Date: December 15, 2008(Prepared by — Brad Chase, MarineFisheries)
Grass pond is a small natural pond from which water flowsthrough Cold Brook to meet Nantucket Sound at SaquatucketHarbor in Harwich, Massachusetts. A maximum size of 24 acres hasbeen reported for Grass Pond, although historical flow manipulations forhydropower and cranberry growing have likely reduced the size of Grass Pond.Presently there is high seasonal variability to the wetted perimeter and oufflowof the pond. The Harwich Conservation Trust (HCT) own 60 acres of formercranberry bog east of Bank Street, Harwich, in the Grass Pond watershed. Theyshare water rights with an adjacent cranberry bog operator (John Sennott)granted from license No. 769 issued in 1927 by the MA Division of Waterways.The HCT has been considering options for land-use and habitat restoration oftheir bog property. They contacted the MA Division of Fish and Wildlife (MassWildlife) and Division of Marine Fisheries (MarineFisheries) foradvice on fish and wildlife restoration. They have also been working with theNational Resource Conservation Services (NRCS)on potential agriculture and habitat restoration options for the property.Observation by HCT, Mass Wildlife, and MarineFisheries confirmedthe presence of American eel in the Grass Pond watershed. MarineFisheries determinedthat the recently rebuilt (2007) Bank Street flumepresented an impediment to eel passage into Grass Pond and recommended that aneel passage restoration project be considered.
Following several site visits and consultations withproperty owners and the Town of Harwich, plans were initiated during the winter of 2008 to install anexperimental eel ramp at the Bank Streetflume to allow migrating eels to pass into Grass Pond. The HCT received fundingfrom NRCS to make improvements to culvert in their bogs and the grant includedfunds for improving eel passage. For the 2008 spring migration, it was decidedto build a temporary wood eel ramp with MarineFisheries funds in orderto assess the utility and performance of an eel pass at this location during amonitored pilot project.
Eel Ramp Construction. The eel ramp was constructed by Luis Carmoand Ed Clark of the MarineFisheries fishway construction crew. The ramp was built of plywood in two 8’sections connected by hinges. The ramp sections were 12” wide, lined with Enkamat,and covered with %“ aluminum screening attached to 3” side walls. The lowersection was set at water level in Cold Brook. The upper section connected to aneel holding tank next to the flume in Grass Pond (photograph). A battery (1 2V,650 amp) powered bilge pump (Rule 360 gph) supplied water to attract eels tothe ramp and to maintain captured eels in the flow-through holding tank. Thebattery could not keep pace with the bilge pump despite frequent charges.Following this experience, a series of experiments were conducted onmaintaining power to the pump with AC power and a Sunsei SE-I 500 solar panel.
Monitoring Methods. Efforts were made to inspect the ramp holding tank each dayexcept Sunday when the pump was operating. With each visit, the time of day andnumber of eels in holder tank were recorded to allow the calculation ofcatch-per-day or catch-per-hour. Eels were counted in the following three sizegroups: glass eel (young-of-the-year, YOY), age-I eel (fully pigmented withminor length gain over YOY), and age-I+ (approx. >10 cm with length/weight
separation from age-I). Notes were recorded on by-catch andramp operations. The following water chemistry parameters were measured next tothe ramp tank with a YSI 6-Series sonde on a monthly basis: water temperature(°C), DO (mg/I), DO saturation (%), specific conductivity (mS/cm), pH, andturbidity (NTU)
Monitoring Results. The monitoring period to capture the typical YOY eelmigration in Massachusetts should be April 1st through June. The ramp was not ready forinstallation until May I 6~’; about the mid-point of the migration season. Theramp passed 78 age-I and age-I + eels during the first night of operation. Thepump operated for seven of the next 10 days catching low numbers of age-I orage-I + eels with the first appearance of YOY eels on May 24th On May 27th many YOY eels were observed inCold Brook immediately downstream of the flume. With this observation, a boardwas added to the flume, causing no flow to exit Grass Pond except pumped flowdown the ramp. On this day, we also converted to AC power from the neighbor’shouse. On May 28th catches of both YOY and larger eels increased dramatically,beginning a 10-day period where catches peaked for the season with over 100eels counted each day. The eel count for the season was 6,414. Overafl catcheswere dominated by YOY eels (4,521, 70%) with evidence of an earlier peak andshorter run duration for age-I eels (1,518, 24%) and age-I + eels (375, 6%).By-catch was not anticipated for this specialized eel pass, yet 15 crayfish,two recently hatched snapping turtles and many freshwater beetles made the tripup the ramp and into the holding tank.
Ramp Operation. The eel ramp performed well as evident by catches the firstnight of operation, large catches during a short season, and no tank mortality.Frequent troubleshooting was needed for the bilge pump power supply. Richard Cooper, an electrical engineer whovolunteered for HCT, conducted detailed tests of the ramp’s power system. It wasclear that the bilge pump load was too much for the battery on a chargingschedule or connected to solar panels. The solar panels were rated for amaximum current output of 1.5 A yet under testing both panels achieved only I.1 A. The best performance was achieved when two solar panels were connectedwith a 25 W rheostat timer set to turn the pump off between 8 am and 6 pm and to limit thepump to 80% capacity while pumping. This configuration kept the pump runningcontinuously (8-day experiment) under conditions of ample summer sun. It isapparent that the panels do not meet their advertised performance and cannothandle a steady load without a timer.
Outlook for 2009 Season. The HCT will use funds received from NRCS toconstruct a more durable eel ramp with a properly sized solar panel for the2009 season. The MarineFislieries fishway crew will construct a customaluminum ramp with the same dimensions as the wood ramp. The aluminum ramp willnot degrade in the wet environment and provide many years of service. Richard Cooper’s recommendations will beused to outfit the ramp with a low-maintenance, solar power source. The rampwill be installed on or near April 1st, and operate through all of April, May, and June and removed when eelcatches approach zero in early July. This seasonality covers the migratoryperiod of glass eels from the ocean and upstream movements of older eels. It isalso consistent with other eel monitoring projects in Massachusetts. The partners will also meet todiscuss other potential eel habitat improvements in the watershed andoperational considerations for the Bank Street flume related to the silver eel emigration in the fall.Mature silver eels exit freshwater habitats on a spawning run to marine watersbetween September and November each fall.
Pump-supplied eel ramps are a newrestoration tool in Massachusetts. The first ramp in a MA coastal river wasinstalled in Saugus in 2007 and the Grass Pond ramp is the second. The largecatches in a small, altered brook were surprising and encouraging. The projectwas dependent on the ideas and cooperation from the bog owners, adjacent homeowners, the Town of Harwich, volunteers, and the MarineFishories fishwaycrew. From this list we appreciate and recognize the efforts of Ben Wright,John Sennott, Shirley Fletcher, John Pashayan, Tom Leach, Richard Cooper, ChristinMarshall, Luis Carmo and Ed Clark.