Evan Roderick

Masters by research student at RLI (UHI)

Investigating the potential of resistivity counters to assess Atlantic salmon stock statusin the Moray Firth

SupervisorsProfessor Eric Verspoor (RLI), Dr Mark Coulson (RLI), Dr Alastair Stephen (SSE), Dr Stephen Gregory (GWCT)

Working in collaboration with SSE and their large collection of counter data

Why counters in the first place?

What is the point of counters?

What do we get from them now?

What could we get from them in the future andretroactively with historical data?

What’s standing in the way of these outcomes?

Objectives

1. Assess the verification of a count through its resistivity reading

2. Find if a resistivity reading can be used to determine size of the Salmon

Issues

• Verification is tough• Conditions often against you for positive verification of counts,

less so in hydro dam installations

Opportunities

• Each count comes with a resistivity reading• What if we could use that reading to confirm a count and what

more could we get from it?

There are regularly observed patterns in the waveforms exhibited by salmon vs other items, individuals or objects

It may be worth whilst taking the time to prove or disprove the use of the reading for “count”To see what additional information it might present.

Size of individual has been linked to egg deposition. This information could feed into a biggerSystem for determining conservation limits

Finding size by resistivity reading is not a new idea, but it has been subject to plenty of issuesin previous examinations.

Better chance of being sure of it’s potential in this region – low conductivity water.

More sure of the readings due to advances in technology.

This study provides three possible outcomes, each of which have the potential to inform theuse of counters in the assessment of stock status – with respect to counters in hydro dams andpotentially other installations.

1. It doesn’t work and it tells us one thing

2. It does work and it tells us another

3. It partly works and we know some of the limits of the system

Objectives

1. Assess the verification of a count through its resistivity reading

2. Find if a resistivity reading can be used to determine size of the Salmon

Outcome Objective 1 Objective 21 Negative Negative

2 Positive Positive

3 Positive(?) Negative(?)

There are currently a substantial collection of counters in Scotland with my focus beingseveral counters which are found in hydro-dams in the Moray Firth

The issues with validation are near universal

The proving or disproving of the use of resistivity readings for count and size could have broad implications

The first thing to find out about counters is “what are they counting?”

We can go on from there.