FASMOP: Management Implications for the River Spey

Spate impacts on Spey juvenile fish stocks

SFCC 2016

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Do spates have an impact? At a population level no

At a fishery level - on the Spey - yes

Hypothesis the greatest impact of a damaging spate will be on the smolt output in the following spring

Looked at catch from smolt year class one year after potentially damaging spate (>500m3/s)

Mean rod catch derived from spate affected smolt years classes was 8,565 compared to 10,142 (p=0.007, t-test) (MSS catch data 1952 to 2010)

Year with spateRod catch from smolt year +1Year without spateRod catch from smolt year +119568676195211511195790641953979819666271195491081970111351955125451978943519588498198182381959853419909587196011656199386101961877019956688196211540199773301963962720007195196494062002890819659556200410229196784632005123931968763420097452196711611201058241971940019721441619736901197412820197515126197612415197714304197988381980106521982113231983142521984107261985104361986978919879526198861731989687619911203919921297719949483199687301998810619996619200187312003100732006981720076314200811008Mean856510142

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General pointsBetween 1961 to 2011 there were significant increases in winter and autumn precipitation in east Scotland ~ 25%

2015 Spey mean daily flow was 15% higher than ten year average

The frequency and intensity of high rainfall events has increased

Trend predicted to be maintained

Catchment resilience to high rainfall events compromised

River flow data provided by SEPA

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Potential causes of spate related mortalityJuveniles:Displacement StrandingPhysical damagePremature marine entryPoor post spate growthPredation

EggsRedd washout

River bed mobility likely to be significant factor at all lifestagesNot a new phenomena on the Spey noted by Ashley Cooper in book published in 1978

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Spate monitoring strategyEstablished network of timed electrofishing survey sites along length of Spey mainstem surveyed annually

Similar surveys completed in the River Fiddich in July 2014

Before spate data available After spate data obtained by resurveying some sites in Aug/Sept

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Timed survey sites61 sites on the Spey covering entire mainstem from tidal limit to source

Average 18.8 salmon fry/min in 2014

Salmon fry at all sites below Spey Dam: none above

Parr also captured

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River Spey mainstem before and after spate electrofishing 2014July total countSept total countSalmon fry1013604Salmon parr73129

Site codeLocationJuly salmon fy/minSept salmon fry/minS007R1Essil Pool16.310.0S017L2Brae 524.76.0S019L2Brae 428.727.0S025L1Brae 223.022.0S034R1Delfur B o'B55.09.3S040L2Delfur66.020S056L1E.Elchies43.729.7S079R1C&L31.336.6S087L1Phones6.07.3S105L2Tulchan D33.720.3S141L1Castle Grant 19.313.3Mean30.718.3Mean river flow24m3/s32.8m3/s

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River Fiddich mainstem pre and post spate electrofishing 2014July total countSept total countSalmon fry873295Salmon parr11277

Site codeLocationBefore salmon fry/minAfter salmon fry/minTSF01Fiddichside Inn107.333.7TSF13Balvenie warehouses25.029TSF19Dullan confluence129.722.3TSF38Bridgehaugh29.013.3Mean72.824.6

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Evidence of displacement/movement?"Rome was built on seven hills, Dufftown stands on seven stills"Fry downstream of Dufftown 25% larger on average due to cooling water dischargesTSF13 only site where mean size of fry had decreased.

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What did we expect to find in 2015?Good fry densities: there were an abundance of good quality spawning gravels, although salmon spawning stock was low Reduced parr densitiesReduced smolt output

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What did we find in 2015?*Good fry densities

* Some observations, didnt set out to prove anything

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What did we find in 2015?Reduced parr densities

Salmon parr/minuteRiverSpey20122013201420151.24.33.81.5

Highest site count 2015 = 6 parr/minuteHighest site count 2013 = 35.7/min

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2013Number salmon parr = 70Parr > 90mm = 5.7% (4)2012Number salmon parr = 24Parr > 90mm = 9.1% (2)

2015Number salmon parr = 27Parr > 90mm = 33% (9)But parr were larger: River Dulnain: Site D22River Fiddich : Sites F4/F7

2014# Parr < 90mm = 165# Parr > 90mm = 38Total = 2032015# Parr < 90mm = 25# Parr > 90mm = 30Total = 55

What did we find in 2015?Reduced smolt output ? River Avon & Fiddich smolt traps 2014/15

2015SalmonTroutNumberMean size mmNumberMean size mmParr1961.9107102.5Pre-smolt564101.5227133.4Smolt4,798115.0423153.1

2014SalmonTroutNumberMean size mmNumberMean size mmParr34763.921788.1Pre-smolt673101.2218139.1Smolt13,161115.2306159.3

Salmon smolt run estimate 2014 107,790+/-12,815

Salmon smolt run estimate 201558,097+/-10,740

By way of contrast River Fiddich overall smolt production almost identical in 2014 and 2015 although trap much higher up the system. 2015 salmon smolts noticeably smaller (114.8mm c/w 128mm) and younger R.A. 3.04 c/w 3.23

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SummaryEx Hurricane Bertha provided an opportunity to assess impact of large spateSalmon fry numbers significantly lower at monitored sitesGreater impact at sites where the river bed mobilisedSalmon parr numbers increased but not significantly overallEvidence of displacement /migration of fry and probably parr

Monitoring suggests smolt production affected, although likely to be site specificParr densities lower in spate year +1 but numbers of large parr not affected to same extentEvidence of enhanced fry growth, possibly due to reduced competition fewer despotic parr!

In the Spey spates have an impact on fish densities but the plasticity inherent within juvenile salmon population allows production gap to be ameliorated by spate year +1

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