Limits...
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.

Show MeSH

Related in: MedlinePlus

Time series of surface temperature reveal both colder (e.g. 1960's) and warmer (e.g. 1990's) time periods relative to the climatology (1961–1990).The red bar indicates the warmest year on average for the upper 50 meters (or to the deepest depth if shallower) while the blue bars indicate the coldest. Surface temperature anomalies (°C left y-axis, black thick line with circles) were smoothed with a 9-year running mean, and plotted with the unsmoothed surface temperature anomalies (°C, left y-axis, light grey), and surface temperature (°C, right y-axis, dark grey lines with light triangles). All time series are shown from 1960 to 2002 for the four studied locations in the North Atlantic.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3049760&req=5

pone-0017456-g002: Time series of surface temperature reveal both colder (e.g. 1960's) and warmer (e.g. 1990's) time periods relative to the climatology (1961–1990).The red bar indicates the warmest year on average for the upper 50 meters (or to the deepest depth if shallower) while the blue bars indicate the coldest. Surface temperature anomalies (°C left y-axis, black thick line with circles) were smoothed with a 9-year running mean, and plotted with the unsmoothed surface temperature anomalies (°C, left y-axis, light grey), and surface temperature (°C, right y-axis, dark grey lines with light triangles). All time series are shown from 1960 to 2002 for the four studied locations in the North Atlantic.

Mentions: To adequately describe realistic environmental properties at each of the four spawning grounds (Fig. 1) we used the Simple Ocean Data Assimilation (SODA, http://www.atmos.umd.edu/~ocean/) database. SODA is a global re-analysis of the ocean climate [18] for the period 1958 to 2002 based on an ocean model with a resolution of 0.5°×0.5° latitude-longitude. The model uses assimilation to constrain simulations to observed temperatures and salinities, which were derived principally from the World Ocean Atlas [27]. For each spawning ground (defined by a single latitude-longitude position), we created a time-series of temperature, salinity, and u and v surface wind stress by spatially interpolating the four surrounding SODA grid points. The result was a time series (1960–2002, 5-day temporal resolution) of temperature for all depths at each spawning ground that we used as input to the IBM. Once read into the IBM, the SODA data were interpolated both temporally and spatially to the larval depth position for the specific time of year. Based on the temperature time-series we also calculated the temperature climatology 1961–1990. This climatology was used to estimate ocean temperature anomalies (Fig. 2), which were further used to modulate the prey concentrations. The u and v surface wind stresses were used to estimate the turbulence level at the depth of each larva using a functional relationship [28].


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

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

Time series of surface temperature reveal both colder (e.g. 1960's) and warmer (e.g. 1990's) time periods relative to the climatology (1961–1990).The red bar indicates the warmest year on average for the upper 50 meters (or to the deepest depth if shallower) while the blue bars indicate the coldest. Surface temperature anomalies (°C left y-axis, black thick line with circles) were smoothed with a 9-year running mean, and plotted with the unsmoothed surface temperature anomalies (°C, left y-axis, light grey), and surface temperature (°C, right y-axis, dark grey lines with light triangles). All time series are shown from 1960 to 2002 for the four studied locations in the North Atlantic.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0017456-g002: Time series of surface temperature reveal both colder (e.g. 1960's) and warmer (e.g. 1990's) time periods relative to the climatology (1961–1990).The red bar indicates the warmest year on average for the upper 50 meters (or to the deepest depth if shallower) while the blue bars indicate the coldest. Surface temperature anomalies (°C left y-axis, black thick line with circles) were smoothed with a 9-year running mean, and plotted with the unsmoothed surface temperature anomalies (°C, left y-axis, light grey), and surface temperature (°C, right y-axis, dark grey lines with light triangles). All time series are shown from 1960 to 2002 for the four studied locations in the North Atlantic.
Mentions: To adequately describe realistic environmental properties at each of the four spawning grounds (Fig. 1) we used the Simple Ocean Data Assimilation (SODA, http://www.atmos.umd.edu/~ocean/) database. SODA is a global re-analysis of the ocean climate [18] for the period 1958 to 2002 based on an ocean model with a resolution of 0.5°×0.5° latitude-longitude. The model uses assimilation to constrain simulations to observed temperatures and salinities, which were derived principally from the World Ocean Atlas [27]. For each spawning ground (defined by a single latitude-longitude position), we created a time-series of temperature, salinity, and u and v surface wind stress by spatially interpolating the four surrounding SODA grid points. The result was a time series (1960–2002, 5-day temporal resolution) of temperature for all depths at each spawning ground that we used as input to the IBM. Once read into the IBM, the SODA data were interpolated both temporally and spatially to the larval depth position for the specific time of year. Based on the temperature time-series we also calculated the temperature climatology 1961–1990. This climatology was used to estimate ocean temperature anomalies (Fig. 2), which were further used to modulate the prey concentrations. The u and v surface wind stresses were used to estimate the turbulence level at the depth of each larva using a functional relationship [28].

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