scholarly journals Seasonal cycles in weight and condition in Atlantic cod (Gadus morhua L.) in relation to fisheries

2005 ◽  
Vol 62 (5) ◽  
pp. 1006-1015 ◽  
Author(s):  
L.G.S. Mello ◽  
G.A. Rose
Keyword(s):  
Gadus Morhua ◽  
Physiological Condition ◽  
Atlantic Cod ◽  
Management Strategies ◽  
Maximum Yield ◽  
Product Yield ◽  
Economic Benefits ◽  
Hepatosomatic Index ◽  
Economic Returns ◽  
Condition Indices

Abstract Seasonal cycle in weight and physiological condition of Atlantic cod (Gadus morhua) influenced productivity and economic impacts of the cod fishery in Placentia Bay, Newfoundland. Condition indices (Fulton's K condition factor and hepatosomatic index – HSI) were lowest during the spawning season (spring) and increased rapidly during the postspawning period, reaching maximum values by fall (K and HSI increased on average 24% and 82% between spring and fall, respectively). Somatic weight and condition indices varied seasonally. Condition indices were correlated with an industry index of product yield. Historically, cod fisheries have been prosecuted during all seasons, but simulations of 1997–1999 fisheries indicate that a fall fishery (period of peak physiological condition) resulted in a 8–17% decrease in the number of cod removed from the stock while maintaining the same weight-based quotas, and profiting from maximum yield and better product quality. Spring and summer fisheries resulted in lower yield (6%) and quality (5–26%) of fish products by weight. Seasonal biological cycles could be used as templates for management strategies that promote fisheries conservation and economic benefits by harvesting fish during periods when biological impacts are minimal and economic returns maximal.

Small-scale temporal and spatial variation in Atlantic cod (Gadus morhua) life history

2003 ◽  
Vol 60 (9) ◽  
pp. 1111-1121 ◽  
Author(s):  
Tara M McIntyre ◽  
Jeffrey A Hutchings
Keyword(s):  
Body Mass ◽  
Life Histories ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Spatial Scales ◽  
Gonadosomatic Index ◽  
Small Scale ◽  
Hepatosomatic Index ◽  
Georges Bank ◽  
High Fecundity

Life histories of Atlantic cod (Gadus morhua) from the Gulf of St. Lawrence south to Georges Bank differ significantly through time and space. Within the Southern Gulf, fecundity per unit body mass differed by more than 40% over short (2 years) and long (42–45 years) periods of time. Significant variation in size-specific fecundity is also evident among populations: Southern Gulf cod produce almost 30% more eggs per unit body mass than those on Georges Bank, whereas fecundity of Scotian Shelf cod is almost half that of cod in Sydney Bight. Compared with those on Georges Bank, Southern Gulf cod life histories are characterized by high fecundity, late maturity, high gonadosomatic index, and large eggs. Relative to the influence of body size, neither temporal nor spatial differences in fecundity can be attributed to physiological condition, as reflected by liver weight, hepatosomatic index, and Fulton's K. Delayed maturity and higher reproductive allotment among Southern Gulf cod can be explained as selection responses to slower growth, higher prereproductive mortality, and fewer lifetime reproductive events. Patterns of covariation in heritable, fitness-related traits suggest the existence of adaptive variation and evolutionarily significant units at spatial scales considerably smaller than the species range in the Northwest Atlantic.

Tracking escaped Atlantic cod (Gadus morhua L.) aggregated around Norwegian farms: Considerations for management strategies

2017 ◽  
Vol 24 (4) ◽  
pp. 265-273 ◽  
Author(s):  
R. D. Hedger ◽  
R. M. Serra-Llinares ◽  
P. Arechavala-Lopez ◽  
R. Nilsen ◽  
P. A. Bjørn ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Management Strategies

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

1998 ◽  
Vol 55 (7) ◽  
pp. 1591-1598 ◽  
Author(s):  
Patrice Couture ◽  
Jean-Denis Dutil ◽  
Helga Guderley
Keyword(s):  
Growth Rate ◽  
Water Content ◽  
Gadus Morhua ◽  
Citrate Synthase ◽  
Atlantic Cod ◽  
Nucleoside Diphosphate Kinase ◽  
Multiple Regression Model ◽  
Hepatosomatic Index ◽  
In The Wild ◽  
Muscle Water

The aim of this study was to examine how the biochemical composition of tissues varied with growth rate and condition in juvenile Atlantic cod (Gadus morhua) caught in the wild and kept in captivity. The hepatosomatic index, brain water content, and muscle sarcoplasmic protein content as well as the activities of phosphofructokinase, lactate dehydrogenase, nucleoside diphosphate kinase, and citrate synthase in the muscle, nucleoside diphosphate kinase and citrate synthase in the intestine, and cytochrome c oxidase and citrate synthase in the brain increased with growth rate or condition factor. Conversely, liver and muscle water contents were lower in fish with a higher growth rate. A multiple regression model that included the hepatosomatic index, water content of muscle and brain, and citrate synthase activity in the intestine explained 79.7% of the variability of growth in mass under our conditions. A similar model, using liver water content instead of muscle water content, explained 82.5% of the variability of growth in length. These easy to measure variables may be used in fisheries management to estimate the growth rate of fish in the wild.

scholarly journals Growth, survival, diet, and on-growing husbandry of haddock Melanogrammus aeglefinus in tanks and netpens

2006 ◽  
Vol 63 (2) ◽  
pp. 376-384 ◽  
Author(s):  
James W. Treasurer ◽  
Harald Sveier ◽  
Warren Harvey ◽  
Roddy Allen ◽  
Christopher J. Cutts ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Vibrio Anguillarum ◽  
Dietary Lipid ◽  
Whole Body ◽  
Melanogrammus Aeglefinus ◽  
Hepatosomatic Index ◽  
First Year ◽  
Starvation Period ◽  
Haddock Melanogrammus Aeglefinus

Abstract Growth of haddock (Melanogrammus aeglefinus) was assessed in onshore tanks in West Scotland. Fish were stocked at a mean weight of 15 g in July 2002, with a second stocking in October 2002 at 25 g. Fish had a mean weight of 755 ± 150 (s.d.) g at 20 months after stocking and were harvested. The specific growth rate of haddock was similar to Atlantic cod (Gadus morhua) during the first year but decreased by 20% after that. Liver biomass was 17.6% of the whole body weight, suggesting haddock had difficulty in utilizing dietary lipid. Reduced lipid levels in the diet had only a short-term effect on hepatosomatic index (HSI). Haddock that were held under 24-h light from the first summer solstice did not mature at an age of two years when compared with complete maturation of fish reared under ambient light. Mortality during the on-growing stage was high (28% of stock) and was attributed to Vibrio anguillarum infection, and possibly to enlarged livers. An assessment of quality found taste and texture to be as good or equal to wild North Sea haddock, and quality was improved with a five-day starvation period. Haddock mean weight, six months after transfer to netpens, was not significantly different from that of fish of the same age grown in tanks.

scholarly journals Condition indices of Atlantic cod (Gadus morhua) biased by capturing method

2012 ◽  
Vol 69 (10) ◽  
pp. 1781-1788 ◽  
Author(s):  
Mikael Ovegård ◽  
Kim Berndt ◽  
Sven-Gunnar Lunneryd
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Geographical Area ◽  
Lower Growth ◽  
Fish Stocks ◽  
Underlying Causes ◽  
The Difference ◽  
Condition Indices ◽  
The Baltic ◽  
Size At Age

Abstract Ovegård, M., Berndt, K., and Lunneryd, S-G. 2012. Condition indices of Atlantic cod (Gadus morhua) biased by capturing method. – ICES Journal of Marine Science, 69: 1781–1788. In studies evaluating the condition and general health status of fish stocks, the method used for catching the fish is seldom considered as a factor of importance. In this study, condition indices were compared between cod caught in pots, gillnets, and on hooks in the same geographical area. The results showed that cod (Gadus morhua) caught on baited gear types (pots and hooks) generally displayed a lower condition and an older age (i.e. suggesting a lower growth rate) compared to cod caught in gillnets. It is unclear whether these results merely illustrate divergent behavioural responses in fish originating from one single population, or if these divergent behavioural components represent distinct subpopulations displaying different mean conditions and growth rates. Regardless of the underlying causes, the results not only show that parts of the Baltic cod stock are in extremely poor condition, they also indicate that different gear types used in the same area could target similar-sized conspecifics exhibiting large differences in condition and size-at-age. The potential impact of the difference in condition between the pots and other gear types could hamper the implementation of the cod pot as a potentially seal-safe and sustainable fishing method.

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

1999 ◽  
Vol 56 (10) ◽  
pp. 1818-1831 ◽  
Author(s):  
J -D Dutil ◽  
M Castonguay ◽  
D Gilbert ◽  
D Gascon
Keyword(s):  
Gadus Morhua ◽  
Cold Water ◽  
Atlantic Cod ◽  
Management Strategies ◽  
Extreme Environments ◽  
Eastern Canada ◽  
Intensive Exploitation ◽  
Growth Production ◽  
Marked Decline ◽  
Size At Age

Northern Gulf of St. Lawrence Atlantic cod (Gadus morhua) is one of several stocks that collapsed in eastern Canada following a long period of intensive exploitation. Surplus and net production per capita became nil or negative in the mid-1980s so that any level of exploitation would have caused a decline of the stock. This was partly explained by a marked decline in growth production and is consistent with smaller sizes-at-age but also lower condition factor values during the same period. Correlations between size-at-age and temperature were not significant when corrected for autocorrelation, but slopes were always positive, suggesting higher growth rates at higher temperatures. Smaller sizes-at-age in the 1980s were not associated with changes in the fishery or increased fishing mortality, nor were they consistent with the density-dependence hypothesis. Lengths at age 8 decreased by more than 10 cm as the stock decreased 10-fold in abundance. While size-at-age and temperature covary in cod when all stocks are examined, size-temperature relationships are not as clear if the analysis is restricted to cold-water stocks, possibly because of differences in food availability. Biological production varies from year to year and among stocks and should be taken into consideration when managing fisheries in variable or extreme environments.

The dispersal pattern and behaviour of Atlantic cod (Gadus morhua) in the northern Gulf of St. Lawrence: results from tagging experiments

2012 ◽  
Vol 69 (1) ◽  
pp. 112-121 ◽  
Author(s):  
Hacène Tamdrari ◽  
Martin Castonguay ◽  
Jean-Claude Brêthes ◽  
Peter S. Galbraith ◽  
Daniel E. Duplisea
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Management Strategies ◽  
Fishing Effort ◽  
Fish Distribution ◽  
Suitable Habitat ◽  
Dispersion Pattern ◽  
Dispersion Index ◽  
Dispersal Pattern ◽  
Centre Of Gravity

We examined how the distribution of Atlantic cod ( Gadus morhua ) is influenced by abiotic (temperature, salinity, depth, suitable habitat) and biotic (stock biomass) factors based on tagging−recapture data collected from 1995 to 2008 by the Department of Fisheries and Oceans Canada in the northern Gulf of St. Lawrence. We calculated a centre of gravity index and a dispersion index using only individuals recaptured more than 1 year after tagging during the summer. The centre of gravity showed a northward expansion and eastward contraction in recent years, reflecting both fish distribution and changes in fishing effort. The dispersion index was significantly related to temperature, habitat suitability, and biomass but not to salinity or depth. These results indicate that interannual fluctuations of temperature and stock abundance both influence the dispersion pattern of cod. This new information could influence spatio-temporal fisheries management strategies for northern Gulf cod.

Condition and energy reserves of Atlantic cod (Gadus morhua) during the collapse of the northern Gulf of St. Lawrence stock

1997 ◽  
Vol 54 (10) ◽  
pp. 2388-2400 ◽  
Author(s):  
Y Lambert ◽  
J -D Dutil
Keyword(s):  
Seasonal Variations ◽  
Gadus Morhua ◽  
Condition Factor ◽  
Atlantic Cod ◽  
Hepatosomatic Index ◽  
Seasonal Cycles ◽  
Interannual Variations ◽  
Energy Reserves ◽  
Tissue Composition ◽  
Feeding Experiments

Interannual variations and seasonal cycles in condition and energy reserves were investigated for the northern Gulf of St. Lawrence cod (Gadus morhua) before and during the collapse of the stock. Significant decreases in cod condition between the late 1980s and the early 1990s coincided with the reduction in biomass. Cod exhibited clear seasonal variations in condition factor (Fulton's K), energy reserves, and tissue composition. Maximum K (0.87-0.91) and highest hepatosomatic index (HSI; 4.3-5.7%) occurred during the autumn while minimum levels occurred in spring. In May, the levels of condition (K, 0.69-0.74; HSI, 2.2-3.0) were below those reported for other stocks. In spring during spawning, a proportion of the wild cod had condition and energy reserves that were within the range that resulted in mortality among unfed fish held in the laboratory. Feeding experiments also indicate that the condition of wild cod in fall was lower than that observed for well-fed fish held in the laboratory. The decline in the condition and energy reserves of cod during several consecutive years may have lowered the productivity of the northern Gulf of St. Lawrence stock. This, along with overfishing, could have contributed to the collapse of this stock.

scholarly journals Measurements of acoustic backscatter and density of captive Atlantic cod with synchronized 300-kHz multibeam and 120-kHz split-beam echosounders

2009 ◽  
Vol 66 (6) ◽  
pp. 1303-1309 ◽  
Author(s):  
Christopher W. D. Gurshin ◽  
J. Michael Jech ◽  
W. Huntting Howell ◽  
Thomas C. Weber ◽  
Larry A. Mayer
Keyword(s):  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Management Strategies ◽  
Acoustic Backscatter ◽  
Standard Sphere ◽  
Factors Affecting ◽  
Acoustic Data ◽  
Nylon Mesh ◽  
Abundance And Distribution

Abstract Gurshin, C. W. D., Jech, J. M., Howell, W. H., Weber, T. C., and Mayer, L. A. 2009. Measurements of acoustic backscatter and density of captive Atlantic cod with synchronized 300-kHz multibeam and 120-kHz split-beam echosounders. – ICES Journal of Marine Science, 66: 1303–1309. Effective management strategies for Atlantic cod (Gadus morhua) in the Gulf of Maine require stock assessments based on accurate estimates of its abundance and distribution. If multibeam echosounders are to provide data for such estimates, the relationship between acoustic backscatter and fish biology must be better understood. Working towards this goal, a series of acoustic measurements was made using a 120 kHz, split-beam echosounder (Simrad EK60) and a 300 kHz, multibeam echosounder (Kongsberg EM3002). The transducers from both systems were fixed to a platform over a submerged 98 m3 cage made of 5 cm stretched-nylon mesh. After standard-sphere calibrations, the cage was stocked with live, mature Atlantic cod, with a mean total length of 80.7 cm (range: 51.5–105.0 cm). The echosounders synchronously collected acoustic data, while the cod were monitored with two underwater video cameras. Cod were incrementally removed from the cage to provide a time-series of acoustic backscatter at four densities (n = 128, 116, 66, and 23). Backscatter measurements of cod are compared between echosounders and over time, and the factors affecting the acoustically derived density estimates are discussed. The benefits and limitations of the EM3002 are highlighted.

scholarly journals Cod recruitment is strongly affected by climate when stock biomass is low

2005 ◽  
Vol 62 (3) ◽  
pp. 339-343 ◽  
Author(s):  
Keith M. Brander
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Environmental Variability ◽  
Atlantic Cod ◽  
Management Strategies ◽  
Pooled Analysis ◽  
The North ◽  
Stock Biomass ◽  
Spawning Stock ◽  
The North Atlantic

Abstract Stocks of Atlantic cod (Gadus morhua) have been declining over much of the North Atlantic for the past 30 years, owing to a combination of overfishing and adverse changes in their environment. In a previous study, environmental effects were introduced as an extra parameter in the stock-recruit relationship, where they act as a multiplier, independent of the level of spawning-stock biomass (SSB). Using a non-parametric pooled analysis of all cod stocks on the European Shelf south of 62°N, it is shown here that environmental variability (as represented by the North Atlantic Oscillation) only has a significant effect on recruitment when the spawning stock is low. This has implications for fisheries management strategies, and for rates of stock recovery, which will be very dependent on environmental conditions.

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