Grayling Biology

Thymallus thymallus

Environment. Broken Water. Fast flowing gravel Bottom Rivers with good oxygen content. Very sensitive to pollution, so water must be clean.
Known to live in some still waters but are usually there as a result of stocking! Fish are howerever known to move from the river system to connecting lake. A good example is the Welsh Dee system when the fish move into lake Bala.
No recorded evidence of fish breeding in still water environment in Uk.

Its cousin the Artic grayling is known to inhabit salt water lake systems.

Diet
Worms. Various Grubs. Pupa. Most freshwater Lava. Water daphnia. Fresh water shrimp. Almost all fly life. Fish eggs/frogs eggs. Cased caddis.

Feeding Conditions.

Clear fined water. Slight warmth will encourage surface feeding (dry fly). Colder conditions encourage bottom feeding. Although a grayling is known to be triggered on occasion in these conditions to a well presented dry over a known run.

Spawning

Spawning requires Photo increasing period 'As Days get longer' March -June
Good mix of well oxygenated water on gravel With some weed cover.

Egg development

Pictures of grayling larvae development week by week.

Larvae1

Larvae2

Larvae3

Larvae4

Larvae5

Larvae-hatching

Larvae-with-yolk-sac

Newly-hatched-larvae

Yolk sac-almost gone

Fish Sexing

Hen fish Dorsal fin Picture

Note more rounded edge to dorsal fin

Female dorsal Fin

Note dorsal fin structure compaired to male. Also note anal /egg orafice protrudes on female fish!

Male dorsal fin Pictures

Note Colour and concave edges. Fin larger, and is used to hold female fish when spawning.

Male Dorsal Fin

Life Span
Up to Seven years in UK. (It has been documented that some fish live longer than this but these are the rare exception)

Growth rate in first year

up to 4 inches

Max life span Suggests 14 years in some countries ( information will be updated as fact emerge!0

Protection.
Slime membrane. (This is why wet hands should always be used when handling fish, It helps to preserve this layer when Handling)
Large Scales.
Bottom dweller.
Broken water/ fast water for cover and protection from predators.

Predators
Cormorants, Mergansers, Goosanders, Heron, Pike, Pearch when fish are small. Large Brown trout, Sea trout and Salmon may also eat smaller Grayling fry. Man. King fishers eat small fish and fry, as do Magpies.

Grayling Hunter wishes to thank the Environment agency for the above pictures taken at Calverton Fish Farm. A special thanks to Alan Henshaw who's guidence whilst creating this Grayling biology page has been Invaluable. All pictures on this page remain the property of Alan Henshaw/Environment agency.