PROBLEMS ASSOCIATED WITH AGING SQUID FROM THEIR STATOLITHS - TOWARDS A MORE STRUCTURED APPROACH

It appears that squid statoliths cannot yet be regarded as accurate an ageing tool as fish otoliths. Statoliths from the same pair, prepared differently for viewing and counting increments, were compared. Incre ment counts do not imply age in days, because this was not validated. One statolith from each pair was examined by light microscopy (LM) aft er preparation following a new method. The other was viewed by Scannin g Electron Microscopy (SEM) with a modified etching solution. Shape of each statolith was similar when compared by multiple regression analy sis (11 variables, n = 53). There was a weak but significant differenc e between sexes (statoliths of females were slightly larger). All othe r differences were insignificant. Microscopic observation and incremen t counts of increments were successfully carried out for 37 pairs of s tatoliths, Significant differences between two independent counts were found for the LM method, but no significant differences were found be tween two independent SEM counts. Counts were significantly different when interpreted by both LM and SEM, probably because of poor resoluti on in the LM readings and over-resolution (growth layers prominent and numerous) in those read by SEM. Recommendations are made on how agein g studies, based on statoliths, should be structured and the results e valuated.