Each of the six lakes we cover has its own season, and they barely overlap. Spring is for trophy bass on Biwa and Kasumigaura, autumn for numbers of bass and Inawashiro's heaviest smallmouth, and winter belongs to wakasagi, from Suwa's heated dome boats and, when the ice allows, through the ice at Ogawara. This calendar shows what's worth planning around in each month. The details, and the rules, are in each lake's own guide.
The year at a glance
- Trophy bass: spring, March to May, on Biwa and Kasumigaura. May is the month most Biwa guides point to.
- Smallmouth bass: Inawashiro, May to November, with the heaviest fish in autumn.
- Numbers of bass: autumn, September to November, on Biwa and Kasumigaura.
- Wakasagi from a heated dome boat: Suwa, roughly late September to March, busiest from December to mid-February.
- Ice fishing for wakasagi: Ogawara (Anenuma), roughly mid-January to early March, only when the ice is safe.
- Salmon: Saroma, pink salmon from summer and chum salmon into autumn.
- Hand-gathering shijimi clams: Ogawara, July 1 to August 31 (2026 dates).
Ice seasons, dome-boat opening days and gathering areas are set fresh each season, and warm winters have cancelled ice fishing outright. Use this calendar to pick a month, then check the lake's own guide and the official notices it links to before you book.
January and February
The coldest months. Bass slow right down, and the action moves to wakasagi, on heated boats and on the ice where it holds.
Peak season for Suwa's heated dome boats, so book ahead for weekends. Some areas close to protect spawning fish from January 1.
Anenuma's managed ice-fishing ground usually opens from mid-January, but only while the ice is safe. In 2026 the cooperative cancelled ice fishing on Uchinuma altogether, so check Ogawara's notices first.
Inawashiro itself doesn't freeze, but the same cooperative runs ice fishing on nearby Lake Akimoto when it can. In 2026 that window lasted barely a week in February.
Bass on Biwa hold in deep water and around structure, especially in the north basin. Bites are few, but a quiet winter day can still turn up a very big fish. Biwa trout are open, by approved boat or charter.
In cold winters, parts of Saroma freeze and people fish for chika through the ice. Ask locally before walking out.
Slow for bass on Kasumigaura, and wakasagi are closed from January 21 to February 28.
March and April
Spring arrives from the south. The wind can be the biggest obstacle, especially on Biwa.
The biggest bass start moving in March, and spawning gets going from mid to late April. Biwa's shallow south basin warms first, and the north basin runs a few weeks behind. Early spring brings the strongest hira-oroshi winds on Biwa.
Flounder fishing on Saroma starts around March and builds through April.
Iwana and yamame open on April 1 at Inawashiro.
Families start fishing for ko-ayu from Biwa's harbors and river mouths from around April.
May and June
Arguably the best all-round months, if you can avoid the Golden Week crowds in early May.
May is the month most Biwa guides point to for a big bass. Ko-ayu peak from May to July.
Heavy pre-spawn smallmouth move onto shallow sandy flats around 2 m deep at Inawashiro. The Japan-record fish came in late May.
Flounder peak from April to June, and the ports get busy around Golden Week.
Bass recover after spawning, and one local guide rates mid-June to mid-July as the most fun stretch of the year on Kasumigaura. Carp are closed from May 11 to June 10 and wakasagi from May 1 to July 20.
July and August
Hot, humid and best early or late in the day.
Ogawara opens its shijimi area from July 1 to August 31 (closed August 13–16 in 2026). Hands only.
Pink salmon arrive at Saroma from summer. Early morning is the classic window, and some river mouths are closed, so check the notices.
Thick weed in Biwa's south basin makes it a game of edges and holes. Ayu are protected from August 21, with rod fishing allowed until August 31.
Little shade on Kasumigaura, so fish the low-light hours and moving water near the sluice gates. The traditional sail-trawling boats sail for visitors from late July.
September and October
Autumn feeding starts, and the wakasagi season opens.
Bass feed up before winter and are easier to catch. Local anglers on Kasumigaura often single out September. Biwa trout close from October 1 to November 30.
Autumn smallmouth at Inawashiro are at their heaviest, fished deep through the day and in the shallows at dawn and dusk. Iwana and yamame close on September 30, and wakasagi run from October.
Shore fishing for small wakasagi is at its best in early autumn, and Suwa's dome boats start between late September and October.
Chum salmon follow the pink salmon into autumn at Saroma.
November and December
The switch from autumn to winter.
Autumn patterns give way to winter ones on Biwa. Biwa trout reopen in December for approved boats and charters.
Dome boats on Suwa are in full swing, and weekends fill up from December.
The smallmouth season at Inawashiro runs to the end of November.
Smelt and cod season starts on Saroma in December.
Nothing to fish on the ice yet. Keep an eye on Ogawara's notices for the coming season.
Every season and date here comes from our lake guides, which link the official sources behind them: the fisheries cooperatives, prefectural rules and the operators themselves. Closed seasons are those in force for 2026, and the Suwa opening day is for the 2026–27 season. Check the guide for your lake, and its sources, before you book.
Pick the month, then the lake, then check that lake's notices the week you go. Seasons here move with the weather, not the calendar.
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Once you've picked your month, our app scores each day for all six lakes and shows the feeding windows, so you can choose between Saturday and Sunday. It's worth checking alongside the weather, not instead of it.
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