dispersed into the Pacific Ocean soon after the Bering Strait opened in the mid-Pliocene, 3.0 to 3.5 million years ago.
60 citations
TL;DR: A study was undertaken to ascertain whether any relationship existed between gill lesions and gill parasites in cod following chronic exposure to petroleum hydrocarbons.
Abstract: Fish gills appear to be more susceptible than other tissues to toxicants. The latter include petroleum aromatic hydrocarbons, which can induce lesions characterized by excessive mucus secretion, hyperplasia, fusion of secondary gill lamellae and capillary dilation. Fish are also natural hosts to several species of ectoparasites, especially monogeneans which live among the gill filaments. A previous study on the interrelation of water quality, gill parasites and gill pathology provided evidence that fish living in habitats degraded by pollutants such as Biscayne Bay, Florida, were heavily infested with monogeneids especially when gill lesions were severe. Atlantic cod, Gadus morhua, are hosts to monogeneans. The authors reported previously that crude oil fractions induced gill lesions in cod and also affected some gastrointestinal parasites. In the light of these reports, a study was undertaken to ascertain whether any relationship existed between gill lesions and gill parasites in cod following chronic exposure to petroleum hydrocarbons.
60 citations
TL;DR: By multivariate treatment of the analytical results, the composition of fatty acids was found to vary between eggs within the same spawning batch from the same female, and a different variation was found between eggs from the first spawningbatch from two different females.
Abstract: Fatty acids were determined in single eggs of Atlantic cod (Gadus morhua). The eggs were obtained a few hours after spawning and fertilization from 4-yr-old cod kept in aquaria. By multivariate treatment of the analytical results, the composition of fatty acids was found to vary between eggs within the same spawning batch from the same female. A different variation was found between eggs from the first spawning batch from two different females. The two females had been reared under identical conditions from the egg stage, but were of different sizes at the time of spawning. The fatty acid content in the eggs from the smallest was 4% lower than in the largest. Eggs from the eighteenth spawning batch contained 23% less fatty acids than those from the first batch from the same female. The decrease differed between the acids: the monoenic acids had decreased by 29%, the polyunsaturated acids by 26%, and the saturated acids by 9%.
57 citations
TL;DR: It is concluded that events at the early life-history stages, involving "retention" of the eggs and larvae in relation to particular physical oceanographic features, are involved in the definition of population richness.
55 citations
TL;DR: It is estimated that considerable losses through mortality and weight gain in young fish occur each year in coastal areas from infections by L. branchialis, particularly in one area where it was estimated that 20% of the population was infected.
Abstract: Development and effects of adult Lernaeocera branchialis were studied following experimental transmission to Atlantic cod, Gadus morhua. Growth from the detection of pennella stages to mature adults was approximately 9-10 mo (September-June of the following year) at which time eggs were released and the adult parasites degenerated. Cod from all size groups were susceptible but the prevalence of infection was greater in small fish. Peak mortality, about 30%, occurred within 4 mo after infection and was greatest in young fish with multiple infections. Death was associated with emaciation, blood loss, open lesions, and probable occlusion of branchial blood vessels and/or ventral aorta. Infected fish, especially subadults that survived, consumed less food, gained less weight, had a lower conversion factor, and were substantially smaller than uninfected controls through a 32-wk period. Many of these fish displayed hyperactivity. Large cod that survived the infection and harboured 1 parasite were apparently unaffected but died when stressed. A previous infection conferred no protection against reinfection. Multiple infections delayed gonadal maturation and resulted in significantly lower gonadal somatic indices than in controls. Exposure of infected fish to crude oil fractions or to infection with a hemoprotozoan, Trypanosoma murmanensis, culminated in mortality, weight loss, or low organ somatic indices. It is estimated that considerable losses through mortality and weight gain in young fish occur each year in coastal areas from infections by L. branchialis, particularly in one area where it was estimated that 20% of the population was infected.
49 citations
TL;DR: The results directly support Templeman and Fleming's hypothesis and indicate that juvenile cod, unlike adults, are capable of surviving the icy marine conditions which p...
Abstract: Adult Atlantic cod (Gadus morhua) produce antifreeze glycopeptides during the winter which help to depress the freezing point of their blood plasma to approximately −1.2 °C. Since the temperature at which fish can freeze and die approximates the freezing point of their blood plasma, it is evident that adult cod do not have the capacity to survive in ice-laden waters when the water temperatures drop to −1.5 °C. Templeman and Fleming hypothesized that small cod are more adapted to cold water than adults. The present study documents the fact that the blood plasma freezing points of juvenile cod (mean length = 33 cm, 3-yr-olds) were significantly lower than those of adult cod (> 45 cm) (juvenile, −1.55 °C; adult, −1.23 °C). This difference was largely attributable to the doubling of plasma antifreeze glycopeptide levels in the juvenile cod. These results directly support Templeman and Fleming's hypothesis and indicate that juvenile cod, unlike adults, are capable of surviving the icy marine conditions which p...
TL;DR: An increase in both the prevalence and intensity of P. decipiens in fillets of cod, especially those originating from the Gulf of St. Lawrence and coastal Nova Scotia is suggested.
Abstract: The prevalence and intensity of larval nematodes in fillets of Atlantic cod, Gadus morhua, were examined and compared with similar data from a previous survey conducted about 30 yr ago. Anisakis simplex occurred more often in the nape of the fillet, whereas Pseudoterranova decipiens was the predominant species in napeless fillets. The results suggest an increase in both the prevalence and intensity of P. decipiens in fillets of cod, especially those originating from the Gulf of St. Lawrence and coastal Nova Scotia.
TL;DR: Protist parasites of the genus Trypanosoma were found in the blood of cod from coastal and fjord waters in mid-Norway during 1985–1987 and were highest in the warmer part of the year.
Abstract: Protist parasites of the genus Trypanosoma were found in the blood of cod, Gadus morhua L., haddock, Melanogrammus aeglefinus (L.). poor cod, Trisopterus minutus (L.) and dab, Limanda limanda (L.) from coastal and fjord waters in mid-Norway during 1985–1987. Prevalence in cod was highest in the warmer part of the year. The species identity of the observed trypanosome is uncertain and the vector unknown. Characteristics of the present parasitism resemble those described for Trypanosoma murmanensis (NIKITIN) of Atlantic cod in Newfoundland and Murman waters. and for which the marine leech Johanssonia arctica (SELENSKV) is vector.
01 Jan 1988
TL;DR: Daily growth increments of otoliths from larval and juvenile Atlantic cod and haddock were enumerated, and growth curves were derived describing the first six months of life, indicating that mortality during the postlar val and juvenile periods may be as critical as that occurring in the egg and larval life stages.
Abstract: Daily growth increments ofotoliths from larval andjuvenile Atlantic cod and haddock were enumer ated, and growth curves were derived describing the first six months of life. Growth for both species was best described by Gompertz-type curves. Inverse regressive methods were employed to construct general models with confidence limits for predicting age (days) for given standard lengths (mm) from hatching through the juvenile period. Microstructural analysis of the otoliths did not discern a settling check at the time when the fish would be expected to leave the pelagic lifestyle for the demersal one, which indicates that the transition is neither physiologically stressful nor abrupt. Fluctuations in the year-class strength of fish stocks are thought to be determined by the rate of mortality during the first year oflife (Moser 1981; Lough et a1. 1985; Neilson and Geen 1986; and others). Calculation of reliable mortality rates, assessment of the influences of size-selectivity, and establishment of precise hatching dates and times during a given year when loss to recruit ment is greatest are dependent upon accurate age and abundance estimates. Recently, investigators have suggested that mortality during the postlar val and juvenile periods may be as critical as that occurring in the egg and larval life stages (Cohen and Grosslein 1982; Sissenwine 1984). Investiga tion ofthis hypothesis by the Northeast Fisheries Center (NEFC) has been ongoing since 1984. Enumeration of daily growth increments de posited on fish otoliths provides the best method for the age determination of larvae and juveniles needed for generating growth curves and estimat ing mortality (Essig and Cole 1986). An excellent review of past and current methodologies em ployed in the study and application of otolith mi crostructure may be found in Campana and Neil son (1985). Atlantic cod and haddock are both spring spawners on Georges Bank (Sherman et a1. 19841 and have pelagic eggs and larvae that undergo similar development. Transformation to thejuve