Techniques for assessing repaired shell damage in dog cockles Glycymeris glycymeris L.

Three techniques for assessing repaired shell damage in dog cockles Glycyme ris glycymeris (visual assessment, x-rays, and shell sectioning) were exami ned for objectivity and repeatability. Visual assessment of the number of Y ears was found to be inaccurate and highly subjective. Image analysis of x- rays suffered from inconsistencies in film development and image quality. H owever, this technique provided an estimate of the area of the shell affect ed by scarring, rather than simply a record of the: number and/or severity of scars. Examination of shell cross-sections provided the most objective a nd repeatable technique, although the methodology had a number of disadvant ages as it was time consuming and scar severity could be underestimated dep ending on the position of the line of section through the shell. This techn ique also offers the opportunity to date the formation of the scars using i nternal annual growth lines.