Anadromous and resident forms of pond smelt, Hypomesus nipponensis, were found to occur in sympatry in Lake Ogawara, Japan. Profiles of Sr:Ca ratios from individuals could be grouped to two patterns (1) a 'resident' pattern with low Sr:Ca ratios from core to edge and (2) an 'anadromous' pattern with relatively low Sr:Ca ratios near the core with abrupt increases in ratios at a location approximately 0.3 mm from the core. Spawners smaller than 60 mm standard length (SL) were resident, between 60 to 80 mm were mixed resident and anadromous, and larger than 80 mm were anadromous. Anadromous individuals first migrated after 40 to 82 days from hatching (mean ± sd, 59.1 ± 13.5 d) and 14.6 to 30.9 mm SL (22.2 ± 5.3 mm). There was no difference in SL between resident and anadromous individuals during age at first migration, suggesting that size may not be the mechanism for divergence of alternative life history styles.
ASJC Scopus subject areas