The lake at Cwmystradllyn
Pwllheli & District Angling Association
Pwllheli & District Angling Association
Pwllheli & District Angling Association

Cwmystradllyn Reservoir

Located in the Snowdonia National Park and regarded as one of Wales' most picturesque lakes. Llyn Cwmystradllyn is fed by several mountain streams and supplies drinking water for the Llŷn Peninsula.

Llyn Cwmystradllyn is truly the location for those who like to fish in wild places. H. M. Gallichan described Cwmystradllyn as a "lake charmingly situated in a green oasis among savage hills."

The reservoir is fished by any method. However, because it is the main water supply for Dwyfor and Eifionydd catchments, there is a strict "no maggot fishing or ground baiting" rule. The worm can be very effective after heavy rainfall, especially by the small feeder streams.

On the whole the water is gin-clear and this can be very productive for fly fishing. Flies that usually produce are: Hawthorn, Heather, Peter Ross, Dunkeld, Invicta, Haul a Gwynt, Mallard & Claret and Black Pennell.

It pays to experiment and the angler who really perseveres will be the most successful.

The lake offers fishing for wild Brown Trout and quality, regularly stocked Rainbow Trout. The Rainbow Trout season extends from March 20th until October 31st, while the Brown Trout season runs from March 20th to September 30th.

An Environment Agency Coarse and Trout Licence is required to fish this water and can be obtained on line at the Environment Agency Website or from your Post Office.

As well as fishing, you can enjoy the rugged upland scenery and varied wildlife of this beautiful valley.


Members are obliged to observe these rules:

  • No cleaning of fish to take place at the lakeside or anywhere in the area surrounding the lake.
  • No fishing before 8.00am and fishing must cease one hour after sunset.
  • Fishing by fly, spinner and worm using single baited hook. Strictly no maggots or ground baiting.
  • Float tackle must not be used with flies.
  • Six fish limit. When the limit is reached, fishing must cease.
  • The dam is for access only. No fishing from the dam.
  • No swimming.
  • No Booby flies.
  • No fish less than 8.5 inches or 21cm must be kept. All undersized fish must be returned unharmed.
  • Spinners with only one treble hook can be used at the lake.

Breach of rules

Anyone found breaking any of the Associations rules or abusing any of the privileges granted to the Association shall be reported to the Executive Committee who will decide what action shall be taken against the offender.

Enjoy your fishing at Cwmystradllyn.