Currently the catch percentage on catching a trash item on max level (including all level locked items) distributes as folows:

19.72% - Base.UnusableWood.
11.83% - Base.TreeBranch.
11.83% - Base.Twigs.
11.83% - Base.RippedSheetsDirty.
7.89% - Base.Socks_Ankle.
7.89% - Base.Shoes_Random.
3.94% - Base.Vest_DefaultTEXTURE_TINT.
3.94% - Base.Trousers_DefaultTEXTURE_TINT.
3.94% - Base.Tshirt_DefaultTEXTURE_TINT.
2.37% - Base.Plank.
1.97% - Base.TinCanEmpty.
1.97% - Base.Plasticbag.
0.99% - Base.WaterMug.
0.99% - Base.Garbagebag.
0.99% - Base.MetalPipe.
0.79% - Base.Shrimp.
0.79% - Base.Crayfish.
0.79% - Base.Squid.
0.59% - Base.WhiskeyWaterFull.
0.59% - Base.WineWaterFull.
0.59% - Base.WaterBleachBottle.
0.51% - Base.WaterPot.
0.51% - Base.Shoes_Wellies.
0.51% - Base.Pan.
0.39% - Base.DeadRat.
0.39% - Base.Lobster.
0.39% - Base.FishingTackle.
0.39% - Base.FishingTackle2.
0.24% - Base.Bag_FannyPackFront.
0.20% - Base.FirstAidKit.
0.12% - Base.Briefcase.
0.08% - Base.WristWatch_Left_ClassicBlack.

For more details on the internal weights, level locks and bonus xp look at the https://github.com/MassCraxx/FishingPlus/blob/main/Contents/mods/FishingPlus/media/lua/client/TrashItems.lua file contained in this mod.

If you have any suggestions or ideas for improvements, including adding or removing items, feel free to write here.