Report on Harmonisation of freshwater biological methods

155. Fish sampling is performed mainly in large lowland rivers (100-300 m wide).Electric fishing (PDC generator, 300 V, 5A) is usually performed from a boat, alongthe banks, by a staff of 3 persons. The prospected area averages 1000 m 2 , e.g. 500 mlong, 2 m wide along the banks, where the mean water depth is 0.8 m. The preferredseason for electric fishing is from late autumn to early spring. Other techniques,including trawling, fyke and frame nets, are also used in large lowland rivers. Thepreferred season for trawling extends from April to October. On the other hand, fykeand frame nets are preferably used from spring (April) to autumn (November). Nets of5-20 m long are set on the bottom of lowland rivers, at a depth of 3 m for periodsranging from 12 to 154 h.United Kingdom156. The specific equipement and strategies used are generally region and sitedependent. Electric fishing is the most common sampling method used although thegear specifications, technique of application and man-power used has been variablebetween Environmental Agency (EA) area teams. The review of the EA MonitoringProgramme and recent R&D programmes have attempted to standardise the samplingstrategy and methods used for each element of the new monitoring programme whilstretaining some flexibility in approach to allow for evolution. The review is also takingfull consideration of CEN requirements.157. Electric fishing surveys are usually carried out in summer months, postspawning season (June - October). However, some regional and site-specific variationoccurs depending upon the purpose of the surveys, the accessibility of the site and theconditions for efficient sampling, e.g. weed growth. The new sampling programmehas proposed methods to suit different sampling data requirements, different habitatconditions and the manpower required to undertake them.Agencies in Scotland andNorthern Ireland are working closely with the EA in developing standardize fishassessment methods.101