Decapod Crustaceans of the Headwater Streams of Pohnpei, Eastern Caroline Islands, Federated States of Micronesia

Abstract

Two species of Macrobrachium (Palaemonidae) and three atyid shrimp (Atyidae) species were identified among 986 decapod crustaceans collected in headwater streams on Pohnpei, Micronesia, during 1999 and among incidental collections in 2000. None is endemic to the island; all are indigenous or at least not of recent human introduction, and all occur widely in the Indo-West Pacific region and have a diadromous life history pattern. Both Macrobrachium lar (Fabricius, 1798) and M. latimanus (Von Martens, 1868) are common in Pohnpei rivers, but M. latimanus outnumbers M. lar especially in the uppermost reaches. Atyoida pilipes (Newport, 1847) accounted for 72% of the atyid sample, and it was the only decapod recorded at elevations as high as 604 m; Caridina weberi (De Man, 1892) composed 21% of the sample and C. typus (H. Milne Edwards, 1837) 6.4%. Ovigerous females were collected throughout the year for three of the five species; the absence of ovigerous Macrobrachium lar and Caridina typus during August-November was possibly due to small sample sizes. Freshwater shrimps do not currently form an important part of the diet of Pohnpei islanders, but historical accounts suggest that shrimps were utilized more in the past when imported foods and advanced technology for harvesting marine resources were not readily available.