Since the introduction of live cars(socks) and mechanized seines inthe 1960s, innovations in catfishharvesting have been largely theresult of trial-and-error by commer-cial net builders, fish producers andcustom seining crews. Althoughthere were minor modifications inthe design of seines and live carsbased on research in the 1970s,research played little part in theearly development of harvest tech-nology.The Southern Regional AquacultureCenter (SRAC) funded a 3-yearstudy in 1990 to develop new andimproved harvest technologies.From that study, several new tech-nologies appeared to have thepotential to improve seining effi-ciency, including modified seineswith rubber-roller mud lines. Littleof this technology was implementedby the catfish industry, and ineffi-cient harvesting and improper fishsizing continued to be major prob-lems. As a result, catfish culturistsrequested that further research beconducted. The Harvest/GearTechnology program began in 1996at the Thad Cochran NationalWarmwater Aquaculture Center(NWAC) in Stoneville, Mississippi,in collaboration with the National

Marine Fisheries Service’s (NMFS)Harvesting Systems Division inPascagoula, Mississippi. The goalof the program was to developnew harvest/grading technologiesfor the catfish industry. The pro-gram was supported, in part, by a3-year SRAC project entitled“Development of ImprovedHarvesting, Grading and TransportTechnology for FinfishAquaculture.” This report presentsthe specifications for a more effi-cient seine/live car based on thisresearch. Although developed forcatfish culture, this technologyshould apply to other fish grownin ponds and harvested by seining.A limited discussion of typical cat-fish harvest techniques is includedto highlight the benefits of theexperimental seine. For a more in-depth description of fish harvest-ing techniques, see SRACPublication No. 394, “HarvestingWarmwater Fish,” or “CatfishHarvesting” (http://msucares.com/aquaculture/catfish/harvest.html).

General harvesting methodsCatfish seines are usually 6, 9 or,more rarely, 12 feet deep. Theyrange from 1,000 to 1,400 feetlong to reach across the longestparts of ponds. Currently, mostfood-size catfish are harvestedwith a 1 5⁄8-inch mesh seine,which allows fish under a pound

to grade through the seine as it ispulled through the pond. Thisgreatly reduces the stress ofcrowding on the fish. Seines typi-cally have 1⁄2-inch poly-plus ropeson the top and bottom with 3-inchx 3-inch floats every three ties onthe top line and a 2-ounce leadevery two ties on the bottom line.Another bundled nylon nettingmud line is tied to the lead line tohelp hold the seine on the bottomas it is pulled. Some seiners paymore for larger floats (4-inch x 3-inch or 3 3⁄8-inch x 5 3⁄8-inch bulletshaped) with grommets, whichreduces losses caused by the pres-sure of the reel on the floats as theseine is reeled in. The larger floatshelp reduce the tendency of theseine to sink below the pond sur-face when mud accumulates alongits bottom. A funnel area is builtinto each seine about 150 feetfrom one or both ends as anattachment point for a live car.A seine is loaded onto a large,tractor-driven, hydraulic reel (Fig.1), which allows it to be reeled inor out easily as needed duringseining. Ponds are usually seinedfrom the deep end to the shallowend to keep fish from escapingunder the seine bottom once thefish are concentrated in the har-vest area. However, ponds can beseined toward the deep end if theseine has sufficient depth to workproperly.

VIPRFebruary 2007

SRAC Publication No. 1805

1 Mississippi State Unoiversity, MississippiState, MS

2 NOAA, Southeast Fisheries Science Center,Pascagoula, MS

Advances in Catfish Harvesting Gear:Seines and Live Cars

C. Douglas Minchew1, Mack W. Fondren1, Edwin H. Robinson1, John W. Watson2 and Charles W. Taylor2

At this point, seining stops and oneor two workers attach a live car tothe seine by joining the zippers inthe end of the live car and seinefunnel (Fig. 4). Then the two sidesof the seine and the attached livecar are pulled slowly and evenly tothe bank, forcing the fish throughthe seine funnel and into the livecar. Generally, several workers willspread out around the sides of theseine to make sure the seine topdoes not go under water, whichcould allow fish to escape. Figure 5illustrates how the sides of theseine, funnel area and live car ofthe experimental seine line up, giv-ing the fish an unrestricted path

Seining and loading procedureshave become relatively standard-ized in the catfish industry. Tobegin seining, the seine-reel tractoris positioned near one corner ofthe pond deep end (with the mudline side of the reel nearest thepond). The free end of the seine isattached to a second tractor thatpulls the seine off the reel andacross the starting levee. Once thesecond tractor is on the other side,both tractors pull the seinethrough the pond toward the shal-low end (Fig. 2). The tractors canbe moved forward simultaneouslyor alternately, depending on howbadly the seine bogs down in themud. A seining boat equippedwith a 25- to 35-horsepower out-board motor and a front-mountedpush-rack (Fig. 3) catches the seinetop and pushes it forward to dumpmud from the seine. Once theaccumulated mud is dumped, thetractor drivers are signaled tomove forward again. Having tocontinually clear mud from theseine can increase seining time byseveral hours, especially in old,shallow, muddy ponds. A harvestarea about 70 x 150 feet in size isestablished once the pull tractorgets around the last pond cornerand reaches a point near the seinereel tractor. Depending on thenumber of fish in the pond, thepond size, and the number of fishgrading through the seine, therecould be 50,000 to 100,000 catfishof various sizes trapped in thissmall area.

Figure 1. Seine being loaded on a seine reel.

Figure 2. A = Seine funnel (closed); B = Pull tractor; C = Seine reel (tractornot pictured).

Figure 3. A = Seine funnel; B = Live car (in bottom of boat); C = Seine push rack.

into the live car. Once all fish arein the live car, it is unfastenedfrom the seine funnel and the zip-per closed. Additional live cars canbe added if all captured fish cannot be safely loaded into a singlelive car. (Photographs in Figures15 were taken during a pond har-vest using an experimental seine.)In hot weather, or if the water isshallow and muddy from fish orworker activity, the detached livecar can be pulled into clear, deep-er water and staked out. At thispoint, most farmers place a slow-turning, tractor-driven paddlewheel or pump near the live carfor aeration; the fish can now besafely held until it is time forthem to be loaded onto the live-haul truck for transport to theprocessor.

Sometimes workers will split asock for loading when the weatheris hot or when the live car is heavi-ly loaded with fish (Fig. 6). Whenpossible, fish are allowed to gradeuntil the majority of fish are thesize needed by the processingplant. Moving small fish to theplant is costly to both the producerand processor. The loading processinvolves crowding the fish to oneend of the sock so that a full basketof fish can be captured with eachdip (Fig. 7) and swung up above anopen tank door on the live haultruck and dumped (Fig. 8).(Photographs in Figures 6-8 weretaken during a pond harvest usinga conventional seine.)Live cars are usually 8 to 10 feetwide by 50 to 100 feet long withlarge floats spaced around the out-side top line. Additional floats areplaced along the inside edge of askirt designed to minimize thenumber of fish escaping over thetop of the live car. Live cars comein a variety of mesh sizes so afarmer can choose a mesh size thatwill hold the size fish needed bythe processing plant and at thesame time release the smaller fishback into the pond. About 50,000to 100,000 pounds of catfish can beheld in one live car at a fish bio-mass as high as 20 pounds percubic foot. The fish may be loaded

Figure 4. A = Live car; B = Seine funnel; C = Pull side of seine; D = Reelside of seine.

Figure 5. A = Harvest area; B = Funnel area (top covered); C = Front end oflive car; note that all areas shown are densely packed with fish.

Figure 6. A = Live car split for loading; B = Loading basket being inserted inthe edge of the live car.

immediately onto the live-haultruck, allowed to grade for a fewhours, or held overnight if theprocessor needs them early thenext morning.

Experimental Design andSeine EvaluationThe catfish industry identified themajor problems with typical har-vesting procedures as inefficientharvesting and improper fish sizing.Our research focused on those

areas. Conventional seining/gradinggear was modified based on recom-mendations from the NMFS’Harvesting System Team. Theseincluded: 1) using webbing hung onthe bar (square shaped) instead ofthe point (diamond shaped) to con-struct the seine and live car; 2)replacing the mesh mud line with a“traveling,” semi-buoyant, rubber-roller mud line attached to the leadline with short links of chain; 3)increasing the width and length ofthe funnel section of the seine; and

4) using marine zippers instead ofsmall metal frames to attach thelive car to the seine funnel.Experimental seines were tested inboth experimental and commercialcatfish ponds. In addition, studieswere conducted in tanks andponds to evaluate the durabilityand fish grading characteristics ofdifferent webbing materials.

Square-meshed webbing

The experimental seine and livecars were constructed of braided,polyethylene, meshed webbing(BPE) hung on the bar (squareshaped) instead of the convention-al twisted, polyethylene, meshedwebbing (TPE) hung on the point(diamond shaped). This bar-hang-ing technique is used in trawls torelease undersized fish. The princi-ple behind the technique is thatthe force on the webbing as it ispulled through the water is trans-ferred along the bars of the web-bing, which maintains a maximummesh opening. When the webbingis hung on the point, the waterforce causes the mesh to elongate,reducing the size of the opening. Tests were conducted in concretevats and in live cars in ponds tocompare the grading characteris-tics of BTE webbing hung on thebar with TPE webbing hung onthe point. In the concrete vat stud-ies, wood grading frames were fit-ted with webbing of the meshsizes listed in Table 1. To conducteach test, 100 food-size channelcatfish were placed in a 6-foot x25-foot vat, crowded to withinabout 6 feet of one end of the vat,and allowed to grade for 1 hour.Efforts were made to keep the sizedistribution of the 100 fish used inall tests relatively equal. Theresults of the vat studies are givenin Table 1. Live car grading studiesconducted in ponds helped deter-mine how many catfish in varioussize ranges remained in the livecar after grading for 6 hours (Table2). Results of these helped partici-pating farmers compare the grad-ing characteristics of conventionallive cars they were accustomed tousing with those of the experimen-tal live cars.

Figure 7. A = Full loading basket being picked up out of the live car.

Figure 8. Loading basket being dumped on live-haul truck.

“Traveling” mud line

Including a “traveling,” rubber-roller mud line on the experimen-tal seine instead of the bundled,mesh mud line commonly used onconventional seines represents amajor change. The purpose of the“traveling” mud line was toimprove seining time and catchefficiency by reducing the numberof times the pull tractors had to bestopped so the push boat coulddump accumulated mud.The bundled, mesh mud line on aconventional seine is tied directlyto the lead line (Fig. 9). The new“traveling,” rubber-roller mud lineis attached to the lead line byshort sections of chain (Fig. 10).This allows the rubber-roller mudline to move in and out of themud on the pond bottom withoutloading the seine with mud. Thecustom-designed, 4-inch x 8-inch,football-shaped, rubber rollers areslightly buoyant, which helps freethem from the mud when theybecome bogged down. Theserollers increase the cost of theseine by about 40 percent.

Enlarged seine funnel and live car

Changes made in the design ofthe seine funnel and live car toreduce the time required to movefish from the harvest area into thelive car, improve live car gradingefficiencies, and reduce stress onfish. The funnel section of the

experimental seine was greatlyenlarged and a 10-foot marine zip-per was installed at the end of thetapered section. A similar zipperwas sewn into one end of the livecar. When open, both zipper cen-ters are located at the bottom cen-ter of the seine funnel and live car,thus aligning them so they can beeasily joined to form a 20-footopening between the seine funneland live car. Replacing the smallmetal frame commonly used toattach the seine funnel and live carwith matching marine zippersgreatly enlarged the openingbetween the seine and live car bylining up the sides of the seine fun-nel with the sides of the live car.The zippers can be fastened only ifthe sock and funnel are alignedcorrectly, which eliminates the seri-ous problem of workers inadver-tently blocking the entry of the livecar by twisting the throat of thesock when tying the metal frameon the live car to the seine funnel.This error often goes unnoticeduntil fish have been severelycrowded as the seine and sock arepulled toward the bank. These changes in the seine-live carsystem are illustrated in Figures 11-14. Figure 11 shows the small fun-nel area of a conventional seineattached to the metal frame on alive car. Figure 12 shows the largefunnel area of an experimental

Table 1. Effect of mesh size and type on the minimum size of channelcatfish retained in live cars.

Size of fish Mesh type Mesh size (in) retained (lb)

Conventional(knotted, twisted, diamond) 1 5⁄8 ≥ 0.75

1 3⁄4 ≥ 1.00 1 7/8 ≥1.25

Experimental(knotted, braided, square) 1 9⁄16 ≥ 0.75

1 5⁄8 ≥ 1.00 1 11⁄16 ≥ 1.25 1 3⁄4 ≥ 1.50

Table 2. Average percentage of various sizes of catfish remaining inexperimental live cars of different mesh size after grading for 6 hours.

Mesh size (in) Size classes (lb) with average percent not graded

<3⁄4 3⁄4 to 1 1 to 1 1⁄4 1 1⁄4 to1 1⁄21 9⁄16 6 23 15 111 5⁄8 1 4 19 241 11⁄16 0 0 3 6

Figure 9. Bundled mesh mud line.

seine attached to the matching zip-per on the wide-throated live car.Figure 13 shows a close-up of alive car zipper zipped to the seinefunnel zipper. Figure 14 illustratesthe differences in the sizes of theopenings produced by a metalframe (A) and a marine zipper (B).The experimental seine is usuallypulled with the seine funnelclosed. Closing the seine funnelinvolves closing the zipper in theback and hooking the matchingsides of the brummel hooks sewnacross the width of the top andbottom of the front of the seinefunnel. A closed seine funnel withhooked brummel hooks is shownin Figure 15. Brummel hooks areexceptionally strong and are rarelyopened accidentally. A close-up ofa closed brummel hook is shownin Figure 16. Both sections of thehook have slots that can be alignedto separate them. While not acommon practice, the seine can bepulled with the live car attached tothe seine funnel and the brummelhooks unhooked. This allows fishto load into the live car as thepond is seined. However, the bot-tom of the seine and sock aremore likely to catch mud becauseof the additional weight and dragcaused by the sock and loadedfish.

Harvest efficiency studies

Studies compared the harvest effi-ciency of a conventional and anexperimental seine. Two empty7acre ponds were stocked with aknown weight of food-size fish.Over a period of weeks, each pondwas seined seven times usingeither a conventional or an experi-mental seine (1 5⁄8-inch mesh). Thetype of seine used in a pond alter-nated after each seining. The origi-nal fish were used multiple timesfollowing an acclimation period.The parameters measured duringeach seining were mean seiningtime, mean live car attachmenttime, number of laborers neededto attach the live car, and meanseining efficiency (Table 3). Theseining efficiency (percent caught)was determined by dividing thepounds of fish caught in a single

Figure 10. Traveling rubber-roller mud line system. A = lead line; B = onechain link; C = rubber-roller mud line.

Figure 11. Conventional seine and live car attached using a small metal frame.A=small seine funnel; B = small metal frame; C = live car.

Figure 12. A = live car and sein funnel zipped together (dark area); B = piled up live car; C = seine funnel.

seining by the total poundsstocked. Using the experimentalseine improved harvest efficiency,required fewer workers to attachthe live car, and reduced seiningtime by reducing the number oftimes the pull tractor had to bestopped so accumulated mud couldbe dumped.The efficiency of the experimentalseine also was evaluated in a studyat the National WarmwaterAquaculture Center. It was usedfor the routine harvest of tenresearch ponds (4- or 10-acre) thatwere being totally harvested at theend of a study (ponds contained asingle year class of fish). Eachpond was seined once and thepounds of fish caught was record-ed. Subsequently, each pond wasdrained and the remaining fish ineach pond were picked up by handand weighed. On average, theexperimental seine caught 94 per-cent of the fish in each pond.

Field trials

Several experimental seines andlive cars were constructed and test-ed in commercial and research cat-fish ponds. The experimental seinewas used by several farmers forextended times and they evaluatedits performance under commercialharvesting conditions. The experi-mental seine features farmers likedmost were the enlarged seine fun-nel and the use of marine zippersinstead of a small metal frame toattach the live car to the seine fun-nel. All farmers who tested theseine were very positive aboutthese modifications.The most disliked experimentalseine feature was the “traveling”mud-roller system, even thoughmost farmers agreed that it greatlyreduced the number of times apush boat had to dump mud fromthe seine. There were some minorobjections to the new mud linetechnology, but cost was the majorfactor farmers thought would limitits adoption by the industry.Adding this technology to a seineincreases its cost by about 40 per-cent.

Figure 13. A close-up of a live car and seine funnel zipped togehter with a pair of marine zippers.

Figure 14. A = old style metal frame used to join live car and seine funnel; B= open zipper in new still seine funnel. Notice the size of the opening inthe back of the new style funnel compared to the metal frame.

Figure 15. A number of fastened brummel hooks attaching the top and bottomof the seine funnel (keeps most fish out of the seine funnel during seining).

Conclusion

Catfish producers who participatedin this project generally liked thelarge floats with grommets, theenlarged seine funnel, the marinezippers for attaching the live carand seine funnel, and a conven-tional rolled, mesh mud line. Themost disliked component of theexperimental seine was the “travel-ing” mud roller system. Some pro-ducers and commercial harvestersthought fish could escape throughthe space between the lead lineand mud roller line. Other issueswere the perceived difficulty ofhandling the mud roller systemwhen getting around aerators andthe dislike of riding the “traveling”mud roller line commonlyexpressed by mud line riders. Even

so, there was general agreementthat in certain pond types wheremudding is a problem the “travel-ing” mud roller system did havemerit. They thought the primaryadvantages of the experimentalseine and live car were: 1) pondscould be seined more quickly withless pushing needed to dumpmud; 2) fish transitioned into thelive car more easily and appearedto be in better condition; 3) fishgraded out of the live car faster; 4)little if any aeration was neededwhen loading the live car; and 5)the braided, polyethylene webbingappeared to be much moredurable. This project has stimulated amajor change in the harvest tech-nologies used in the catfish indus-

try. One large net manufacturernow puts large funnels andmarine zippers in 80 to 90 percentof the new seines and live carsbuilt and has installed 400 to 500marine zippers in existing seinesand live cars since 2004. Mostseines and live cars continue to bebuilt with knotted, twisted, poly-ethylene webbing hung on thepoint (diamond shaped) instead ofthe braided, polyethylene webbinghung on the bar (square shaped)used in the experimental equip-ment. Seines with mesh hung onthe point (diamond shaped) areeasier to repair in the fieldbecause the meshes next to dam-aged areas can usually be sewntogether quickly without reducingthe effectiveness of the seine. Ripsand holes in square-mesh seinesmust be fixed by cutting out thedamaged area and sewing in cor-rectly cut patches. This is timeconsuming and requires moreskill. Higher cost, weight and per-ceived usability issues limited theacceptance of the “traveling,” rub-ber-roller mud line technology.Consequently, most seines builttoday use the bundled mesh mudline. Many producers and customseining crews now cover the backhaves of their live cars with web-bing to prevent rapidly loadingfish from sinking the live car andescaping.

Materials sources and netbuildersExperienced net builders can takethe information given in Figures17-20 and build a 9-foot-deep, 1 3⁄4-inch mesh experimental seineand live car. They will also beable to construct seines of differ-ent depths and mesh sizes andlive cars of different lengths andmesh sizes by modifying thesespecifications.

Sources

Netting:

Ultra ServicesP.O. Box 80504Lafayette, LA 70598-0504Phone: (337) 237-6596

Figure 16. A = Closed brummel hook.

Table 3. Harvest efficiency data: CTPE = conventional seine with twist-ed polyethylene webbing; EBPE = experimental seine with braidedpolyethylene webbing.

Seine type

CTPE EBPE CTPE EBPEParameters Year 1 Year 2

Mean seining time (min) 90 60 152 76Mean live car attachment time (min) 11 5 10 6Laborers needed to attach sock 2 1 2 1Mean catch efficiency (% caught in

one seining) 69 83 55 63

Brummel hooks:

Donovan MarineP.O. Box 19100New Orleans, LA 70179Marine Zippers:

YKK USA, Inc.Midwest Division232 Shadow Wood CourtLoveland, OH 45140

Floats:

Delta Net & Twine Co. Inc.3148 Highway 1 SouthGreenville MS 38701 Rubber mud rollers:

National Warmwater AquacultureCenterMississippi State UniversityP.O. Box 197Stoneville, MS 38776-0197

Experienced Net Builders

S & S TrawlP.O. Box 789Supply, NC 28462Delta Net & Twine Co. Inc.3148 Highway 1 SouthGreenville MS 38701

150 feet 25 feet 850 feet 150 feet

60 floats 60 floats

25 feet

60 leads284 rollers341 leads

341 floats

60 leads51 rollers

ZippersWeights 3⁄8-inch tennex rope36 inches 36 inches

3 1⁄2 inches 3 1⁄2 inches 3 1⁄2 inches 3 1⁄2 inches 3 1⁄2 inches

Funnel

Floats

Figure 17. Construction diagram and specifications for making a 9-foot-deepexperimental seine.

Webbing: 3 1⁄2-inch (=1⁄2-inch mesh) x 3mm PE; 45 1⁄2 inches deep

Hanging: 3 meshes on 7 1⁄2 inchesHanging ratio: 3 1⁄2 webbing on square 71%Float line: constructed of 3⁄8-inch tennex rope;

15-foot leg (bare rope) on each sideFloat type: White OS4SC (Spongex Manufacturing Co.

product number) float with grommetFloat spacing: 30 inches apartLead line: constructed of 1⁄2-inch polytron ropeLead type: 2-ounce center holeLead spacing: 30 inches apartMud line: constructed of 3⁄8-inch tennex rope;

15-foot leg (bare rope) on each sideMud roller type: 4- x 8-inch football shapeMud line drops: 5 links of 3⁄16-inch galvanized chainMud line drop spacing: 36 inchesFunnel: 25- x 25-feet with zipper Zippers: VFOR-151 (YKK Manufacturing Co.

product number), 3-meter marine zipperwith big teeth and stainless steel slides

57 meshes

120 meshes45.5 meshes

9 feet

4 feet

Left and right side panels Top and bottom panel

21 meshes

120 po

ints

(24)

2B

4P

63 m

esh

es57

mes

hes

Top (1-pound 2-ounce float/22.5 inches)

(28) 2B 1P

Bot

tom

(2-o

unce

lead

/22.

5 in

ches

)

Sq

uare S

qu

are

Figure 18. Design pattern for making the funnel section of a 9-foot-deep experimental seine.

158 bars Openzipper 82 bars

10 bars

28 bars

62 bars

10 bars

28 bars

10 bars

Figure 19. Design pattern for making a live car (75-foot, 1 1⁄2-mesh).

Hanging: 4 bars on 6 1⁄2 inches Floats: 1 float every 3rd tie on the inside and outside

float line Float type: White K4SC float with a grommet Zipper: YKK#10 with big teeth and stainless steel slides;

9.84 feet (3 m) longLeads: 2-ounce lead every 18 squares as needed on the bot-

tom of the live car

Skirt

Open zipper(starts in center)

Bottom panel

Side panel

Rear panel

Figure 20. Stylized three-dimensional drawing of a typical live car with a zipper in one end for attaching the live car to the seine funnel.

The information given herein is for educational purposes only. Reference tocommercial products or trade names is made with the understanding thatno discrimination is intended and no endorsement by the Southern RegionalAquaculture Center or the Cooperative Extension Service is implied.

The work reported in this publication was supported in part by the Southern Regional Aquaculture Centerthrough Grant No. 2004-38500-14387 from the United States Department of Agriculture, Cooperative StateResearch, Education, and Extension Service.

SRAC fact sheets are reviewed annually by the Publications, Videos and Computer Software SteeringCommittee. Fact sheets are revised as new knowledge becomes available. Fact sheets that have notbeen revised are considered to reflect the current state of knowledge.

Acknowledgments:We are indebted to many people who worked on this project over theyears. We thank all those at NMFS and NWAC and the catfish farmerswho cooperated with us. A special thanks to Jason Yarbrough, JamesBledsoe and Tommy Thompson. We also thank Danny Oberle for manyof the photographs, Donnie Rutherford for the drawings, and SusanBailey and Rachel Beecham for their editorial assistance.