Eel Report

It was a good time at the USGS Northern Appalachian Experimental Labs in Asaph yesterday. Two lab employees (Vinca and Jeff) who are directing the transplant/research of the eels-mussel project were on hand to direct/assist as members of the Tiadaghton Audubon Society (TAS)--and a couple of guests from California--implanted computerized tags (PIT tags) beneath the skin of fifty young eels. Each eel's weight and length were measured (my job) and recorded along with their PIT tag numbers.

Gary and I thought we might have only three folks there to assist Vinca and Jeff. We ended up with eight (five TAS members, two California guests of members, and a high school senior (James) working in the labs for the summer). Add Vinca and Jeff and we had a heck of a crew to gang up on the poor eels.

The eels had been collected from the Susquehanna River down in Maryland below the dams that currently make their migration upstream next to impossible. Each measured between 18 and 29 cm in length and had a weight of approximately 1 gram for each cm. They were being held in the labs vast array of holding tanks. Gary would scoop a couple of eels from the holding tank and place them in a cooler of water containing an anesthetic solution. One of the California guests (Mike?) would monitor the eels and when they seemed docile enough he would pluck on from the water and try to get a firm grip on it. Jeff would take a special needle designed to puncture the skin and, with a plunger-like inner structure, implant a PIT tag beneath the eel's skin. A scanner would record the number of the PIT tag (James' job) which the recorder (Diane of TAS). Once the tag was in place I would place the eel on the scale and take its weight and then try to stretch it out straight to get its length before placing it in a recovery tank. We processed 52 eels in all with two of the little devils getting pricked by the needle but having their muscles spit the PIT tag back out.

The entire procedure took us close to two hours. Things might have gone faster but we kept bumping into one another in the small confines of the aisle/doorway in which we worked. I left Phil (TAS President) to assist his daughter (Vinca) in transporting a separate batch of eels to Pine Creek fro release.

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I mentioned yesterday that the eels serve as a symbiotic host to the larvae of mussels living in the creek/river. There were some mussels recently collected from the Susquehanna down in southern PA in a large aquarium that had everyone pretty excited. The tank, approximately 2' x 5' had a dozen or so mussels scattered evenly across its graveled bottom on Wednesday. By yesterday, most of the mussels had moved to an area about 18" square nearer the inflow from the filter where O2 levels were higher. As interesting as the migration of adult mussels might be, even more exciting was the display of fish lures by five or six of the larger female mussels.

The mussels were wedged into the gravel so their open edges would stick up high into the water. From those edges protruded soft tissues that looked for all the world like small, one-inch long, minnows with fins waving in the current. Each little "fish" even had what appeared to be a dark eye-spot to complete the illusion. The idea, apparently, is to lure a larger fish (or eel) into range of the mussel, the larvae of which will hitch a ride in the gills of the more mobile creature. The mimicry of a small fish was excellent and, if you didn't have the entire mussel visible to you, you could easily be fooled into thinking it was indeed a fish. They sort of reminded me of the long fins and tail of some koi or a Siamese fighting fish.

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Future tagging and release of eels into Pine Creek is planned. And, as soon as Vinca and Jeff choose an antenna/sensor design they want to work with, we'll be on the creek attempting to locate the eels that have been tagged and released.