Fishery and Biology of Atlantic Cod (Gadus morhua) off the Southwest Coast of Newfoundland

1969 ◽  
Vol 26 (12) ◽  
pp. 3133-3164 ◽  
Author(s):  
Allenby T. Pinhorn
Keyword(s):  
Growth Rates ◽  
Food Supply ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Total Mortality ◽  
Mortality Rates ◽  
Limited Data ◽  
Southwest Coast

Data collected from the fishery off the southwest coast of Newfoundland indicated a decrease in the proportions of larger and older cod in ICNAF Division 3Pn in recent years. Changes in total mortality rates in 3Pn and on Burgeo Bank have been attributed to fluctuations in total landings and effort. Decreased growth rates for the younger cod and increased followed by decreased growth for the older cod were attributed to increased food supply superimposed on decreased bottom temperatures. Cod from Burgeo Bank grow faster than those from 3Pn. Sizes caught by various types of inshore boats were similar but larger fish were caught in deeper water, in eastern rather than western localities, and in the latter part of the season. Peak spawning occurs in May. Males were predominant in longline catches and matured at an earlier age and smaller size than females. Fish in the 3Pn area matured earlier and at a smaller size than Burgeo Bank fish. Vertebral averages at different localities in the area were similar but averages have decreased in recent years. Limited data on weights and fecundity are presented. Results are discussed in light of the separation of West Newfoundland and Burgeo Bank stocks.

Relationships Between RNA–DNA Ratio, Prey Density, and Growth Rate in Atlantic Cod (Gadus morhua) Larvae

1979 ◽  
Vol 36 (12) ◽  
pp. 1497-1502 ◽  
Author(s):  
L. J. Buckley
Keyword(s):  
Growth Rate ◽  
Nutritional Status ◽  
Growth Rates ◽  
Prey Density ◽  
Gadus Morhua ◽  
Slow Growth ◽  
Atlantic Cod ◽  
Larval Fish ◽  
Dry Weight ◽  
Dna And Rna

The protein, DNA, and RNA content of larvae maintained at 1.0 plankter/mL increased at the rates of 9.3, 9.9, and 9.8% per day, respectively, for the 5 wk after hatching. Protein reserves of larvae held at 0 or 0.2 plankters/mL were depleted by 45 and 35%, respectively, prior to death 12–13 d after hatching. Starved larvae had similar protein concentrations (percent of dry weight), lower RNA concentrations, and higher DNA concentrations than fed larvae. Larvae held at higher plankton densities had higher RNA–DNA ratios and faster growth rates than larvae held at lower plankton densities. The RNA–DNA ratio was significantly correlated (P < 0.01) with the protein growth rate. The RNA–DNA ratio appears to be a useful index of nutritional status in larval Atlantic cod (Gadus morhua) and may be useful for determining if cod larvae were in a period of rapid or slow growth at the time of capture. Key words: RNA–DNA ratio, starvation, protein, nucleic acids, growth, larval fish, Atlantic cod

Comparison of size-at-age of larval Atlantic cod (Gadus morhua) from different populations based on size- and temperature-dependent growth models

2005 ◽  
Vol 62 (5) ◽  
pp. 1037-1052 ◽  
Author(s):  
A Folkvord
Keyword(s):  
Growth Rates ◽  
Laboratory Experiments ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Growth Models ◽  
Larval Growth ◽  
Growth Potential ◽  
Temperature History ◽  
Temperature Dependent ◽  
Dependent Growth

This study presents the first intraspecific evaluation of larval growth performance across several different experimental scales, environments, and regions of a marine fish species. Size- and temperature-dependent growth models for larval and early juvenile Atlantic cod (Gadus morhua) are developed based on selected laboratory experiments with cod fed in excess. Observed sizes-at-age of cod from several experiments and stocks are compared with predictions from the models using initial size and ambient temperature history as inputs. Comparisons with results from other laboratory experiments reveal that the model predictions represent relatively high growth rates. Results from enclosure experiments under controlled seminatural conditions generally provide growth rates similar to those predicted from the models. The models therefore produce suitable reference growth predictions against which field-based growth estimates can be compared. These comparisons suggest that surviving cod larvae in the sea typically grow at rates close to their size- and temperature-dependent capacity. This suggests that climatic influences will strongly affect the year-to-year variations in growth of cod during their early life history owing to their markedly temperature-dependent growth potential.

Effects of Intermediate and Low Salinity Conditions on Growth Rate and Food Conversion of Atlantic Cod (Gadus morhua)

1994 ◽  
Vol 51 (7) ◽  
pp. 1569-1576 ◽  
Author(s):  
Yvan Lambert ◽  
Jean-Denis Dutil ◽  
Jean Munro
Keyword(s):  
Growth Rate ◽  
Food Intake ◽  
Growth Rates ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Food Conversion ◽  
Coastal Regions ◽  
Low Salinity ◽  
Feeding Regimes ◽  
Food Conversion Efficiency

Growth rates of Atlantic cod (Gadus morhua) were measured under different salinity conditions to test the hypothesis that growth would be best in an isosmotic environment. The results of two experiments (spring and autumn 1991) conducted at three different salinities (7, 14, and 28‰) and two feeding regimes indicate a significant effect of salinity and ration on growth rate. Within each experiment, growth rates were highest for cod maintained in intermediate salinity conditions (14‰). Growth rates in low salinity conditions (7‰) were higher than in seawater (28‰) during the spring, but during the autumn, growth rates of cod held under low salinity conditions and in seawater were similar. Higher growth rates at lower salinities resulted from an increase in food conversion efficiency. They were not associated with an increase in food intake, changes in composition (proteins, lipids, or water), or relative allocation of energy to the tissues (muscle, liver, and gonads) of cod. The results indicate that rearing cod at intermediate salinities, such as would occur in estuaries or coastal regions, could confer an advantage for cod aquaculture.

Spatiotemporal variations in juvenile mortality and cohort strength of Atlantic cod (Gadus morhua) off Newfoundland and Labrador

2020 ◽  
Vol 77 (3) ◽  
pp. 625-635
Author(s):  
Fan Zhang ◽  
Rick M. Rideout ◽  
Noel G. Cadigan
Keyword(s):  
Newfoundland And Labrador ◽  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Survival Rates ◽  
Mortality Rates ◽  
Spatiotemporal Variations ◽  
Juvenile Mortality ◽  
Modelling Framework ◽  
Fish Recruitment

Juvenile mortality is an important factor affecting the spatiotemporal dynamics of fish recruitment, but estimation of the spatiotemporal variations in juvenile mortality rates remains challenging. We developed a state-space metapopulation dynamics model to simultaneously estimate spatiotemporal variations in juvenile mortality rates and cohort strength and applied this general modelling framework to data from multiple surveys for juvenile (ages 2–5) Atlantic cod (Gadus morhua) stocks off Newfoundland and Labrador (NL). We found large-scale synchronized dynamics of decreasing juvenile mortality rates and increasing cohort strength from offshore surveys off eastern and southeastern NL, suggesting improving reproduction and survival rates for juvenile cod. No synchronized patterns of juvenile mortality rates and cohort strength were detected for cod stocks off southern and western NL, indicating more complex cod population spatial structures in those areas. Our study demonstrates the potential of juvenile mortality to cause temporally variable and spatially synchronized dynamics of fish recruitment, and the spatial patterns of juvenile mortality and cohort strength indicate some potential mismatch between cod population structure and current management units off NL.

Interpopulation differences in growth rates and food conversion efficiencies of young Grand Banks and Gulf of Maine Atlantic cod (Gadus morhua)

2000 ◽  
Vol 57 (11) ◽  
pp. 2223-2229 ◽  
Author(s):  
Craig F Purchase ◽  
Joseph A Brown
Keyword(s):  
Growth Rates ◽  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Larval Fish ◽  
Food Conversion ◽  
Life History Variation ◽  
Grand Banks ◽  
In The Wild ◽  
Conversion Efficiencies

Geographically separated Atlantic cod (Gadus morhua) stocks in the northwest Atlantic exhibit life history variation and have been shown to differ genetically. The genetic and environmental contributions to phenotypic differences, however, have not yet been measured. We used common environment experiments to evaluate the importance of temperature on the observed growth variation between Grand Banks (GB) and Gulf of Maine (GOM) cod stocks. Larvae from the GB grew faster than GOM larvae at both 7 and 12°C. Growth rates of juveniles were not different, but GB juveniles had higher food conversion efficiencies than those from the GOM (at both ambient and warm temperatures). The results indicate that faster growth of GOM cod in the wild is not due to a higher genetic capacity for growth rate in GOM than in GB fish. The findings give evidence of genetically based phenotypic variation, which is in agreement with molecular studies on population differentiation in cod, and support the theory of countergradient variation in growth rates of larval fish.

Reporting and shedding rate estimates from tag-recovery experiments on Atlantic cod (Gadus morhua) in coastal Newfoundland

2006 ◽  
Vol 63 (9) ◽  
pp. 1944-1958 ◽  
Author(s):  
Noel G Cadigan ◽  
John Brattey
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Mortality Rates ◽  
First Year ◽  
Commercial Fisheries ◽  
Dorsal Fin ◽  
Temporal And Spatial Variability ◽  
Temporal And Spatial ◽  
Reporting Rates ◽  
Tag Shedding

It is important to have good estimates of tag reporting rates when inferring exploitation rates and other mortality rates from tagging experiments. We estimate the reporting rates of single- and double-tagged Atlantic cod (Gadus morhua) caught in commercial fisheries around coastal Newfoundland, Canada, based on an extensive series of multi-reward tagging experiments conducted during 1997–2004. Reporting rates for single-tagged cod varied from 58% to almost 100%, with significant temporal and spatial variability. The odds of reporting a double-tagged cod was almost double that of a single-tagged cod. Returns from double-tagged cod allow us to estimate tag shedding rates. Tag shedding rates suggested that 22% of fish lost their tag during their first year at liberty; subsequently, tag shedding rates were much lower (<10%). We also found that twice as many fish lost tags when the tags were attached anteriorly at the base of the first dorsal fin compared with a position more towards the posterior end.

Nucleic acids and enzymes in Atlantic cod (Gadus morhua) differing in condition and growth rate trajectories

1998 ◽  
Vol 55 (4) ◽  
pp. 788-795 ◽  
Author(s):  
Jean-Denis Dutil ◽  
Yvan Lambert ◽  
Helga Guderley ◽  
Pierre U Blier ◽  
Dany Pelletier ◽  
...  
Keyword(s):  
Nucleic Acids ◽  
Food Deprivation ◽  
Growth Rates ◽  
Gadus Morhua ◽  
White Muscle ◽  
Atlantic Cod ◽  
Direct Result ◽  
Muscle Lactate ◽  
Lactate Dehydrogenase Activity ◽  
Feeding Regimes

Atlantic cod (Gadus morhua) were exposed to one of four feeding regimes, 16 weeks of food deprivation (U) or satiation feeding (F) or two 8-week periods of food deprivation followed by satiation feeding (UF) or vice versa (FU), to determine whether relationships between nucleic acids or enzymes and growth rates result from a general enhancement of individual condition or are a direct result of enhanced growth rates. Final condition factor (K) differed between treatments, but did not differ between the mixed treatments after either 8 weeks of negative growth (FU) or 8 weeks of positive growth (UF). Intestinal cytochrome c oxidase activity matched the expected short-term growth rates, not only in fed and unfed fish but also in cod exposed to the mixed treatments (FU and UF). White muscle lactate dehydrogenase activity reflected growth rates, but initial levels were not reached within 8 weeks in FU cod. The liver glutamate pyruvate transaminase : DNA ratio reflected differences in K, but not differences in recent growth rates. Myofibrillar proteins decreased in unfed cod, while sarcoplasmic proteins followed changes in K more closely. The RNA:DNA ratio in white muscle did not reflect changes in K or changes in growth rates.

Mortality, movement, and body size: critical scales for Atlantic cod (Gadus morhua) in the Northwest Atlantic

1999 ◽  
Vol 56 (S1) ◽  
pp. 180-187 ◽  
Author(s):  
David C Schneider ◽  
Tammo Bult ◽  
Robert S Gregory ◽  
David A Methven ◽  
Danny W Ings ◽  
...  
Keyword(s):  
Life History ◽  
Body Size ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Critical Time ◽  
Life History Stage ◽  
Critical Space ◽  
Limited Data ◽  
Graphical Technique ◽  
Pelagic Juveniles

The problem of scaling spatially and temporally limited data to larger scale questions can no longer be ignored as evidence accumulates that the importance of any given process, relative to another, depends on spatial and temporal scale. A recently developed graphical technique allows identification of critical space and time scales, which separate scales at which one rate prevails from scales at which another rate prevails. We used data from the literature to test a series of hypotheses concerning change in critical scales with change with life history stage in Atlantic cod (Gadus morhua). The critical scales for mortality relative to kinematics increased slightly for pelagic juveniles relative to drifting eggs, decreased substantially for demersal juveniles relative to pelagic juveniles, increased again in adults, and, contrary to expectation, remained high in large adults ("mother fish"). Critical time and space scales were found to be linked and cannot be taken as constants.

In what direction should the fishing mortality target change when natural mortality increases within an assessment?

2016 ◽  
Vol 73 (3) ◽  
pp. 349-357 ◽  
Author(s):  
Christopher M. Legault ◽  
Michael C. Palmer
Keyword(s):  
Mortality Rate ◽  
Empirical Evidence ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Total Mortality ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Limanda Ferruginea ◽  
Trade Offs

Traditionally, the natural mortality rate (M) in a stock assessment is assumed to be constant. When M increases within an assessment, the question arises how to change the fishing mortality rate target (FTarget). Per recruit considerations lead to an increase in FTarget, while limiting total mortality leads to a decrease in FTarget. Application of either approach can result in nonsensical results. Short-term gains in yield associated with high FTarget values should be considered in light of potential losses in future yield if the high total mortality rate leads to a decrease in recruitment. Examples using yellowtail flounder (Limanda ferruginea) and Atlantic cod (Gadus morhua) are used to demonstrate that FTarget can change when M increases within an assessment and to illustrate the consequences of different FTarget values. When a change in M within an assessment is contemplated, first consider the amount and strength of empirical evidence to support the change. When the empirical evidence is not strong, we recommend using a constant M. If strong empirical evidence exists, we recommend estimating FTarget for a range of stock–recruitment relationships and evaluating the trade-offs between risk of overfishing and forgone yield.

Modelling feeding, growth, and habitat selection in larval Atlantic cod (Gadus morhua): observations and model predictions in a macrocosm environment

2007 ◽  
Vol 64 (1) ◽  
pp. 136-151 ◽  
Author(s):  
Trond Kristiansen ◽  
Øyvind Fiksen ◽  
Arild Folkvord
Keyword(s):  
Habitat Selection ◽  
Growth Rates ◽  
Prey Density ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Food Limitation ◽  
Limited Growth ◽  
Individual Parameter ◽  
Model Predictions ◽  
Developmental Features

Individual-based models (IBMs) integrate behavioural, physiological, and developmental features and differences among individuals. Building on previous process-based models, we developed an IBM of larval Atlantic cod (Gadus morhua) that included foraging, size-, temperature-, and food-limited growth, and environmental factors such as prey-field, turbulence, and light. Direct comparison between larval fish IBMs and experimental studies is lacking. Using data from a macrocosm study on growth and feeding of larval cod, we forced the model with observed temperature and prey-field and compared model predictions with observed distribution, diet, size-at-age, and specific growth rates. We explored implications of habitat selection rules on predicted growth rates. We analyze the sensitivity of model predictions by the Latin Hypercube Sampling method and individual parameter perturbation. Food limitation prevented larvae from growing at their physiological maximum, especially in the period 5–17 days post hatch (DPH). Active habitat selection had the potential to enhance larval growth rates. The model predicted temperature-limited growth rates for first-feeding larvae (5–20 DPH) when prey density is >5 nauplii·L–1. After age 20 DPH, maximum modelled growth required a diet of copepodites. Simulated growth rates were close to observed values except for the period just after the start of exogenous feeding when prey density was low.

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