Remediation – Dredging & Leaks

Most everything associated with a drought seems negative, and that certainly is the case for most facets of pond management. However, there are a few opportunities that a drought offers that regular weather patterns and rainfall can make difficult and expensive. 

The first and seemingly most popular opportunity among Alabamians is to remediate the pond from a structural aspect.  Over time, most ponds experience siltation, that is the margins and basins begin to fill-in and shallow as surface water runoff brings with it topsoil and sediments that ultimately settle out to the pond bottom. As ponds age and sediments accumulate the overall decrease in depth brings along several issues. Besides the obvious loss of water volume, aquatic weeds can also be a significant issue as shallow, silty, waters provide an ideal habitat for excessive weed growth. This growth can impact livestock watering, fish production and balance, irrigation, aesthetics, and so on. As drought is prolonged, water levels recede and shorelines soils dry, offering opportunity to dredge, or remove this excess, unwanted silt and sediment. However, it is not as simple as just digging away with a dozer or track hoe, careful planning must first take place as many ponds could end up ruined at this time.    

Understand that if the compaction layer of a pond is disturbed a leak may develop. Many ponds hold water because of careful and calculated clay compaction at first construction, with some sites even having clays hauled in order to provide proper compaction. If the compacted layer of pond bottom is disturbed and not sufficiently compacted after dredging, the risk of a leak is high. Also, consider what you will do with the ‘spoil’ or material that is removed, all of that sediment has to go somewhere.  Often times there may be a location on the property, but, if not, with a few calls to area farmers or landscapers it may not be difficult to find a taker. If placed on-site, remember to select a location downstream or outside of the watershed of the pond, after-all you don’t want rains carrying all of that material back into the pond. Lastly, once rain is on the forecast it is a good idea to seed or cover crop the spoil area to reduce erosion.

The next question of such an undertaking is cost. Generally, such a job is charged by the hour. Depending on size and type of machine, you can expect hourly rates in the range of $100-$200. Costs can vary widely based on location, soil moisture, and the need to haul and/or spread the spoil.  

Another opportunity during a time of drought is the ability to repair a leaking pond. Again, exposed pond bottoms provide opportunity to properly compact soils or investigate that nagging leak. Perhaps a bedrock seam or sink has been exposed, those holes or rusted areas in the standpipe can now be addressed, or that area of the pond that wasn’t able to be properly compacted now has the chance. Ponds can leaks come develop in a head-spinning amount of ways, but a drought may provide the chance to pinpoint and fix the problem in a more timely and economical way than with a pond at full pool.

Remediation – Docks, Cover, and Structure

The chance to more easily replace or create a dock, structure and cover in recreational fish ponds is another ‘positive’ brought on by drought. If fishing is a point of interest, then having areas for fish and anglers to congregate can greatly improve angler catch rates and enjoyment. The terms of structure and cover are often used interchangeably, but they are very different terms. Structure should be known as changes in depth or bottom contour, such as break lines, troughs, underwater islands, ridges, etc. Cover, on the other hand, are things that provide a ‘roof’ over the fish’s head, things like rock piles, brush piles, pallets, stumps, stake beds, etc. In the case of both, as ponds age much of the cover and structure degrades, but drought is a time that both can be carefully and easily placed or replaced throughout the pond. This is because working with dry soils makes forming bottom sediments, backing a truck down the pond bank, or dragging trees a much easier proposition than when wet soils or a boat is involved. When placing cover be sure to anchor it well and don’t place it any deeper than 6-8’ as most ponds won’t have suitable oxygen levels beyond those depths in the summer. Also, keep in mind the average annual low water level and keep cover as deep or deeper, otherwise the cover can be exposed or end up entirely out of water which could create an eyesore and limit its effectiveness. And, do not overdo it, too much cover or structure can be as bad as none at all. By creating too much habitat fish can be spread out and make the fishing slow. Finally, be sure to GPS the locations or place markers, such as duck decoys or anchored jugs over the habitat so you and your anglers can know where to focus their efforts. In terms of dock construction, be sure to construct it at a height that will not be flooded or far above water line at full pool.

Shoreline Growth

Although it is not an issue during the time of drought, terrestrial plant growth on the newly exposed shoreline sediments of a pond during the time of drought will impact management once rains return. Some species more adapted to aquatic life may persist for some time, but many of the grasses and broadleaves that take advantage of the newly exposed soil will die off once flooded with winter rains. As they die and decompose the nutrients released can create an excessive growth of filamentous algae, particularly as temperatures rise above 50°^F in the spring. However, this algae growth can be limited by maintaining water clarity at 18”-24” by applying pond dye or through proper fertilization. In addition, stocking grass carp at a rate of 10-20 per acre can do well to control algae, however, delay stocking until ponds return to at least ¾ pool. Still, be prepared to control excess algae by use of herbicides, namely diquat and copper based products, both of which may be purchased or ordered through farm supply stores or on-line vendors. However, know that copper can be toxic to fish if over applied, particularly in ponds with low alkalinity. An alkalinity test can be conducted by your regional agent to guide you towards the amount of copper that can be safely applied.

Fish Crowding and Imbalance

As drought is prolonged and waters continue to recede, sportfish can be concentrated to the point at which predator (largemouth bass) and prey (bream) are literally side-by-side one another. Throughout this process bluegill and other prey fish populations are often decimated by bass. Drought can leave a pond in an immediate state of imbalance and poor fishing. Angler catch rates and calculation of the body condition of bass (relative weight) will help to guide management decisions. Low bream catch rates and skinny bass are indicators that supplemental bream may need stocked and bass will require higher harvest rates.  In general, 500 3-5” bream stocked per acre prior to their spawn in early April will help towards rebuilding their numbers and 14” and smaller bass harvested at an increased rate of 20-25 lbs. per acre in unfertilized ponds and 25-30 lbs. per acre in fertilized ponds will help towards regaining a balanced fishery. After a crowding event it is recommended to have the fishery assessed either through an electrofishing survey via a private lake management consultant or by a seine assessment that can be conducted by your regions Forestry, Wildlife, & Natural Resource Management Agent. Electrofishing assessments are best conducted in the spring and fall of the year, while seine assessments are best conducted during the month of June.

Fish Kills

Inevitably, in times of drought the phones of county extension offices will ring with reports of fish kills. These kills happen for two primary reasons, low water that creates crowding and poor water quality, or oxygen depletions from over-fertilization and/or excessive weed growth. Often, pond owners do not have many options towards managing around such drought impacts. However, there are a few management techniques that can be applied to reduce the chances or impacts of a fish kill during a drought.  

If low oxygen levels are suspected, indicated by fish gathering at the pond edge and surface in the early morning hours, or a fish kill has begun to occur, the first and foremost action would be to provide surface aeration. This is best done with commercial paddlewheels or floating surface aerators. The idea is to thrash the surface of the water to incorporate atmospheric oxygen back into the pond. However, bush hogs, outboard motors, and trash pumps can all be rigged to thrash the water surface, but care must be taken to not muddy the pond as this can worsen the issue. The idea here isn’t to save each and every fish in the pond, but rather to create a pocket(s) of oxygenated water to holdover the majority of fish. Know that as the sun sets and photosynthesis ceases, pond oxygen levels decrease and are the lowest right before the sunrises, making this period the most critical time to aerate. Of course, if feasible, it is best to maintain serviceable water levels by pumping from other sources of water, whether it be a well, nearby pond, lake, etc. 

In terms of prevention, reducing and controlling aquatic weed growth as described above goes a long way towards reducing fish kills, even in a year of normal precipitation. Although aquatic plants provide the water and other aquatic life with oxygen during the day, plants use oxygen from dusk through dawn.  If plant density is too high (greater than 30% of the pond) a fish kill may be at risk, and ever increasing as water levels decrease. The same situation goes for the phytoplankton bloom we purposely create when fertilizing a pond. If over fertilized (that is water clarity is less than 18”) the risk of a fish kill is high. On top of that, phytoplankton densities continue to increase with heat as do the microscopic zooplankton that feed on them. Add all of this up and the oxygen demand in the evening and early morning is more than what the pond can provide and a fish kill is the result. Fertilize carefully and only as water clarity indicates fertilizers are necessary, and, in the case of a drought, halt fertilization all-together.

Also directly related to the topic of crowding discussed above is the impact of poor water quality, high water temperatures, and transfer of bacterial disease, fungus, viruses, and parasites. Illnesses can be magnified as drought crowds fish and results in poor water quality. Heat and low oxygen related stress can cause fish to eat very little and go into survival mode.  In addition, as fish are in close proximity and come in contact with one another the probability of contracting a sickness can increase dramatically, particularly if the population is already in poor health and high stress from prolonged drought. Symptoms of these issues are often exhibited as blotchy reddish/white sores, degraded fins, pale and discolored gills, and/or extremely skinny fish. To know exactly what your fish are ailing from requires a fresh (preferably live) sample rushed to the Auburn University’s Fish Disease Laboratory or the Alabama Fish Farming Center in Greensboro, AL, whichever location is nearest to you.  Use ANR-0562 Guidelines for Collecting and Shipping Diseased Fish(referenced below). Know that medicated antibiotic feeds are available but they are only effective on specific bacterial infections and are with specific limitations, rates, and times of effectiveness. Also, medicated feed is not a cure all and can be a substantial expense that is most feasible for commercial operations with substantial losses at stake. Lastly, severely sick fish may feed very little if at all, limiting the effectiveness of treatment. Rarely do bacterial disease, fungus, viruses, or parasites result in a complete fish kill, as they are often present in fish populations and run their course naturally.