What You'll Find at Grassy Lake

Grassy Lake is a shallow, brackish impoundment in St. Mary Parish that holds redfish and spotted seatrout year-round, with occasional tarpon and permit pushing into the shallows during summer. The lake sits roughly 15 miles south of Morgan City and covers about 3,000 acres of marsh, grass flats, and open water. Depths run 2 to 6 feet across most of the lake, with deeper holes near the eastern and western edges where water drains to the Gulf.

The grass beds — mostly smooth cordgrass and widgeon grass — are the reason fish stack here. Redfish hunt the grass edges and shallow flats year-round, and spotted seatrout move in during fall and winter when water temperatures drop. Spring brings tarpon cruising the deeper channels, and summer heat pushes both redfish and trout into the deeper holes and the mouths of incoming bayous where cooler water flows in.

Access is limited. There is no public boat launch directly on Grassy Lake itself. Most anglers launch from nearby waters — Morgan City, Atchafalaya Bay, or smaller ramps in the parish — and run through connecting bayous and canals to reach the lake. The run takes 20 to 45 minutes depending on your launch point and water levels.

Key Takeaways

  • Grassy Lake holds redfish and spotted seatrout in shallow grass flats, with depths of 2 to 6 feet across most of the lake.
  • There is no public boat launch on Grassy Lake; you will need to launch from Morgan City, Atchafalaya Bay, or another nearby ramp and run through connecting waterways.
  • Redfish bite year-round on the grass edges and shallow flats, while spotted seatrout move in during fall and winter when water cools.
  • Tarpon and permit show up in spring and summer, especially in deeper channels and near bayou mouths where cooler water enters the lake.
  • Shallow-water techniques — poling, sight-casting, and working grass edges — are more effective than deep-water trolling on Grassy Lake.

Redfish on the Grass Flats

Redfish are the most consistent target on Grassy Lake. They hunt the edges where grass meets open water, and they feed in the grass itself during high tide when water covers the shallow flats. Early morning and late afternoon are peak times, but redfish will bite throughout the day if you work the right depth and cover.

Sight-casting is the most effective method. Pole your skiff slowly along grass edges in 2 to 4 feet of water and watch for tails, wakes, or dark shapes moving through the grass. When you spot a fish, cast ahead of its path with a 1/4-ounce jig tipped with a small shrimp or a 3-inch soft plastic. Let the lure sink slowly and twitch it along the bottom. Redfish often follow a lure before committing, so be ready for a sudden strike.

If sight-casting is not producing, work the grass edges with a slow retrieve. Cast parallel to the grass line and retrieve just fast enough to keep the lure off the bottom. Redfish will come out of the grass to hit a lure moving along the edge. During high tide, when water floods the flats, redfish spread out into shallow water; during low tide, they concentrate in deeper holes and along the deepest grass edges.

Spotted Seatrout in Fall and Winter

Spotted seatrout move into Grassy Lake in October and stay through March, following cooler water and baitfish migrations. They prefer slightly deeper water than redfish — 3 to 5 feet — and hold near grass edges, channel drops, and the mouths of bayous where fresh water mixes with the lake.

Trout respond well to small shrimp patterns and 2- to 3-inch soft plastics in natural colors: white, tan, and light gray. Cast near grass edges and work the lure with a steady, medium-speed retrieve. Trout often hit on the pause, so stop the retrieve for a second or two every few feet. Early morning and the hour before sunset are most productive, but trout will bite throughout the day if you stay in deeper water and avoid the shallowest flats.

During winter, when water temperatures drop below 55 degrees, trout move to the deepest holes in the lake and the mouths of incoming bayous. Focus on areas 5 to 7 feet deep where water from Atchafalaya Bay or connecting bayous flows in. These spots stay slightly warmer and hold baitfish, which concentrate trout in small areas.

Spring Tarpon and Summer Permit

Tarpon enter Grassy Lake in April and May, following mullet and other baitfish into the shallows. They cruise the deeper channels and the mouths of bayous, and they will eat large topwater plugs and 4- to 6-inch soft plastics. Tarpon fishing requires heavy tackle — 20- to 30-pound class rods and 50-pound fluorocarbon leader — and patience; they often follow a lure without eating it.

Permit show up in June and July, feeding on crabs and shrimp in shallow water. They are spookier than tarpon and require longer casts and lighter presentations. A 1/4-ounce crab pattern or small shrimp fly works well, but permit will refuse a lure if they sense your presence. Pole slowly, cast ahead of the fish, and let the lure sink naturally.

Both tarpon and permit are catch-and-release fish in Louisiana. Check the current regulations before you fish, as rules change year to year.

Tides, Water Levels, and Seasonal Timing

Grassy Lake is tidally influenced but not as dramatically as open Gulf waters. Tides run 1 to 2 feet, and water levels are also affected by rainfall, Atchafalaya River discharge, and wind. High tide pushes water into the shallow flats and spreads redfish across the lake; low tide concentrates fish in deeper holes and along channel edges.

Spring (March through May) brings rising water levels and cooler temperatures — good for redfish and the start of tarpon season. Summer (June through August) heats the lake and pushes fish into deeper water and bayou mouths; permit and tarpon are active, but redfish and trout move to cooler refuges. Fall (September through November) cools the water and brings spotted seatrout back; this is the most consistent season for both redfish and trout. Winter (December through February) is coldest and best for trout, but redfish remain active in deeper water.

Wind direction matters. North and northeast winds push water out of the lake and lower levels; south and southwest winds push water in and raise levels. A rising tide combined with a south wind is often the most productive combination.

Getting There and What to Bring

Launch from Morgan City (Atchafalaya River access), Amago Marina near Atchafalaya Bay, or smaller parish ramps if you know locals. From Morgan City, run south through Atchafalaya Bay and enter Grassy Lake through the connecting bayous — the route is marked but narrow in places. From Amago, the run is shorter but requires navigating tidal flats. Ask at the launch about current water levels and the best route; levels change with rainfall and river discharge.

Bring a shallow-draft skiff or flats boat — 18 to 22 feet is ideal. Grassy Lake is too shallow for deep-V hulls, and you will spend more time poling than running. A push pole or electric trolling motor is essential. Bring polarized sunglasses, a good pair of wading boots if you plan to wade, and a net for landing fish. The sun reflects hard off shallow water, so sunscreen and a hat are not optional.

Insect pressure is moderate to heavy, especially in summer and early fall. Bring bug spray and consider long sleeves and pants during dawn and dusk.

Regulations and Seasons

Louisiana Department of Wildlife and Fisheries sets the rules for Grassy Lake. Redfish have a year-round season with a daily bag limit of three fish per person (check current regulations, as limits change). Spotted seatrout have a year-round season with a daily bag limit of 25 fish per person. Tarpon and permit are catch-and-release only; you cannot keep them.

A Louisiana fishing license is required for all anglers 16 and older. You can purchase a license online through the LDWF website or at most bait-and-tackle shops in Morgan City. Licenses are available as short-term (3-day) or annual options.

Seasons and bag limits change year to year, so check the LDWF website or call the Morgan City office before you fish. Regulations are posted at most launch ramps as well.

Frequently Asked Questions

Can I wade Grassy Lake?

Yes, but only in specific areas. The lake bottom is soft mud in many places, and wading is slow and exhausting. Stick to grass-edge areas where the bottom is firmer, and wear wading boots with good ankle support. Poling or drifting is more efficient than wading on Grassy Lake.

What is the best time of year to fish Grassy Lake?

Fall (September through November) is most consistent for both redfish and spotted seatrout. Spring (March through May) is excellent for redfish and the start of tarpon season. Summer is slower for redfish and trout but good for tarpon and permit. Winter is best for spotted seatrout in deeper water.

Do I need a guide to fish Grassy Lake?

No, but the lake is large and navigation can be confusing if you are unfamiliar with the bayou system. A guide is helpful your first time, especially if water levels are low. Many Morgan City guides fish Grassy Lake regularly and know the best spots and routes.

What size tackle do I need?

For redfish and trout, 7- to 8-foot medium-power spinning rods with 15- to 20-pound braided line work well. For tarpon and permit, step up to 8- to 9-foot medium-heavy rods with 20- to 30-pound braided line and 50-pound fluorocarbon leader.

Are there other fish species in Grassy Lake?

Largemouth bass, catfish, and sheepshead are present but not the primary target. Sheepshead show up in spring and will eat small shrimp and crab patterns near structure. Bass fishing is possible but inconsistent compared to redfish and trout.