Growth Of Cod Research Articles

Reduced growth of Atlantic cod in non-lethal hypoxic conditions

Reduced growth of Atlantic cod in non-lethal hypoxic conditions

Empirical evidence of a trade–off between reproductive effort and expectation of future reproduction in female three-spined sticklebacks

Optimal life-history models generally predict that the reproductive effort of iteroparous organisms may increase with age, as their expectation of future reproduction decreases. The population of three–spined sticklebacks ( Gasterosteus aculeatus ) in the Camargue (Rhone River Delta, France) is annual, all adults dying after their first breeding season. As the three–spined stickleback is a multiple spawner, we tested the hypothesis that reproductive effort may increase during the breeding season on field data. From 1987 to 1998, 653 female sticklebacks were collected in the field during the breeding seasons. The body size, body weight and weights of the liver, gonads and carcass were measured for these individuals. Only gravid females with mature eggs (176 fish) were included in the analysis. Considering the female three–spined stickleback as a capital breeder, the energetic resources available for allocation between soma and gonads were estimated by its body weight. Somatic condition decreased during the breeding season and reproductive effort (gonad weight relative to body weight) increased. These patterns did not vary significantly between years. These observed variations in reproductive effort during the breeding season can be interpreted as empirical evidence of a trade–off between reproductive effort and expectation of future reproduction.

Growth and maturation of cod ( Gadus morhua) of different year classes in the Northwest Atlantic, NAFO subdivision 3Ps

Using data collected in fishery-independent bottom-trawl surveys of cod in NAFO subdivision 3Ps, we examine (1) the variations in growth and maturation of cod among year classes from 1969 to 1990 and (2) inter-relationships between growth and maturation of cod. To reduce impacts of outliers on data analyses, a robust maximum likelihood estimator is used to fit the von Bertalanffy growth function to size-at-age data. An overall indicator for pre-maturity growth of cod is developed using a robust principal component analysis. This study suggests that cod born during 1980s have smaller length-at-age values when compared with cod born in 1970s. The age at maturity declined steadily from the highest of 7 yr old for the 1981 year-class to 5 yr old for the 1990 year-class. Growth and maturation were significantly related to each other. A cohort of cod that had a higher growth rate in their young ages tended to mature earlier. The impacts of the findings in this study on the management of the fish stock are discussed.

Gastrointestinal evacuation of particulate matter in polar cod Boreogadus saida

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 188:201-205 (1999) - doi:10.3354/meps188201 Gastrointestinal evacuation of particulate matter in polar cod Boreogadus saida Bjørn-Steinar Sæther1,*, Jørgen Schou Christiansen2, Malcolm Jobling1,2 1Norwegian College of Fishery Science, University of Tromsø, 9037 Tromsø, Norway 2Norwegian Institute of Fisheries and Aquaculture, 9291 Tromsø, Norway *E-mail: bjoerns@nfh.uit.no ABSTRACT: Gastrointestinal evacuation of inert particles was monitored in the polar cod Boreogadus saida (Lepechin), held at a temperature of 0.5°C. Fish (31.8 g ± 0.8 SD) were fed a moist diet, based on natural prey items, containing a particulate marker. Evacuation of marker from the gastrointestinal tract started 48 h after ingestion of a meal. The average time needed to evacuate 50% of the marker was estimated to be 132 h, whereas the total evacuation time was approximately 400 h. This may indicate that the polar cod does not feed on a daily basis at temperatures close to zero because of the prolonged time needed to evacuate meals. This work provides a methodological basis for studies of feeding and growth in polar cod using X-radiography. KEY WORDS: Polar cod · Boreogadus saida · Food intake · Gastrointestinal evacuation · Radiography Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 188. Publication date: November 03, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Growth, condition, and environmental relationships in Atlantic cod (<i>Gadus morhua</i>) in the northern Gulf of St. Lawrence and implications for management strategies in the Northwest Atlantic

Growth, condition, and environmental relationships in Atlantic cod (<i>Gadus morhua</i>) in the northern Gulf of St. Lawrence and implications for management strategies in the Northwest Atlantic

Temperature- and size-dependent growth of larval and early juvenile Atlantic cod (<i>Gadus morhua</i>): a comparative study of Norwegian coastal cod and northeast Arctic cod

Temperature- and size-dependent growth of larval and early juvenile Atlantic cod (<i>Gadus morhua</i>): a comparative study of Norwegian coastal cod and northeast Arctic cod

Effect of size‐selective mortality on growth of coastal cod illustrated by tagging data and an individual‐based growth and mortality model

In a release experiment with cod in Norway, the apparent mean growth rates of 3+ cod, calculated by sampling the released cohorts at different ages, were very slow (<0·08 mm day−1). However, when individual growth rates of individual tagged cod of the same size range were measured, the mean growth rates were much faster (0·24 mm day−1). These observations were attributed to size‐selective fishing mortality and were illustrated by an individual based simulation model of a cohort of cod with variable individual growth rates. The effects on mean length at age of the surviving cohort of increasing fishing intensity were demonstrated. The model showed that size‐selective fishing with the observed individual growth variation, removed the fastest‐growing individuals at proportionally higher rates than the slower‐growing ones, leading to decreased apparent mean growth rate. The fishing pattern which gave the optimum yield, changed when individual variation was included, and when the apparent growth rate was used in the model the yield per recruit reduced dramatically. This study has shown that individual growth heterogeneity and size‐selective mortality are factors which should be considered in future fisheries management models.

Effect of size-selective mortality on growth of coastal cod illustrated by tagging data and an individual-based growth and mortality model

Effect of size-selective mortality on growth of coastal cod illustrated by tagging data and an individual-based growth and mortality model

Biochemical correlates of growth and condition in juvenile Atlantic cod (<i>Gadus morhua</i>) from Newfoundland

Biochemical correlates of growth and condition in juvenile Atlantic cod (<i>Gadus morhua</i>) from Newfoundland

Effects of Long-Term Temperature Acclimation on Thyroid Hormone Deiodinase Function, Plasma Thyroid Hormone Levels, Growth, and Reproductive Status of Male Atlantic Cod,Gadus morhua

The recent collapse of the Northwestern Atlantic cod fisheries has coincided with a cooling of water temperatures. During this time the condition factor of cod has been poor. The objective of the present study was to determine the effects of long-term temperature acclimation on growth reproduction and thyroid function in laboratory held Atlantic cod (Gadus morhua). One of the key parameters used to assess thyroid function is the peripheral metabolism ofl-thyroxine (T4) by microsomal deiodinase enzymes. Deiodinase function has not been described for gadid fish. T4outer-ring deiodinating activity (apparentKm1–2 nM) was confined primarily to liver. Its properties resembled those for hepatic T4ORD activity of other teleosts and the mammalian type II deiodinase. The T4ORD activity of cod liver exceeded that of salmonids and could explain the high plasma T3levels (10–18 ng/ml), which were 2–5 times greater than T4levels. T4and T3inner-ring deiodination was confined mainly to brain. In order to determine the effects of long-term temperature acclimation on cod, somatic growth, reproduction, and thyroidal status were assessed monthly in 400–900-g satiation-fed male Atlantic cod captured in June from the St. Lawrence Estuary and then acclimated from August to the following June under a natural photoperiod at 2–4°C (LT) or 6–10°C (HT). Reproductive status was determined from the gonadosomatic index (GSI), plasma testosterone (T) and 11-ketotestosterone (11-KT) levels, and the appearance of milt; thyroidal status was determined from plasma T4and 3,5,3′-triiodo-l-thyronine (T3) levels and hepatic T4ORD activity to produce biologically active T3. Testis maturation (high levels of T and 11-KT, and milt release) occurred in April and May and was uninfluenced by acclimation temperature. LT cod grew more slowly than HT cod. Differences in body weight were particularly evident from December to February. In conclusion, (i) cod possess outer- and inner-ring deiodinase activities, predominating respectively in liver and brain, and with properties resembling those of other teleosts, (ii) T4ORD activity of liver is unusually high and may account for the high plasma T3levels in this species, (iii) T4ORD activity tends to increase during periods of increased somatic growth, and (iv) chronic acclimation of male cod to 2–4°C, as opposed to 6–10°C, decreases somatic growth but does alter circulating levels of thyroid hormones and androgens and it does not change the time of sexual maturation.

Growth of cod (Gadus morhua) estimated from mark-recapture programs on the Scotian Shelf and adjacent areas

Growth of cod (Gadus morhua) was estimated from length increment data compiled from tagging programs conducted between 1978–1985 in the Southern Gulf of St Lawrence, on the Scotian Shelf, in the Western Bay of Fundy and on Georges Bank. A model developed by Francis was used to estimate growth parameters gα and gβ which represented mean annual growth rate at chosen reference lengths 45 and 65 cm respectively. Individual growth variability was modelled as proportional to the expected change in length, which in turn was a function of time at liberty and initial size. The model was fit using a maximum likelihood technique. The tails of the distribution of residuals were longer than normal, reflecting the scatter of the data. The residuals did not show any pattern with either of the independent variables (time-at-liberty, length-at-release). Mean growth was greatest in the Western Bay of Fundy and Georges Bank, intermediate on the Scotian Shelf (Brown's Bank, Halifax and Banquereau Bank) and least in Sidney Bight and the Gulf of St Lawrence. The regional trend in growth estimated from tagging data was consistent with trends in growth estimated from size-at-age distributions. Regional growth differences reflected the underlying hydrographic regime. The correlation between gα and bottom temperature was r=0.84 (df=7, p=0.004) while that between gβ and bottom temperature was r=0.88 (df=7, p=0.002). The estimate of individual variability of growth is large, and suggests that size-at-age distributions among regions would overlap. Based on the geographic distribution of recaptures, fish from the Scotian Shelf migrated shorter distances than did fish from the Gulf of St Lawrence, Brown's Bank, Western Bay of Fundy and George's Bank; fish from adjacent regions were more likely to mix than fish from more distant regions.

Development of NDE technology to evaluate fatigue damage of steam generator tube: Goto, T., Enami, K., Fukui, S. and Uesugi, N. 13th International Conference on NDE in the Nuclear and Pressure Vessel Industries, Kyoto, Japan (22–25 May 1995) 427–434

In situ SEM observations and measurements were made of near-tip COD and crack growth at small, thumb-nail cracks subjected to a single overload during fatigue at constant load amplitude in 2024-T351 aluminium alloy. A delayed retardation in crack growth was observed at R = 0.05, but not at R = −1. During retarded growth at R = 0.05, near-tip COD decreased below that measured before overload and the level of crack closure increased. These events were not evident at R = −1. An elastic/plastic finite element modelling of the growth of similar small cracks predicted enhanced residual compressive stresses ahead of the crack tip for R = 0, but not for R = −1. The experimental and modelling work are consistent in linking differences in the crack growth profiles at the two R ratios with differences in COD, crack closure and residual compressive stress ahead of the crack tip following overload.

In situ SEM observations of the contrasting effects of an overload on small fatigue crack growth at two different load ratios in 2024-T351 aluminium alloy

In situ SEM observations and measurements were made of near-tip COD and crack growth at small, thumb-nail cracks subjected to a single overload during fatigue at constant load amplitude in 2024-T351 aluminium alloy. A delayed retardation in crack growth was observed at R = 0.05, but not at R = −1. During retarded growth at R = 0.05, near-tip COD decreased below that measured before overload and the level of crack closure increased. These events were not evident at R = −1. An elastic/plastic finite element modelling of the growth of similar small cracks predicted enhanced residual compressive stresses ahead of the crack tip for R = 0, but not for R = −1. The experimental and modelling work are consistent in linking differences in the crack growth profiles at the two R ratios with differences in COD, crack closure and residual compressive stress ahead of the crack tip following overload.

Bioenergetic analysis of the effects of temperature and prey availability on growth and condition of northern cod (<I>Gadus morhua</I>)

Bioenergetic analysis of the effects of temperature and prey availability on growth and condition of northern cod (<I>Gadus morhua</I>)

Bioenergetic analysis of the effects of temperature and prey availability on growth and condition of northern cod (Gadus morhua)

Atlantic cod (Gadus morhua) stocks of the Northwest Atlantic have experienced steady decreases in growth rate since 1989 and in physiological condition since 1988. The declines have been attributed to various factors, including size- selective fishing pressure, anomalously low temperature fields, and a decline in available prey. The precise balance of these factors is unknown. We applied simple correlation models to determine that bottom water temperature and capelin ( Mallotus villosus) biomass together explain 52% of the interannual variance in mean condition of 2J3K cod and 23% of the interannual variance in 2J3KL mean cod growth rates. Bioenergetic models can potentially improve our understanding of the mechanisms behind these relationships because they allocate energy as a function of environmental parameters such as water temperature and prey consumption. We developed a bioenergetic model for Atlantic cod to determine whether temperature could explain the observed decreases in growth rate of northern cod stocks. Our results suggest that the low growth rates of 2J3K northern cod observed in recent years are not due to physiological temperature limitation, while the growth rates of cod inhabiting cooler waters on the northern Grand Banks (3L) may, at least in certain years, be temperature limited.

Introduction to the Northwest Atlantic Cod Symposium

The papers appearing in this supplement are some of those presented at the Symposium on the Biology and Ecology of Northwest Atlantic Cod which was held at the Delta St. John’s Hotel in St. John’s, Newfoundland, from 24 to 28 October 1994. With two major specially-funded fisheries research programs being concluded, it seemed timely that a symposium should be held to review recent research in federal fisheries laboratories and universities in eastern Canada on Atlantic cod (Gadus morhua) and its marine environment. In particular, research results produced under the auspices of the Government of Canada’s Northern Cod Science Program (NCSP) and the government/industry-funded Ocean Production Enhancement Network (OPEN) program were to be presented. The goal of the Symposium was to summarize the current knowledge on Atlantic cod biology and ecology with emphasis on the Northwest Atlantic and provide a forum for application of recent research results in addressing specific fisheries problems. The following papers were selected, in keeping with the overall policies of this Journal, for their original contributions to our knowledge of the life history, physiology, population dynamics, habitat, and interspecific interactions of Atlantic cod. The NCSP itself was designed as an intensive 5-yr (1990– 1995) fisheries science effort established, and funded to a total of about $28 million, to improve our knowledge of the basic biology and environment of the northern (NAFO Div. 2J and 3KL) Atlantic cod stock. The Program consisted of 25 study initiatives, involving about 50 fisheries and oceanographic researchers in Atlantic Canada and it provided funding for studies on cod reproduction, growth, migration, distribution and diet, and new initiatives in seal abundance, movements, and diet. A major effort in physical oceanography expanded the data base and clarified the broad features of the physical environment off Newfoundland and Labrador. Research in hydroacoustic and survey gear technology was funded to enhance development of systems to add to the tools available to fisheries science in the future. Related studies on the vital parameters of Atlantic cod were also conducted in the OPEN (1990–1994) program. OPEN was established to investigate the processes that control survival, growth, reproduction, and distribution of fish and shellfish, principally Atlantic cod and scallops. With respect to Atlantic cod, OPEN focussed on recruitment, distribution, physiology, marine genetics, and coastal ocean dynamics. The OPEN research program consisted of 33 projects involving researchers at eight universities and the Department of Fisheries and Oceans with funding totalling about $20 million over the 4-yr period. The Symposium was attended by over 180 scientists and fisheries specialists from Department of Fisheries and Oceans science branches and from universities in Atlantic Canada. The Symposium was organized into eight sessions where 80 papers were orally presented and 30 papers displayed by poster. The sessions were most ably chaired as follows: Recruitment and Early Life History (Michael M. Sinclair); Physiology (Garth L. Fletcher); Coastal Oceanography (Keith R. Thompson); Population Identification and Characterization (Chris T. Taggart); Growth, Feeding, Predation, and Behaviour (E. Michael Chadwick); Distribution and Population Dynamics (Kenneth T. Frank); Fisheries and Monitoring (D. Bruce Atkinson); Poster Session (M. Ben Davis). I wish to thank the other members of the Steering Committee, namely Larry W. Coady, George A. Rose, and Kevin M. Keough, and gratefully acknowledge the assistance provided by the local organizing committee made up of Crystal Delaney, Jim Helbig, Larry Jackson, Pierre Pepin, Michelle Roberge, and Joe Wroblewski. Financial support for the Symposium was provided by the Department of Fisheries and Oceans, the Ocean Production Enhancement Network, and the Office of Research, Memorial University of Newfoundland.

Age and growth of red cod (Pseudophycis bachus) off the south‐east coast of South Island, New Zealand

Abstract A method is described to determine the age of red cod using the bands in sectioned otoliths. The technique was validated by examining the state of otolith margins over a 1‐year period, and by following the progression of length modes in length‐frequency distributions (for age classes 0+ to 3+). Von Bertalanffy growth parameters are estimated for red cod off the south‐east coast of the South Island. Few fish appear to live longer than 4 years. Because of the few age classes in the population at any time, age distributions may be obtained for most of a sample using length modes.

An experimental investigation of the 'match/mismatch' hypothesis using larval Atlantic cod

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 130:29-37 (1996) - doi:10.3354/meps130029 An experimental investigation of the 'match/mismatch' hypothesis using larval Atlantic cod Gotceitas V, Puvanendran V, Leader LL, Brown JA The match/mismatch hypothesis suggests that the degree of overlap between larval fish and their prey affects larval growth, survival and recruitment. For example, some fish species have a relatively fixed spawning period while peak production of their food varies yearly, depending on abiotic factors, creating a match or mismatch between the two. In this study, we investigated the influence of a match or mismatch on growth of cod (Gadus morhua) larvae. Larvae were exposed to 1 of 5 different food treatments: (1) high food (HF) (match); (2) low food (LF), (3) HF then LF (HF-LF), and (4) LF then HF (LF-HF) (2, 3 &AMP 4 mismatch); and (5) no food (NF) (complete mismatch). In treatments including a switch in food level, the switch took place on Day 11 post-hatch. Larvae were sampled every 5 d, and standard length, body depth, dry weight, and gut fullness recorded. Specific growth rate (% dry wt d-1) of larvae reared under the different food treatments was calculated. The experiment was repeated to examine the influence of Treatments 1 to 4 on survival of larval cod. All larvae in the NF treatment died by Day 20 post-hatch. Larvae under HF conditions were significantly larger than those in all other treatments by Day 20 post-hatch, while at Day 35, there was no difference between larvae from the HF and LF-HF treatments. Larvae under the LF-HF treatment were significantly larger than those from the HF-LF and LF treatments by Day 30 post-hatch. There was no significant difference in size between larvae from the HF-LF and LF treatments throughout the experiment. Specific growth rate was highest when larvae were exposed to a HF level. A switch between LF and HF resulted in a significant increase in specific growth rate in the LF-HF treatment and decrease in the HF-LF treatment. The number of larvae surviving to Day 35 post-hatch, and through to metamorphosis, was highest for the HF treatment, followed by the LF-HF, HF-LF, and LF treatments. Our results suggest that a mismatch and its timing can significantly influence the growth and survival of cod larvae. Atlantic cod larvae . Match/mismatch hypothesis . Gadus morhua . Feeding . Growth . Survival Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 130. Publication date: January 11, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

Trophodynamic and advective influences on Georges Bank larval cod and haddock

Using a model-based approach, the relative effects of advective and trophodynamic (feeding and growth) processes are considered on populations of larval cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) on Georges Bank. Building on previous studies that describe the role of advection, this study incorporates trophodynamic relationships to examine starvation mortality and growth rates at the level of individual larvae on the Bank. Estimates of prey concentrations and flow fields appropriate for late winter/early spring are used. Both trophodynamic processes and advection influence larval losses from the Bank where, in the absence of starvation, advective losses are on the order of one-fifth of the eggs and larvae spawned on the Bank. Starvation is most important in the first feeding larvae and is much reduced for older larvae. The contact rates between larval fish and zooplankton prey when turbulence is included are 2–5 times greater than the contact rates with no turbulence, and allow the model cod larvae to achieve growth rates similar to those observed on the Bank, although mean rates for larval haddock are still lower than observed. Turbulence-enhanced contact rates are thus determined to be a necessary component in our description of the growth of cod and haddock larvae on Georges Bank. Model cod larvae with growth rates comparable to those observed in the field are located below the surface layer (deeper than 25 m) and inside the 60 m isobath. The region of highest retention due to circulation processes (Werner et al., 1993; Fisheries Oceanography, 2, 43–64) coincides with the region of highest growth rates and highest larval survival. Therefore, there is a complementary interaction between trophodynamic and circulation processes, with those larvae most likely to remain on the Bank also being those in the most favorable feeding regions. Haddock larvae require higher prey densities than cod larvae to survive.

Effects of habitat on settlement, growth, and postsettlement survival of Atlantic cod (Gadus morhua)

Settlement and growth of age 0+ cod were monitored using snorkel and self-contained underwater breathing apparatus (SCUBA) in four distinct habitat types (sand, seagrass, cobble, and rock reef) in St. Margaret's Bay, Nova Scotia. Newly settled cod were marked with acrylic dye, allowing repeated visual length estimates of individual fish. Settlement of cod did not differ between habitat types, but postsettlement survival and subsequent juvenile densities were higher in more structurally complex habitats. These differences appear to be due to increased shelter availability and decreased predator efficiency in structurally complex habitats. Growth rate was highest in seagrass beds, while the efficiency of cod predators was lowest and cod survival was highest on rocky reefs and cobble bottoms. Thus, trade-offs occur between energy gain and predation risk. In St. Margaret's Bay, the population structure of Atlantic cod may be less influenced by patterns of larval supply than by postsettlement processes such as habitat-specific growth and mortality.