Showing papers on "Gadus published in 1983"
TL;DR: The application of the relationship between growth rate and fish size is demonstrated by examining the effects of environmental temperature on growth rates of cod, Gadus morhua, and it is suggested that the optimum temperature for growth of cod is 13–15° C.
Abstract: The relationship between growth rate and fish size is described by the equation logeGw=a—0·4 loge W, where Gw is the specific growth rate and W is fish weight. Since the intercept (a) represents the loge Gw of a fish unit size, the relationship presents a method allowing comparison of data from experiments involving fish of different sizes. The application of the method is demonstrated by examining the effects of environmental temperature on growth rates of cod, Gadus morhua, and it is suggested that the optimum temperature for growth of cod is 13–15° C.
165 citations
TL;DR: The relative constancy of the fatty acid composition of PI in the two salt-secreting tissues and its similarity to mammalian phospholipids is considered to reflect its specialized role in biomembranes.
Abstract: Fatty acid analyses were carried out on phosphoglycerides isolated from microsomal fractions of the rectal gland of the dogfish,Scyliorthinus canicula, and gills of the cod,Gadus morhua. Ratios of (n-3)/(n-6) polyunsaturated fatty acids were ca. 10 for phosphatidylcholine, (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS) from cod gills, reflecting high concentrations of 20∶5 (n-3) and 22∶6(n-3). The ratio for phosphatidylinositol (PI) from cod gills was 1.3, reflecting high concentrations of 20∶4(n-6) as well as (n-3) polyunsaturates. PC, PE and PS from rectal glands all had much lower (n-3)/(n-6) ratios than in cod gills, reflecting higher concentrations of 20∶4(n-6), but the lowest ratio was again present in PI. The latter phospholipid had high concentrations of 18∶0 in both tissues. The relative constancy of the fatty acid composition of PI in the two salt-secreting tissues and its similarity to mammalian phospholipids is considered to reflect its specialized role in biomembranes.
97 citations
TL;DR: Fish abundance, based upon commercial fish catches and numbers offish-feeding birds, is shown to increase southward along the Labrador Shelf from Hudson Strait, and yearly abundance of Labrador Atlantic cod using virtual population analysis is shows to be closely correlated with salinity changes at Station 27 off St John's, Newfoundland.
Abstract: Fish abundance, based upon commercial fish catches and numbers offish-feeding birds, is shown to increase southward along the Labrador Shelf from Hudson Strait. Also, yearly abundance of Labrador Atlantic cod (Gadus morhua) using virtual population analysis is shown to be closely correlated with salinity changes at Station 27 off St. John's, Newfoundland. We suggest these observations are related to physical oceanographic events originating within Hudson Strait. Analysis of available data indicates nutrient enrichment of the surface waters through physical mixing in Hudson Strait. These waters are carried by the residual circulation onto the northern Labrador Shelf. Our interpretation of the southward increase in fish abundance is that fish production develops downstream of the area of nutrient injection due to the southward flow of the Labrador Current coupled with the time required for food chain development. The yearly variation of cod is interpreted as arising from the variation of the nutrient supply...
87 citations
01 Jan 1983
TL;DR: Median length and age at sexual maturity of Atlantic cod on the Scotian Shelf declined about 50% in most stocks between 1959 and 1979, and virtually all Atlantic cod age 5 andolder were mature.
Abstract: Median length and age at sexual maturity of Atlantic cod on the Scotian Shelf declined about 50% in most stocks between 1959 and 1979. Atlantic cod in more northerly stocks matured at older ages than did those in more southerly stocks. Males generally matured at younger ages and smaller sizes than did females. Large, immature Atlantic cod disappeared from the stocks between 1959 and 1979. During 1975-79, virtually all Atlantic cod age 5 andolderwere mature. The decline in medianlengthand age at sexual maturity may be due to the commercial fishery removing larger, older immature fish, a general decline in stock biomasses between 1960 and 1975 due to heavy exploitation, or both. Vertebrate population dynamics are determined by the composite effects of reproduction, growth, dis persal, and mortality. The median age at which in dividuals attain sexual maturity profoundly impacts potential population growth (Cole 1954; Stearns 1976). Size and age at sexual maturity are the direct linkage between individual growth and reproductive potential of a population, and therefore they are parameters of prime concern in population dyna
87 citations
TL;DR: In this paper, it was shown that the cod can discriminate between pure tones emitted alternately from two aligned sound projectors at different distances, which suggests that the fish is well able to locate low-frequency sound sources in 3D space.
Abstract: Recent experiments have shown that the cod, Gadus morhua L., is able to determine the direction of a sound source without ambiguity in three-dimensional space1,2. This ability can be explained in terms of the detection of particle acceleration by the otolith organs of the labyrinth, which are strongly directional in their response to oscillatory motion3,4. Ambiguities in determining the direction of propagation are resolved by the fish detecting phase differences between the particle acceleration and the sound pressure2,5. The phase relationship between these two quantities varies with distance from a source, and might therefore provide distance cues to the fish2,6. We now report an experiment performed in the field which confirms that cod can discriminate between pure tones emitted alternately from two aligned sound projectors at different distances. Our results suggest that the cod is well able to locate low-frequency sound sources in three-dimensional space.
72 citations
01 Jan 1983
TL;DR: The model of Elliott and Persson was used to estimate the daily ration of silver hake, Merlurdus bilinearis, and Atlantic cod, Gadus morhua, collected in the western North Atlantic during the years 1973-76, based on stomach samples collected by the Northeast Fisheries Center, National Marine Fisheries Service.
Abstract: The model of Elliott and Persson was used to estimate the daily ration of silver hake, Merlurdus bilinearis, and Atlantic cod, Gadus morhua, collected inthe western North Atlantic between Cape Hatteras and Nova Scotia during the years 1973-76. The model required field measurements of the weight of food in the stomachs during consecutive 3-h periods over 24 h, and laboratory estimates of the exponential gastric evacuation rate. The silver hake and Atlantic cod were each grouped into two size classes for analysis (:520 cm and >20 cm, and :530 cm and >30 cm, respectively). Upperand lower daily ration estimates were 3.2 and 2.9% body weight (BW) per day for hake :520 cm, 2.2 and 0.8% BW per day for hake >20 cm, and 1.5 and 0.9% BW per day for cod >30 cm. There were insufficient small cod to estimate daily ration. These ration es timates are intermediate between two previous estin1ates for silver hake and Atlantic cod on Georges Bank obtained by different methods. With the increasing interest in multispecies manage ment and total ecosystemmanagement, it is essential to understand the role of fish predators within the ecosystem. As a part of this, it is necessary to deter mine the feeding habits and the daily ration of the major species. Here we estimate the daily ration of silver hake, Merluccius bilinearis, and Atlantic cod, Gadus morhua, in the northwest Atlantic, based on stomach samples collected by the Northeast Fisheries Center, National Marine Fisheries Service. The model ofElliott and Persson (1978) was used to investigate dieI feeding periodicity and to estimate the daily ration, based on field measurements of stomach contents, and ldboratory estimates of the exponential evacuation rate R.
65 citations
TL;DR: Proteolytic enzymes in the sarcoplasmic fluid of Pacific whiting were studied to determine which proteases might be involved in the severe textural defect associated with this species, and enzymic activity was greater in whiting than in cod.
Abstract: Proteolytic enzymes in the sarcoplasmic fluid of Pacific whiting (Merluccius productus) were studied to determine which proteases might be involved in the severe textural defect associated with this species. The results were compared to those obtained for true cod (Gadus macrocephalus), a fish having firm texture. Two pH optima of enzymic activity were noted for whiting, pH 3.5–3.9 and 7.1–7.2. Two pH optima were also observed for cod, pH 3.2–3.6 and 7.8–8.0. Whiting but not true cod contained enzymic activity similar to cathepsin B. Cathepsin C activity was greater in whiting than in cod.
59 citations
Journal Article•
53 citations
TL;DR: The behaviour of cod towards a baitedhook was observed in a ring tank, with a modification of the behaviour developing after experience with the baited hook, irrespective of actual hooking.
49 citations
TL;DR: Fewer parasites present in fish exposed to oil might be attributed to direct toxicity induced by drinking water soluble fractions of crude oil and/or modification of the gut environment brought about by changes in host physiologv.
Abstract: To assess the effect of crude oil on selected gastrointestinal parasites of fish, winter flounder (Pseudopleuronectes americanus) naturally infected with a digenetic trematode (Steringophorus furciger), were exposed to contaminated sediment or water soluble fractions of Venezuelan crude oil for 34 and 160 days respectively. Similarly, Atlantic cod (Gadus morhua) harboring an acanthocephalan (Echinorhynchus gadi), were treated with extracts of Hibernia and Venezuelan oils for periods of 81 to 140 days. In all cases prevalence and intensity of parasitic infections were lower in oil-treated fish. The effect appeared to be more pronounced within fish exposed to water soluble extracts than to oil-contaminated sediment. Fewer parasites present in fish exposed to oil might be attributed to direct toxicity induced by drinking water soluble fractions of crude oil and/or modification of the gut environment brought about by changes in host physiologv.
41 citations
TL;DR: The content of ribosomal RNA but not that of DNA per g wet wt of muscle decreased during the 8 days of starvation and regained the normal fed fish level within 8 hr of refeeding.
Abstract: 1. 1. Cod ( Gadus morhua ) was starved for 3, 5 or 8 days. After 8 days of starvation the fish was fed ad libitum and killed 4, 8 or 12 hr later. 2. 2. Amino acid incorporating activity was determined by ribosomes isolated from white trunk muscle. Activity was reduced to 12–18% that of normal fed fish after 8 days of starvation. Activity was restored close to the level of normal fed fish after 12 hr of refeeding. 3. 3. Polyribosomal aggregates decreased in concentration during starvation and increased again within 4 hr of refeeding. 4. 4. The content of ribosomal RNA but not that of DNA per g wet wt of muscle decreased during the 8 days of starvation and regained the normal fed fish level within 8 hr of refeeding.
01 Jun 1983
TL;DR: The Symposium on the Propagation of Cod Gadus morhua L. as mentioned in this paper took place on 14-17 June, 1983 in Arendal by invitation of the Flodevigen Biological Station.
Abstract: The symposium on the Propagation of Cod Gadus morhua L. took place on 14-17 June, 1983 in Arendal by invitation of the Flodevigen Biological Station.
TL;DR: LDH A zynlograrns appear to be useful as a practically diagnostic tool for the identification of the pelagic fish eggs usually found in Norwegian coastal waters by means of isoelectric focusing and histochemical staining techniques.
Abstract: We studied inter- and intra-specific variation at LDM (lactate dehydrogenaase; EC I. 1.1.27) loci in 1 1 gadoid and 6 flatfish species regularly occurring in Norwegian coastal waters by means of isoelectric focusing and histochemical staining techniques. No two species showed identical locus A (white skeletal muscle predominating) zymograms. Polymoaphism at LDH A was observed in haddock (Gadus aeglclfdrtus), coalfish (G. virsns), Norway gout (G. esmarkii), four-bearded rockling (0~0s cimbriebs), and dab (Lirnarada limanda). The allelic naturc of observed LDH variants was confirmed by controlled crossings in cod (G. rnc~rhua, locus B), Norway pout (Iocus A), and haddock (locus A). Analyses of artificially fertilized eggs (in four species) and prenatal eggs from ripening ovaries (in 10 species) revealed a general predominance of locus A products. 736 maternal LDH A activity present in newly released eggs was overtaken by embryo-synthesized enzyme 1-2 d after fertilization. No unique embryonic LDH loci were observed. LDH A zynlograrns thus appear to be useful as a practically diagnostic tool for the identification of the pelagic fish eggs usually found in these waters. The identification method, applied to samples of pelagic eggs collected at the coast of northern Norway during March-May 1981 and 1982, showed that ira a total of - 1500 eggs, the following species were represented: cod. Norway pout, haddock, coalfish, dab, plaice (Pleuronecbes platessa), and long rough dab (Hippogkossoi6Hes platessoides). The species composition in these egg samples varied considerably with sampling location and sampling depth.
TL;DR: Potassium sorbate dip (3% w/v) was applied to head-on cod and cod fillets for 10 or 30 days, with subsequent storage at 1°C for 15 days.
Abstract: Potassium sorbate dips (3% w/v) were applied to gutted, head-on cod and cod fillets for 10 or 30 s, with subsequent storage at 1°C for 15 days. Microbiological counts (total aerobes, Altero/nonas putrefaciens [formerly Pseudomonas putrefaciens]), TMA determinations, and sensory evaluations (taste panels and raw quality grading) were performed every 3 d for the duration of storage. Results indicate that sorbate dips (either 10 or 30 s) were effective in extending shelf life of cod fillets, but were ineffective for gutted fish. Growth of A. putrefaciens on sorbate dipped fillets was significantly suppressed in comparison with the control, although total aerobes were not reduced. Microbial assessment of gutted cod did not reveal consistently lower counts for sorbate treated fish. TMA values were significantly lower for sorbate dipped fillets than for the controls; significant differences were not achieved for the gutted fish. Taste panel results and raw quality grading correlated well with the laboratory analyses.
TL;DR: Findings indicate that marine fish, following long-term exposure to crude petroleum, tend to use up their stored energy of neutral lipids and develop changes in membrane structure and function.
TL;DR: An age-structured model was used to analyze the Hecate Strait Pacific cod fishery for the years 1960–80, finding evidence of a density-dependent trend in natural mortality and time-dependent trends in catchability.
Abstract: An age-structured model was used to analyze the Hecate Strait Pacific cod (Gadus macrocephalus) fishery for the years 1960–80. The data consisted of estimates of fishing effort, together with estimates of numbers of fish at age caught in each year. The latter estimates were derived from length–frequency analysis. A stock–recruitment relationship of the Ricker type with an additional environmental factor was estimated. The data is also analyzed for evidence of the existence of age-dependent trends in natural mortality, density-dependent trends in natural mortality and catchability, and for time-dependent trends in catchability. Evidence of a density-dependent trend in natural mortality was discovered. The average level of natural mortality was also estimated to be 0.65.
TL;DR: Inshore cod, Gadus morhua L., sometimes have heavy gill infections of Loma morhua, and in some of these cases many cysts were also found throughout the viscera, especially in the heart and spleen.
Abstract: Inshore cod, Gadus morhua L., sometimes have heavy gill infections of Loma morhua. In some of these cases many cysts were also found throughout the viscera, especially in the heart and spleen. Some cysts consisted of an hypertrophied host cell containing spores and earlier stages of the parasite. Other cysts had been invaded by phagocytes, which had engulfed the spores, and fibroblasts that had formed a wall around these. Some cysts had undergone coagulative necrosis. Often spores were seen with the typical morphology of Loma morhua.
01 Sep 1983
TL;DR: The apparent existence of considerable natural and artificial selection forces acting upon cod haemoglobin genotypes makes Hbl allele frequencies unreliable for use in population structure analyses.
Abstract: 276 specimens of Atlantic cod (Gadus morhua L.) were caught during spawning in a restricted area of the Trondheimsfjord, Norway, in April and May 1979. Genotypes at the polymorphic haemoglobin locusHbl differed significantly with respect to mean age at maturation (in males) and mean gonadic development stage (in females). There was no indication of population mixing in the genotypic composition atHbl or at any of the 4 polymorphic tissue enzyme loci investigated (LDH-3, IDH-1, PGM, andPGI-1. The findings obtained were considered with regard to temperature-related differences in the functional properties of Hbl molecules, and genotypic differences in growth, age at maturation, and fishing mortality. At the present stage of investigation, the natural selection pattern seems directional and strong. However, theHbl allele frequencies observed in cod from the examined areas reveal no detectable changes over a period of two decades (∼ 4 generations). The current pattern of commercial exploitation causes, through size selection, a modification of the rate of erosion of the inferior allele, but additional factors must be in force, which play a role in its current abundance in an evolutionary perspective. The observedHbl genotypic differences in the exact within-season time for spawning might be one such factor. A potential sexual difference in genotypic fitness might be another, but this has yet to be confirmed. The apparent existence of considerable natural and artificial selection forces acting upon cod haemoglobin genotypes makesHbl allele frequencies unreliable for use in population structure analyses.
TL;DR: The concentrations of several common polychlorinated hydrocarbons found in the environment were determined in the cod livers and there was no apparent concentration-histopathologic relationship.
Abstract: In a sample of 100 live Atlantic cod (Gadus morhua) collected near the entrance of Halifax Harbour, Nova Scotia, in August 1980, 73% had histopathological lesions in their livers similar to those produced by toxicants such as polychlorinated hydrocarbons. These lesions were characterized by fatty degeneration and, in a few samples, desquamation of the epithelia of bile ducts. Only 8% of the fish sampled, all males and at the lower end of the size spectrum, had liver tissue with apparently normal parenchyma. The remaining 19% had early indications of pathologic alterations.
TL;DR: Feeding Aroclor 1254 to juvenile cod to produce liver concentrations of approx 900 microgram X g-1 (wet wt) induced ethoxycoumarin O-de-ethylase approx 30-fold, but had no effect on ethoxyresorufin o-deethylase activity.
TL;DR: In this article, the authors examined the chemical changes of Gadus macorcephalus in the round in ice and in CO2 modified refrigerated seawater (MRSW), and examined for chemical changes as well as changes in palatability of steamed portions of blocks of fiiets.
Abstract: Pacific cod, Gadus macorcephalus, were held in the round in ice and in CO2 modified refrigerated seawater (MRSW), and examined for chemical changes as well as changes in palatability of steamed portions of blocks of fiiets. Sensory evaluation of raw and cooked flesh indicated that the quality of cod was acceptable to 6 days in ice and to 9 days in MRSW. Absorption of salt may present a problem for holding cod in MRSW. Trimethylamine and total volatile acid content was significantly correlated with flavor scores.
TL;DR: The behaviour of 21 cod ( Gadus morhua L.) was observed in a specially designed sea-water olfactometer where diluted samples of oil fractions could be injected in predetermined doses as discussed by the authors.
TL;DR: In this article, the effects of spoilage on certain dielectric properties of frozen cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and lemon sole (Microstomus kitt) have been measured at − 78.5°C in the frequency range 0.025-10 kHz.
Abstract: Using a time-domain technique to obtain low frequency dielectric data the effects of spoilage on certain dielectric properties of frozen cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and lemon sole (Microstomus kitt) have been measured at − 78.5°C in the frequency range 0.025–10 kHz. The spoilage varied with the period of storage in ice prior to freezing. The measurements revealed a relaxation, the frequency of which in cod and haddock depended on pre-freezing quality of the fish. The relationship is discussed between this dependence and various other parameters and the relaxation is tentatively identified as that of a Maxwell-Wagner mechanism.
TL;DR: Egg samples seemed to provide reliable estimates of population allele frequencies in cod, haddock, and Norway pout and the results were related to current knowledge of the population structure of these species in Norwegian waters.
Abstract: Pelagic fish eggs were sampled in Lofoten and Vesteralen, northern Norway, during March to May 1981 and 1982. Individual eggs were identified by their species-specific LDH zymograms as revealed by isoelectric focusing and histochemical staining. Genetic polymorphisms at enzyme loci expressed in eggs provided a basis for the estimation of population allele frequencies. Egg-sample allele frequencies in cod, Gadus morhua L., haddock, Melanogrammus aeglefinus (L.), and Norway pout, Trisopterus esmarkii (Nilsson), were compared with observed values in samples of adult fish from the same areas and from Trondheimsfjorden. Egg samples seemed to provide reliable estimates of population allele frequencies. The results were related to current knowledge of the population structure of these species in Norwegian waters. Only Norway pout showed regional differences in allele frequencies.