1.
Coarse Fish Scale Reading
Gareth D Davies
National Fisheries Service
Technical Officer 1
March 2015

2.
Why age coarse fish?
WFD
Age structure of fish populations
Core Fisheries Monitoring Programme
Pre/ Post-Habitat Rehabilitation
Stock Assessments
Project Work
Climate Change
Invasive Non-Native Species

3.
Structures used in age determination
Pharyngeal
teeth
Operculum
Fin rays
Otolith
Scales Vertebrae

4.
Scale Morphs

5.
Scale Proportion Hypothesis

6.
Advantages of Back-Calculation
0
200
400
600
800
1000
1200
1 2 3 4 5 6 7 8
NumberoffishusedtocalculateMLA
Age

7.
Advantages of Back-Calculation
0
200
400
600
800
1000
1200
1 2 3 4 5 6 7 8
NumberoffishusedtocalculateMLA
Age

8.
0
50
100
150
200
250
1 2 3 4 5 6 7 8
Length(mm)
Age (years)
Annuli
oMLA
Advantages of Back-Calculation

9.
Growth Performance
0
100
200
300
400
500
600
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Length(mm)
Age (years)
Fast
Very fast
Average
Slow
Very slow
R.Waverney
Percentage standard growth = 110%
x

10.
Example 1. Salmonid Scale

11.
Example 2. Coarse Scale

12.
Fishery Management

13.
Fishery Management
3+ ?

14.
Fishery Management
1+ !

15.
Case Study
Chub (Leuciscus cephalus)
Long lived species – 20+ years
Multiple/ protracted spawing
Length @ end of 1st growing season ranges
from <25 mm to > 70 mm
Can lead to errors in scale analysis

16.
Case Study
193 mm 196 mm

17.
Thank you
Any questions?
Twitter: @GarethDDaviesEA
E-mail:Gareth.d.davies@environment-agency.gov.uk

18.
Chub
365 mm
13+

19.
Chub
365 mm
13+

20.
Barbel
565 mm
21+