Habitat Modifications

PG13-2 TIP SHEET Private Waters NEBRASKA Program Management Assistance for POND GUIDE Lakes, Ponds, Pits & Streams HABITAT MODIFICATIONS he natural foods of fish are either produced and weeds then become underwater structures and T in the pond, washed in by rain, or fall into the create an excellent, nutrient-rich environment. These pond. A pond has a series of food chains, or more underwater structures then: accurately a food web, that starts with nutrients in • provide shade and cover for fish the watershed and ultimately ends with big fish. Small fish concentrate the energy they get from their food and, in return, become high-energy food AQUATIC FOOD CHAIN for larger fish. Since bluegills are lower on the food chain, a pond will support 5 to 10 times as many pounds of bluegills as it does largemouth bass. The total biomass (weight) of fish that a pond can support is called the carrying capacity. This is much like a pasture being able to only support so many cattle, or a garden that can only grow so many vegetables. Without supplemental feeding, an average pond in Nebraska supports about 250 one pound pounds of fish per acre — about 190 pounds of largemouth bluegill, 35 pounds of bass, and 25 pounds of catfish and/or other species. Once carrying capacity is reached (about 3 to 4 years after initial fish stockings), fish growth rates decline. Individual populations can 10 pounds - bluegill be comprised of many small fish, a few large ones, or a combination of small, intermediate, and large, but the total weight will be the same and equal what the pond can support. 100 pounds Depending on management goals, the produc- small fish food items tivity of a pond and the immediate surrounding land can be increased by modifying and/or supplementing aquatic and terrestrial environments. Changes will then benefit associated wildlife, whether it is a rabbit, 1,000 pounds microscopic animals a small catfish, or even a dragonfly. AQUATIC HABITAT Trees and brush removed during construction 10,000 pounds can be returned to the pond basin before the pond microscopic plants fills. Upon filling, the flooded trees, brush, grass, PG13-2 TIP SHEET Private Waters NEBRASKA Program Management Assistance for POND GUIDE Lakes, Ponds, Pits & Streams • are substrate on which aquatic organisms, usually will be about 40% covered with emergent and such as aquatic insects, can grow and feed submergent vegetation. These types of aquatic plants: • concentrate fish — small fish eat the aquatic • provide cover, food, and nesting sites for insects and in return are eaten by bigger fish. fish and other organisms However, as the pond ages, underwater structures • help to oxygenate the water and reduce decay and disappear, reducing the amount of fish a nutrient levels pond can support. The subsequent habitat loss can • improve water clarity by decreasing wave be counteracted by development of natural habitat strength and minimizing shoreline erosion and/or addition of artificial habitat. • tie up/utilize nutrients which reduces the likelihood of algal blooms that can cause NATURAL HABITAT fish kills. Aquatic vegetation is also considered structure Emergents (rigid, shoreline plants with the and will become established in most ponds. It is bulk of plant above the water surface) can become often considered a nuisance and removed by established naturally or transplanted to speed pond owners. It is, however, a natural and necessary colonization. Or, top soil from a nearby wetland component of a healthy pond. A good fishing pond (when permitted) can be transported to the new AQUATIC HABITAT • 2 • PG13-2 TIP SHEET Private Waters NEBRASKA Program Management Assistance for POND GUIDE Lakes, Ponds, Pits & Streams seeds and plant fragments. Ideally there should be Transplanting a band of aquatic vegetation around the majority Roots of of the pond — starting with emergents immediately Emergents along the shoreline and transitioning into submergents that extend a short distance out into the pond. Submergents will likely also colonize the shallower New Shoots portions of underwater terraces and humps installed in deep areas of the pond. Some submergent Nodes types (curlyleaf pondweed, Eurasian watermilfoil, and coontail) can extensively colonize shallow-water areas if adequate depths aren’t present to restrict their growth. See PG13-1 regarding pond depth, capacity, and slopes. Although it is best to transplant locally acquired pond site and spread out so that the seed present plants, contact your area Commission fisheries in it can establish wetland plants. Most emergents personnel for a listing of aquatic vegetation dealers. (especially cattail, bulrush, and arrowhead) transplant See PG13-9 for additional information on easily. Transplanting should be done in the spring identification, benefits, potential problems, and when new growth starts. Rootstock can be dug up, control of aquatic vegetation. cut or pulled apart with at least two new shoots/ Some of the natural effects of aging and nodes per section (especially for cattails), and planted subsequent habitat loss can also be counteracted along the shoreline. Some of the sections should with water level manipulation. Ponds with gated be planted at and immediately above the water draw-down valves can be lowered 2 to 3 feet line, with others planted in water less than 10 (commence in late spring) and maintained at the inches deep. Emergents can also be planted on lower level for an extended period of time. Make the tops of pond basin fish habitats (underwater sure adequate depth remains to prevent a summer terraces, humps, and land projections) that are fish kill. Grasses and broadleaf plants will sprout within 2 to 3 feet of the water surface. They will become a vegetative breakwater and create slack Seeding water that should lessen the severity of shoreline Seeding Mudflats erosion and provide additional habitat for a Mudflats multitude of organisms. Keep in mind cattails are very aggressive and can spread extensively. They may need to be eliminated with chemical or mechanical means in wading, swimming, and some fishing areas. Even though submergents (non-rigid plants, typically completely submerged and attached to the bottom) can also be transplanted, they usually become naturally established by waterfowl transporting seeds and/or incoming water transporting • 3 • PG13-2 TIP SHEET Private Waters NEBRASKA Program Management Assistance for POND GUIDE Lakes, Ponds, Pits & Streams naturally on the exposed bottom. Or, mud flats can be hand seeded with Japanese millet or grain sorghum when they are initially exposed and still moist. The pond should be refilled to flood the established vegetation, either in the fall if a winter fish kill is possible or the following spring. Although pumps can be used to partially drain or refill ponds for water level manipulation, pumping costs could be considerable. Water level manipulation can also be used to: • enhance emergents with dewatering starting about mid-May and a slow, refilling process starting in September • crowd fish, which makes small bluegill more Cedars and Blocks Used susceptible to predators. For Artificial Habitat Water level manipulations should ideally be done every 4 to 5 years. obtained from the Army Corps of Engineers (Omaha Office 402-896-0723). ARTIFICIAL HABITAT As a pond is being built, structures can be quickly Pond owners can install underwater structures, built by: commonly referred to as artificial habitat. Structures • pushing downed trees together and anchoring made of brush and trees are the most economical them in place and effective types; however, rocks, wooden pallets, • leaving standing timber intact whenever drain tiles, and piles of bricks can also be used. possible. Before adding any structure into any surface waters Hardwoods, osage orange, red cedar, or any of the state, a Section 404 Permit must first be large tree work best and will last for decades once they are inundated. Christmas trees shouldn’t be used because they decompose rapidly, nor should large pines because of their acidity. Trees can either be tied together, anchored separately, or attached to stumps. They can be anchored with concrete blocks or attached to steel posts driven into the bottom, as long as there is no concern about the posts causing the pond to leak or becoming a boating hazard. Plastic banding, polypropylene rope, cable, or heavy, non-corrosive wire can be used to facilitate anchoring. Or, a tree can be placed upright in a hole that has been made Pallets Used For in the bottom and subsequently held in place with Artificial Habitat poured concrete. Structures can also be installed on top of deep water humps and terraces or near the • 4 • PG13-2 TIP SHEET Private Waters NEBRASKA Program Management Assistance for POND GUIDE Lakes, Ponds, Pits & Streams notches of underwater terraces. See PG13-1 for more As mentioned earlier, a good fish pond will have information regarding pond bottom design concepts. aquatic vegetation associated with about 40% of its Shoreline structure can be made by felling trees surface area — subsurface artificial habitat can be along the edge of the pond into the pond. These a portion of this percentage. Structures placed in 5 trees can be kept in place by cabling them to the to 10 feet of water can be used by fish year-round; stumps, or half cut them, leaving a portion of the top whereas, those placed in water deeper than 10 feet connected to the stump. may not be used during summer months if insuffi- Artificial habitat can also be added after the cient oxygen is present. Good attractors will be about pond fills to intentionally attract and concentrate fish 10 by 15 feet, or larger. Trees are more effective if for anglers. The best locations for attractors are near grouped together in several large piles instead of natural gathering places for fish (off points, at the spreading individual trees across the entire bottom.

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