Session B1 - Biological and Engineering Studies of American Eel Anguilla Rostrata at the Conowingo Project

As part of a broad bioengineering investigation at Conowingo Hydroelectric Dam, MD, the distribution and abundance of juvenile American eel, Anguilla rostrata, downstream of the dam was studied for two years. Results of the study were expected to provide potential location and feasibility information as part of the broader bioengineering analysis. Elvers and yellow eels were sampled between 24 June and 6 September 2011 using elver ramps (with Enkamat and AkwaDrain substrates) and eel pots (for yellow eels). A total of 1,159 eels (1,100 elvers collected from the elver ramps and 59 yellow eels in pots) were collected in the spillway side downstream of Conowingo Dam compared to 166 elvers and 92 yellow eels collected in 2010. Capture of elvers differed between substrate type and location of ramps. The East ramps (located farther from the powerhouse), collected 539 elvers, with 133 collected in the Enkamat substrate, and 406 elvers collected in the AkwaDrain substrate. The West ramps (located near the powerhouse) collected 561 elvers, with 405 collected in the Enkamat substrate, and 156 elvers collected in the AkwaDrain substrate. High elver collections on both sides were ramps parallel to walls suggesting elvers orient themselves upstream to structure. The collection locations of elvers were subject to spillage during the study period which caused extensive damage to the collection gear, and it was observed that the integrity of any potential structure below the spillway could be at risk during spillage. Elver lengths ranged from 87 to 188 mm TL, with an average size of 124.9 mm. Yellow eels harvested from the eel pots totaled 151 for both study years; with the exception of one, all yellow eels were collected near the powerhouse location. The length range of eels collected in pots ranged from 300 to 689 mm TL, with an average length of 515.4 mm. Most elvers were split at age I or II, and III to V years of age at 30%, respectively. A large gap in age at year VI to VIII was apparent; larger eels were aged IX to XVII, plus one at XIX years of age. The study compared lunar cycle and rain events to eel collections; a strong relationship was not observed. Three nighttime surveys conducted in 2011 documented areas of elver congregation in the spillway