Freshwater · Trolling season mainly November to July under Shiga prefecture permit rules
Biwa Trout
Oncorhynchus masou rhodurus
The biwa trout is a landlocked subspecies of masu salmon found only in Lake Biwa — and nowhere else. It is listed as Near Threatened (NT) on the Environment Ministry Red List, and its fishery runs under Shiga prefecture rules with a permit and a set season. From boats it is taken mainly by trolling (hikinawa) from winter into early summer.
Seasons · Peak
Identifying features
- Streamlined salmon body, silvery with darker back, like a lake-going masu salmon
- Black spots on the upper body, fewer and fainter than in river yamame
- Parr marks faint or absent in open-water adults
- Deep-pink to red flesh when cut, a famed trait of this fish
- Occurs only in Lake Biwa — any similar trout elsewhere in Japan is not this subspecies
Habits
- Landlocked subspecies of masu salmon found only in Lake Biwa
- Feeds mainly on small fish such as wakasagi and juvenile fish in open water
- Moves between deep cold water and shallower areas with the seasons
- Spawns in autumn in rivers flowing into the northern lake
- Fishery is regulated: a Shiga prefecture permit and set season apply
Distribution
Regional coverage expanding
Where to find them
- Deep northern basin of Lake Biwa off Nagahama, Shiga
- Open water around Chikubu Island in northern Lake Biwa
- Northern Lake Biwa off the Hikone coast, Shiga
Where they live
How to catch them
Trolling (hikinawa) the northern basin Lake
Rig: Boat trolling rods with spoons or plugs behind depth-control weights, trolled slowly over the deep northern basin
Bait/lure: Trolling spoons and small plugs
Key tip: Depth is everything: keep lures in the temperature layer where wakasagi schools are marked on the sounder.
Trolling off river mouths Lake
Rig: Trolling gear as above, worked in long passes off the mouths of inflowing rivers in the northern lake
Bait/lure: Fish-profile plugs and spoons
Key tip: Work dawn and dusk and wind lanes; biwa trout hunt small fish near the surface in low light.
Best baits & lures
Baseline setup
- Rod: Boat trolling rods, often used in pairs with planer-style spreading in local hikinawa practice
- Line: 10-16 lb line suitable for trolling, with long leaders
- Terminal: Trolling spoons, plugs, dodgers and depth-control gear (weights or downriggers)
Recommended gear for this species
Rod · Best value
9' 5-weight fly rod outfit
≈ US$180-260
Covers chironomid lakes and small rivers with one setup.
Flies · Budget
Chironomid assortment (30 patterns)
≈ US$25-40
Chironomids are 60% of a lake rainbow's diet in spring.
Picks come from our rule library — never paid placements. Prices are guides; affiliate links may earn us a commission.
Typical size
Common 16-24 in (40-60 cm); large fish to about 28 in (70 cm)
On the table
Excellent and highly prized — rich, deep-pink flesh unique to Lake Biwa; eaten as sashimi and in local Shiga dishes. Only legally permitted fish should be kept.
Similar species
Regulations vary by area and can change in-season — always check the official rules for your area before you fish. Regulations guide →
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