Dedicated To The Tribal Aquaculture Program

 

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Topics Of Interest:

Fish Truck Goes to LCO

Bird Netting

Winter Pond Management

Fish Health

Hatchery Tips

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Fish Truck Goes to LCO
By: MTAN

Frank Stone (Ashland FRO) arranged for the transfer of a surplus 1986 fish distribution truck (from the Welaka NFH, Florida) to be reassigned to the Lac Courte Oreilles (LCO) Indian Reservation. The truck is equipped with a 1,000 gallon fish tank plus oxygenation and water recirculating life support systems. The LCO Tribal Fish Hatchery program paid the travel expenses for Frank to fly to Florida and drive the vehicle back to northern Wisconsin (1,650 miles). The Tribe will use the vehicle to help transport hatchery fish to various stocking sites near the Reservation.

Over the past nine years the Ashland FRO has arranged for the transfer of several hundred thousand dollars worth of fish distribution trucks, fish hatchery equipment, generators and vehicles to Tribal resource programs in Region 3. By making surplus equipment transfers like this possible, we not only prolong the intended use for the equipment but also help free up funds by the receiving agency to be used in other natural resource areas.

 

Bird Netting
By: Greg Faulkner, Fish Farming News, January/February 1999

It looked really good. It went up easily and it was very inexpensive, maybe 4 cents a square foot. The mesh was small enough that even the kingfishers couldn't get through. Then came the rain and the wind. It took about 15 minutes for 3,500 square feet of that light netting to shear itself apart. It just fell in shreds.

This fish farmer's experience with ultralight bird netting was not a good one. The bursting strength of the netting was adequate enough, but he hadn't accounted for the effects of flex and wind resistance. Hanging netting in the air is quite different from placing it in water. Netting hung in the air is at the mercy of gravity and wind. Burst strength, which is tested by placing an even strain all along the meshes, has little meaning when a limb or pile of leaves accumulates on the net and wind resistance increases by 200%-300%. The whipping action of erratic winds coming from different angles causes the material to flex and twist. With that combination, the netting can just break.

Is this to say that the farmer's choice of material was wrong or that the netting is ill-suited for bird cover? Absolutely not! What he could have done to save his cover was as simple as fastening in several Aguy@ ropes to suppress movement and support the net. A 3/16" braided line every 12' or 15' would have kept the netting from "whipping" itself back and forth in the wind. Debris collection and the increased wind resistance it produces would have been partially supported by the guys.

Extruded

Extruded netting comes in numerous thicknesses. The thicker and heavier the product, the more rigid it is and the greater the expense. These heavier sizes are the backbone of the cage industry and can outlast most nylon netting in the water. The flat, offsided joint that holds the extruded meshes to one another is not a knot. It is simply a melted joint. Burst strengths on the lightweight materials run 20 pounds or so. In the heavier densities, burst strength runs into the 100-pound range.

In the lighter, bird netting sizes, the netting is adequate to support itself but requires some underlying guy lines if it is going to be stretched over a large area. One such ultra lightweight extruded net with guy lines in place every 8' has remained undamaged for 3 years in an outside environment.

Knitted

Another popular material often seen in fruit tree protection is a loosely woven knitted material. The samples I have worked with were all polypropylene or polyethylene material. They were ultra light and the material came in gigantic rolls of hundreds of feet long by 30'-40' wide. This material is very loosely woven as evidenced by the amount of space in between the fibers. You can see daylight. If pulled, it loses its shape quickly and can be torn with less than 20 pounds of strain. Cost-wise, it is the most inexpensive of all materials, perhaps 2-3 cents a square foot.

Be aware that you will have to contend with a lot of sagging in the material if you try to span a large area without supports. It can be used to cover a small pond or tank quite easily and is often used in applications where netting must be rolled back frequently to access a tank.

Knotless Polyethylene

An offshoot from the commercial seine industry, this material has just found its way into the bird predation scene. Two strands of polyethylene are twisted and "z" locked at the joining. It can be used as a diamond or a square-shaped netting. Square-shaped netting has less wind resistance and produces less sag when hung up in the air. Knotless poly (brand name K-Less) can be stretched over a greater span than most other nettings. In some applications it can be pulled tightly over a 65'-75' expanse with little or no sag. Bursting strength of the lightest of the materials is well over 70 pounds and the medium weight materials can hit 200. That means guy lines can be placed 50'-60' or more apart.

K-Less comes in multiple sizes from 1-1/2" to 12" mesh. it can be manufactured in diamond or square mesh form. Cost is in the 5-9 cents a square foot range.

In a 1995 experiment, a 13,000-square foot pond cover was hit by 75 mph winds twice in one year along with two ice storms. No damage was reported.

Knotted Poly or Nylon

The most widely accepted netting material has always been the knotted version. In this knotted form, either poly or nylon can be pulled across great expanses. Shortcomings of nylon are that it will absorb water and sag and that it must be removed and treated with net coating from time to time. Knotted poly is not affected by water absorption, but ultraviolet (UV) rays can be a problem. In a black or dark blue color, poly is able to tolerate years of UV exposure. In lighter colors such as green or orange it can wither very quickly.

These knotted nettings are relatively inexpensive and can be found in almost any net shop or netting supply house. Prices are from 4-8 cents a square foot. There are numerous mesh sizes of each and these two nettings have probably the widest array of twine thicknesses of any of the nettings on the market. At a cost of 8 cents, #12 2"x2" square mesh can be used to cover extremely large open areas with just a few upright pvc poles in the center of the net.

Monofilament

Used for years in the commercial gillnet and cast net fisheries, this material is ultralight and readily available. Its tensile strength is adequate, although I wouldn't put too much strain on it without supports. The stiffness of monofilament makes it ideal for sites with lots of debris and it cleans itself rather easily. While available in colors, monofilament is translucent and has little UV protection. In constant sunlight it will break down. One consideration is that it is so clear that it can be a hazard to some birds. Mono comes in a variety of mesh sizes and depths. Costs range from 5-7 cents a square foot.

Bird Netting Terminology

Sag:The amount of drooping a net will do when it is in place up in the air. Sag can only be reduced by tightening the webbing or placing guy lines. Diamond shaped material will always have greater sag than will square shaped material.

Flex: The amount of bending a netting can take either from water action or wind. Tensile and burst strength mean nothing here. If the material cannot flex, it will snap off, not pull apart.

Ultraviolet (UV): This is nature's own microwave oven. Generally speaking, draw a line east and west through Memphis, TN. Above this line UV is weaker and below it you had better watch the nettings' colors.

Catchability: If a bird did hit your net, what would happen? Catchability refers to how much entangling capability your net has. Will the bird just bounce off or will it gets its feet or wings entangled.

Burst strength: This is the gauge used to test at what amount of pull a netting will break. It is always done with even rows of meshes under a controlled environment. It does not take into account sudden twists or jerks caused by debris or wind.

Diamond mesh: Just as it says, a four-sided, diamond-shaped mesh.

Square mesh: A four-sided box-shaped mesh. Square mesh are generally cut from diamond mesh in knotted and K-Less netting.

Structure: The amount of poles and supports needed to hold up a bird net. This includes the guy lines underneath the net.

Chafe resistance: The amount of wear and tear a netting can take as it slides back and forth along guy lines or frame work.

Retractable: Some types of nets can be made in such a style that the entire net can be slid from one end of the pond to the other.

Nesting: Some small mesh bird netting will offer an attractive nesting area to some birds.

Periphery cover: Some first-time net users forget that cranes and egrets often walk into a pond. It is important to have your cover extend around your entire pond edge as well as up in the air.Most birds that do become entangled in your net do so by getting their feet caught first. Too much sag in your net will get you in trouble with trapped and dead birds.

 

Winter Pond Management

As water temperatures fall and daylight hours get shorter, out door activities turn from fishing to other pursuits such as hunting and football.

Many of the routine activities associated with maintaining the pond cease--fertilization is no longer needed, and weeds tend to die back. A pond owner could believe management isn't important during winter and that the pond can be forgotten until early spring, but that's not the case. Winter pond management is less critical to the function of the pond than summer management. However, for activities such as harvesting and fertilization, winter provides opportunities to make changes to the pond that result in higher fish production.

In established ponds, fall and winter are the best times to correct structural defects. Water level can be drawn down to allow maintenance of piers, boathouses, and fertilizer platforms without the risk of oxygen depletion. Also, since fish are less active and feed less in cold weather, they can be concentrated in less water without harming populations.

With water levels down, shallow shorelines can be deepened, reducing the amount of pond area that is less than 2 feet in depth. Deepening the edge of a pond can be done with tractors or other earthmoving equipment once the exposed pond bottom is dry. Deepening reduces the chance of too many pond plants growing in shallow water and causing problems during summer.

Drawdown can reduce weed problems in the pond even without deepening pond edges. Drawdown allows the pond bottom to dry and the cold weather will freeze the plants and their roots. To be effective, the drawdown must be maintained through the coldest period of winter. Exposing the bottom of the pond for three consecutive winters may be necessary to control some problem weeds. Don't use drawdown to control needlerush, Southern watergrass, or hydrilla. These plants can be spread throughout the pond by drawdown.

 

Fish Health
By: George W. Klontz, M.S., D.V.M., Technical Services Advisor, Nelson and Sons, Inc., Moscow, Idaho

In late winter and early spring, when water temperatures begin to increase, these organisms frequently emerge from their winter hibernation and cause problems for their fish hosts. The problems are often quite serious because the defensive mechanisms of the fish are still quite depressed because of the low water temperatures. In addition, the nutritional status of the fish, in many cases, is also compromised from the winter conditions. Thus, both conditions favor the reproductive cause(s) of the organisms. In many cases, to administer a chemical such as formalin at this time could cause more problems than it would cure because of the reduced capability of the fish to withstand such an activity.

When considering the use of formalin to remove external protozoa, metazoa, or bacteria, the following process should be followed to insure optimum safety for the fish and optimum efficiency in removing the offending organisms:

1. Do not feed the fish during 24-36 hours prior to the treatment.

2. Conduct a bioassay to determine the safe and effective concentration of chemical. This process is usually not done because of its perceived complexity. However, its omission from the treatment process is probably the chief reason for the chemical-related fish kills.

Examine the gills and pectoral fins of a few (2-3) fish for external organisms. This step may be omitted if one assumes that organisms are present because clinical episodes have occurred in the past.

Prepare at least 3 concentrations of the candidate chemical in 15-20 l of water. For example, if formalin is to be used, prepare concentrations of 1:4,000; 1:5,000; and 1:6,000 in water from the pond to be treated. Provide aeration using airstones and an aquarium pump.

Place 2-3 clinically healthy fish and 2-3 not-so-healthy ("screen-hangers") fish into each container. During the ensuing 60 minutes, observe the fish for signs of distress.

At the end of 60 minutes, examine the gills and pectoral fins of the fish for organisms. This step is often omitted, but it should not be.

The resultant concentration of chemical to administer is that which does not compromise the well-being of the fish and does kill the resident organisms.

3. While the bioassay is in progress, the dimensions of the water volume and the water inflow of the pond to be treated should be determined with as much accuracy as possible.

Obtaining the water dimensions of most ponds is quite straightforward. In cases where the pond has an irregular shape, time should be spent in acquiring the proper measurements.

The determination of water inflow can, in many cases, be described as a S.W.I.G. (a Scientifically-Wild Intuitive Guess). There are many methods to determine pond inflow. The simplest, in my opinion is the Filling Time Method. In this method, the water level is reduced by, for example, 25 cm. At that point, begin recording the time required for the water depth to increase 20 cm. Divide the volume (liters) replaced by the time (minutes or seconds) to determine the LPM or LPS water inflow.

In most raceway systems, the 60-minute continuous drip is the most effective and safe method to administer the majority of water-administered chemicals approved for treating diseases of foodfish. When calculating the correct water volume to be treated, the volume of water displaced by the fish should be considered. In the case of most salmonids, 1.018 kg fish displaces 1.0 l of water. Many fish farmers are often quite surprised to note that, in high density conditions, perhaps 1/3 of the water volume is displaced by fish. To treat such a condition would result in a significant increase in chemical concentration and, perhaps, a significant unnecessary mortality.

In circulating water systems; e.g., circular ponds or rectangular circulating ponds, the most effective treatment method is a combination of the bath and drip methods. The proper amount of chemical is spread in diluted form throughout the pond. Also, a 60-minute drip system is set to replace the chemical discharged during the 60-minute period.

In applying water-administered chemicals to prevent and/or treat diseases in fish, there are a few caveats to be observed. The major consideration is the nature of the chemical. The majority of water-administered chemicals for fish were not developed and marketed for such use and as such the manufacturer of the chemical assumes no liability for problems occurring in such use. Secondly, the margin of safety; i.e., the "distance" between killing the offending organism and negatively affecting the fish, is often minimal. Thirdly, the efficacy and safety of the majority of chemicals used in fish farming are affected by the physical and chemical nature of the water. Thus, dosages recommended in texts and magazine articles may not be suitable for use in all water systems. Fourthly, prior to using a water-administered chemical, all calculations should be validated by a second person.

In summary, to a large degree, the statement is true that water-administered chemicals have killed more fish than the organisms they were supposed to kill. It can be a very hard but unnecessary lesson to learn. Perhaps the foregoing presentation will prevent some future unwanted problems and the fish farmer can spend more time indoors in front of a warm fireplace instead of out in the cold removing morts from the screens.

 

Hatchery Tips
By: Aquatic Eco-Systems, Apopka, FL.

Shipping Live Fish

The art of shipping live fish has been mastered by the tropical fish industry who ship fish around the world. Before the fish are packed, many factors must be considered. Questions you need to address include: Are warm water fish being shipped to a cold climate or vice versa? What is the duration of the shipment before the box will be unpacked? Are the fish aggressive and need to be isolated, or can they be packed as a group? Do they have sharp spines which require double or triple bagging?

Eight and one-half techniques commonly used for shipping live fish in commercial quantities include:

1. Only ship healthy fish that have not been fed for 2-4 days.

2. If the fish are cold tolerant, such as trout, blue gill, striped bass, temperatures should be lowered gradually to 60 F (the metabolic rate of the fish will be reduced).

3. Know the quality of the water the fish will be released into at their destination, the quality of your water should be adjusted slowly to the same levels (pH, alkalinity, salinity, etc.).

4. The clean water used for shipping should be held separate from the fish before packing. Salt is typically added to the water at a rate of 1 to 5 ppt (parts per thousand); that is 0.8 to 4 pounds of salt per 100 gallons or 3.8 to 19 grams per gallon. This reduces osmatic stress on freshwater fish.

5. Various substances such as zeolite, activated carbon, and ammonia locking solutions are also used.

6. Fill shipping bags 1/3 full with the pretreated water and gently place fish into the bags.

7. Compress the bag to remove all air and refill with pure oxygen. The typical ratio is 1/3 water 2/3 oxygen.

8. Seal the bags with rubber bands.

9. Place the bags in insulated containers and add heat or cool packs to maintain temperature.

Table of Equivalents

To convert units appearing in Column 1 (left column) into equivalent values in Column 2 (center column), multiply by factor in Column 3.  Example: To convert 7 feet into meters multiply 7 x .3048 = 2.13 meters.  To convert units appearing in Column 2 (center) into equivalent values of units in Column 1 (left), divide by factor in Column 3. Example: To convert 25 horsepower into BTU per minute, divide 25 by 0.02356 = 1061.

Storage and Care of pH Electrodes

Proper handling and storage of your pH electrodes can not only help in prolonging the life of your electrode, but also ensure fast, accurate readings. General guidelines include:

1. Electrodes should be rinsed between samples with deionized or distilled water.

2. Never wipe an electrode dry, this can cause erroneous readings due to static charges.

3. Never store your electrodes in water, doing so will cause a sluggish response.

4. Always keep the tip of your pH electrode moist. Electrode storage solution is a solution of 4m KCL. If unavailable, a pH4 buffer solution will also work temporarily.

5. In general, pH buffers only have a two year shelf life unopened. Once opened, the shelf life drops to
2-3 months, pH 10 buffer solution only as a 30 day shelf life once opened.

Float Switches

Automatic float switches can burn out motors if they cycle too frequently. Pumps should not be started and stopped every few minutes. The switches will wear out prematurely and the motor can overheat. Never let cascading water or wave action cause a float switch to bounce because this will quickly burn out the motor. Design your sump large enough (or your pump small enough) so that your pump does not turn on more than once every five minutes.

Water Pumps

With the variety of water pumps available today, selecting the ideal model for your application can be tricky. The following are a few useful definitions, helpful hints to aid you in your decision:

Centrifugal Pump: Medium to moderate pressure, flooded suction or self priming pump. An impeller is used to "sling" water to the outside, pumping by centrifugal force.

Check Valves: Installed on pump outlet to prevent back siphoning when off.

Flooded Suction: Water must enter pump by gravity.

Foot Valve: Installed on a pump inlet to prevent the loss of prime during nonoperational periods.

Freshwater Pumps: Freshwater pumps can be used with salt water for brief periods and experience only minimal corrosion. Be sure to rinse with fresh water after use.

Head: The amount of pressure that a pump must work against during operation. Total head equals feet of vertical lift plus friction. The amount of head is an important value when sizing a pump correctly. One psi equals 27 inches of water.

Friction: The loss in pressure and volume that occurs when liquids travel through pipes, fittings and other restrictive elements of a piping system.

GPM: U.S. gallons per minute.

Pedestal Pump: A self-supporting pump mounted above a long shaft with the motor above water and the intake below the water level.

Pressure Curves: Motor overload can occur if pumps are operated below the lowest pressures depicted by the curves shown in the pumps specifications. If your application does not have sufficient head pressure to stay within the curve you should throttle the outlet with a valve or other restriction. Use an amp meter for guidance.

Propeller Pump: A submersible pump with a propeller which draws water through a housing. Propeller pumps are usually high volume low head.

Saltwater Compatible: Salt water compatible pumps are rated for long-term continuous duty with salt water. Little corrosion should occur within 1 year.

Spherical Pump: A silent pump that has only one moving part -- an induction driven impeller. Spherical pumps have no motor shaft, seals or bearings, making them virtually maintenance free.

Trash Pump: A centrifugal pump that can pass large objects, including sand, gravel and mud. Often used for dewatering ponds.

Vertical Pump: A centrifugal pump mounted in a vertical direction. Vertical pumps usually have a long shaft with the motor mounted above water.

 

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Last updated: August 28, 2009

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