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-8.5
-8.0
-7.5
-7.0
-6.5
-6.0
YEAR
Ln M
n (
Ln (
mm
ol/m
ol))
1998 1999
-2.0
-1.9
-1.8
-1.7
-1.6
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-1.4
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1998 1999
0.2
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Ln S
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1998 1999
-7.4
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-7.0
-6.8
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Ln B
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1998 1999
-6 -4 -2 0 2 4 6
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Campana S., Hanson J., Frechet A., and Brattey J. 2000 Fisheries Research 46: 343-357
Longerich H., Jackson S.E., and Gunther D. 1996. Journal of Analytical atomic Spectrometry 11: 899-904
Thanks to CFER staff and students, CREAIT staff, Mike Tubrett, Clare Lewis, Dr.s Steven Campana, Craig Purchase and Ian Bradbury.
Genevieve D’Avignon1 and George Rose2 Centre for Fisheries Ecosystem Research, Memorial University of Newfoundland, St. John's, NL A1C 5S71,2
Genevieve.D’[email protected]
ICES CM 2012/J:34
HC SS
3HC BH
4. RESULTS
5. CONCLUSIONS
1. INTRODUCTION
Two decades after the moratorium on Newfoundland and Labrador Atlantic cod (Gadus morhua) fisheries, science has yet to unravel their complex stock structures and distributions. Rebuilding these depleted stocks requires better knowledge of movement patterns and the degree of connection between major spawning groups. The chemical signatures of otoliths provide chronological data on the life environment of fish enabling study of natal sites, life migration patterns and connectivity among spawning sites.
3. METHODS
6. REFERENCES & ACKNOWLEDGEMENTS
2. OBJECTIVE
To investigate the spatial and temporal variability of chemical fingerprints of cod otoliths in Newfoundland and Labrador waters, to determine if these techniques can differentiate the major spawning groups.
Distinguishable otolith signatures exist at large spatial scales in Newfoundland and Labrador Atlantic cod from 4 spawning areas - remained stable over 2 years.
Signature classification >90% suggests signatures can be used to track connectivity between groups – essential for rebuilding stocks and sustainable management.
Otolith signatures may enable tracking of cod movements, thus marking distribution shifts with changing climate, and potentially the contribution of each spawning group to fisheries.
Future work should focus on analysing cod otolith signatures over longer time periods and using signatures to test specific ecological hypotheses.
Figure 2: Otoltih preparation for Laser ablation inductively coupled mass spectrometry following Campana et al. (2000) A. Removal of cod otolith B. Material decontamination C. Sectioning of otolith to expose growth increments D. Triplicate 40µm diameter spots on the dorsal edge of an otolith
sampled by LAICPMS (SEM photography). Elemental concentrations were estimated according to procedures established by Longerich, Jackson and Gunther (1996)
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Variation among spawning locations is stronger than variation over time (Figure 3)
Chemical composition differs among cod spawning aggregations (MANOVA, Pillai’s Trace=1.87, F=464.64, p< 0.001)
91-99% correct classification of fish into their spawning group using discriminant function analysis (Figure 4)
Figure 4: Elemental fingerprint based on the discriminant functions for signatures from cod collected in both years at each location. Each data point within an area represents a single fish (n= 659). Correct classification in percentages are HC= 99%, 3HC= 94%, SS= 95% and BH= 91%. Ellipses represent the centroid and 95% confidence interval. Spawning groups are Bar Haven (BH), Hawke Channel (HC), Halibut Channel (3HC), and Smith Sound (SS).
Figure 3: Interaction plots show variation in mean elemental concentration among spawning locations per year. Significant differences marked by different letters. Spawning groups are Bar Haven ( ), Hawke Channel ( ), Halibut Channel ( ), and Smith Sound ( ).
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Sampling area
Figure 1: Map showing the 2 inshore and 2 offshore cod spawning locations sampled in 1998 (filled symbols) and 1999 (empty symbols).
Otolith preparation and analysis
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