scholarly journals Assessing changes in age and size at maturation in collapsing populations of Atlantic cod (Gadus morhua)

2005 ◽  
Vol 62 (4) ◽  
pp. 811-823 ◽  
Author(s):  
Esben Moland Olsen ◽  
George R Lilly ◽  
Mikko Heino ◽  
M Joanne Morgan ◽  
John Brattey ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Life Histories ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Reference Points ◽  
Reaction Norms ◽  
Commercial Fishing ◽  
Evolutionary Changes ◽  
Survival And Growth ◽  
Maturation Age

By estimating probabilistic reaction norms for age and size at maturation, we show that maturation schedules of Atlantic cod (Gadus morhua) off Labrador and Newfoundland shifted toward earlier ages and smaller sizes during the late 1980s and early 1990s, when these populations underwent a severe collapse in biomass and subsequently were closed for directed commercial fishing. We also demonstrate that this trend towards maturation at younger ages and smaller sizes is halted and even shows signs of reversal during the closure of the fisheries. In addition, our analysis reveals that males tend to mature earlier and at a smaller size than females and that maturation age and size decrease with increasing latitude. Importantly, the maturation reaction norms presented here are robust to variation in survival and growth (through phenotypic plasticity) and are thus strongly indicative of rapid evolutionary changes in cod maturation as well as of spatial and sex-specific genetic variation. We therefore suggest that maturation reaction norms can provide helpful reference points for managing harvested populations with evolving life histories.

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.

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

Heritability, polymorphism, and population dynamics: individual-based eco-evolutionary simulations

2021 ◽  
pp. 329-340
Author(s):  
Anna Kuparinen
Keyword(s):  
Population Dynamics ◽  
Life Histories ◽  
Evolutionary Dynamics ◽  
Atlantic Cod ◽  
Population Projections ◽  
Phenotypic Traits ◽  
Evolutionary Changes ◽  
Future Challenges ◽  
Evolutionary Simulations ◽  
Main Message

Contemporary evolution that occurs across ecologically relevant time scales, such as a few generations or decades, can not only change phenotypes but also feed back to demographic parameters and the dynamics of populations. This chapter presents a method to make phenotypic traits evolve in mechanistic individual-based simulations. The method is broadly applicable, as demonstrated through its applications to boreal forest adaptation to global warming, eco-evolutionary dynamics driven by fishing-induced selection in Atlantic cod, and the evolution of age at maturity in Atlantic salmon. The main message of this chapter is that there may be little reason to exclude phenotypic evolution in analyses of population dynamics, as these can be modified by evolutionary changes in life histories. Future challenges will be to integrate rapidly accumulating genomic knowledge and an ecosystem perspective to improve population projections and to better understand the drivers of population dynamics.

The influence of maternal effects in larval survival on fishery harvest reference points for two life-history patterns

2014 ◽  
Vol 71 (1) ◽  
pp. 151-161 ◽  
Author(s):  
Paul D. Spencer ◽  
Sarah B.M. Kraak ◽  
Edward A. Trippel
Keyword(s):  
Life History ◽  
Pacific Ocean ◽  
Maternal Effects ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Larval Survival ◽  
Reference Points ◽  
Life History Pattern ◽  
Gadus Macrocephalus ◽  
Potential Interactions

Increased larval viability with increased spawner age (i.e., maternal effects) have been observed in Atlantic cod (Gadus morhua) and Pacific rockfish (Sebastes spp.) stocks. Analytical results from a Beverton–Holt recruitment model indicate density-independent maternal effects affected the relative stock productivity and fishing rate reference points. We simulated populations based on Pacific cod (Gadus macrocephalus) and Pacific ocean perch (Sebastes alutus) to explore how estimates of reference points Fmsy and Fcrash are affected by maternal effects and potential interactions with life-history pattern, recruitment autocorrelation, and exploitation rate. Estimates of Fmsy and Fcrash were made from populations with maternal effects using either total larvae (proportional to eggs) or viable larvae (incorporating the maternal effect). Maternal effects have the largest impact upon estimated population productivity at high fishing rates. Estimates of Fmsy and Fcrash for cod were also affected by autocorrelated recruitment variability because of their reduced longevity compared with Pacific ocean perch. These results suggest the importance of evaluating the influence of maternal effects on estimated stock productivity on a case-by-case basis, particularly for depleted stocks composed of relatively young spawners.

Comparative Survival and Growth of Two Strains of Atlantic Cod (Gadus morhua) through the Early Life Stages in a Marine Pond

1994 ◽  
Vol 51 (5) ◽  
pp. 1012-1023 ◽  
Author(s):  
Geir Blom ◽  
Terje Svåsand ◽  
Knut E. Jørstad ◽  
Håkon Otterå ◽  
Ole I. Paulsen ◽  
...  
Keyword(s):  
Body Size ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Larval Mortality ◽  
Food Limitation ◽  
Juvenile Stage ◽  
Average Growth ◽  
Juvenile Mortality ◽  
Early Juvenile Stage ◽  
Survival And Growth

Survival and growth of two strains of Atlantic cod (Gadus morhua) were compared through the larval and juvenile stages in a marine pond in western Norway in 1990 and 1991. Strain A was homozygous for the genetic marker allele GPI-1*30 at the glucose phosphate isomerase (GPI) locus expressed in white muscle, and Strain B possessed other GPI-1* genotypes, in 1990 the frequency of Strain B increased significantly from the larval to the juvenile stage; however, in 1991 the frequency of Strain A increased slightly but not significantly from the larval to the juvenile phase. Larval mortality did not differ significantly between strains any year, but juvenile mortality was significantly lower in Strain B in 1990 and Strain A in 1991. Average growth rates in length estimated from regressions were not significantly different between strains during the larval and juvenile period any year, but initial length was significantly larger in Strain B in 1990 and Strain A in 1991. Our results indicated that food limitation during the early juvenile stage induced differential size-selective mortality among the strains due to small differences in body size and actual age between strains. Body size did not become important for survival until the food-limited regime had occurred.

scholarly journals Environmentally mediated trends in otolith composition of juvenile Atlantic cod (Gadus morhua)

2015 ◽  
Vol 72 (8) ◽  
pp. 2350-2363 ◽  
Author(s):  
Ryan R. E. Stanley ◽  
Ian R. Bradbury ◽  
Claudio DiBacco ◽  
Paul V. R. Snelgrove ◽  
Simon R. Thorrold ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Inductively Coupled Plasma ◽  
Life Histories ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Environmental Influence ◽  
Inductively Coupled ◽  
Baseline Information ◽  
Significant Temperature ◽  
Species Specific

Abstract We evaluated the influence of environmental exposure of juvenile Atlantic cod (Gadus morhua) to inform interpretations of natal origins and movement patterns using otolith geochemistry. Laboratory rearing experiments were conducted with a variety of temperature (∼5, 8.5, and 12°C) and salinity (∼25, 28.5, and 32 PSU) combinations. We measured magnesium (Mg), manganese (Mn), strontium (Sr), and barium (Ba), expressed as a ratio to calcium (Ca), using laser ablation inductively coupled plasma mass spectrometry (ICP-MS), and stable carbon (δ13C) and oxygen (δ18O) isotopes using isotope ratio monitoring mass spectrometry. Temperature and salinity significantly affected all elements and isotopes measured, except salinity on Mg:Ca. We detected significant interactions among temperature and salinity for Mn:Ca and Ba:Ca partition coefficients (ratio of otolith chemistry to water chemistry), with significant temperature effects only detected in the 32 and 28.5 PSU salinity treatments. Similarly, we detected a significant interaction between temperature and salinity in incorporation of δ13C, with a significant temperature effect except at intermediate salinity. These results support the contention that environmental mediation of otolith composition varies among species, thus limiting the ability of generalized models to infer life history patterns from chemistry. Our results provide essential baseline information detailing environmental influence on juvenile Atlantic cod otolith composition, punctuating the importance of laboratory validations to translate species-specific otolith composition when inferring in situ life histories and movements.

Fathers modify thermal reaction norms for hatching success in Atlantic cod, Gadus morhua

2016 ◽  
Vol 474 ◽  
pp. 148-155 ◽  
Author(s):  
F.T. Dahlke ◽  
S.N. Politis ◽  
I.A.E. Butts ◽  
E.A. Trippel ◽  
M.A. Peck
Keyword(s):  
Gadus Morhua ◽  
Hatching Success ◽  
Atlantic Cod ◽  
Thermal Reaction ◽  
Reaction Norms

A strategy to detect fish discarding by combining onboard and onshore sampling

1997 ◽  
Vol 54 (12) ◽  
pp. 2955-2963 ◽  
Author(s):  
Jacques Allard ◽  
Ghislain A Chouinard
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Nonparametric Test ◽  
Reference Points ◽  
Sampling Distribution ◽  
Small Fish ◽  
Conservation Problem ◽  
Cost Efficient ◽  
Using Data ◽  
The Cost

Discarding of small fish is considered to be an important conservation problem and has become illegal in some fisheries. We present a cost-efficient strategy to help enforce regulations against discarding. A discarding indicator is defined using the change in slope between two reference points on the empirical length-frequency density of the catch. This discarding indicator is then used according to the external distribution concept: the sampling distribution of the discarding indicator, when no discarding occurred, is obtained directly from samples taken by onboard observers; the value of the discarding indicator observed by onshore observers from a boat not covered by onboard observers is then compared with this sampling distribution. This procedure offers a nonparametric test for discarding. Application of the strategy is illustrated using data from the 1991 Atlantic cod (Gadus morhua) fishery in the southern Gulf of St. Lawrence. We describe several enforcement frameworks within which the method can be applied. The cost efficiency of the strategy comes from shifting resources from high-cost onboard observation to lower cost onshore observation.

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