It has been an extremely bust two weeks for MulkearLIFE and our work colleagues in Inland Fisheries Ireland as the project completed a full catchment wide electrofishing survey. Unlike in 2012, this work was scheduled and completed according to plan, as was the case in 2010 and 2011.
Two boat crews work towards downstream net, June 2013 (Image: Bríd O’ Connor)
This work, the 4th annual fish stock survey, took place in various rivers throughout the catchment which, thankfully, were at near normal levels. Over the past four years, MulkearLIFE has, with the support of Inland Fisheries Ireland colleagues, undertaken electrofishing survey work at various sites on the Bilboa, Newport, Doonana, Cahernahillia, Annagh, Killeenagarriff, Gortnageragh and Mulkear rivers.
Two boat crews work towards downstream net, June 2013 (Image: Glen Wightman)
The focus of the 16 sites this year was primarily the Mulkear, the Annagh, Newport and Bilboa rivers. The relatively good weather conditions over the past two weeks allowed the project to undertaken the catchment wide electro-fishing survey without incident or disturbance.
Removing all fish from downstream net, June 2013 (Image: Ruairí Ó Conchúir)
What is Electrofishing?
Electrofishing involves the use of specifically designed equipment which passes an electric current through the water in a river. This temporarily stuns the fish within the radius of the electrode (usually no more than a few meters in diameter) and causes the fish to float to the surface (turn) where they are then collected with a net. MulkearLIFE uses both backpack equipment and equipment which can be placed in a boat. The sites are surveyed to the Water Framework Directive (WFD) standard so that ecological status can be assigned to each site. The entire basis on the work is to assess fish stocks throughout the catchment. To get a snap shot of the stability or otherwise of fish stock and to assess what beneficial impact the instream works undertaken as part of the work programme of MulkearLIFE is having on fish stocks and especially what impact have such works have had on salmon numbers.
All fish are recorded from minnows to large sea lamprey (Image: Ruairí Ó Conchúir)
How Does MulkearLIFE Carry Out Electrofishing Survey Work?
All sites used by MulkearLIFE are different. Hence, the recourse requirements (staff, boats, nets, electrofishing packs) differ also. The basic elements of the work consist of the installation of nets across the width of a river channel. These nets are secured at locations upstream and downstream of the selected site (section of river channel) which forms part of MulkearLIFE’s network of sites throughout the catchment in which annual electrofishing takes place. In a survey involving two boats, as indicated in the images from the 19th June 2013, the electrofishing equipment is placed in the boats and used by MulkearLIFE / IFI staff in that section of river channel between the nets. Fish are drawn towards the electrode net and are collected with nets as they turn in the water. The fish are quickly captured, transferred by net into larger temporary holding tanks and fully recorded before being immediately released.
All fish species are measured and weighed, June 2013 (Image: Ruairí Ó Conchúir)
Once recorded all fish are returned unharmed to the river (Image: Ruairí Ó Conchúir)
Why Does MulkearLIFE Electrofish?
MulkearLIFE is required to undertake annual electrofishing surveys to assess the status of fish stocks at selected sites throughout the catchment. Having established a baseline in previous years, the electrofishing survey allows MulkearLIFE to calculate the total number of fish species that are present in a particular site or river channel. The catchment wide survey allows the project to build up a picture across the entire catchment. The analysis of the data allows the project to assess the condition of the fish, together with their size and age. This is an extremely useful indicator of the quality of the water courses in the catchment and their importance in supporting fish and aquatic life in general.
The annual fish stock survey is a major operation (Image: Ruairí Ó Conchúir)
As the month of June closes out, MulkearLIFE is delighted that it has managed to electrofish all of its survey sites throughout the catchment this year. The data from the 2013 survey sites, once fully analysed, will greatly assist the project in assessing the merits of its instream work.
The boatmen – Noel Sheehan and Flan Ryan, June 2013 (Image: Ruairí Ó Conchúir)