scholarly journals Spatial variation in abundance, size composition and viable egg production of spawning cod (Gadus morhua L.) in Icelandic waters

2000 ◽  
Vol 57 (4) ◽  
pp. 824-830 ◽  
Author(s):  
G Marteinsdottir
Keyword(s):  
Spatial Variation ◽  
Egg Production ◽  
Gadus Morhua ◽  
Size Composition ◽  
Icelandic Waters

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

scholarly journals Fishery-induced changes in Norwegian red king crab (Paralithodes camtschaticus) reproductive potential

2013 ◽  
Vol 71 (2) ◽  
pp. 365-373 ◽  
Author(s):  
Ann Merete Hjelset
Keyword(s):  
Egg Production ◽  
Barents Sea ◽  
Reproductive Potential ◽  
Size Composition ◽  
Red King Crab ◽  
Paralithodes Camtschaticus ◽  
King Crab ◽  
Males And Females ◽  
Induced Changes ◽  
Individual Fecundity

Abstract Hjelset, A. M. 2014. Fishery-induced changes in Norwegian red king crab (Paralithodes camtschaticus) reproductive potential. – ICES Journal of Marine Science, 71: 365–373. The introduced red king crab (Paralithodes camtschaticus) in the Barents Sea supports a valuable fishery in northern Norway. In this paper, I examine the effect of the increased harvest rate and the recently added female quota on the potential egg production of the stock. The size ranges of males and females in the period 1995–2011 were recorded, and estimated stock abundance of ovigerous females and established individual fecundity parameters from 2000–2007 were used to assess the reproductive potential of the stock from 1995–2011. The upper size ranges of males and females decreased throughout the period studied, presumably mainly due to fishing. The change in size composition among ovigerous females and functional mature males, and the reduced mean individual fecundity in the stock seem to have had a negative effect on the potential egg production of the stock.

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 Contribution of different spawning components to the mixed stock fishery for cod in Icelandic waters

2007 ◽  
Vol 64 (9) ◽  
pp. 1749-1759 ◽  
Author(s):  
Ingibjörg G. Jónsdóttir ◽  
Gudrun Marteinsdottir ◽  
Steven E. Campana
Keyword(s):  
Maximum Likelihood ◽  
Gadus Morhua ◽  
Fish Length ◽  
Minor Importance ◽  
Otolith Chemistry ◽  
Marine Science ◽  
Otolith Shape ◽  
Mixed Stock ◽  
Feeding Grounds ◽  
Icelandic Waters

Abstract Jónsdóttir, I. G., Marteinsdottir, G., and Campana, S. E. 2007. Contribution of different spawning components to the mixed stock fishery for cod in Icelandic waters. – ICES Journal of Marine Science, 64: 000–000. Otolith chemistry and length-at-age were used to estimate the contribution of different spawning components to the harvested stock of cod (Gadus morhua) at two of their main feeding grounds northwest and east of Iceland. Spawning cod were sampled at different spawning locations around Iceland in spring of 2002 and 2003. Significant differences were detected between cod from the different spawning locations. Cod of unknown stock origin were also sampled at two of the main feeding grounds in October of the same years. Analyses based on maximum likelihood were used to estimate the proportion of each spawning group in the mixed stock catches using otolith chemistry and fish length-at-age. Attempts to use otolith shape to estimate the contribution of the spawning groups to the mixed harvested stock were, however, unsuccessful. The results indicated that spawning locations northwest and north of Iceland, as well as in water deeper than 125 m south of Iceland, contributed the most to the harvested stock. Cod spawning shallower than 125 m south of Iceland did not contribute to the feeding grounds in October of 2002 and 2003. Therefore, exploitation of the feeding stock mixtures seems to be based on spawning components that have previously been considered to be of minor importance to the Icelandic cod stock.

scholarly journals Historical changes in genotypic frequencies at the Pantophysin locus in Atlantic cod (Gadus morhua ) in Icelandic waters: evidence of fisheries-induced selection?

2011 ◽  
Vol 4 (4) ◽  
pp. 562-573 ◽  
Author(s):  
Klara B. Jakobsdóttir ◽  
Heidi Pardoe ◽  
Árni Magnússon ◽  
Höskuldur Björnsson ◽  
Christophe Pampoulie ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Historical Changes ◽  
Icelandic Waters

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.

Substock variation in reproductive traits in North Sea cod (Gadus morhua)

2010 ◽  
Vol 67 (5) ◽  
pp. 866-876 ◽  
Author(s):  
Marion Harrald ◽  
Peter J. Wright ◽  
Francis C. Neat
Keyword(s):  
Spatial Variation ◽  
North Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Liver Weight ◽  
Adaptive Divergence ◽  
Female Size ◽  
Common Environment ◽  
Relative Liver Weight ◽  
Trade Offs

The North Sea stock of Atlantic cod ( Gadus morhua ) is comprised of a number of subcomponents that differ both genetically and phenotypically. A potential cause for such spatial variability is adaptive divergence, which may be linked to differences in thermal environment and (or) historical fishing pressure. Here we present evidence that spatial variation in maturity–size relationships in the wild has a significant intrinsic component. Using a common-environment experiment on wild-caught juveniles raised through to maturity, we demonstrate that cod from the southern North Sea (SNS) mature at larger sizes than those from the northwestern North Sea (NWNS) despite broadly similar growth rates. Consistent with these experimental results, year-class-specific maturity ogives for recent maturing year classes (1999–2001) suggested that the length at which 50% of females reached maturity was 11 cm greater for SNS than for NWNS cod. Under a common environment, smaller female size at maturity partly reflected higher relative liver weight, with NWNS females having a higher relative liver weight than SNS females. By investigating maturation under controlled conditions, our study provides evidence for life history trade-offs in energy allocation between growth, energy storage, and reproduction that may underlie the spatial variation observed in the field.

scholarly journals Developing Baltic cod recruitment models. II. Incorporation of environmental variability and species interaction

2001 ◽  
Vol 58 (8) ◽  
pp. 1534-1556 ◽  
Author(s):  
Friedrich W Köster ◽  
Hans-Harald Hinrichsen ◽  
Michael A St. John ◽  
Dietrich Schnack ◽  
Brian R MacKenzie ◽  
...  
Keyword(s):  
Egg Production ◽  
Gadus Morhua ◽  
Environmental Variability ◽  
Species Interaction ◽  
Larval Transport ◽  
Factors Affecting ◽  
Oxygen Conditions ◽  
Modelling Studies ◽  
Spawning Sites ◽  
Baltic Cod

We investigate whether a process-oriented approach based on the results of field, laboratory, and modelling studies can be used to develop a stock–environment–recruitment model for Central Baltic cod (Gadus morhua). Based on exploratory statistical analysis, significant variables influencing survival of early life stages and varying systematically among spawning sites were incorporated into stock–recruitment models, first for major cod spawning sites and then combined for the entire Central Baltic. Variables identified included potential egg production by the spawning stock, abiotic conditions affecting survival of eggs, predation by clupeids on eggs, larval transport, and cannibalism. Results showed that recruitment in the most important spawning area, the Bornholm Basin, during 1976–1995 was related to egg production; however, other factors affecting survival of the eggs (oxygen conditions, predation) were also significant and when incorporated explained 69% of the variation in 0-group recruitment. In other spawning areas, variable hydrographic conditions did not allow for regular successful egg development. Hence, relatively simple models proved sufficient to predict recruitment of 0-group cod in these areas, suggesting that key biotic and abiotic processes can be successfully incorporated into recruitment models.

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