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 Weaning of Burbot, Lota lota (L.) from Live to Dry Feed Using NaCl as Dietary Attractant

2017 ◽  
Vol 9 (3) ◽  
pp. 7
Author(s):  
Franz Lahnsteiner ◽  
Manfred Kletzl
Keyword(s):  
Body Mass ◽  
Sedimentation Rate ◽  
Condition Factor ◽  
Mortality Rates ◽  
Hepatosomatic Index ◽  
Lota Lota ◽  
Live Feed ◽  
Feeding Experiments ◽  
Feeding Attractant ◽  
Weaning Protocols

Weaning of 150 days post hatch Lota lota from live feed (zooplankton) to formulated dry feed (FDF) was investigated. L. lota could not be forced from live feed to FDF. They refused FDF for periods up to 21 d. Body mass decreased for 20%, condition factor for 15%, and hepatosomatic index for 50%. In 21 days lasting co-feeding experiments with FDF and live feed L. lota selected exclusively the live feed organisms. NaCl in a concentration of 5% was a dietary feeding attractant for L. lota. When FDF was supplemented with 5% NaCl, L. lota could be abruptly weaned from live to dry feed. During a 21 d lasting experiment body mass increased for circa 40%, total length for 10%, condition factor for 5% and hepatosomatic index remained constant. These values were similar to live zooplankton feeding. However, increased mortality of > 20% was recorded for fish fed with the 5% NaCl containing FDF. To reduce mortality FDF was supplemented with zooplankton meal to upgrade its quality and extruded to optimize its density and sedimentation rate. With the adjusted FDF mortality rates were reduced to < 5%. Using the optimized dry feed easy and sustainable weaning protocols were developed where NaCl and zooplankton meal were gradually reduced to adapt fish to pure FDF.

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.

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.

scholarly journals Quality of Nephrops as food for Atlantic cod (Gadus morhua L.) with possible implications for fisheries management

2004 ◽  
Vol 61 (6) ◽  
pp. 983-991 ◽  
Author(s):  
Björn Björnsson ◽  
Maria Álvaro Dongala Dombaxe
Keyword(s):  
Growth Rate ◽  
Gadus Morhua ◽  
Specific Growth ◽  
Condition Factor ◽  
Atlantic Cod ◽  
Gonadosomatic Index ◽  
Conversion Ratio ◽  
Food Conversion ◽  
The Mean

Abstract Nephrops was found to be of low quality as food for cod. In a laboratory experiment the mean specific growth rate of 1 kg cod was 0.184 and 0.415% d−1 when fed to satiation on Nephrops and capelin, respectively. This large difference in growth rate resulted not only from less intake of Nephrops (1.19 kg cod−1) than capelin (1.55 kg cod−1) but also because more Nephrops (4.6 kg) than capelin (2.2 kg) were required to produce each kilogramme of cod. Higher food conversion ratio was consistent with lower fat content of Nephrops (1.3%) than capelin (9.2%) but the exoskeleton also reduced the digestion rate of Nephrops. In the groups where Nephrops and capelin of equal mean weight were offered simultaneously, 40% of the diet consisted of Nephrops during the first week and 10% during the final seven weeks of the experiment. At the end of the experiment, condition factor, liver index, and gonadosomatic index were significantly lower for cod fed on Nephrops (0.967, 5.7, 7.1, respectively) than for those fed on capelin (1.086, 15.8, 11.2, respectively). These results suggests that predation by cod on Nephrops might be reduced by regular release of capelin or other similar food in the distributional areas of Nephrops.

Energetic consequences of reproduction in Atlantic cod (Gadus morhua) in relation to spawning level of somatic energy reserves

2000 ◽  
Vol 57 (4) ◽  
pp. 815-825 ◽  
Author(s):  
Yvan Lambert ◽  
Jean-Denis Dutil
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Good Condition ◽  
Reproductive Potential ◽  
Reproductive Investment ◽  
Energy Losses ◽  
Commercial Fishing ◽  
Energy Reserves ◽  
Poor Condition ◽  
Somatic Energy

The influence of a lower condition on reproductive investment, somatic energy losses, and postspawning condition of Atlantic cod (Gadus morhua) was examined under the hypothesis that females, in response to lower available energy reserves, would reduce reproductive investment in order to limit somatic energy losses. Laboratory experiments revealed that female cod with high prespawning condition factors ended reproduction in better condition than females with low prespawning condition factors. Fecundity and total egg dry weight were significantly lower in poor-condition females. The loss in somatic mass and energy in these poor-condition females was nevertheless higher, in relative terms, than the losses experienced by females in good condition. Consequently, energy reserves invested in reproduction by poor-condition females increase their risk of mortality. In the northern Gulf of St. Lawrence during the early 1990s, reproductive females had lower fecundities and were in worse prespawning and postspawning condition. The condition of spent females suggested a greater impact of changes in environmental conditions on adult than on immature cod. Reproductive potential and possibly recruitment may have suffered from that situation and could have contributed to the failure of that stock to recover despite the moratorium on commercial fishing.

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.

Sperm competition and fertilization success in Atlantic cod (Gadus morhua): effect of sire size and condition factor on gamete quality

1999 ◽  
Vol 56 (12) ◽  
pp. 2315-2323 ◽  
Author(s):  
Ana Rakitin ◽  
Moira M Ferguson ◽  
Edward A Trippel
Keyword(s):  
Body Size ◽  
Sperm Competition ◽  
Gadus Morhua ◽  
Condition Factor ◽  
Atlantic Cod ◽  
Sperm Quality ◽  
Fertilization Success ◽  
Male Body ◽  
Single Female ◽  
Male Condition

Sperm competition experiments were conducted to test the null hypothesis that sperm quality is not affected by male body size in Atlantic cod (Gadus morhua). Genetic markers (allozymes) were used to determine the proportion of larvae sired by pairs of males when their sperm was combined with eggs of a single female simultaneously. Significant differences in fertilization success between males were not explained by differences in body size. Fertilization success was positively associated with male condition factor (K) and with spermatozoa density in each male's semen when equal volumes of semen from each male were used. Male K was positively associated with male fertilization success when the volume of semen used from each male was adjusted to add approximately equal numbers of spermatozoa from each male. The relative fertilization success of males varied depending on which female was the egg donor, suggesting that female "choice" at the gamete level may be occurring in cod.

scholarly journals Timing and determination of potential fecundity in Atlantic cod (Gadus morhua)

2006 ◽  
Vol 63 (2) ◽  
pp. 310-320 ◽  
Author(s):  
Jon Egil Skjæraasen ◽  
Trygve Nilsen ◽  
Olav S Kjesbu
Keyword(s):  
Egg Production ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Explanatory Power ◽  
Temporal Variations ◽  
Energy Reserves ◽  
Potential Fecundity ◽  
Time Determination ◽  
Spawning Periods

Studies using annual averages of lipid storage or estimated quality of the feeding season have shown that energy reserves influence egg production in Atlantic cod (Gadus morhua). However, vitellogenesis starts months before spawning. Therefore, energy reserves near the start of vitellogenesis might provide better proxies of fecundity and hence egg production than yearly averages. If so, proxies with large temporal variations (e.g., weight and lipid energy) should vary similarly in their predictive power, and females with different spawning periods should have their fecundity determined at different times. We exposed cod to two photoperiods to induce different spawning seasons. Growth before spawning was monitored, and potential fecundity was measured at the onset of spawning. The date yielding the greatest explanatory power differed between photoperiods. As proxies, length varied less and had lower explanatory power than weight. Lipid energy at the onset of spawning was a poor proxy. The greatest explanatory power was found ~3–4 months before spawning around the start of vitellogenesis, indicating that potential fecundity was highly influenced by female energy reserves at this time. Determination of potential fecundity early in vitellogenesis may be a common feature for determinate teleost spawners.

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