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DIDSON units prove their worth on the Eagle River

This year DFO NL Salmon scientist Dave Redden did in-river testing of DIDSON recording units. The DIDSON can record accurate migration information on many species, in this case it was Atlantic salmon. These units are about the size of an average suitcase, they require little power and the data can be uploaded for analysis. DIDSON units offer unparalleled opportunity to get accurate full migration counts that, up to now, just weren’t possible.

We asked Dave if he could summarize his research on Eagle River this summer.

We have had a very successful field season with the DIDSONs. As you know we decided that this summer should be dedicated to learning their capabilities in various settings, learning how to deploy and implement DIDSON on our rivers, and obtaining information from Eagle River that would allow us to pick a site for next year.

We initially deployed the DIDSONs at the smolt fence on Campbellton River, Nfld in May. We had them operating within a couple of hours and were easily able to pick out salmon kelts released from the smolt trap including smolts. In fact, all the fish released (~ 75) were observed by the DIDSON. We also measured fish of known length which proved very successful. The r=0.9 with very little observed bias. This was done with the Std DIDSON on High Frequency mode. We also tested a site at Salmonier River with the updated software and implemented the extended windows feature which worked out well. At Sand Hill River, we looked at smolts moving downstream which leaves me optimistic that sometime we may be able to enumerate smolts as well. We also tested the power setup required for remote operation.

At Eagle River, we have picked out a site about 200 m below the Gorge and near the Eagle River Salmon Club. The Salmon Club were extremely helpful in providing a base of operations which made life a lot more comfortable then it would have been otherwise. The river at the site is about 84 m wide and we can detect salmon from one side to the other. We have a bottom profile done at the site which will help in aiming the DIDSONs for a best count. We also have shown Atlantic salmon as opposed to some other salmon species utilize the entire river width for migration at least at Eagle River. Unfortunately, this means we have to look at the entire river rather then a section of it as they have been doing in BC and Alaska.

In general, it was very good to have purchased a piece of equipment that actually does what it is advertised to do. Also the support from the company and my colleagues in DFO-Nanaimo and at the Marine Institute, Ireland was terrific and much appreciated. They made our learning curve much easier to climb. I look forward to full implementation next summer at Eagle River.

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