AGE OF PACIFIC TARPON, MEGALOPS CYPRINOIDES, AT ESTUARINE ARRIVAL ANDGROWTH DURING METAMORPHOSIS

The age of Pacific tarpon, Megalops cyprinoides (Broussonet), at estua rine arrival was estimated by counting otolith growth increments from specimens collected in the Gongshytyan Brook estuary of northern Taiwa n on 15 to 24 September 1995. The daily deposition of otolith growth i ncrements provided a mean to estimate age of individuals. Tarpon at es tuarine arrival were in the Ist metamorphic stage. Their body lengths ranged between 17.8 and 32.9 mm TL (mean = 25.6 mm TL) and ages betwee n 20 and 39 d (mean = 28.5 d). A metamorphic mark within the otolith i ndicated that the fish had begun to metamorphose several days before a rriving at the estuary. Negative correlations between age estimates, a nd both somatic and otolith growth rates indicate that faster-growing tarpon arrived at the estuary earlier than did slower-growing ones. Ot olith growth continued while body length was reduced during metamorpho sis. The duration of metamorphosis for Pacific tarpon was estimated to be approximately 14 d.