Influence of water salinity on the strontium:calcium ratios in otoliths of the giant mottled eel, Anguilla marmorata

The otolith strontium (Sr):calcium (Ca) ratios have been widely used to reconstruct the migratory history of anguillid eels. However, factors affecting the Sr:Ca ratios in otoliths are incompletely understood in tropical anguillid species. To determine the salinity effect on the otolith Sr:Ca ratios, the Sr and Ca contents of otoliths of the giant mottled eel, Anguilla marmorata, reared for 60 days in four salinities (0 psu, 10 psu, 20 psu, 28 psu) were examined. The Ca and Sr contents and the resultant Sr:Ca ratios in the rearing water significantly increased with salinity. The otolith Sr:Ca ratios were also positively correlated with salinity. These results indicated that the Sr:Ca ratios in otoliths of a tropical eel could be used to reconstruct the migratory history of the fish as well as those of temperate species by differentiating when the fish migrated between fresh water and seawater.