scholarly journals Egg production of Baltic cod (Gadus morhua) in relation to variable sex ratio, maturity, and fecundity

2002 ◽  
Vol 59 (12) ◽  
pp. 1908-1920 ◽  
Author(s):  
Gerd Kraus ◽  
Jonna Tomkiewicz ◽  
Friedrich W Köster
Keyword(s):  
Sex Ratio ◽  
Egg Production ◽  
Gadus Morhua ◽  
Reproductive Potential ◽  
Relative Fecundity ◽  
Spawning Stock ◽  
Class Strength ◽  
The Difference ◽  
Eastern Baltic ◽  
Baltic Cod

Observed fluctuations in relative fecundity of Eastern Baltic cod (Gadus morhua L.) were related to food availability during the main feeding period and were used to develop a predictive model that explained 72% of the interannual variations in fecundity. Time series of sex ratios, maturity ogives, and relative fecundity were combined with mean weights-at-age and stock sizes from an analytical multispecies model to estimate the potential egg production (PEP). Relationships between PEP and independent estimates of realized daily and seasonal egg production from egg surveys were highly significant. The difference between estimates of potential and realized seasonal egg production was of a magnitude corresponding to the expected loss of eggs as a result of atresia, fertilization failure, and early egg mortality. The removal of interannual variability in sex ratio, maturity, and fecundity on estimates of PEP deteriorated the relationships in all three cases. PEP proved to be superior to spawning stock biomass as measure of the reproductive potential in a stock-recruitment relationship of Eastern Baltic cod. PEP in combination with the reproductive volume explained 61% of the variation in year-class strength at age 2.

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.

scholarly journals Effect of changes in reproductive potential on perceived productivity of three Northwest Atlantic cod (Gadus morhua) stocks

2005 ◽  
Vol 62 (1) ◽  
pp. 65-74 ◽  
Author(s):  
M. Joanne Morgan ◽  
John Brattey
Keyword(s):  
Sex Ratio ◽  
Interannual Variability ◽  
Egg Production ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Relative Rate ◽  
Reproductive Potential ◽  
Basic Information ◽  
Northern Cod ◽  
Spawning Stock

Abstract Variation in maturity-at-age, sex ratio, and potential egg production (through changes in length at age) were examined for northern cod (NAFO Division 2J + 3KL), southern Grand Bank cod (3NO), and southern Newfoundland cod (3Ps). All showed significant interannual variability in each stock. Estimates of reproductive potential were produced by sequentially incorporating estimates of proportion mature at age, sex ratio at age, and potential egg production. The estimates of reproductive potential produced by each method were broadly similar, but there were important differences. This leads to differing perceptions of stock productivity, as measured by relative rate of recruitment of a stock and in the spawning stock produced per recruit. These differing perceptions can have a major impact on expectations for the recovery of depleted stocks and the sustainability of various levels of fishing. Efforts should be made to improve estimates of reproductive potential by further exploring the impacts of changes in the spawning characteristics of populations, and by collecting such basic information as fecundity data.

Robustness of egg production methods as a fishery independent alternative to assess the Eastern Baltic cod stock (Gadus morhua callarias L.)

2012 ◽  
Vol 117-118 ◽  
pp. 75-85 ◽  
Author(s):  
Gerd Kraus ◽  
Hans-Harald Hinrichsen ◽  
Rüdiger Voss ◽  
Eske Teschner ◽  
Jonna Tomkiewicz ◽  
...  
Keyword(s):  
Egg Production ◽  
Gadus Morhua ◽  
Production Methods ◽  
Eastern Baltic ◽  
Baltic Cod

Egg production methods applied to Eastern Baltic cod provide indices of spawning stock dynamics

2020 ◽  
Vol 227 ◽  
pp. 105553 ◽  
Author(s):  
Friedrich W. Köster ◽  
Bastian Huwer ◽  
Gerd Kraus ◽  
Rabea Diekmann ◽  
Margit Eero ◽  
...  
Keyword(s):  
Egg Production ◽  
Production Methods ◽  
Spawning Stock ◽  
Eastern Baltic ◽  
Baltic Cod

scholarly journals Does increased information about reproductive potential result in better prediction of recruitment?

2011 ◽  
Vol 68 (8) ◽  
pp. 1361-1368 ◽  
Author(s):  
M. Joanne Morgan ◽  
Alfonso Perez-Rodriguez ◽  
Fran Saborido-Rey
Keyword(s):  
Reproductive Biology ◽  
Egg Production ◽  
Gadus Morhua ◽  
Reproductive Potential ◽  
Essential Element ◽  
Greenland Halibut ◽  
Greenland Halibut Reinhardtius Hippoglossoides ◽  
Difficult Challenge ◽  
The Relationship ◽  
Hippoglossoides Platessoides

The relationship between stock size and recruitment is an essential element in the understanding of the productivity of a population. However, predicting the number of recruits produced by a population has proven to be a difficult challenge. This may in part be a result of poor estimation of reproductive potential (RP). We determined if including increased information on reproductive biology in indices of RP results in better predictions of recruitment. We investigated some of the conditions that lead to better (or worse) recruitment prediction when more biologically complex indices of RP are used. Data from four populations in the Northwest Atlantic were examined: southern Grand Bank (NAFO Division 3NO) cod ( Gadus morhua ), Flemish Cap (NAFO Division 3M) cod, Newfoundland (NAFO Division 3LNO) American plaice ( Hippoglossoides platessoides ), and Greenland halibut ( Reinhardtius hippoglossoides ) (NAFO Subarea 2 + Division 3KLMNO). Stock–recruit models paired with complex indices of RP gave a better estimate of recruitment in slightly more than half of the tests conducted. When there were larger trends in the reproductive biology (maturity at age, sex ratio and egg production), more complex indices of RP were more likely to provide a better estimate of recruitment.

scholarly journals Slave to the rhythm: seasonal signals in otolith microchemistry reveal age of eastern Baltic cod (Gadus morhua)

2015 ◽  
Vol 73 (4) ◽  
pp. 1019-1032 ◽  
Author(s):  
K. Hüssy ◽  
J. Gröger ◽  
F. Heidemann ◽  
H.-H. Hinrichsen ◽  
L. Marohn
Keyword(s):  
North Sea ◽  
Gadus Morhua ◽  
Statistical Significance ◽  
Structural Break ◽  
Age Determination ◽  
Element Concentrations ◽  
Visual Contrast ◽  
Growth Zones ◽  
Eastern Baltic ◽  
Baltic Cod

Abstract Annual growth zones in cod otoliths from the eastern Baltic stock are less discrete than in other cod stocks leading to biased age reading, which recently led to a failure of age-based assessment in the eastern Baltic cod stock. In this study, we explored the applicability of minor and trace element patterns in cod otoliths for age determination. By first identifying elements of interest in a stock without ageing problems, western Baltic cod, we then tested their applicability on another stock without ageing problems, North Sea cod, and finally applied this knowledge to estimate age of eastern Baltic cod. In western Baltic cod, matching patterns with respect to occurrence of minima and maxima in both otolith opacity and element concentrations were found for Cu, Zn, and Rb, and inverse patterns with Mg and Mn. No match was found for Pb, Ba, and Sr. In the test stock, the North Sea cod, the same patterns in Cu, Zn, Rb, Mg, and Mn signals occurred. All eastern Baltic cod with low visual contrast between growth zones exhibited clearly defined synchronous cycles in Cu, Zn, Rb and Pb. Using a combined finite differencing method and structural break models approach, the statistical significance of the local profile minima were identified, based on which their age could be estimated. Despite extensive environmental differences between the three areas examined, the element concentrations of Cu, Zn, and Rb were strongly correlated in all individuals with similar correlations in all three areas, suggesting that the incorporation mechanisms are the same for these elements and independent of environmental concentrations.

scholarly journals Stable Isotope Evidence for Late Medieval (14th–15th C) Origins of the Eastern Baltic Cod (Gadus morhua) Fishery

PLoS ONE ◽  
2011 ◽  
Vol 6 (11) ◽  
pp. e27568 ◽  
Author(s):  
David C. Orton ◽  
Daniel Makowiecki ◽  
Tessa de Roo ◽  
Cluny Johnstone ◽  
Jennifer Harland ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Gadus Morhua ◽  
Late Medieval ◽  
Isotope Evidence ◽  
Eastern Baltic ◽  
Baltic Cod
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