PIGMENTATION, OTOLITH RINGS, AND UPSTREAM MIGRATION OF JUVENILE AMERICAN EELS (ANGUILLA-ROSTRATA) IN A COASTAL RHODE-ISLAND STREAM

American eels of < 250 mm total length were collected in late summer and fall from three stations on the coastal Annaquatucket River. All eels possessed the yellow-green pigmentation characteristic of the yellow phase. Transition of partially pigmented elvers to fully pigmented yellow eels occurred during the summer month following the spring entry into fresh water and was accompanied by significant growth. Mean total length and mean number of annulus-like otolith rings increased significantly with distance upstream, suggesting that elvers migrate a limited distance in the 1st year, but continue on for at least several years thereafter as yellow eels. Upstream progress of eels in this system may be impeded by low winter temperatures, high stream gradient, dams and impoundments.