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.

Natural mortality from poor condition in Atlantic cod (Gadus morhua)

2000 ◽  
Vol 57 (4) ◽  
pp. 826-836 ◽  
Author(s):  
Jean-Denis Dutil ◽  
Yvan Lambert
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Negative Impact ◽  
Fish Muscle ◽  
Early Summer ◽  
Wild Fish ◽  
Natural Mortality ◽  
Muscle Lactate ◽  
Lactate Dehydrogenase Activity ◽  
Poor Condition

The extent of energy depletion was assessed in Atlantic cod (Gadus morhua) in spring and early summer (1993-1995) to assess relationships between poor condition and natural mortality. Several indices of condition were compared in wild fish in the northern Gulf of St. Lawrence and in fish exposed to a prolonged period of starvation in laboratory experiments. Discriminant analyses classified only a small fraction of the wild fish as similar to cod that did not survive and a much larger fraction as similar to cod that survived starvation. This percentage increased from April to May and peaked in June 1993 and 1994. Condition factor and muscle somatic index allowed a clear distinction between live and dead fish. Muscle lactate dehydrogenase activity suggested that cod had experienced a period of negative growth early in 1993, 1994, and 1995. Fish classified as similar to starved individuals were characterized by a higher gonad to liver mass ratio than others. Reproduction may have a negative impact on survival not only in spring but also later into summer, as some individuals were found not to have recovered by late summer. This study shows that natural mortality from poor condition contributed to lower production in the early 1990s.

Chapter 3 Effects of Climate Change and Commercial Fishing on Atlantic Cod Gadus morhua

2009 ◽  
pp. 213-273 ◽  
Author(s):  
Nova Mieszkowska ◽  
Martin J. Genner ◽  
Stephen J. Hawkins ◽  
David W. Sims
Keyword(s):  
Climate Change ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Commercial Fishing

scholarly journals Reproductive investment in Atlantic cod populations off Newfoundland: Contrasting trends between males and females

FACETS ◽  
2017 ◽  
Vol 2 (2) ◽  
pp. 660-681 ◽  
Author(s):  
Loïc Baulier ◽  
M. Joanne Morgan ◽  
George R. Lilly ◽  
Ulf Dieckmann ◽  
Mikko Heino
Keyword(s):  
Life History Theory ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Temporal Trends ◽  
Reproductive Investment ◽  
Male Reproductive Success ◽  
Density Dependent ◽  
Theoretical Predictions ◽  
Two Populations

Life history theory predicts selection for higher reproductive investment in response to increased mortality among mature individuals. We tested this prediction over the period from 1978 to 2013 for three populations of Atlantic cod ( Gadus morhua) off Newfoundland. These populations were heavily fished for a long period. We considered changes in standardized gonad weight as a proxy for changes in gonadal investment. We accounted for the allometry between gonad and body weight, individual body condition, water temperature, and potential spatial and density-dependent effects. Males display significant temporal trends in gonadal investment in all populations; in agreement with theoretical predictions, these trends show increased gonadal investments during the earlier part of the time series when mortality was high, with the trends leveling off or reversing after the later imposition of fishing moratoria. In contrast, females display patterns that are less consistent and expected; significant trends are detected only when accounting for density-dependent effects, with females in two populations unexpectedly showing a long-term decline in gonadal investment. Our results support the hypothesis that fisheries-induced evolution has occurred in gonadal investment in males, but not in females, and suggest that gonadal investment is more important for male reproductive success than expected in this lekking species.

scholarly journals Systematic bias in estimates of reproductive potential of an Atlantic cod (Gadus morhua) stock: implications for stock–recruit theory and management

2006 ◽  
Vol 63 (5) ◽  
pp. 980-994 ◽  
Author(s):  
C Tara Marshall ◽  
Coby L Needle ◽  
Anders Thorsen ◽  
Olav Sigurd Kjesbu ◽  
Nathalia A Yaragina
Keyword(s):  
Egg Production ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Reproductive Potential ◽  
Threshold Level ◽  
Systematic Bias ◽  
Stock Status ◽  
Relative Fecundity ◽  
Time Period ◽  
Spawning Stock

Stock–recruit relationships that use spawning stock biomass (SSB) to represent reproductive potential assume that the proportion of SSB composed of females and the relative fecundity (number of eggs produced per unit mass) are both constant over time. To test these two assumptions, female-only spawner biomass (FSB) and total egg production (TEP) were estimated for the Northeast Arctic stock of Atlantic cod (Gadus morhua) over a 56-year time period. The proportion of females (FSB/SSB) varied between 24% and 68%, and the variation was systematic with length such that SSB became more female-biased as the mean length of spawners increased. Relative fecundity of the stock (TEP/SSB) varied between 115 and 355 eggs·g–1 and was significantly, positively correlated with mean length of spawners. Both FSB and TEP gave a different interpretation of the recruitment response to reductions in stock size (overcompensatory) compared with that obtained using SSB (either compensatory or depensatory). There was no difference between SSB and FSB in the assessment of stock status; however, in recent years (1980–2001) TEP fell below the threshold level at which recruitment becomes impaired more frequently than did SSB. This suggests that using SSB as a measure of stock reproductive potential could lead to overly optimistic assessments of stock status.

Energy losses due to routine and feeding metabolism in young-of-the-year juvenile Atlantic cod (Gadus morhua)

2003 ◽  
Vol 60 (8) ◽  
pp. 929-937 ◽  
Author(s):  
Myron A Peck ◽  
Lawrence J Buckley ◽  
David A Bengtson
Keyword(s):  
Body Size ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Effect Of Temperature ◽  
Energy Losses ◽  
The North ◽  
A Value ◽  
Different Temperatures ◽  
Body Sizes ◽  
Environmental Temperatures

We examined the effects of body size (3–13 cm total length) and temperature (4.5, 8.0, 12.0, and 15.5 °C) on routine (RR) and feeding (RSDA) energy losses by laboratory-reared, young-of-year juvenile Atlantic cod (Gadus morhua). The magnitude of the effect of temperature on RR, expressed via the Q10, was nonlinear. Q10 values were greatest at temperatures between 4.5 and 8.0 °C and were lowest between 8.0 and 15.5 °C, with larger fish tending to exhibit the greatest change in RR irrespective of the temperature combination. Energy losses resulting from RSDA were ~4% of consumed energy, a value less than half that estimated for larger, year-1+ juvenile cod fed similar-sized rations. Data from this and other studies were combined to generate an equation estimating routine energy loss at different temperatures and body sizes for cod. The equation describes RR over the eight orders of magnitude difference in body size from young larvae to adults within a range of environmental temperatures experienced by this species on Georges Bank and other areas in the North Atlantic.

Why the Atlantic cod (Gadus morhua) stock off eastern Nova Scotia has not recovered

2001 ◽  
Vol 58 (8) ◽  
pp. 1613-1623 ◽  
Author(s):  
Caihong Fu ◽  
Robert Mohn ◽  
L Paul Fanning
Keyword(s):  
Nova Scotia ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Commercial Fishing ◽  
Sudden Increase ◽  
Annual Variations ◽  
Structured Population ◽  
Population Dynamics Model ◽  
Structured Population Dynamics ◽  
Age Structured

An age-structured population dynamics model, incorporating interactions between Atlantic cod (Gadus morhua), the fishery, and the grey seal (Halichoerus grypus) population, was applied to the cod stock off eastern Nova Scotia (Northwest Atlantic Fisheries Organization Divisions 4Vs and 4W, commonly abbreviated to 4VsW), a stock that has dramatically declined since the late 1980s. Mortality was modeled as having three components: fishing mortality (F), seal predation (Mp), and all other sources of natural mortality (M). Specifically, M was assumed to be distinct for immature cod (ages 1–4; Mi) and mature cod (age 5 and older; Mm), and respective annual variations were estimated. Parameters estimated also included recruitment (cod abundance at age 1; R), F, and Mp. Based on our estimates of F, Mp, and M, it is unlikely that the collapse of the 4VsW cod stock can be attributed to a sudden increase in M; fishing appears to have been the primary cause for the stock's decline. However, after the moratorium on commercial fishing in 1993, increasing Mp and Mm and low R may have contributed to the failure of the 4VsW cod stock to recover.

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.

Potential effects of maternal factors on spawning stock–recruitment relationships under varying fishing pressure

1999 ◽  
Vol 56 (10) ◽  
pp. 1882-1890 ◽  
Author(s):  
Beth Scott ◽  
Gudrun Marteinsdottir ◽  
Peter Wright
Keyword(s):  
Gadus Morhua ◽  
Reproductive Output ◽  
Atlantic Cod ◽  
Reproductive Potential ◽  
Fishing Pressure ◽  
Age Composition ◽  
Standard Population ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Stock Recruitment

The use of spawning stock biomass as a direct measure of reproductive potential may not be valid because of age- or size-specific differences in fecundity and the effect of maternal size and condition on offspring viability. In this study, we examine the potential significance of these effects using modelled Atlantic cod (Gadus morhua) populations. We quantify how changes in the age composition of the spawning stock, due to a range of fishing pressures and under different stock-recruitment relationships, could influence the reproductive output. Quantitative comparisons were made between a "standard" population where all age-classes only suffer natural instantaneous mortality (M = 0.2) and populations that suffer increasing levels of fishing pressure (F = 0.0-1.0). The results of the modelling exercise suggests that if the effects of the loss of more fecund older/larger individuals in the population are not considered, the number of potential recruits produced by populations under higher levels of fishing mortality could be overestimated by as much as 60%. When age/size-related maternal effects on egg viability are also considered, the amount of potential recruits can be overestimated by a further 10% in the heavily exploited populations.

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