The Manila clam, Ruditapes philippinarum was introduced into Norway in 1987 and used in aquaculture until 1991. In 1988-91spat were seeded on five Norwegian beaches in three regions at 60 °N, 64 °N and 65 °N. Manila clams were recovered from three sites, at, or near where they had been released. They were distinguished from native R. decussates, Tapes pullastra, and T. aurea using morphological features, confirmed by comparison of polymorphic isozyme loci using starch gel electrophoresis. Fifty-one specimens were recovered, were 31-59 mm in shell length and ranged from 4 to 7 years of age, and were in good condition. Age of the recovered clams coincided with the time of the spat re- leases. Histological examinations revealed eggs and sperm in different stages of maturity, including spent ovaries, suggesting that spawning have taken place. No juvenile or small specimens were found. |
