Lafourche 'pocket' shrimp seine"I wish we would have had all this new stuff back when we were shrimp seining Barataria Bay," said Antoine Alario in a conversation 20 years ago. "Those old number 18 cotton and tar seines took 20 men to pull and we had to strain with that." Antoine Alario, one of the oldest names in the Gulf Coast netting industry, was referring to a time in the 1920s when shrimp were seined up in the mud flats of coastal Louisiana. The old seine crews are gone, as are the cotton nets and even Mr. Antoine, but the basic principle of the Lafourche shrimp seine is as solid as it was in the old days.
Cotton has been replaced by nylon, and nylon has been somewhat replaced by polyester and polyethylene. The old "left lay right lay" twisted hauling lines are long gone and braided polypropylene and blended poly-dacron lines have been substituted. Real cork floats from Portugal are now tapered polyfoam with grommets from the Spongex Corp. and cotton hanging twine is surpassed in strength by its successor, spun nylon. So if all of the basic components have been replaced, what makes the Lafourche design so relevant in the new millennium? My answer would simply be the unique design regardless of what materials are used to construct it.
Netting The Lafourche design is not so radically different from a beach seine for fish. It has adequate flotation, enough lead weight to hold bottom, and just enough slack in the webbing to hold yet not gill. The net has closely tied hangs, a soft pocket, and a versatile mud line that can be used in almost any pond or canal. The construction of this seine begins with the choice of netting. Nylon raschel in a mesh size of 9 millimeter (mm) or 12 mm is adequate for 100 count shrimp and over. Knotted nylon or polyethylene in a 20 mm through 30 mm mesh will suffice for 80-100 count. A 30 mm through 35 mm will do for larger prawns and specimens in a 70-80 count and larger. Raschel netting is preferable for smaller mesh as it has no knots and can be made in very small mesh sizes. Tetron from Japanese manufacturer Fukui and Badinotti from Italy are excellent nettings in that they have a very uniform size and shape. The Tetron appears to have a stronger tensile strength and less shrinkage while the Badinotti is more readily available in square mesh.
Hanging coefficient Pocket seines usually are no longer than about a 250' headrope length (see Figure 1). The wings of the net are calculated to take up 4/7ths of the total headrope length of the seine, which means about 70' each with a 250' headrope. The "shoulders" or "fenders" of the seine are that portion of the net immediately adjacent to the pocket. Whether the seine is going to be used with a pocket placement that is near one end of the wing or directly in the middle, this fender area is critical for efficiency in catching and holding shrimp. The fenders take up 2/7ths of the overall headrope length, or about 36' each. This leaves us with 1/7th of the overall seine length for the actual pocket. The amount of webbing hung to a specific amount of line is referred to as hanging coefficient. The wings of the Lafourche seine use approximately a 30% coefficient. An example of this would be 3 meshes of 25 mm stretched mesh hung on the line every 53 mm. This makes the Lafourche shrimp seine pocket better in shallow water. This ratio of netting to line is critical in the wings of the seine whether it is used in ponds or an open mud flat. Too large of coefficient in the wing area, say 38%-40%, and you produce large bulging pockets that prevent shrimp from moving along towards the pocket. Too little of a coefficient, 20%-28%, and you produce a tight webbing and very taut net that is extremely difficult to keep in contact with the bottom. The fender area can be built with the same size mesh netting or with smaller mesh. Its only function is to provide a sloping wall that aids in pocketing the catch while not allowing the seine's footrope to leave bottom. This sloping wall is obtained by hanging in the netting to the line with a ratio or coefficient of 38%. An example of this would be 3 meshes of 25 mm mesh hung to the line every 47 mm. The pocket is now formed by hanging in the remaining netting at a 45% coefficient. An example of this would be 3 meshes of 25 mm mesh hung to the line every 41 mm. Floats are critical to the performance of any seine. The Lafourche shrimp seine is no different. If the net is to be used in a 4'-5' deep pond, floats should be placed along the headrope every 18" at least.
Leading edge footrope The footrope or leadline of the seine differs from most other seines in that the Lafourche design does not have an evenly matched floatline and leadline. This design calls for a slightly tighter footrope. This tighter or shorter footrope causes the bottom of the seine to slice into the mud without flopping behind or "trailing." Trailing is the most common problem when headropes and footropes are evenly hung. It occurs when the leadline trails behind the headline so much that it begins to leave bottom. Fish and shrimp swim under the flopping bottom of the seine. With the Lafourche design, the shape of the seine as it cuts through the pond is similar to that of a bulldozer blade. If you notice carefully, you see the blade is curved with the bottom leading edge slightly ahead of the top of the blade. Years of seining flounder and red drum on the mud flats taught me that the Lafourche design with its leading edge footrope, out-produced conventional seines two to one. This leading edge effect is produced by lessening the measurement of the bottom hangs so that the total length of the footrope is 1' shorter for every 75' of headrope. This is easily done by reducing every so many hangs on the bottom, by the amount of 1/4". To achieve that 1 to 75 proportion, the trick is to reduce 48 hangs by 1/4" per every 75' of headrope (i.e., 48@1/4"=12" less).
Mudline In the pond, this seine may require a mudline. The mudline allows the bottom of the seine to maintain contact with the mud, but hopefully keeps the net from plowing so deeply it becomes bogged down. Bunched up lengths of nylon webbing work very well under some conditions as does the "many ends line," which is composed of 7-9 strands of 3/8" diameter polyester soft lay rope. These numerous lines are lashed together, cable like, and then fastened to the footrope of the seine. Polyester has a specific gravity of 1.70 which makes it heavier than water and allows it to sink much quicker than a nylon webbing mudline, which has specific gravity of only 1.14. In combination with a solid core leadline, this type of mudline can wipe the pond bottom clean, giving you very efficient harvesting.
Square mesh box seine As with any good story, there is always a teaser. In this case, the teaser is a new twist on shrimp seine design known as the box seine. This design calls for the use of all square mesh netting. This fully open square mesh allows for maximum water flow, maximum culling of juveniles, and a serious decrease in the amount of mud that is picked up. The square mesh box seine is hung with a totally different ratio of mesh to line. It has only a 5%-7% slack coefficient. The square mesh pulls easier and has approximately 25% less webbing in the water. As research and development testing nears an end in the months ahead, you can expect a full and comprehensive report on this high tech net.
Greg Faulkner operates a net shop and can be reached at PO Box 115, Milton, LA 70558, or e-mail: [email protected]
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