Mayfield Reservoir

In 2025, WDFW logged 19 release dates at Mayfield Reservoir, spread over 5 months from Apr 3, 2025 to Aug 26, 2025. That is about 3,419 fish a date.

WDFW data through Oct 30, 2026. Page updated November 5, 2026.

Key information

Size: 2,021.9 acres, 428 ft above sea level
Where: About three miles west of Mossyrock.
Bank fishing: Rated good, though public access is limited. Fair shore fishing at Ike Kinswa State Park and the Mossyrock Trout Hatchery.
Boats: Lewis County park off US-12, Ike Kinswa State Park and a private resort.
Stocking, per WDFW: Managed for catchable rainbow trout; surplus hatchery coho and fall Chinook may be added.
Fish listed: Rainbow trout, coastal cutthroat, coho, Chinook, largemouth bass, tiger muskie, yellow perch and others.
Rules to check: Two-pole fishing is NOT allowed here. WDFW lists the water as Mayfield Lake, a reservoir formed by Mayfield Dam.

From the WDFW page for this water, read on November 5, 2026. Access, rules and closures change, so check that page and the current fishing rules before you go.

Mayfield Reservoir in numbers

catchable trout in 2025: 64,970
so far in 2026, through Oct 30: 72,001
2025 against the 2015–2025 average of 65,546 a year: −1%

2026 is running close to 2025: 72,001 fish through Oct 30, against 64,970 by the same date a year earlier. The latest batch, 2,220 rainbow trout, went in on Aug 25, 2026, 72 days before this page was built.

WDFW lists Mayfield Reservoir as 2,021.9 acres in Lewis County, at 428 ft. The 2025 releases work out to about 32 catchable trout per acre here; 30 of the 37 waters on this site with a WDFW acreage were stocked more densely. It is the larger of the 2 Lewis County waters on this site.

Release log

Every release since January 2025

38 species-date records, newest first. Fish per lb is the figure WDFW reports for each batch.

Latest batch, Aug 25, 20262,220rainbow trout, 15 oz each

Summer 2026

Aug 25Rainbow trout2,2201.1 per lb · avg 15 oz

Aug 19Rainbow trout2,3201.2 per lb · avg 13 oz

Aug 11Rainbow trout2,5201.3 per lb · avg 12 oz

Aug 5Rainbow trout2,5051.3 per lb · avg 12 oz

Jul 29Rainbow trout2,6601.3 per lb · avg 12 oz

Jul 21Rainbow trout2,8001.4 per lb · avg 11 oz

Jul 14Rainbow trout2,5001.3 per lb · avg 12 oz

Jul 9Rainbow trout2,5002.5 per lb · avg 6 oz

Jul 8Rainbow trout3,1201.6 per lb · avg 10 oz

Jun 30Rainbow trout3,3201.7 per lb · avg 9 oz

Jun 23Rainbow trout2,9801.5 per lb · avg 11 oz

Jun 16Rainbow trout3,5601.8 per lb · avg 9 oz

Jun 10Rainbow trout3,6641.8 per lb · avg 9 oz

Jun 3Rainbow trout3,7321.9 per lb · avg 8 oz

Spring 2026

May 28Rainbow trout10,8002.7 per lb · avg 6 oz

May 21Rainbow trout5,4002.7 per lb · avg 6 oz

May 5Rainbow trout4,8002.4 per lb · avg 7 oz

Apr 9Rainbow trout5,2002.6 per lb · avg 6 oz

Apr 2Rainbow trout5,4002.7 per lb · avg 6 oz

Summer 2025

Aug 26Rainbow trout2,5601.3 per lb · avg 12 oz

Aug 20Rainbow trout2,6651.3 per lb · avg 12 oz

Aug 11Rainbow trout2,5261.3 per lb · avg 12 oz

Aug 5Rainbow trout2,7671.4 per lb · avg 11 oz

Jul 29Rainbow trout2,6601.3 per lb · avg 12 oz

Jul 23Rainbow trout2,8601.4 per lb · avg 11 oz

Jul 16Rainbow trout3,1601.6 per lb · avg 10 oz

Jul 8Rainbow trout3,1201.6 per lb · avg 10 oz

Jul 2Rainbow trout3,4601.7 per lb · avg 9 oz

Jun 25Rainbow trout3,5521.8 per lb · avg 9 oz

Jun 18Rainbow trout1,7001.7 per lb · avg 9 oz

Jun 17Rainbow trout1,7001.7 per lb · avg 9 oz

Jun 11Rainbow trout3,9151.9 per lb · avg 8 oz

Jun 4Rainbow trout4,1052 per lb · avg 8 oz

Spring 2025

May 29Rainbow trout4,4002.2 per lb · avg 7 oz

May 22Rainbow trout4,4002.2 per lb · avg 7 oz

May 1Rainbow trout4,8002.4 per lb · avg 7 oz

Apr 10Rainbow trout5,4002.7 per lb · avg 6 oz

Apr 3Rainbow trout5,2202.6 per lb · avg 6 oz

2015 – 2026

Fish released each year

2025 is yellow. 2026 is outlined because the year is not over: the data runs to Oct 30, 2026. A dash means WDFW has no record for that year. The busiest full year was 2023, with 18 release dates and 68,390 fish; the 2015–2025 average is 18.1 release dates a year.

2015: no record
2016: no record
2017: 67,900 catchable fish on 18 release dates
2018: 66,667 catchable fish on 18 release dates
2019: 66,665 catchable fish on 18 release dates
2020: 60,530 catchable fish on 18 release dates
2021: 61,960 catchable fish on 18 release dates
2022: 67,928 catchable fish on 19 release dates
68k2023: 68,390 catchable fish on 18 release dates
2024: 64,902 catchable fish on 17 release dates
65k2025: 64,970 catchable fish on 19 release dates
72k2026 (to Oct 30): 72,001 catchable fish on 19 release dates

How big are these fish?

4 to 8 oz: 58,320 fish, 43%
8 to 16 oz: 78,651 fish, 57%

Weight is 1 ÷ fish per lb, as WDFW reports it for each batch. It is a batch average, not a guarantee for any one fish. Counts cover every release since January 2025.

Notes from the records

The biggest single batch since January 2025 was 10,800 rainbow trout on May 28, 2026. The heaviest fish were 2,220 rainbow trout on Aug 25, 2026, at 1.1 per lb, about 15 oz each.

Timing shifts from year to year. Treat this as a pattern, not a promise.