Fisheries Monitoring and R&D
Fishtek can provide a wide range of techniques for monitoring fish populations in both freshwater and marine environments. These can be used to determine when and how fish are moving within river corridors, the link between such movements and biotic and abiotic factors, quantification of fish populations and assessments of fish behaviour. Specific techniques are as follows:
Surveys of fish populations are carried out to enable effective fisheries management of a water body. In addition to electro-fishing, we are able to carry out surveys using a variety of netting techniques. A few examples of previous projects that we have been involved in include surveys of eel populations in drains on the Somerset levels, an assessment of fish stocks in a large lake using seine-netting and fyke-netting and a large-scale assessment of the mortality incurred by fish passing through a pumping station. The latter was conducted using a custom built frame and net, designed and built at Fishtek.
Abstraction Entrainment Studies
Any abstraction of water from an overground water source has the potential, unless well screened, to entrain fish. Fishtek has undertaken several studies investigating the degree of entrainment of fish into (e.g.) consumptive water abstractions that are not fitted with fine screens. Such work is useful to quantify the degree of entrainment occurring, if any, and subsequent mitigation and screening measures that may be required to reduce this.
Pit-tagging can be used to monitor individual fish movements and migrations within both lotic and lentic environments. Electro fished individuals of known species and size can be tracked to observe behavioural responses to potential barriers and their movements past such barriers, as well as movements over both the short and long-term.
Specific project examples where we have used pit-tagging include a series of large studies looking at low-cost mitigation methods to improve fish and eel passage at gauging weirs. Low-cost solutions were installed on several weirs in the midlands and fish were captured, pit-tagged and released below the weir. Their subsequent movement were then monitored using pit-tag antennae to ascertain the effectiveness of the installed mitigation measures.
Underwater video cameras provide an effective method for monitoring fish behaviour in conditions of low turbidity and reasonable water clarity. Footage is stored on a hard drive and analysed manually by visual inspection or use of image analysis software that records fish passage events. Total fish counts and even species identification can be made with high levels of accuracy. Typical locations for a camera monitoring system include fish passes and hydro turbine installations.
The size of the installation determines the number of cameras required. A large Larinier fish pass may need 6 cameras, while 2 would be sufficient for an Alaskan A pass. Infra-red lighting panels improve image quality and the efficiency of fish detection.
For remote sites without electricity, there are a number of options for powering the system including Hydrogen fuel cells, solar panels or micro water turbines. Equipment is housed in weather proof stainless steel boxes and all equipment and housings can be provided by Fishtek. PIT tagging can be used alongside camera monitoring to give a comprehensive picture of fish behaviour.
The DIDSON (Dual-Frequency Identification Sonar) is an acoustic camera which uses sonar to create high resolution video imaging underwater. We used this technology to observe fish behaviour (including the interaction between fish and intake screens and anthropogenic structures), to count and measure fish, and to conduct assessments of fish migration movements within a river.
The DIDSON can be used to successfully monitor fish in more turbid conditions than is possible with cameras but can be used alongside cameras to provide species identification as well as counts and assessments of behaviour.
Specific examples of projects where we have employed a DIDSON include work on the Somerset levels, where a DIDSON was used to investigate the behaviour of eels at the intake screen to a pumping station and link their migratory movements to changes in environmental parameters, including temperature, river flow, rainfall and time of day. A DIDSON was also used to assess the upstream migratory movements of salmon and sea-trout in a Westcountry river and link patterns of migration to environmental triggers, particularly river flow.
Smolts are a key stage within the life cycle of salmon and sea-trout. Fishtek, working in conjunction with the Environment Agency, has designed and fabricated a unique smolt trap that can be employed on small rivers to trap downstream migrating smolt for subsequent counting, measuring and tagging (if necessary).