Assessing the Conservation Status of Salmon in Scotland August 2017

Background

The Conservation of Salmon (Scotland) Regulations 2016 outlined a system whereby the killing of Atlantic salmon in inland waters will be managed on an annual basis by categorising the conservation status of their stocks. Scottish Government made the decision to assess stocks using the best available information and thus allow some killing where sustainable rather than the alternative measures of closing rivers to fishing or enforcing blanket catch and release. This approach hasled to a process of incremental changes in the way the assessments are undertaken but the underlying rationale remains the same: determining whether or not the estimated number of salmon spawning is likely to be above a critical threshold level. Although this overall method is relatively straightforward, managing the uncertainties in this assessment process results in some complexity. ICES1 have developed pragmatic 1 International Council for the Explo- approaches for applying conservation limits and these methods have ration of the Seas been drawn on to construct the system for Scotland. At present the Regulations, in line with advice from NASCO2, 2 North Atlantic Salmon Conservation determine conservation status at the river level, where possible. How- Organisation ever, within-river geographical structuring of salmon stocks with different biology is known to exist and there can be differences in the status of such stocks. This situation is exemplified by the well doc- umented sustained relatively poor status of salmon stocks returning to rivers during the spring months. These spring salmon are provided with national safeguards independent of the Conservation Regulations process and work is underway to investigate how conservation status may be determined for sub-stocks. In the meantime, the Regulations apply to the river as a whole, with local management measures provid- ing additional protection where deemed necessary, for example local voluntary measures put in place to safeguard spring fish. In such cases national and local measures are complementary. Assessments are undertaken at the river level, except in those areas where fishery catch cannot be assigned to individual rivers. Assessable areas also include SACs, which in some cases form only part of a river. The process for each assessable area is summarised below as 5 steps. These steps are carried out for each assessable area for each of the most recent 5 years. assessing the conservation status of salmon in scotland 2

Step 1: Converting Reported Rod Catches to Numbers of Returning Salmon

In Scotland there are a few rivers with fish counters on their lower reaches that can be used to estimate numbers of returning adult salmon directly. In common with other countries, catches of salmon are used to estimate salmon numbers in areas without counters. Dis- cussions around previous assessment models identified a number of issues which would ideally be explored more fully by the assessment process, although many are limited by the availability of data. Here we outline the model for the 2018 assessment which takes a systematic 58 degrees 56.5 degrees 55 degrees approach to model the relationship between catches and stock size in relation to geographic location as well as improving estimates of stock 1.00 size outwith the fishing season. This model has been discussed with 0.75 representatives of the local Fishery Boards and Trusts through the 0.50 Salmon Liaison Group. 0.25 Correction factor (CF) Correction factor 1. New modelling approach. A new, more intuitive, modelling 0.00 Feb Apr Jun Aug Oct approach has been taken and is detailed below. Month

• Rather than directly estimating counts the model instead examined Figure 1: Monthly correction factors (CF) shown for three different the relationship between suggested predictor variables (see below) latitudes. and a correction factor (CF) which is a number bounded between 0 and 1 which can be used to convert catches to counts.3 3 count = catch/CF

• The CF is the catch expressed as a proportion of the count for each month (or set to 1 where catch is greater than count, approximately 2% of observation primarily in October).

• A generalised additive mixed model was used to determine the relationship between the CF and a variety of fixed (month, flow, longitude, latitude, river area) and random effects (year, site, site/month combination, and an identify effect to account for overdispersion).

• Similar to previous models, the CF was found to be related to month and flow rate (Figures 1 and 2). Of the geographic fixed 1.00

effects (longitude, latitude and river area) only latitude was found 0.75 to be a predictor of CF. While it is unclear what the cause of the this relationship is is does fit with anecdotal evidence provided to 0.50 the Salmon Liaison Group by local biologists. 0.25 Correction factor (CF) Correction factor

• In addition to the monthly pattern, higher during the early and 0.00 1 2 3 4 late months, CF can be seen to increase with latitude (Figure 1). Adjusted flow • The CF also increases with flow rate, suggesting that, all other Figure 2: Relationship between flow and correction factor (CF) shown for things being equal, salmon may be less catchable during low flow September. conditions (Figure 2). assessing the conservation status of salmon in scotland 3

2. Number of sites. Ideally the relationship between catches and salmon numbers would be available for a greater number of sites.4 4 Previously information was available Work was undertaken to make data available from: for counters at the following sites: the Awe, Beauly, Kirkcudbrightshire Dee, • River Helmsdale - counter data are available and the fishery North Esk and Pitlochry. owners provided information regarding catches above and below the counter. • River Ugie - counter data provided by the Ugie DSFB for 2014- 2016 (only 2015 having a full year of data) and information regarding catches above and below the counter obtained. • River Morar - it was not possible to use data from the River Morar counter as no information was available regarding the location of catches with respect to the counter. 3. Dealing with small catches. In the previous model the relationship between catch and abundance varied such that the correction was larger for small compared to large catches.

• However, in applying such a relationship generally, it is not possible to differentiate between cases where small catches are the result low proportion caught or simply due to small numbers available. While the data from the sites examined provide good evidence for such variation 5 in the catch/count relationship, they may not cover 5 such a relationship was also found the full range of Scottish rivers and may be a potential source of in the analysis undertaken below but was not used in the final model. error when applied more generally. Therefore a more precautionary approach is taken in the current model where the correction used does not change with numbers caught.

Returns Outwith Angling Season

The method detailed above (using catches to estimate the number of salmon entering rivers each month) does not allow the number of salmon entering outwith the angling season to be estimated. To do so, the pattern of monthly returns at the Awe, Beauly, Dee, Helmsdale, North Esk and Ugie counters were examined6. Figure 3 shows the 6 both the Helmsdale and Ugie have pattern of mean monthly returns, expressed as a proportion of the been added since the 2016 assessment annual total, over the period 2008-2016. There are clear differences among the different sites and discrim- inant analysis was used to determine which counter best described any new sites. In order to do this the rod catches for the 6 counter sites were used as the training data to produce the model used for the classification (Figure 4). The 5 year average monthly catches foreach individual river, expressed as a proportion of their total, were used to predict which counter site best described the observed pattern. Once assessing the conservation status of salmon in scotland 4

Figure 3: Mean monthly counts for 0.4 the 6 counter sites expressed as a site proportion of annual total 2008-2016. River Awe 0.3 River Beauly River Dee (Kirkcudbrightshire) 0.2 River Helmsdale River North Esk 0.1 River Ugie Proportion Count of Annual 0.0 Jan Mar May Jul Sep Nov Month

each new river was allocated to one of the counter sites the following procedures was used to estimate the out of season stock levels.

0.5 Figure 4: Mean monthly catches for the 6 counter sites expressed as a site proportion of annual total 2008-2016. 0.4 River Awe River Beauly 0.3 River Dee (Kirkcudbrightshire) 0.2 River Helmsdale River North Esk 0.1 River Ugie Proportion Catch of Annual 0.0 Jan Mar May Jul Sep Nov Month

For each month during the post-season (up to end December) estimated stock was derived using information estimated using the ap- propriate counter site. For each month a ratio was calculated between that months stock and the stock in the last month of the new rivers fishing season. To estimate stock levels this ratio was applied toesti- mated stock in the last month of the fishing season for the new river. e.g. for rivers where the fishing finishes at the end of October andthe ratio of November to October fish was 0.75 a stock estimate of 100fish in October would produce a stock estimate of 75 fish in November (100 x 0.75). Pre-season estimates (January onward) were undertaken using a similar procedure but using stock estimates from the first full month of the fishing season. assessing the conservation status of salmon in scotland 5

Step 2. Converting Numbers of Returning Salmon to Numbers of Spawning Females

The total number of returning salmon is then used to determine the number of spawning females. The number of female salmon is required in order to estimate egg numbers. This requires information on the number of years spent at sea as the percentage of female fish differs between one sea winter (grilse) and multi-sea winter salmon. Identi- fication of the ages of salmon is not always straightforward andages reported by the rod fisheries have been shown to be unreliable7. Adult 7 Shearer, W. M. (1992). The Atlantic scales from sampling programmes were used to estimate the age struc- salmon: natural history, exploitation and future management.; MacLean, ture of salmon returning to Scottish rivers. J. C., Smith, G. W., & Laughton, R. (1996). An assessment of the grilse error associated with reported Age of Returning Salmon salmon, Salmo salar L., catches from two rod‐and‐line fisheries on the Information on the ages of salmon in Scotland was obtained from sam- River Spey, Scotland, UK. Fisheries ples held by Marine Scotland Science and those provided by Fishery Management and Ecology, 3(2), 119- Trusts and Boards. In total the sea ages of 407171 individual salmon 128. were available from 38 rivers throughout Scotland (Table 1).

Table 1. The number of scale samples (nScales) from each river across site n years.sampled a range of years (years.sampled) used to examine ages of returning Culag 1 1998 salmon. Samples provided by Marine Scotland Science; River Dee Trust; Fhorsa 252 1990;1992-93 Deveron, Bogie and Isla Rivers Trust; Halladale River 78 2001-02 Galloway Fishery Trust; Kyle of Sutherland Fishery Trust; River Naver Kyle of Sutherland 681 1986;1993-1994 Fisheries; Ness and Beauly Fisheries Little Gruinard 79 1990-91;1994;1996 Trust; The Spey Foundation, The Loch Morsgail system 15 1993 Tweed Foundation, West Sutherland Fisheries Trust. Rhiconich River 3 2016 River Annan 39 2000 River Ayr 11 1981 River Beauly 96 2015-16 River Blackwater (Lewis) 57 1987-88;1993 River Bladnoch 136 2007;2011-13;2015-16 River Cree 127 2007;2010-13;2015-16 River Dee 7242 1974-76;1982-86; 1988-89;2011-15 River Dee (Kirkcudbrightshire) 14 2006-07;2012 River Deveron 487 2004-2015 River Dionard 238 1991-92;2001-03;2008 River Doon 72 1981 River Gruinard 289 1990;1994-96 River Helmsdale 452 1994;2000 River Hope 3 1998;2008 assessing the conservation status of salmon in scotland 6

site n years.sampled River Inver 21 1998;2000;2016 River Kirkaig 1 2016 River Laxdale 25 1980 River Laxford 118 1998;2008-09 River Lochy 146 1989-91 River Morar 73 1982;1990-92 River Naver 68 2015 River Ness 223 2014-16 River Nith 149 1981;1991 River North Esk 92148 1963-2016 River Oykel 451 2013-15 River Polla 93 1997-2004;2006; 2008;2011 River Polly 1 2008 River Spey 40596 1970-78;1980-2000; 2011-2016 River Stinchar 60 1981 River Tay 24981 1968-80;1982-96 River Thurso 157 1976-77 River Tweed 36752 1968-78;1980;1982-89; 1991-96;1998-2015 Urr Water 50 2005-07;2011-12; 2016 Water of Girvan 7 1981 Water of Luce 18 2016

This scale data was used to estimate the proportion of one-sea winter fish in different parts of the country.8 The same method was 8 Generalised additive mixed models used to estimate the proportion of two-sea winter (2SW) fish in the were constructed with methods of capture (rod/net), month (as factor), msw fish sampled. longitude, latitude and a smoother for The estimated sea age composition of fish returning to a selection year as fixed effects and river, year as random effects. of rivers in Scotland are illustrated in Figure 5. These age composition data are used to estimate numbers of one-, two-, and three-sea winter fish from total numbers of salmon.

Number of Female Spawners

In order to estimate the number of spawning salmon the numbers re- moved by the fishery and through natural mortality, are subtracted from the estimated number in each of the different ages classes. Re- ported catches of multi-sea winter salmon are assumed to contain the same percentage of 2SW to 3SW salmon as the stock. A catch and release mortality of 10% is assumed and a natural mortality of 9%, assessing the conservation status of salmon in scotland 7

Figure 5: Estimated monthly propor- River Tweed SAC River Ythan River Thurso SAC tion of salmon of different sea ages 1.00 returning to 6 sites in Scotland.

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Proportion 3sw 0.75

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0.00 Feb Jun Oct Feb Jun Oct Feb Jun Oct Month

based on radio tracking studies, is also used. These overall salmon numbers are converted to the number of females using available information from 10 sites throughout Scotland which found that 49.5% of grilse and 71.4% of multi-sea winter salmon were female. assessing the conservation status of salmon in scotland 8

Step 3: Converting Numbers of Spawning Females to Numbers of Eggs

In order to estimate the total number of eggs produced by salmon returning to a river information is required on the number of eggs contained in each female one- and multi-sea winter salmon.

Fish length to number of eggs

The number of eggs produced by a spawning female salmon is known to be relate to a number of factors including their size and age. All the available data on egg contents of individual salmon in Scotland were used to investigate these relationships. Complete information was available from a total of 1115 individuals, although this was not spread evenly by site, with each site containing between 1 and 14 years worth of data (Table 2).

Table 2. The sites where data on the relationship between length, age river Years of Data Samples and number of eggs was available for female salmon. The number of years River Conon 6 332 and numbers of individuals sampled is given. Samples provided by Marine River Dee SAC 11 152 Scotland Science; Cromarty Firth River Nith 1 17 Fishery Trust; Glasgow University; Nith Catchment Fishery Trust; Spey River North Esk 7 299 Fishery Board/Spey Foundation and River Spey SAC 2 58 the Tweed Foundation River Tay SAC 20 206 River Tweed SAC 3 51

The model9 allows egg numbers to be predicted for fish of known 9 Negative binomial mixed model length as shown in Figure 6. with length and sea/river age as fixed effects and year and site as random effects. assessing the conservation status of salmon in scotland 9

Figure 6: General relationship be- 1SW 2SW tween egg numbers and fork length, 20000 smolt and sea age 15000 s1 10000 5000

20000 15000 s2 10000 5000 egg numbers 20000 15000 s3 10000 5000

50 60 70 80 90 50 60 70 80 90 fork length (mm)

Information on length and ages of fish

Information on the lengths of salmon of known ages were available for a subset of the scales samples used to examine fish ages (step 2 above). The number of fish available from each river is given in Table 3.

Table 3. The number of salmon with both age and length information site n years.sampled (n) from each river with the years sampled (years.sampled). Samples Culag 1 1998 provided by Marine Scotland Science; River Dee Trust; Deveron, Bogie and Halladale River 12 2001-02 Isla Rivers Trust; Galloway Fishery Kyle of Sutherland 681 1986;1993-1994 Trust; Kyle of Sutherland Fishery Trust; River Naver Fisheries; The Little Gruinard 66 1990-91;1994;1996 Spey Foundation, The Tweed Foun- Loch Morsgail system 8 1993 dation, West Sutherland Fisheries Rhiconich River 3 2016 Trust. River Annan 37 2000 River Ayr 10 1981 River Blackwater (Lewis) 53 1987-88;1993 River Bladnoch 92 2007;2011-13;2015-16 River Cree 85 2007;2010-13;2015-16 River Dee 6727 1974-76;1982-86; 1988-89;2011-15 River Dee (Kirkcudbrightshire) 5 2006-07 River Deveron 327 2004-2015 River Dionard 213 1991-92;2001-03;2008 River Doon 69 1981 assessing the conservation status of salmon in scotland 10

site n years.sampled River Gruinard 241 1990;1994-96 River Helmsdale 452 1994;2000 River Hope 3 1998;2008 River Inver 21 1998;2000;2016 River Kirkaig 1 2016 River Laxdale 25 1980 River Laxford 106 1998;2008-09 River Lochy 125 1989-91 River Morar 69 1982;1990-92 River Naver 35 2015 River Nith 148 1981;1991 River North Esk 91605 1963-2016 River Oykel 73 2013-15 River Polla 80 1997-2004;2006;2008;2011 River Polly 1 2008 River Spey 40364 1970-78;1980-2000; 2011-2016 River Stinchar 57 1981 River Tay 24962 1968-80;1982-96 River Thurso 153 1976-77 River Tweed 36137 1968-78;1980;1982-89; 1991-96;1998-2015 Urr Water 18 2005-07;2012; 2016 Water of Girvan 7 1981 Water of Luce 18 2016

Estimating eggs in an individual fish

The age and length of the fish detailed in Table 2 were used to estimate the egg content of an equivalent female using the fecundity relationship presented above. This information was then used to ex- plore patterns in the egg content of individual salmon throughout Scotland10. The number of eggs was found to increase through the 10 Generalised additive mixed models year for fish of each sea age class of salmon, with a tendency forrel- were constructed with methods of capture (rod/net), month (as factor), ative egg numbers to be higher in the south of Scotland compared to longitude, latitude and a smoother for the north (Figure 7). There were also differences in egg content be- year as fixed effects and river, year as random effects. tween years, reflecting changes in the sizes of salmon coming backto rivers in different years. This model allows egg contents of individuals to be estimated for months and areas where samples are not available. assessing the conservation status of salmon in scotland 11

Figure 7: Estimated egg content of River Tweed SAC River Ythan River Thurso SAC salmon of different ages in 6 different areas of Scotland. 15000

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5000 seaAge 0 1sw River Creed River Clyde River Annan 2sw 3sw 15000

Estimaetd egg content 10000

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Estimating total egg numbers

The number of eggs for each sea age of salmon can be estimated by multiplying the number of females by the number of eggs in each individual, e.g.:

Eggs(1SW total) = F emales(1SW ) ∗ Eggs(individual) (1)

The total number of eggs is then simply the eggs produced by one- two- and three-sea winter salmon added together:

Eggs(total) = Eggs(1SW total) + Eggs(2SW total) + Eggs(3SW total) (2) assessing the conservation status of salmon in scotland 12

Step 4. Egg Requirement

Determining the egg requirement for a given river involves combining information on the the conservation limit (expressed as eggs per unit area) and the total area available to a given stock of salmon.

Conservation limit

The production of conservation limits relies on the determination of a stock recruitment relationship for a given salmon stock which is then used to estimate a biological reference point to be used in setting a conservation limit. The issues of determining stock recruitment relationships and biological reference points for salmon stocks has been the subject of considerable debate and work.11 Here we summarise 11 e.g.Prévost, É., & Chaput, G. parts which are particularly relevant to their application in the Con- (2001). Stock, recruitment and reference points: assessment and man- servation Regulations. agement of Atlantic salmon. Editions Quae.; Potter, E. C. E., MacLean, J. C., Wyatt, R. J., & Campbell, R. N. Stock recruitment of salmon populations B. (2003). Managing the exploitation of migratory salmonids. Fisheries The salmon lifecycle can be thought of in two stages which show dif- Research, 62(2), 127-142. fering dynamics: Freshwater phase (density dependent)

Nsmolts = f (Nstock) (3) where f is a stock recruitment function Marine phase (density independent)

Nrecruits = γNsmolts (4) where γ is a measure of marine sur- vival There are a large number of different stock recruitment relationships (f ) that can be used to describe the density dependent phase of the salmon lifecycle, with a Ricker curve being one of the most common (Figure 8).

Biological Reference Points

A number of potential biological reference points are available for use in salmon management. These tend to be based on three properties Recruits of the stock recruitment curves, illustrated in Figure 8 using a Ricker relationship. MSY Smax Sr Spawners • Sr (replacement point) Under equilibrium (i.e. without shifts in Figure 8: Common biological refer- natural mortality, carrying capacity or removal by humans) the ence points illustrated using a Ricker relationship (black solid line).The stock will oscillate around this point and it represent an upper replacement line is also shown (black limit to natural spanner numbers. This point exists for all stock broken lice). recruitment curves. assessing the conservation status of salmon in scotland 13

• Smax (maximum recruitment) This is the stock value which equates to the top of a dome shaped stock recruitment relationship (e.g. Ricker) and produces the maximum possible number of recruits. An analo- gous measure can be obtained for hockey stick relationships where the break point defines the change from density independent mortality and the asymptote value where density-dependent mortality does not allow any increase in recruitment. For asymptotic curves such as the Beverton-Holt the maximum recruitment occurs at in- finity so Smax cannot be calculated, although stock sizes which produce a proportion of the theoretical maximum recruitment can be estimated.

• MSY (maximum sustainable yield) MSY is the stock value that maximises the difference between the stock recruitment model and the replacement line.

The use of MSY to set conservation limits is recommended by NASCO. While MSY was developed for harvest fisheries to allow maximum harvest of stocks that is not it’s function when used for salmon management. In order to maximise harvest MSY should be set as a target, i.e. the aim of management is for stocks to be at the MSY point. However, for salmon conservation MSY is used as a lower limit, i.e. the aim of management is for stocks to be maintained above the MSY point. It should therefore be clear that using MSY as a limit reference point for salmon stocks will result in managing for higher stock abundance than would be the case if MSY were used as a target There is limited data available to produce conservation limits for Scottish rivers. In the absence of specific data it is assumed that they fall into the range 1.1 to 9.8 eggs m-2 derived using MSY from inter- nationally monitored rivers at the same latitudes as Scotland12. The 12 Crozier, W. W., Potter, E. C. exception to this in the current assessment is the North Esk where the E., Prevost, E., Schon, P. J., & O’Maoileidigh, N. (2003). A coordi- -2 derived CL of 9.8 eggs m is used. nated approach towards the develop- ment of a scientific basis for management of wild Atlantic salmon in the Area North-East Atlantic (SALMODEL). Queens University of Belfast, Belfast. The wetted area available to salmon for each assessable area has been calculated using the most up to date information on the distribution of salmon from historical records and two recent consultations with local Fishery Trusts and Boards. Each part of the distribution has been classified into loch and river habitat. In Canada different values ofegg deposition requirements are set for fluvial and lacustrine rearing habitat 13. Such information is not available for Scotland and therefore the 13 Crozier et al. 2003 model follows the Norwegian approach in assuming that salmon are restricted to a 10m broad area adjacent to the bank and that the egg requirement for these areas is the same as that for fluvial habitat. assessing the conservation status of salmon in scotland 14

The estimates of total area account for uncertainties in the distribution of salmon and in whether or not salmon are using loch areas using the following method:

U(0, Riverunknown) represents a Rivertotal = Riverpresent + U(0, Riverunknown) (5) uniform distribution with the lower limit set at 0 and the upper limit set at the area of unknown salmon For each loch, areas used are either the 10m broad area from the presence. bank or the total loch area whichever is smaller. Loch areas are then estimated using:

Lochtotal = U(0, Lochpresent) + U(0,U(0, Lochunknown)) (6)

This approach accounts for the uncertainties both in salmon distribution and whether lochs within the designated range are actually utilised by salmon or dominated by other species. The total wetted area is then simply the sum of the river and lochs areas. To further reflect the uncertainty over how salmon use loch areas, each area is assessed with and without loch areas included.

Egg requirement

The egg requirement is simply estimated as the Conservation Limit multiplied by the area. assessing the conservation status of salmon in scotland 15

Step 5. Number of Eggs vs. Egg Requirement

With perfect information, the conservation status can simply be assessed as whether or not the number of eggs deposited by spawning salmon is greater than the egg requirement. However, such perfect information does not exist and there is uncertainty in estimates of the egg deposition, egg requirement and the area accessible to salmon.14 14 A Monte Carlo simulation with For each year/river combination the conservation status is expressed 10,000 simulations is used to account for these uncertainties. Whether or as the probability of meeting the egg requirement. not the egg requirement is met is determined for each iteration and the overall proportion of iterations passed Gradings calculated. This proportion provides an estimate of the probability that the The conservation status of each river/group is defined using the proba- egg requirement for the area has been bilities of meetign the egg requirement over a five year period. Rather met. than a simple pass or fail stocks are allocated to one of the following three grades each with their own recommended management actions:

• Grade 1 At least an 80% mean probability of CL being met in the last 5 years. – Exploitation is sustainable and therefore no additional management action is currently required. • Grade 2 60-80% mean probability of CL being met in the last 5 years. – Management action is necessary to reduce exploitation; mandatory catch and release will not be required in the first instance, but this will be reviewed annually.

• Grade 3 Less than 60% mean probability of CL being met in the last 5 years.

– Exploitation is unsustainable and mandatory catch and release (all methods) for 1 year will be required.

Due to uncertainties over how salmon use loch areas, the rivers are assessed with and without loch areas included. Those grade 3 rivers that would have achieved a higher category without loch areas being included are awarded grade 2. assessing the conservation status of salmon in scotland 16

Worked Example: River Conon

Step 1: Converting Reported Rod Catches to Numbers of Returning Salmon Reported catches

Figure 9: Monthly reported catches 2012 2013 from the River Conon 2012-2016. 500 Released = grey, retained = green 400 300 200 100 0 2014 2015 500 400 300 200 100 0 Reported catch Feb Jun Oct 2016 500 400 300 200 100 0 Feb Jun Oct Month assessing the conservation status of salmon in scotland 17

Monthly flow data

Figure 10: Monthly reported catches 2012 2013 from the River Conon 2012-2016. 1.0 0.5 0.0 −0.5

2014 2015 1.0 0.5 0.0 −0.5 Adjusted Flow Feb Jun Oct 2016 1.0 0.5 0.0 −0.5

Feb Jun Oct Month assessing the conservation status of salmon in scotland 18

Monthly correction factors

Figure 11: Estimated monthly correc- 2012 2013 tion factors (CF) for the River Conon 1.00 2012-2016. 0.75

0.50

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Monthly stock estimates

Figure 12: Estimated number of 2012 2013 salmon returning to the Rive Conon during each month 2012-2016. Red filled boxes indicate out of season 7,500 estimaets where rod catches are not available. 5,000

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Annual estimated stock

Figure 13: Estimated annual number of salmon returning to the River Conon 2012-2016.

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2012 2013 2014 2015 2016 Year assessing the conservation status of salmon in scotland 21

Annual catch as a proportion of stock

0.25 Figure 14: Annual reported catch expressed as a proportion of annual stock estimate for the River Conon 2012-2016. 0.20

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Step 2. Converting Numbers of Returning Salmon to Num- bers of Spawning Females Ages of fish

Figure 15: Estimated monthly sea age composition of salmon returning to 1sw 2sw 3sw the River Conon during 2012-2016.

2012 2013 1.00 0.75 0.50 0.25 0.00 2014 2015 1.00 0.75 0.50 0.25 0.00 Feb Jun Oct Proportion of salmon 2016 1.00 0.75 0.50 0.25 0.00 Feb Jun Oct Month assessing the conservation status of salmon in scotland 23

Monthly number of spawning females

Figure 16: Estimated monthly number 1SW 2SW 3SW of spawning females returning to the River Conon during 2012-2016 broken 6,000 down by sea age. 2012 4,000 2,000 0 6,000 2013 4,000 2,000 0 6,000 2014 4,000 2,000 0

Estimated number 6,000 2015 4,000 2,000 0 6,000 2016 4,000 2,000 0 Feb Jun Oct Feb Jun Oct Feb Jun Oct Month assessing the conservation status of salmon in scotland 24

Step 3: Converting Numbers of Spawning Females to Num- bers of Eggs Egg contents of females

Figure 17: Estimated monthly egg content of individual salmon returning age 1sw 2sw 3sw to the River Conon during 2012-2016 shown by sea age.

2012 2013 15000 10000 5000 0 2014 2015 15000 10000 5000 0 Feb Jun Oct Number of eggs 2016 15000 10000 5000 0 Feb Jun Oct Month assessing the conservation status of salmon in scotland 25

Monthly number of eggs

Figure 18: Estimated monthly number 1SW 2SW 3SW of eggs produced by salmon returning to the River Conon during 2012-2016 shown by sea age.

10,000,000 2012

5,000,000

10,000,000 2013

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10,000,000 2014

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10,000,000 2015 Estimated egg numbers 5,000,000

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0 Feb Jun Oct Feb Jun Oct Feb Jun Oct Month assessing the conservation status of salmon in scotland 26

Total annual egg numbers

Figure 19: Estimated annual egg production of salmon returning to the 40,000,000 River Conon during 2012-2016.

30,000,000

20,000,000

10,000,000 Estimated egg numbers

0 2012 2013 2014 2015 2016 Year assessing the conservation status of salmon in scotland 27

Step 4. Egg requirement Table 4. Areas of salmon habitat in the River Conon broken down by category square meters type. Rivers with Salmon 2457814 Rivers unknown salmon 325447 Lochs with salmon 911461 Lochs unknown salmon 113761

Figure 20: Estimated annual egg requirement for the River Conon 30,000,000 during 2012-2016.

20,000,000

10,000,000 Egg requirement

0 2012 2013 2014 2015 2016 Year assessing the conservation status of salmon in scotland 28

Step 5. Number of Eggs vs. Egg Requirement Table 5. The percentage probability that the egg requirements have been year Assessment with loch area Assessment without loch area reached for the years 2012-2016 in the River Conon. Also presented is the 2012 95.84 99.44 mean value over the past 5 years. 2013 86.60 96.05 2014 46.08 56.29 2015 75.40 88.14 2016 72.64 85.40 Mean 75.31 85.06

The mean probability of the egg requirement being met falls between 60-80% and the the Conon is therefore Grade 2.