The Menai Strait and the Swellies
Tidal race · Salt water · in Anglesey
A twenty-five-kilometre tidal channel separating Anglesey from the Welsh mainland, narrowing at the Swellies between the two bridges to a few hundred metres of rock-strewn channel with submerged reefs and islets in the middle of it.
Safety: moving water and currents — can cause serious injury or death. 3 more points apply here.
FishingHQ describes what this place is. It does not say whether you may fish it: access rights, permits, licences, byelaws, closures and protected areas all apply, all differ and all change. Who to ask is below.
Also associated with this ground
Recorded as present here without a documented method or strength behind them.
European sea bass · Pollack · Atlantic mackerel · Thick-lipped grey mullet · Blue mussel · European flounder
How people fish it
Practised here: Sea fishing, Kayak fishing.
Methods the sources name for this ground. Each one is explained in full on its own page.
- Spinning
Casting an artificial lure and retrieving it so that it moves like something alive — the most direct form of lure fishing.
- Float fishing
Suspending a bait at a controlled depth beneath a buoyant indicator — the most visual, most controllable and most widely applicable method in angling.
- Ledgering
Fishing a bait on the bottom held by a weight, with no float — the simplest way to fish at distance, in depth, or in wind.
The ground and the water
- The ground
- A twenty-five-kilometre tidal channel separating Anglesey from the Welsh mainland, narrowing at the Swellies between the two bridges to a few hundred metres of rock-strewn channel with submerged reefs and islets in the middle of it.
- Exposure
- Sheltered from ocean swell along its whole length. Every hazard here is tidal rather than meteorological, which is precisely why it catches people out.
- Depth
- Deep and scoured through the narrows; extensive drying sand and mussel ground at both ends.
- Tide and flow
- The defining feature and one of the most complex tidal regimes in Britain. The strait fills from both ends at different times, so the streams meet, reverse and run at up to eight knots through the Swellies, with whirlpools and overfalls around the mid-channel rocks. There is a very short window of workable water and it moves daily.
Through the year
Bass through the warmer months, which the strait is well documented for; mullet in summer in the sheltered reaches; flatfish and whiting through the colder half. Historically and currently one of the most important mussel grounds in Britain.
Safety
Moving water and currents — Can cause serious injury or death
Streams of up to eight knots through a rock-strewn channel, with whirlpools, overfalls and an unusually short slack window. The strait fills from both ends, so 'the tide' here does not behave the way a tide table teaches, and a craft that misjudges the timing is committed.
What reduces it: Plan entirely from tidal stream data for the Swellies specifically rather than from tidal height, transit only at the recognised slack window, and treat local pilotage knowledge as a requirement rather than an advantage.
Worse when:
- On spring tides, when the streams are strongest and the slack window shortest.
Cold water shock — Can cause serious injury or death
UK coastal and inland water is cold enough for most of the year to trigger the involuntary gasp and the loss of swimming ability that decides most immersion deaths, and it does so within the first minute, long before hypothermia is relevant.
What reduces it: Wear a buoyancy aid rather than carry one, carry a means of calling for help on the person rather than in a bag, and plan on the assumption that an unplanned entry into the water is survivable only if somebody knows immediately.
Tides and being cut off — Can cause serious injury or death
The flood fills the ground behind an angler before it covers the ground in front, so the water arrives between them and the shore while the position they are standing on is still dry.
What reduces it: Read the tide table before going rather than after arriving, set a leaving time from the tide rather than from the fishing, and identify the exit and how long it takes while the ground is still uncovered.
Cliffs and rock platforms — Can cause serious injury or death
Rock marks on the north and west coasts take swell generated over a long Irish Sea fetch, and a set considerably larger than the prevailing sea can arrive without warning. Falls from wet rock and being swept from a platform are the mechanisms.
What reduces it: Watch a mark for a full set before committing to it. Wear a buoyancy aid on any rock platform. Never fish a rock mark alone in swell, and treat a forecast that mentions swell separately from wind as the one that matters.
Worse when:
- Swell arriving from a distant system in otherwise calm local conditions
- Rising tide on a platform with a single exit
- Night fishing on unfamiliar rock
Rules and access
FishingHQ does not know the current access position here. Shore angling in Wales is not rod-licensed, but access rights, landowner permission, local authority and harbour byelaws, national and inshore fisheries measures, and site designations all apply and all change. Check the current position with Natural Resources Wales, the harbour or local authority, and the landowner before going.
Particular to this water: Shellfish harvesting areas are classified for food safety and are opened and closed on monitoring results a gatherer cannot see. Neither cooking nor appearance removes a biotoxin. Check the current classification with the local authority before taking anything. This ground carries conservation designations that constrain access, vehicles, bait collection and disturbance independently of any fishing rule.
Who holds the answer:
- Natural Resources Wales, which administers marine and fisheries regulation in Welsh waters.
- The local authority and, where one exists, the harbour authority, for access, byelaws and shellfish classification.
- The national fisheries authority for Wales, for sea fisheries measures, licensing and enforcement.
- The inshore fisheries and conservation body for the area, for local byelaws, closed areas and gear restrictions.
- The food safety authority and the local authority, for shellfish bed classification and closures, which change continually.
- The harbour authorities and the port authority for the strait, for navigation, launching and access.
- The maritime and coastguard agency and the lifeboat service, for safety information and rescue in an area with genuine tidal hazard.
- The landowner, club or fishery, for permission to fish any freshwater on the island.
- The harbour authorities at either end of the strait, for navigation.
Nearby fishing
Other publicly documented places within about 40 km, by distance. Positions are approximate public geography and are never exact marks.
- Caernarfon and the Menai south entrance — 10–25 km · Tidal channel
- Penmon Point — 10–25 km · Headland
- Llanddwyn Island — 10–25 km · Island
- The Conwy estuary — 10–25 km · Estuary
- Llyn Alaw — 10–25 km · Reservoir
- Point Lynas — 10–25 km · Headland
- The Great Orme — 10–25 km · Headland
- The Conwy at Llanrwst — 25–40 km · River reach
Sources for this place
- JNCC species and habitat conservation advice — Joint Nature Conservation Committee (Conservation authority)Relied on for: Description, designation and habitat characterisation of the named coastal and marine features of the United Kingdom, and the species characteristically associated with them.States this directlyCitation checked — the work exists and is described correctly
- Cefas science, advice and data on marine and freshwater environments — Centre for Environment, Fisheries and Aquaculture Science (Government fisheries body)Relied on for: Marine environmental science for UK shelf seas: sediment characterisation, estuarine process, shellfish bed distribution, tidal range and the monitoring that describes them.States this directlyCitation checked — the work exists and is described correctly
- Met Office shipping forecast, inshore waters forecast and marine warnings — Met Office, United Kingdom (Government fisheries body)Relied on for: That inshore waters forecasts, sea state and swell are the operative inputs for shore and small-craft decisions in these waters.States this directlyCitation checked — the work exists and is described correctly
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Long-running published description of British sea angling practice by region, ground type and named mark.FishingHQ's interpretation of what it saysCitation checked — the work exists and is described correctly
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated public descriptions of which places are conventionally fished and how, recorded as practitioner consensus rather than as scholarship, and not relied on for access, permission or any current rule.Background and mechanism onlyCitation checked — the work exists and is described correctly
- RNLI water safety guidance: cold water shock and Float to Live — Royal National Lifeboat Institution (Water-safety or diver-training authority)Relied on for: Cold water shock and the immersion response, tidal cut-off, and water-safety guidance for shore anglers and small-craft users.States this directlyPassage read and verified
How FishingHQ labels evidence is explained in the evidence policy. Last reviewed 2026-08-16.