Monitoring Changes in the Tweed Brown Trout Population
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Monitoring Changes in the Tweed Brown Trout Population
2014 Brown Trout Catches
• Anglers reported having an exceptional first half to the trout season in 2014
• “Best for a long time”
• Some anglers had evenings where they caught over 30 trout over 10”+ (25cm) in only a couple of hours
• Complaints about there being “naetroot” went down dramatically (but some still persisted with some anglers)
Trout Log Book Scheme
• Started in 2006
• Given our with season tickets
• Get around 50 - 80 returns each year
• www.anglingdiary.org.uk
• 500 - 1,000 fishing trips
• 1,500 - 3,000 hours of fishing effort
• 2014 catch records confirmed angling reports
Oversize (25cm+) Brown Trout Ave. Annual CPUE/4H – 2006 to 2014
2014 = 16 anglers, 197 fishing trips, 627 hours of fishing effort
Oversize (25cm+) Brown Trout Annual CPUE/4H – 2006 to 2014
2014 = 17 anglers, 204 fishing trips, 644 hours of fishing effort
Oversize (25cm+) Brown Trout Annual CPUE/4H – 2006 to 2014
2014 = 14 anglers, 115 fishing trips, 370 hours of fishing effort
Oversize (25cm+) Brown Trout Annual CPUE/4H – 2006 to 2014
2014 = 10 anglers, 59 fishing trips, 181 hours of fishing effort
Oversize (25cm+) Brown Trout Annual CPUE/4H – 2006 to 2014
2014 = 6 anglers, 26 fishing trips, 83 hours of fishing effort
Monthly Variations – Lower Tweed
Trout Size – Lower Tweed
Scale Sampling• Made an appeal in 2014 for
scale samples for sex ID
• Therefore got more samples than normal
• One Lower Tweed angler took samples from every “oversize” trout he caught
• 64 scale samples collected
• Able to age the trout which made up the extra catches in 2014
Scale Results
• Mix of 2 and 3 winter trout but majority (90%) of the trout had one thing in common
• They had just spent their first full summer and winter in the larger channels of the Tweed system
• Previous years main stem/larger tributaries parr)
• For some reason these trout appear to have experienced survival which was far greater than normal/average
Typical 2014 season Brown trout
26cm Brown Trout April 2014, 3 winters
27cm Brown Trout May 2014, 2 winters
2014 Lower Tweed Brown Trout25 – 35cm
River Winters Number %
0 1 2
1 47 89
2 5 9
3 0 0
0
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100
0 1 2 3
Pe
rce
nta
ge
River Winters
Lower Tweed Scale Read River Winters 2014 - 25cm-35cm Brown Trout (sample of 53 trout)
Gala Fish Counter Results –Brown trout 20-40cm
Gala Fish Counter Results – Trout
0
50
100
150
200
250
300
350
Nu
mb
er
Re
co
rde
d
Length - 5cm Length Class
Gala Fish Counter Trout Length frequency Chart - 2014
0
50
100
150
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350
Nu
mb
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co
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d
Length - 5cm Length Class
Gala Fish Counter Trout Length frequency Chart
Ave. 2008-2013
2014
Year 2008 2009 2010 2011 2012 2013Ave.
08-132014
Trout Recorded 20cm - 40cm
381 377 232 559 239 304 350 873
Why such good survival?
• Short, mild winter (2013/2014)? – Good survival of Grayling recorded too
• Poor survival of previous 1st River Winter Brown trout? –prolonged winter 2012/2013 (scale reading)
• Change in migration? – prolonged winter 2012/2013
• Predators? – overwintering Goosander numbers dropping
• Other factors?
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