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Age and Growth 


Grayling Scale

 

The easiest way to age relatively young grayling is by taking a scale sample for examination under a low powered microscope or microfiche. 

Scales develop when grayling reach a length of 33-40mm (1,2). Scales first begin to form along the lateral line close to the caudal fin (2,3,4,5). They provide protection to the grayling and the ridges on their surface have a show pattern of wide summer rings and narrower winter rings.

 

Grayling become more difficult to age from scales as they get older because their rate of growth decreases and the distinction between summer and winter growth becomes more difficult.

 

Grayling in some waters have a relatively short life span of 3-5 years, but other populations are longer lived. Particularly old individuals can be found at higher latitudes and altitudes with associated lower water temperature (6). Males often mature at a lower mean age than females.

 

Scales grow as the grayling grows, although not exactly in proportion to the fish size. Appropriate correction for this allometric growth allows fisheries scientists to calculate the size of the fish at the end of each year's growth. This is called back-calculation. Growth in length is fastest in the first year and decreases as fish age. Grayling in the UK become sexually mature between 2 and 4 years old. Male grayling grow faster than females, this often becomes evident with the onset of sexual maturity, and the terminal length (Linfinity) is usually greater in males.

 

Many factors abiotic and biotic affect the growth rate of grayling including; temperature, flow, food availability, population density and predation.

 

Grayling growth curve (Britton 200&)

 Graphical presentation of reference grayling growth rate bands and expected growth curve as described by Britton (2007), based on UK populations. 

 

 

References 

1 Wootton, R.J. (1990). Ecology of teleost fishes. Chapman and Hall. Fish and Fisheries Series 1.

2 Taylor, R.J. (2012). Applications of fish scale analysis to understand growth dynamics of fish populations.

PhD Thesis. University of Hull.

3 Brown, C.J.D. (1943). Age and growth of Montana grayling. Journal of Wildlife Management 7,        

353 - 364.

4 Gustafson, K.J. (1948). Movements and growth of grayling. Report of the Institute of Freshwater

Research, Drottningholm 29, 35 - 44.

5 Peterson, H.H. (1968). The Grayling, Thymallus thymallus (L.), of the Sundsvall Bay area. Institute of

Freshwater Research, Drottningholm 48, 36 - 56.

6 Cihar, J. (1998). Freshwater Fish. Blitz Editions.

7 Britton, J.R. (2007). Reference data for evaluating the growth of common riverine fishes in the UK.

Journal of Applied Ichthology 23, 555 - 560.


 

Latest News

New DNA study needs Anglers help!

In 2008/09, anglers collected over 1100 grayling adipose fin clip samples from 27 catchments the UK. The samples were used to extract DNA and for the first time, help us understand the genetic make up and diversity of grayling across the UK. This information was later used to influence stocking of UK grayling (Summary).

We now have another genetic study and need new samples. However, instead of fin clips we will be using swabs (cotton buds) to collect DNA from the mouth and gill cavity. The sampling invloves taking a swab of the mouth and gills of fish, an estimate of fork length and condition of the fish and a record of the date and geographic location. We need a minimum of 30 samples per catchment. If you feel you are able to contribute samples to the project, please contact us. Further details.

More News ...

 

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