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Atlantic Surfclam: QA/QC Exercise Results

Results of the QA/QC exercises for ageing surfclam.

Atlantic Surfclam, Spisula solidissima

Image
Illustration of white Atlantic surfclam made of triangular shell with yellowish tan, rounded edges. Credit: NOAA Fisheries/Jack Hornady

Nina Shepherd (NS) has been working with Atlantic Surfclam since 2018; before that, the age reader was Blanche Jackson (BJ, retired). A section is taken from the hinge of the shell and viewed with reflected light.

In tests where agreement is below 90%, bias indicates either the P-value of a symmetry test or ‘n/s’ (test not significant at the α = 0.05 level). The Evans & Hoenig test was used to test bias starting 1/2022; prior to that, a Bowker's test was used.

Sample Source Test Type Date Completed Age Reader Number Aged Number Tested CV (%) Agree-ment (%) Bias
2018 Clam Survey (201860) Precision 4/2020 NS 659 94 0.43 95.7  
2015 Clam Survey (201560) Precision 12/2015 BJ 717 100 0.26 94.0  
2012 Clam Survey (201260) Precision 11/2015 BJ 328 70 0.09 97.1  
2013 Clam Survey (201360) Precision 8/2015 BJ 94 35 0.29 94.3  
2011 Clam Survey (201104) Precision 10/2012 BJ 444 95 2.25 72.6 n/s
2008 Clam Survey (200808) Precision 10/2008 BJ 840 100 3.13 76.0 n/s
2005 Clam Survey (200507) Precision 8/2005 BJ 889 141 3.43 65.2 n/s
2002 Clam Survey (200206) Calibration 6/2005 BJ 609 1.75 84.2 n/s

Last updated by Northeast Fisheries Science Center on December 23, 2022

Age and Growth