Seine crew. Five to seven persons form a seining crew for large ponds. Two to four persons inside the pond keep the weighted line on the bottom near each levee toe, two drive the tractors, and one operates a boat to dump mud from the bottom line.
An experienced crew can seine a large pond and concentrate fish in one to two hours.
Seining technique:
The shape of the pond determines how it should be seined. Usually the proper length of seine is stretched across the narrow end of the pond in front of the drain structure: A bracket on the bow of the boat, or the float line laid over the bow, helps push the seine as it collects mud.
Watch the float line for indications that the net is “mudding up.” The floats will be pulled underwater if this occurs. The seine boat should quickly move to roll or dump the mud from the seine so that fish do not escape. A 14- foot boat with a 25-horsepower outboard motor is adequate. A chemical boat also works well and has ample space for carrying a livecar.
Pull the seine slowly with a zig-zag motion at about 25 to 45 feet per minute to prevent the seine from lifting off the bottom. Seines will have to be pulled over or pushed under aerators, depending on how they are anchored.
Seines can be pulled manually or with small tractors, trucks or four wheelers in small ponds less than several acres. A seine longer than several hundred feet, however, is difficult to pull manually in ponds with soft, muddy bottoms. A bag that is woven into the seine is a nice feature for small seines. It provides a good area to capture, hold and harvest fish.
Land the seine near a water supply or aerator where fresh, oxygenated water can be provided if needed. When fish are crowded, they can rapidly deplete the dissolved oxygen in a localized area, especially in warm weather.
Holding fish:
A device called a livecar, or sock, is used to crowd and hold fish. Attach it to the seine after fish are crowded with the harvesting seine. This lessens the chance of the livecar hanging up on snags and decreases the pulling drag. A short piece of rope ties off the funnel end of the harvesting seine until the livecar is attached.
The livecar has a metal loading frame which attaches to the seine with drawstrings. The metal loading frame sets up a narrow chute to funnel fish into the livecar as the seine is beached. Without the chute, many fish can remain in the seine as it is landed.
They will then be much harder to move into the livecar. Water should beat least 2 ½ to 3 feet deep for easy fish transfer. If water temperatures are below 60°F, fish can be held many hours and overnight. However, if temperatures are in the low 80s or higher, fish should beheld only for a short time and carefully monitored. Water temperatures affect fish activity and ease of grading in socks before harvesting.
Use one mesh size larger than normal, and allow overnight grading before harvesting fish in winter. This will avoid harvesting many offsized, unmarketable fish. The sock needs to be in good condition or fish will escape overnight. Hauling trucks can be scheduled with assurance when fish are held in livecars.
Minimize stress:
When holding fish, move the sock to deeper water to provide more room and clearer water. In warm or hot weather, it is helpful to cool fish before harvest by moving the sock near a flowing well but not under it or directly in the high current area.
Fish in socks are usually so crowded that little water movement takes place within the sock, and the increased current probably stresses the fish on the exterior of the sock as they constantly swim against the current.
Harvesting stakes can be used to secure the lead line into the pond bottom and hold the float line about 1 foot above the water surface.
If the sock if not properly anchored, currents from a well or an aerator can roll up the livecar and kill fish. Also, beware of the possibility of theft when fish are held overnight. Livecars are more secure for holding catfish than seines because they have a solid mesh bottom and double float line that prevent fish from jumping out.
Fish are good escape artists. Several livecars may be required if many fish are harvested. About 5,000 pounds of fish can be held in each 10-foot length of a standard-sized sock at temperatures below 80°F. The increasing frequency of “red fillet syndrome” in catfish is thought to be directly related to harvest and holding stressors.
If fish must be landed in shallow water, or a large number must be harvested, consider another harvest method. Harvest fish as before, but stake out the harvesting seine. Do not use a livecar. Pull a short cutting seine of the desired mesh through the fish to roughly grade and concentrate them for loading. If fish require overnight holding, leave them in the larger area of the staked harvesting seine.
Watershed ponds:
Harvesting is more difficult in watershed ponds because pond depths are usually more than 10 feet. Obstacles are common in bottoms and on banks. Fresh water is usually absent at the harvesting site.
Watershed ponds usually have to be drained to a smaller area with a maximum depth of 6 to 8 feet. The height from the harvesting area to the levee top makes loading a transport truck difficult and time consuming without the use of mechanized equipment.
Ideally, fish are harvested in colder months so stress on fish is less and ponds can refill with runoff water during late winter and early spring. Most baitfish are harvested by seining because it is faster than using lift nets.
Fish are crowded into the bag portion of the seine, then the bag is staked. Minnows are dip netted into floating holding boxes with nylon walls. Summer harvests are stressful because of warm surface waters.
Pumping cool well water near the harvesting operation helps reduce stress and losses. Minnows are harvested frequently to keep up with customer orders.
When manually beaching a seine, pull it slowly and carefully to keep the lead line on the pond bottom. Too often there is an unnecessary rush to land the seine, and many fish escape under the lead line when it is accidentally lifted off the bottom. Four persons can beach a seine. Two pull in each of the loose ends.
One keeps the lead line on the bottom, and the other helps pull and piles the seine on the bank. When the lead line is on shore, raise it and close off both ends by slipping your arm under the seine and lifting it out of the water.
This forms a hammock shape that traps fish. Concentrate fish into the middle, and move the seine to deeper water to stake it if desired. Harvesting stakes free up labor to move fish rather than just hold the seine.
Fish pumps:
A fish pump can be used for harvesting. There are various models. They move fish rapidly and safely from tanks or ponds to hauling trucks. Crowding is required, then the pump intake is placed where it can move fish and water to a dewatering tower or box. The water returns to the ponds, and fish are loaded into the transport tank.
Pumps can be portable units mounted on trailers or fixed units mounted on a transport truck. They are commonly used in the trout industry and are being evaluated for use with warmwater species.
The use of fish pumps often means fish weights are determined by water displacement rather than with scales. This weighing method is less stressful on fish than scale weighing and can be accomplished quickly. One pound of water is displaced by 1.02 pounds of fish, and 1 gallon of water weighs 8.35 pounds.
To determine fish weights by water displacement, just determine the change in water volume in gallons in the transport tank after fish are loaded and use a simple formula. For example, if loaded fish increase (displace) the water volume in a tank by 50 gallons, then the weight of fish is equal to 50 gallons x 8.35 pounds/gallon x 1.02 or 425.8 pounds.
A water displacement tube on the outside of the tank, or a clear viewing plate in the tank wall, can be used to calculate the amount of water displaced. This is a new technique for most warmwater fish farmers but offers some real advantages and promise.
Authors:
Gary L. Jensen and Martin W. Brunson
