Case Studies

To study the seasonal variation in habitat use by salmon in an English chalk stream.

Panels In Stream
2 x 16-Channel Multi-Point Decoder (DEC-MPD-16)
32 x Circular Panel Antenna (ANT-SP-DISC-250)
260 x PIT Tag 12mm x 2.2mm FDX in sterilised needle (TAG-P-122IJ)
4 x 12v (85Ah) sealed lead-acid batteries.
A total of 260 salmon (57mm-183mm) were caught, tagged and released. Antennae were deployed in four rows across the stream (average width 3.8m) spaced at 60cm intervals using metal tent pegs to hold them in place Rows were 5m apart. The rows of antennae were moved downstream and batteries replaced every two days, to sample a stretch of stream 270m long. In this way the study site was sampled at the same 350 locations over a period of 28 days during September/October (feeding period) and January/February (over-wintering period)
More than 20,000 positional fixes were successfully logged. It was found that salmon parr tended to occupy water 25-55cm deep with a velocity between 0.4 and 1.0m/s. First year salmon were associated with gravel substrate during the daytime and aquatic weed at night. In autumn, 1+ salmon were associated with hard mud substrates by day and marginal tree roots by night, while in winter, they were located on gravel by day and mud and gravel by night.
The system allows continuous remote monitoring of numerous individual fish with high spatial and temporal resolution and will deliver consistent sampling even under difficult conditions such as shallows, fast flowing or turbid water and at night. The small size of antennae and relatively small detection range allows targetting of specific microhabitats and their sequential polling permits close antenna positioning without affecting performance. Increasing the battery capacity to 140Ah increased the interval between battery changes to 5-6 days. The findings suggest that weed cover is an important habitat feature for salmon parr and have important implications for the management of chalk stream habitat, where aquatic weed is typically cut back at regular intervals.

Riley, W.D., Ives, M.J., Pawson, M.G., Maxwell, D.L. (2006). "Seasonal variation in habitat use by salmon (Salmo salar L.), trout (Salmo trutta L.) and grayling (Thymallus thymallus L.) in a chalk stream." Fisheries Management and Ecology 13, 221-236.
Riley, W.D., Eagle, M.O., Ives, M.J., Rycroft, P. & Wilkson, A. (2003). "A portable passive integrated transponder multi-point decoder system for monitoring habitat use and behaviour of freshwater fish in small streams." Fisheries Management and Ecology 10, 265-268.
Riley, W.D., Eagle, M.O. & Ives, S.J. (2002). "The onset of downstream movement of juvenile Atlantic salmon, Salmo salar L., in a chalk stream." Fisheries Management and Ecology 9, 87-94.

To determine: (1) the preferred activity and shelter pattern of Atlantic salmon parr during summer; and (2) their response to variations in food availability when balancing growth rate and mortality risk (expressed through time out of shelter).

Equipment:Shelter Antenna
1 x 16-Channel Multi-Point Decoder (DEC-MPD-16)
8 x Tubular Shelter Antenna (ANT-SP-CUSTOM)
20 x
PIT Tag 12mm x 2.2mm FDX loose (TAG-P-122GL)
Shelter use and growth of wild 1 + Atlantic salmon parr were measured in an indoor stream-channel under conditions of either high (n = 11) or low (n = 9) food availability. Water from the adjacent river flowed through the stream-channel at ambient temperature (range: 12 to 21 °C). Part of the stream-channel was divided into test arenas (0.9 x 0.35 m). A single tubular antenna (shelter) was buried in the gravel substratum of each test arena. The substratum was formed from fine gravel and pebbles so that the tubular antenna provided the only place for a fish to shelter. After being weighed, a single fish was placed in each test arena on the first day of the experiment. Shelter use was monitored continually for the next week, after which fish were removed from their test arena and weighed again. Each fish was used once and subjected to one feeding treatment. The experiment was carried out over three runs, each lasting one week, between 23 May and 13 June 2003. At least 3 replicates of each treatment were obtained from each run.
Patterns of activity and shelter use were influenced strongly by food availability. Fish subject to high food availability were less active during the day than those subject to low food availability. However, regardless of food availability, fish were highly active at night. Growth rate did not differ significantly according to food availability. The predominantly nocturnal activity pattern and overall lower activity shown by fish subject to high food availability shows that Atlantic salmon are diurnal only to the extent needed to sustain a growth rate, and this extent depends upon food availability.
The system allowed the movements of fish into and out of shelter to be monitored continuously and remotely over the course of a week. A particular strength of the system was the ability to record patterns of shelter use at night since this is of particular interest with regards to the ecology of juvenile salmonids. The volume and accuracy of the data could not have been obtained using more traditional "snap shot" observations over the time-scales involved.
Orpwood, J. E., Griffiths, S. W. & Armstrong, J. D. (2006). "Effects of food availability on temporal activity patterns and growth of Atlantic salmon." Journal of Animal Ecology, 75, 677-685.

The effects of supplementary feeding on the survival and fecundity of mountain hares.

Hare Data Logger
Mountain hare populations in Scotland show unstable dynamics with regular seven to ten year fluctuations in abundance. The ecological mechanisms causing these fluctuations are currently unknown. Large-scale experiments on cyclic populations of snowshoe hares suggest that predation and food availability interact to destabilise hare populations. However, in Scotland mountain hares typically occur on sporting estates where predators are rigorously controlled thus it is unlikely that in Scotland predation causes mountain hare cycles.
Previous work on both mountain and snowshoe hares has shown that fecundity is influenced by female body condition over winter and that mountain hares can become food limited in winter. It is therefore postulated that over winter food availability may limit body condition and subsequent reproduction.
8 x 6-channel HDX Multi-point Decoder 12vdc
16 x 12v 26Ah SLA battery
4 x SLA battery charger
16 x Tripple-rod antennae (orange in photo)
1 x Hand-held PIT reader
200 x 23mm x 4mm HDX PIT tag
The experimental design comprised 4 blocks of ground, each measuring 0.25km-2, that have similar habitat and harbour similar hare densities in the same phase of population growth: two blocks were subject to supplementary feeding and provisioned with supplemental feed, and two blocks acted as controls. Mountain hares in the Scottish Highlands have home ranges of 10-12ha which equates to a circular area of radius 180-190m. Four feeding stations were spaced in each treatment giving all hares in the block access to at least one feeding station. To minimise movement between experimental blocks, blocks were located not less than 1km from each other.
Hares were live trapped in September-October. Each individual was aged, sexed, weighed and the hind foot measured. All hares had a PIT tag attached by means of a collar and a sub-sample (10 per block) fitted with radio-tags to the same collar.
Each feeding station comprised a covered feeding trough with tripple rod-type PIT antenna attached to each side lip of the trough. The tag reader (decoder/data logger, and battery) was housed adjacent to the trough. Batteries were cycled every 5 days. The identity of hares, the number of visits and the time each hare spends at a feeding stations was logged and later downloaded to a laptop computer or PDA.
Reliability of equipment including PIT tags has been very high and data is still being collected and analysed - multi-year project.
An overview of the project was published in "Shooting Times and Country Magazine", 9th March 2006 p.38-39

To objectively measure the efficiency of a hydro-power dam pool and weir/orifice fish pass under set conditions and determine the affects of season and variation of flow

Background:Orifice Antenna
The pass consists of 30 pools with weir or orifice and 4 "resting" pools giving a total rise of some 21m from river to reservoir. Three powered sluice gates in the dam wall allow the flow through the pass to be automatically regulated by tracking the reservoir level.
13 x HDX Single Point Decoder 12vdc (DEC-HDX-AL)
13 x 12v PSU
13 x HDX custom frame antennae
100 x 23mm x 4mm HDX PIT tag in 50mm x 15mm plastic bolus
1 x PC based data capture and transmission system
The thirteen antennae were installed at key points in the fish pass including the exit from each sluice Sluice Antennagate into the reservoir. Close collaboration with the hydro power company enabled antennae to be designed that were able to work effectively in close proximity of substantial metalwork and be robust enough to withstand water-borne debris. HDX decoders were installed in close proximity to the antennae and connected back to a small building that housed 240v to 12v power supplies and data capture PC. Software installed on the PC collected data from the decoders in real time, storing the data locally and automatically e-mailing system status and data files to selected users on a daily basis via a broadband connection. Broadband access to the PC was setup to allow remote operation for diagnostic purposes.
Returning adult salmon were caught below the ladder by trap or electrofishing, weighed, measured and bolus applied into the gullet, then released.
2007 has been used to investigate options for catching fish and to ensure efficient system operation. Several tagged fish have succesfully been logged passing through the pass during this initial period.
Sample Actual Data:
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1 18/11/07 14:08:04 091B51F0
2 18/11/07 16:16:23 091B51F0
3 18/11/07 16:49:20 091B51F0
3 18/11/07 19:35:47 091B51F0
3 19/11/07 00:53:53 091B51F0
4 19/11/07 09:45:23 091B51F0
4 19/11/07 09:51:19 091B51F0
5 19/11/07 10:16:49 091B51F0
6 19/11/07 10:33:02 091B51F0
7 19/11/07 11:38:17 091B51F0
7 19/11/07 11:40:42 091B51F0
7 19/11/07 11:49:08 091B51F0
8 19/11/07 12:21:41 091B51F0
9 19/11/07 12:40:59 091B51F0
10 19/11/07 13:35:09 091B51F0
12 19/11/07 14:21:59 091B51F0

The effectiveness of stocking a stream feeding a loch with salmon fry as opposed to stocking downstream of a hydro-power dam.

Equipment:Borland Lift Antenna
1 x Single channel High Performance Single Point Decoder with 230vac PSU in fan-cooled 19in enclosure. (DEC-HPSPD-RK-1)
1 x HP Antenna-Custom Frame 108cm x 33cm (ANT-HP-CUST-FRAME)
2000 x PIT Tag 12mm x 2.2mm FDX loose (TAG-P-122L)
A custom HP antenna was fitted to the downstream end of a Borland Lift flume connected to a rack-mounted, mains powered HPSPD installed in a nearby plant room. The HPSPD was configured to operate in logging mode, time-date stamping all PIT tag events.
Hatchery reared salmon parr were PIT tagged and released into a stream feeding the reservoir upstream of the hydro-power dam. Parr were also released into the loch below the hydro-dam. By collecting the IDs of returning adults, a comparison can be made as to the effectiveness of stocking above and below the dam.
This is an on-going experiment and data is still being collected and analysed.

22/12/07 11:21

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