Settlement and pigmentation of glass eels (Anguilla rostrata Lesueur) in a coastal lagoon

Abstract

American eel (Anguilla rostrata Lesueur) is born in the Atlantic Ocean, but larvae redistribute throughout diverse habitats of North American estu- aries and freshwater streams. We hypothesized that early stage A. rostrata differed in abundance among sites within a single coastal lagoon, Newport Bay (Maryland) for two sampling seasons (March-May in 2007 and 2008). Catch per unit effort (CPUE) of early stage A. rostrata was usually similar between years at a site, except that it was higher at one site in 2008 than in 2007. The CPUE varied among sites within Newport Bay, but not significantly so because of high, intra-annual variance in CPUE at a site. As reported for New Jersey coastal estuaries, variation in the CPUE tended to be higher in brackish water habitats. Intra-annual variation in CPUE from March until May was partially explained by oxygenation and salinity. The CPUE of settling eels was greatest when water was well-oxygenated (dissolved oxygen >8 mg·L −1 ) and mildly brackish (0.3-3.2 ppt). While larval supply to a coastal estuary may annually influence the magnitude of potential settlers, temporal differences in habitat conditions within Newport Bay also influenced settlement patterns. Differences in habitat conditions can affect the pigmentation rates of settling early stage eels. We measured rates of pigmentation, which corresponded with age of the fish. However, rates did not differ among sites or vary with habitat conditions. Pigmentation levels from March to May increased at a rate of about 0.02% per week. Monitoring programs for early phase American eel should consider the steepness of habitat gradients within estuaries and habitat covariates when assessing population status.