Title

Biological Studies of American Eel at the Conowingo Project

Item Type

Presentation

Location

Elaine Langone Center, Terrace Room

Session

Aquatic and Terrestrial Ecology and the Chesapeake Bay, moderator Steven Jordan

Start Date

22-11-2014 9:00 AM

End Date

22-11-2014 10:30 AM

Description

As part of a broad bio-engineering investigation at Conowingo Hydroelectric Dam, MD we studied the distribution and abundance of juvenile American eel, Anguilla rostrata, downstream of the dam for two years. Results of our study were expected to provide potential location(s) for an eel fish way when and if deemed desirable for the migrating population. Elvers and yellow eels were sampled between 24 June and 6 September 2011 using elver ramps (with Enka Mat and Akwa Drain 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 Enka Mat substrate, with 406 elvers collected in the Akwa Drain substrate. The West ramps (location near the powerhouse) collected 561 elvers, with 405 collected in the Enka Mat substrate, with 156 elvers collected in the Akwa Drain 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 spill age which caused extensive damage to the collection gear. It was observed that the integrity of any 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 1 or 2, and 3 to 5 years of age at 30%, respectively. A large gap in age at year 6 to 8 was apparent; larger eels were aged 9 to 17, plus one at 19 years of age. The study period encompassed three new moon periods and two full moon periods; a strong relationship was not observed between the number of elvers captured and lunar phase. Elvers were observed in abundance below crest gate 30.

Language

eng

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Nov 22nd, 9:00 AM Nov 22nd, 10:30 AM

Biological Studies of American Eel at the Conowingo Project

Elaine Langone Center, Terrace Room

As part of a broad bio-engineering investigation at Conowingo Hydroelectric Dam, MD we studied the distribution and abundance of juvenile American eel, Anguilla rostrata, downstream of the dam for two years. Results of our study were expected to provide potential location(s) for an eel fish way when and if deemed desirable for the migrating population. Elvers and yellow eels were sampled between 24 June and 6 September 2011 using elver ramps (with Enka Mat and Akwa Drain 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 Enka Mat substrate, with 406 elvers collected in the Akwa Drain substrate. The West ramps (location near the powerhouse) collected 561 elvers, with 405 collected in the Enka Mat substrate, with 156 elvers collected in the Akwa Drain 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 spill age which caused extensive damage to the collection gear. It was observed that the integrity of any 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 1 or 2, and 3 to 5 years of age at 30%, respectively. A large gap in age at year 6 to 8 was apparent; larger eels were aged 9 to 17, plus one at 19 years of age. The study period encompassed three new moon periods and two full moon periods; a strong relationship was not observed between the number of elvers captured and lunar phase. Elvers were observed in abundance below crest gate 30.