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Recruitment variability in North Atlantic cod and match-mismatch dynamics.

Kristiansen T, Drinkwater KF, Lough RG, Sundby S - PLoS ONE (2011)

Bottom Line: However, the cumulative effect of higher growth rates and survival through the entire spawning season in warm years was substantial with 308%, 385%, 154%, and 175% increases in survival for Georges Bank, Iceland, North Sea, and Lofoten cod stocks, respectively.We also found that the importance of match-mismatch dynamics generally increased with latitude.This prolonged season enhances cumulative growth and survival, leading to a greater number of large individuals with enhanced potential for survival to recruitment.

View Article: PubMed Central - PubMed

Affiliation: Institute of Marine Research and Bjerknes Centre for Climate Research, Bergen, Norway. tk@trondkristiansen.com

ABSTRACT

Background: Fisheries exploitation, habitat destruction, and climate are important drivers of variability in recruitment success. Understanding variability in recruitment can reveal mechanisms behind widespread decline in the abundance of key species in marine and terrestrial ecosystems. For fish populations, the match-mismatch theory hypothesizes that successful recruitment is a function of the timing and duration of larval fish abundance and prey availability. However, the underlying mechanisms of match-mismatch dynamics and the factors driving spatial differences between high and low recruitment remain poorly understood.

Methodology/principal findings: We used empirical observations of larval fish abundance, a mechanistic individual-based model, and a reanalysis of ocean temperature data from 1960 to 2002 to estimate the survival of larval cod (Gadus morhua). From the model, we quantified how survival rates changed during the warmest and coldest years at four important cod spawning sites in the North Atlantic. The modeled difference in survival probability was not large for any given month between cold or warm years. However, the cumulative effect of higher growth rates and survival through the entire spawning season in warm years was substantial with 308%, 385%, 154%, and 175% increases in survival for Georges Bank, Iceland, North Sea, and Lofoten cod stocks, respectively. We also found that the importance of match-mismatch dynamics generally increased with latitude.

Conclusions/significance: Our analyses indicate that a key factor for enhancing survival is the duration of the overlap between larval and prey abundance and not the actual timing of the peak abundance. During warm years, the duration of the overlap between larval fish and their prey is prolonged due to an early onset of the spring bloom. This prolonged season enhances cumulative growth and survival, leading to a greater number of large individuals with enhanced potential for survival to recruitment.

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The relationship between number of recruits (millions), temperature anomalies, and 0-group index (index for number of juveniles).Upper panel shows number of recruits (red line, left axis) and temperature anomalies (white, right axis) as a function of year for a) Lofoten, b) Iceland, c) North Sea, and d) Georges Bank respectively. The lower panel shows a scatter plot of the number of recruits versus 0-group index (5–6 months old).
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pone-0017456-g005: The relationship between number of recruits (millions), temperature anomalies, and 0-group index (index for number of juveniles).Upper panel shows number of recruits (red line, left axis) and temperature anomalies (white, right axis) as a function of year for a) Lofoten, b) Iceland, c) North Sea, and d) Georges Bank respectively. The lower panel shows a scatter plot of the number of recruits versus 0-group index (5–6 months old).

Mentions: To analyze the importance of survival through the larval and juvenile stages on recruitment we quantified the relationship between empirical data on the number of recruits with data on the number of juveniles. The correlation coefficents between observations of juvenile abundance (0-group index, 5–6 months) with recruitment were r = 0.53 (p = 0.09) and 0.52 (p = 0.0016) for the North Sea and Lofoten respectively, while Iceland and Georges Bank were −0.08 (p = 0.32) and −0.05 (p = 0.89) respectively. Temperature conditions during the larval and juvenile stages can have a strong influence on the number of individuals that survive to recruitment. To analyse how environmental conditions during larval and juvenile stages affect survival to recruitment, correlations were calculated between temperature and number of recruits. The temperature was lagged by 1 year for the North Sea and Georges Bank and 3 years (age at recruitment) for Lofoten, and Iceland. The correlation coefficients were r = −0.39 (p = 0.01), 0.14 (p = 0.35), 0.29 (p = 0.05), and 0.01 (p = 0.96) for the North Sea, Iceland, Lofoten, and Georges Bank, respectively. Finally, we calculated correlations between juveniles and temperature and found r = −0.03 (p = 0.92) , −0.08 (p = 0.65), 0.48 (p = 0.002), 0.38 (p = 0.22) for the North Sea, Iceland, Lofoten, and Georges Bank, respectively (Fig. 5).


Recruitment variability in North Atlantic cod and match-mismatch dynamics.

Kristiansen T, Drinkwater KF, Lough RG, Sundby S - PLoS ONE (2011)

The relationship between number of recruits (millions), temperature anomalies, and 0-group index (index for number of juveniles).Upper panel shows number of recruits (red line, left axis) and temperature anomalies (white, right axis) as a function of year for a) Lofoten, b) Iceland, c) North Sea, and d) Georges Bank respectively. The lower panel shows a scatter plot of the number of recruits versus 0-group index (5–6 months old).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3049760&req=5

pone-0017456-g005: The relationship between number of recruits (millions), temperature anomalies, and 0-group index (index for number of juveniles).Upper panel shows number of recruits (red line, left axis) and temperature anomalies (white, right axis) as a function of year for a) Lofoten, b) Iceland, c) North Sea, and d) Georges Bank respectively. The lower panel shows a scatter plot of the number of recruits versus 0-group index (5–6 months old).
Mentions: To analyze the importance of survival through the larval and juvenile stages on recruitment we quantified the relationship between empirical data on the number of recruits with data on the number of juveniles. The correlation coefficents between observations of juvenile abundance (0-group index, 5–6 months) with recruitment were r = 0.53 (p = 0.09) and 0.52 (p = 0.0016) for the North Sea and Lofoten respectively, while Iceland and Georges Bank were −0.08 (p = 0.32) and −0.05 (p = 0.89) respectively. Temperature conditions during the larval and juvenile stages can have a strong influence on the number of individuals that survive to recruitment. To analyse how environmental conditions during larval and juvenile stages affect survival to recruitment, correlations were calculated between temperature and number of recruits. The temperature was lagged by 1 year for the North Sea and Georges Bank and 3 years (age at recruitment) for Lofoten, and Iceland. The correlation coefficients were r = −0.39 (p = 0.01), 0.14 (p = 0.35), 0.29 (p = 0.05), and 0.01 (p = 0.96) for the North Sea, Iceland, Lofoten, and Georges Bank, respectively. Finally, we calculated correlations between juveniles and temperature and found r = −0.03 (p = 0.92) , −0.08 (p = 0.65), 0.48 (p = 0.002), 0.38 (p = 0.22) for the North Sea, Iceland, Lofoten, and Georges Bank, respectively (Fig. 5).

Bottom Line: However, the cumulative effect of higher growth rates and survival through the entire spawning season in warm years was substantial with 308%, 385%, 154%, and 175% increases in survival for Georges Bank, Iceland, North Sea, and Lofoten cod stocks, respectively.We also found that the importance of match-mismatch dynamics generally increased with latitude.This prolonged season enhances cumulative growth and survival, leading to a greater number of large individuals with enhanced potential for survival to recruitment.

View Article: PubMed Central - PubMed

Affiliation: Institute of Marine Research and Bjerknes Centre for Climate Research, Bergen, Norway. tk@trondkristiansen.com

ABSTRACT

Background: Fisheries exploitation, habitat destruction, and climate are important drivers of variability in recruitment success. Understanding variability in recruitment can reveal mechanisms behind widespread decline in the abundance of key species in marine and terrestrial ecosystems. For fish populations, the match-mismatch theory hypothesizes that successful recruitment is a function of the timing and duration of larval fish abundance and prey availability. However, the underlying mechanisms of match-mismatch dynamics and the factors driving spatial differences between high and low recruitment remain poorly understood.

Methodology/principal findings: We used empirical observations of larval fish abundance, a mechanistic individual-based model, and a reanalysis of ocean temperature data from 1960 to 2002 to estimate the survival of larval cod (Gadus morhua). From the model, we quantified how survival rates changed during the warmest and coldest years at four important cod spawning sites in the North Atlantic. The modeled difference in survival probability was not large for any given month between cold or warm years. However, the cumulative effect of higher growth rates and survival through the entire spawning season in warm years was substantial with 308%, 385%, 154%, and 175% increases in survival for Georges Bank, Iceland, North Sea, and Lofoten cod stocks, respectively. We also found that the importance of match-mismatch dynamics generally increased with latitude.

Conclusions/significance: Our analyses indicate that a key factor for enhancing survival is the duration of the overlap between larval and prey abundance and not the actual timing of the peak abundance. During warm years, the duration of the overlap between larval fish and their prey is prolonged due to an early onset of the spring bloom. This prolonged season enhances cumulative growth and survival, leading to a greater number of large individuals with enhanced potential for survival to recruitment.

Show MeSH
Related in: MedlinePlus