Main submerged plant in this pond thread as pictured (https://ibb.co/HPvpP7S
) is due to the forked leaves called coontail aka hornwort. Coontail does not have true roots, sometimes forms false roots, and the plant base thrives close to or on the bottom with upper stems higher in the water column to form large tangled masses to become a pest. It reproduces mainly by forming winter buds that in fall, separate, and sink to the bottom to perpetuate the plant in spring. Not needing roots it also grows from stem pieces.
It competes with phytoplankton for dissolved nutrients thus when abundant it can promote clear water.
Coontail is one of the most common underwater plants in the US. It can compete with other more beneficial submerged plants. Luckily I do not have it.
Best way to sample the sunfish is with a small hook, pieces of worm under a small thin bobber. Catch several sizes and photograph those that appear different. We can help identify them.
jpsdad has referenced one of the best research studies on single species in small ponds.