Atlantic Cod Gadus Morhua Research Articles

Electroencephalogram recordings from the olfactory bulb of juvenile (0 year) Atlantic cod in response to amino acids

Olfactory sensitivity of juvenile (0 year) Atlantic cod Gadus morhua to 20 L‐amino acids was studied by recording electroencephalograms (EEG) from the olfactory bulb. Leucine, methionine, asparagine, glutamine, alanine and threonine were highly stimulatory; proline, phenylalanine, aspartic acid and tryptophan were the least stimulatory. Threshold concentrations determined for four amino acids were 10−8 M for alanine, 10−7 M for arginine and leucine and 10−6 M for glutamic acid.

An application of generalized linear models in production model and sequential population analysis

In fitting production models and age-structured models to an index of the relative abundance of a fish population, errors are usually assumed to follow a log-normal or normal distribution, without any diagnostic analyses. A generalized linear model can readily deal with many types of error structures. In this paper, a generalized linear model is coupled with a production model and a sequential population model to assess the stock of the Atlantic cod (Gadus morhua) 2J3KL. This study suggests that the parameter estimates in these models can be greatly influenced by the assumption about the error structures in the estimation and that log-normal and gamma distributions are appropriate for the production model in assessing the Atlantic cod 2J3KL stock, whereas gamma distribution is appropriate for the sequential population model. We recommend that generalized linear models should be used to identify the appropriate error structure in modeling fish population dynamics.

Size-dependent foraging of larval Atlantic cod (Gadus morhua)

Most marine fish larvae are thought to be gape-limited predators, and the presence of suitably sized prey at the appropriate time in the foraging environment is a key factor for their growth and survival. Two experiments were carried out: in experiment 1, we investigated feeding of Atlantic cod (Gadus morhua L., 1758) larvae from 5 to 35 days post hatch on prey of three different sizes: two different-sized strains of rotifers, small rotifers (SR) and large rotifers (LR), and Artemia Leach, 1819 nauplii (AN), or an equal mixture of the three types of prey (MIX). In experiment 2, cod larvae were fed SR, LR, or a combination of SR and LR (MIX-R) at concentrations of 1500 and 4000 prey·L–1 from 4 to 20 days post hatch. Feeding incidence, number of prey in the gut, mouth gape, and prey selection were measured. In experiment 1, feeding incidence was initially higher in the SR treatment, while larvae failed to start feeding in either the LR or the AN treatment at 5 dph. Larvae in the LR treatment started feeding at 8 dph, and feeding incidence was comparable to that in the SR treatment, but the total number of prey eaten was higher in the SR than in the LR treatment until 20 dph. Larvae did not start feeding on AN until 26 dph, although they attacked them from 5 dph. In the MIX-R treatment in experiment 2, larvae fed selectively on LR at 4000 prey·L–1, whereas no selection was observed at 1500 prey·L–1. Our results suggest that cod larvae are gape-limited predators and the concentration of prey affects prey selection.

Spatial Considerations in the Management of Atlantic Cod off Nova Scotia, Canada

AbstractA spatial, age‐structured population dynamics model was developed for a stock of Atlantic cod Gadus morhua off eastern Nova Scotia to examine alternative management options. The model incorporates stock structure, seasonal migration, predation, Allee effects, and variation in natural mortality. The simulated dynamics of two substocks were compared under three management options: (1) historical catch levels; (2) combined management (substocks are managed as one unit) with a constant fishing mortality rate (F) of 0.4; and (3) separated management (substocks are managed individually) with the same F level. Three major conclusions emerged from the simulations. First, the population dynamics under historical catch levels tended to vary widely from complete extinction to a fourfold increase. Second, constant‐F management produced stable population dynamics, reduced the probability of stock decline, and yielded a higher average catch. Third, the combined management option resulted in overfishing the more vulnerable substock; separated management helped to prevent the more vulnerable substock from collapse, but its performance was compromised when there was net immigration to the more vulnerable substock.

Recombinant Trypsin Y from Atlantic Cod—Properties for Commercial Use

This paper describes the production of the novel recombinant trypsin Y polypeptide from Atlantic cod (Gadus morhua)in a Pichia pastorisexpression system and gives a characterization of the enzyme. It presents the first biochemical data supplementing the molecular description of the putative group III trypsins. Unexpectedly, the results demonstrate that the recombinant trypsin Y has a dual substrate specificity demonstrating both trypsin and chymotrypsin activities. It shows increasing proteolytic activity at temperatures between 2-21 °C, and it is completely inactivated at 30°C. These properties may be important for the commercial use of recombinant trypsin Y, as other cold-adapted proteolytic enzymes from the Aüantic cod have proven their usefulness in various industrial and medical applications.

The development of haddock and Atlantic cod sperm cryopreservation techniques and the effect of sperm age on cryopreservation success

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.

Efficacy of egg surface disinfectants in captive spawning Atlantic cod Gadus morhua L. and haddock Melanogrammus aeglefinus L.

In an effort to optimize the efficiency of high-density incubation of Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus eggs, the per cent hatch of eggs treated with four disinfectants (3% hydrogen peroxide, 1% polyvinylpyrrolidone iodine, 0.1% sodium hypochlorite and a 0.005% antibiotic solution – penicillin/streptomycin) was compared in both species. The per cent hatch of eggs of each species was greatest after a 24 h treatment with the antibiotic solution. The hatching success of eggs treated within the different disinfectant treatments depended upon the embryonic developmental stage in both species. The sodium hypochlorite treatment had the lowest % coverage of colony growth after disinfected haddock eggs were plated onto sterile agar media, highest survival rates to the end of the embryonic period, but the lowest per cent hatch.

The Effect of Photoperiod on Sexual Maturation, Appetite and Growth in Wild Atlantic Cod (Gadus morhua L.)

An experiment was conducted to examine (a) the effects of photoperiod on timing of sexual maturation (b) the relationship between plasma steroid levels, appetite and growth in male and female Atlantic cod (Gadus morhua L.). Wild caught Norwegian coastal cod were subjected to either a 6L/18D photoperiod typical of January at 60° N-(Short day group) or a simulated natural photoperiod (Normal day group) from June 2000 until spawning started. Appetite of individual fish were measured twice weekly, while weight, length and plasma levels of the sex steroids testosterone (T), 11 keto-testosterone (11-KT) and estradiol-17β (E2) were monitored bimonthly. Cod in the Short day group matured 3 months ahead of the cod in the Normal day group and started spawning in early November. Appetite decreased in both sexes 2–3 months prior to spawning in both groups, but this reduction was stronger among males. In both sexes, length growth was reduced concurrently with the appetite loss. Overall, females had significantly higher somatic growth, put relatively less energy into length growth and had developed larger livers compared to males at the time of spawning in the Short day group. Plasma steroid levels increased in both groups throughout the experiment, reaching peak levels of ca 10 ng ml−1 (T) and 15–20 ng ml−1 (11-KT) in males, and 1.5–2 ng ml−1 (T) and 12–18 ng ml−1 (E2) in females at the onset of spawning. Steroid levels increased more rapidly among Short day cod verifying the earlier onset of maturation. These results confirm that photoperiod is a major cue to maturation in cod and imply that the high cost of spawning for females incur differences in appetite between the sexes.

Life‐history variation among local populations of Atlantic cod from the Norwegian Skagerrak coast

Small‐scale spatial variation in life history was found among genetically distinct local populations of Atlantic cod Gadus morhua from the Norwegian Skagerrak coast. Among populations, age at 50% maturity varied from 2·6 to 3·8 years, total (LT) length at 50% maturity from 35 to 60 cm, annual survival from 33 to 64%, mean LT at age 4 years from 43 to 63 cm, and mean backcalculated LT at age 1 year from 8 to 12 cm.

Environmentally low-temperature kinetic and thermodynamic study of lactate dehydrogenase from Atlantic cod ( G. morhua) using a 96-well microplate technique

Analyses of temperature-dependent kinetic parameters in enzymes extracted from tissues of ectothermic animals are usually carried out within the range of physiological temperatures (0–40 °C). However, multisample spectrophotometers (so-called microplate readers) with efficient wide-range temperature control (including cooling) have previously been unavailable. This limits the statistical quality of the measurements. A temperature-controlled microplate was designed for a 96-well microplate reader to overcome this limitation. This so-called T-microplate is able to control assay temperature between the freezing point of a liquid sample and 60 °C with high stability and accuracy in any data acquisition mode. At 4 °C the accuracy of the temperature control was ±0.1 °C and temperature homogeneity across the microplate was ±0.3 °C. As examples, analyses of the temperature dependence of Michaelis–Menten ( K ′PYR m) and substrate inhibition ( K si PYR) constants for pyruvate, of the maximal rate of reaction ( V ′ max), of the apparent Arrhenius activation energy ( E A), and of the Gibbs free-energy change ( ΔG ‡ ) of lactate dehydrogenases from muscle of Atlantic cod Gadus morhua acclimated to 4 °C are described. The large dataset obtained allowed evaluation of a new mechanism of metabolic compensation in response to seasonal temperature change.

The effect of reduced temperature and salinity on the blood physiology of juvenile Atlantic cod

The osmolality and ionic composition of the blood of juvenile Atlantic cod Gadus morhua and their response to conditions of reduced temperature and salinity in summer‐ and winter‐acclimated individuals was investigated. Haematocrit percentage was relatively stable throughout the experimental procedures. Summer‐acclimated juvenile Atlantic cod had higher plasma osmolality than winter‐acclimated fish in ambient conditions. Plasma Na+ levels were, however, higher in winter conditions, while Cl− did not vary between seasons. Temperature reduction (12, 9 and 6° C in summer and to 6 and 4° C in winter) induced a significant response in plasma osmolality and Na+ levels in summer, but only in Na+ levels in winter‐acclimated fish. A pronounced effect was seen in the summer 6° C treatment. Salinity treatments (24, 16 and 8) had a significant effect on almost all the variables in both summer and winter and resulted generally in dilution of ionic and osmotic concentrations of the plasma. This effect was pronounced in the lowest temperature treatments, with the greatest reduction observed in the summer 6° C treatment. This could suggest that winter‐acclimated fish are physiologically adapted to cope with lower seawater temperatures as opposed to summer‐acclimated fish.

Survey gear calibration independent of spatial fish distribution

Trawl surveys provide important information for evaluation of relative stock abundance fluctuations over time. Therefore, when survey gears or vessels are changed, it is important to compare the efficiency and selectivity of old and new gears and vessels. A method for estimation of conversion factors is developed based on a survey design where paired hauls are taken in the same trawl track line. The method explicitly accounts for changes in fish density caused by trawling disturbance. A generalized linear model for paired hauls catches is analytically derived and the gear conversion and disturbance parameters with their precision are obtained using standard software. Simulation studies carried out additionally showed that the estimated conversion factors were practically unbiased. Because of the independence of the spatial fish distribution, the new method is preferable to the traditional paired hauls design for which it is generally not possible to obtain the statistical properties of the estimated conversion factors. The paper is concluded with suggestions on how to optimize survey design. The method was used to estimate conversion factors for Atlantic cod (Gadus morhua) from Danish gear calibration experiments in the Baltic Sea.

Mitochondrial Cytochrome b DNA Variation in the High-Fecundity Atlantic Cod: Trans-Atlantic Clines and Shallow Gene Genealogy

Abstract An analysis of sequence variation of 250 bp of the mitochondrial cytochrome b gene of 1278 Atlantic cod Gadus morhua ranging from Newfoundland to the Baltic shows four high-frequency (>8%) haplotypes and a number of rare and singleton haplotypes. Variation is primarily synonymous mutations. Natural selection acting directly on these variants is either absent or very weak. Common haplotypes show regular trans-Atlantic clines in frequencies and each of them reaches its highest frequency in a particular country. A shallow multifurcating constellation gene genealogy implies young age and recent turnover of polymorphism. Haplotypes characterizing populations at opposite ends of the geographic distribution in Newfoundland and the Baltic are mutationally closest together. The haplotypes are young and have risen rapidly in frequency. Observed differentiation among countries is due primarily to clinal variation. Hypotheses of historical isolation and polymorphisms balanced by local selection and gene flow are unlikely. Instead the results are explained by demic selection of mitochondria carried by highly fit females winning reproductive sweepstakes. By inference the Atlantic cod, a very high-fecundity vertebrate, is characterized by a high variance of offspring number and strong natural selection that leads to very low effective to actual population sizes.

Inter‐individual differences in rates of routine energy loss and growth in young‐of‐the‐year juvenile Atlantic cod

Inter‐individual differences in rates of routine (non‐feeding) metabolism and growth were evaluated in young‐of‐the‐year (YOY) juvenile Atlantic cod Gadus morhua. Rates of O2 consumption, CO2 production and ammonia (TAN) excretion were measured in 64, 25–43 mm standard length (LS) YOY growing at different rates (0·27–0·47 mm day−1) in a common rearing tank. Parameter rates (y) increased allometrically (y = a·Mb) with increasing body mass (M) with b‐values for O2 production, CO2 consumption and TAN excretion equal to 0·81, 0·89 and 0·56, respectively. In some cases, residuals from these regressions were significantly negatively correlated to fish growth rate. In no cases did residuals of parameter rates increase with increasing growth rate. These data suggest that, during unfed periods, relatively fast‐growing fish were more metabolically efficient than slower‐growing fish from the same cohort. The fish condition factor, derived from , also significantly decreased with increasing growth rate. Results indicated differences in both the rates of routine energy loss and the patterns of growth allocation among YOY Atlantic cod. Since these physiological attributes were positively correlated with growth rate, they may be indicative of ‘survivors’ in field populations.

Cannibalism Reduction in Juvenile Barramundi Lates calcarifer by Providing Refuges and Low Light

Cannibalism is a special form of predation to kill and consume the whole of an individual of the same species. Cannibalism has been found in 36 of 410 fish families and can take place at various sizes or ages depending on species and environments (Hecht and Pienaar 1993). The occurrence of cannibalism in larval and juvenile fish is of considerable concern for aquaculture (Smith and Reay 1991). Intracohort cannibalism is one of the most important issues to address in intensive fish aquaculture. Among commonly aquacultured fish species, cannibalism has been reported in catfish Clarias gariepinus (Hecht and Appelbaum 1988). walleye Stizostedion vitreum (Cuff 1980), common carp Cyprinus carpi0 (Damme et al. 1989), Atlantic cod Gadus morhua (Folkvord 199 I) , Perca Jluviatilis (Melard et al. 1996), and many others. Since cannibalistic behavior has been widely found in fish culture, determination of factors influencing cannibalism is important in order to reduce its impact. Factors causing cannibalism fall into two primary categories: genetic and behavioral factors. Within the genetic category the principal cause of cannibalism is size variation within a cohort (Valerio and Barlow 1986). The behavioral category of causative factors is obviously linked to the genome, but environmental factors are closely linked to agonistic behaviors (Fox 1975; Hecht and Appelbaum 1988). Barramundi Lates calcarifer is an important species for aquaculture in Australia and

Habitat use and early winter movements by juvenile Atlantic cod in a coastal area of Newfoundland

Acoustic telemetry was used to monitor the movements and landscape scale habitat use of age 2–3 year juvenile Atlantic codGadus morhuain Newman Sound, a coastal fjord of Newfoundland, during late autumn and early winter (24 October 1999 to 22 January 2000). Substratum, bathymetric relief and depth use were studied to determine if it differed from the pattern expected given an absence of selectivity (habitat use proportional to habitat availability). Prior to winter migrations, most Atlantic cod maintained small home ranges (0·5–33·4 ha, median = 2·1 ha) although a few individuals moved more widely. No relationship between total length (LT) and home range size was detected. In Inner Newman Sound, Atlantic cod occupied depths of 10–29 m more than expected given availability, while depths of 0–9 and 40–59 m were underutilized. No significant relationship between depth andLTwas detected. Areas of medium (5–10%) or high (>10%) bathymetric relief and boulder or kelp habitats were used significantly more than expected given the availability of these habitats. Sand and eelgrass substrata were underutilized given availability, although many Atlantic cod used sandy‐bottomed areas to some degree. Flexibility in habitat use by the individuals that were studied suggested reduced predation risk relative to younger conspecifics. Winter migrations to deeper water beyond Newman Sound began in mid‐November, coinciding with the disappearance of the thermocline, and continued until 27 December. Approximately 30% of monitored individuals did not migrate and maintained their home ranges into the winter season. No significant differences inLTbetween migrating and resident groups were detected, however, the condition of migrating fish was significantly higher than in resident fish. This finding supports the theory that feeding history plays a role in the decision to undertake migration.

Evaluation of the Use of Visible Implant Tags in Age-0 Atlantic Cod

The visible implant elastomer (VIE) tag and the soft visible implant alphanumeric (VIAlpha) tag were evaluated as methods for tagging age-0 Atlantic cod Gadus morhua. Tank experiments on laboratory-bred Atlantic cod (82–141 mm) lasted 150 d. The VIE tag proved to be a good alternative when put on the dorsal part of the fish, with no tag loss and good tag visibility. When put on the ventral part of the fish, however, many VIE tags were covered by growing silvery scales. Retention of soft VIAlpha tags injected behind the eye was quite low (67%), but larger fish had higher tag retention than smaller fish. Survival of experimental fish was high (96%). Mean specific growth rates ranged from 0.46% to 0.51% per day. Both VIE and soft VIAlpha tags were used to individually tag age-0 Atlantic cod (85–290 mm) in the wild. Skin pigmentation of wild Atlantic cod made reading soft VIAlpha tags difficult, while VIE tagging on the dorsal part of the fish still worked well. We suggest that VIE tags are a good alternative for short-term demographic studies on age-0 Atlantic cod, while low retention rates cast doubt on the use of soft VIAlpha tags on these small fish.

Positive Darwinian Selection at the Pantophysin (Pan I) Locus in Marine Gadid Fishes

Maximum-likelihood models of codon substitution were used to test for positive Darwinian selection at the vesicle protein pantophysin in two allelic lineages segregating in the Atlantic cod Gadus morhua and in 18 related species of marine gadid fishes. Positive selection was detected in the two intravesicular loops of the integral membrane protein but not in four membrane-spanning regions or the 3' cytoplasmic tail. The proportion of positively selected sites (24.9%) and the mean nonsynonymous/synonymous rate ratio (omega = d(N)/d(S) = 5.35) were both greater in the first intravesicular (IV1) domain compared with the second intravesicular (IV2) domain (11.0% positively selected sites with mean omega = 3.76). Likelihood ratio tests comparing models that assume identical omega ratios along all branches of the phylogeny to those that allow omega ratios to vary among lineages were not significant for either the IV1 or IV2 domains, indicating that the selective pressures favoring amino acid replacements have operated consistently in both regions during the diversification of the group. Positive selection was observed in the IV1 domain in both G. morhua allelic lineages, and, although three of the four codons that differ between alleles were targets of positive selection in the broader group, no similar polymorphisms were detected in other taxa. The two G. morhua Pan I alleles appeared to have evolved before the speciation event separating it from its sister taxon, Theragra chalcogramma, and on the basis of a standard mtDNA clock are estimated to be at least 2 Myr old. Although the function of pantophysin remains unknown, the strong signal of positive selection at specific sites in the IV1 and IV2 domains may help clarify its role in cellular trafficking pathways.

Behavioural consequences of density-dependent habitat use in juvenile cod Gadus morhua and G. ogac: the role of movement and aggregation

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 272:257-270 (2004) - doi:10.3354/meps272257 Behavioural consequences of density-dependent habitat use in juvenile cod Gadus morhua and G. ogac: the role of movement and aggregation B. J. Laurel1,*, R. S. Gregory1,2, J. A. Brown1, J. K. Hancock1, D. C. Schneider1 1Memorial University of Newfoundland, Ocean Sciences Centre, St. John¹s, Newfoundland A1C 5S7, Canada 2Department of Fisheries and Oceans, St. John¹s, Newfoundland A1C 5X1, Canada *Email: blaurel@mun.ca ABSTRACT: Fish behaviour can change to accommodate a variable environment, but changes in behaviour have not been considered in the context of density-dependent habitat use. In Bonavista Bay, Newfoundland, we measured how fish density movement and schooling behaviour changed with habitat in 2 gadids, Atlantic cod Gadus morhua and Greenland cod Gadus ogac, using a combination of field-seines, mark-recapture and laboratory experiments. Density estimates from seines (n = 427) over 5 yr (1996, 1998 to 2001) indicated that these species associated with eelgrass but periodically were detected in high abundance over unvegetated habitat (i.e. sand). Within-site catch variation indicated both species aggregated more in sand than eelgrass habitat, and, in Atlantic cod, aggregations over sand increased as density in eelgrass increased. Although such patterns in catch data could be interpreted as due to the effects of differential mortality between habitats, a mark-recapture experiment indicated that both species of cod were not site-attached and moved between seine locations. Furthermore, video-analysis from laboratory experiments demonstrated that cod formed tighter aggregations over sand compared to eelgrass habitats. Our results suggest that juvenile cod modify their behaviour with changing density, possibly as a means of exploiting poor-quality habitats when high-quality habitats are saturated with conspecifics. Consequently, habitat suitability for Atlantic cod may be a dynamic rather than fixed variable in density-dependent habitat models. KEY WORDS: Density-dependence · Habitat selection · Atlantic cod · Greenland cod · Aggregation · Shoaling Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 272. Online publication date: May 19, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Growth pattern and growth dependent mortality of larval and pelagic juvenile North Sea cod Gadus morhua

We investigated growth patterns and evidence of growth dependent survival for a pop- ulation of Atlantic cod Gadus morhua using analysis of their otolith microstructure. Central concen- trations of a population of cod larvae and juveniles in the north-eastern North Sea were sampled twice (in April and May 2001), and larval/juvenile growth history from each of the sampling sequences was outlined. Growth rate was estimated by fitting a Laird-Gompertz equation to lengths- at-age, and we found the mean specific growth rate in length at age 20 d was 3.2% d -1 , declining to 1.9% d -1 at an age of 90 d. Otolith radius and larval standard length were highly correlated, and otolith growth was used as a measure of larval somatic growth. The larvae were divided into 3 groups dependent on their hatch-date, and for each hatch group, the same period of past growth was com- pared between fish sampled in April and May. A 2-way repeated-measurement ANOVA revealed a significant higher past growth of fish sampled in May in 2 of the 3 hatch-groups, implying a higher mortality of the slow growing larvae. Additionally, otolith size at age differed significantly between the April and May sampling of the oldest larvae. Using the obtained information we illustrate the consequences of being larger at age by nonparametric spline functions. These show up to 10-fold differences in the relative survival probabilities between cod of smallest or largest size at age, suggesting that mortality can be strongly dependent on growth.