Vol. 22, No. 1, Winter 2005

Arkansas Aquafarming

COOPERATIVE EXTENSION PROGRAMUniversity of Arkansas at Pine Bluff

University of Arkansas at Pine Bluff, United States Department of Agriculture, and County Governments Cooperating

Extension Contacts

Larry DormanExtension Fisheries Specialist870-265-8055/870-489-1115ldorman@uaex.eduMartha FittsExtension Assistant870-265-8055mfitts@uaex.eduAndy GoodwinExtension Fish Pathologist870-575-8137/870-540-7811agoodwin@uaex.eduDavid HeikesExtension AquacultureSpecialist870-575-8143/870-489-1083dheikes@uaex.eduWes NealAssistant Professor, Small Impoundments870-575-8136wneal@uaex.eduMelanie NewmanExtension Associate501-676-3124mnewman@uaex.eduSteeve PomerleauResearch Associate(Aquaculture Verification)870-575-8139/870-692-3709spomerleau@uaex.edu Jo SadlerExtension Fish HealthSpecialist501-676-3124/870-489-1544jsadler@uaex.eduGeorge SeldenExtension AquacultureSpecialist870-512-7837/870-540-7805gselden@uaex.eduNathan StoneExtension Fisheries Specialist870-575-8138/870-540-7810nstone@uaex.eduHugh ThomfordeExtension AquacultureSpecialist501-676-3124/870-692-3398hthomforde@uaex.eduJeremy TrimpeyResearch Associate,Aquaculture Verification870-575-8140jtrimpey@uaex.edu

Web address:www.uaex.edu/aqfi/

Making Payments, MakingMoney--Rapid Evaluation of Variation in Prices and Feeding StrategiesCarole R. EngleDirector, Professor of Economics

Winter is an excellent time to plan for theupcoming production season. An analysis ofprofit or loss (from the income statement),changes in net worth and financial position(from the balance sheet) and cash flow for theyear (from the cash flow budget) should bedone at the end of the fiscal year to under-stand the strengths and weaknesses of thebusiness. We have self-guided tutorials avail-able on request (on disk and in notebookform) to assist in conducting this analysiseach year.

Once the financial performance of thebusiness over the past year is understood, thenext step is to plan for improving the farmbusiness over the next year. The cash flowbudget is the best tool to use to compare dif-ferent stocking, feeding and harvesting strate-gies to improve financial performance overthe next year. However, it can be difficult tocome up with the numbers for the pounds offish to be harvested and feed fed in eachmonth. These numbers are needed to do thekind of comprehensive cash flow analysis that is needed to make good managementdecisions.

David Heikes and Steeve Pomerleau, ofthe UAPB Aquaculture/Fisheries Center, havecome up with a catfish growth model devel-oped as an EXCEL spreadsheet that may beof help. This spreadsheet is available uponrequest. The model is based on an inventoryestimate for each pond by size group. Sincemany banks required catfish farmers to obtaininventory estimates this past year, a numberof farms have this information. If your farmhas not had an inventory estimate done, youcan contact Extension personnel for assis-tance. The model tracks growth and feed foreach size group of fish.

Table 1 shows the summary table in thespreadsheet. The starting or ending date, theprice of catfish, the price of feed, the marketsize and the percent of satiation feeding canbe changed in the spreadsheet to see whateffect these changes will have. When any ofthese values is changed (in EXCEL), the sum-mary table immediately shows the resultingchanges in the quantity of feed required, thefeed cost, the quantity of fish ready to be soldand the revenue for each month. These valuesare what is needed for the cash flow budgetand, when the best options are found, can becopied and pasted into the cash flow budgetfor the upcoming year. For example, Table 1shows the results for feeding fish from April 1through the end of December 31, 2005. Table1 is based on feeding to satiation, with anFCR of 2.0, a feed price of $267/ton, and sell-ing fish at a price of $0.67/lb. In this case,14,760,277 lb of feed are fed and net returnsabove feed costs are $2,676,014.

What happens if feed price increases to$285/ton? Then, net returns above feed costsdrop to $2,543,172 (Table 2). What if werestrict feeding to 75 percent of satiation atfeed prices of both $267/ton and $285/ton? Atthe higher feed price of $285/ton, with 75 per-cent restricted feeding, net returns are$2,244,342 (Table 2). At the lower feed priceof $267/ton, net returns with a 75 percentrestricted feed are $2,335,483. The higherfeed price results in a 5 percent decrease innet returns. Net returns also decrease with the75 percent satiation feeding. For the samefeed price, net returns are 12-13 percent lowerif feed is restricted to 75 percent of satiation.It is important to note from Table 2 that thenet returns were higher at the higher feedprice fed to 100 percent satiation than at thelower feed price, when feeding to 75 percentsatiation. Even at higher feed prices, it ismore profitable to feed close to satiation thanto drastically restrict feeding.

Farmers with substantial debt loads mayhave difficulty obtaining enough capital to

continued on page 2

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Growing period Month Pounds Dollar Pounds Dollar

Starting date 4/01/05 Jan. 0 0 0 0

Ending date 12/31/05 Feb. 0 0 0 0

No. of days 273 March 0 0 0 0

Prices April 1,831,770 244,541 333,124 223,193

Catfish ($/lb) 0.67 May 2,344,844 313,037 980,000 656,600

Feed ($/ton) 267 June 2,237,672 298,729 1,099,429 736,617

Feeding information July 1,165,316 155,570 2,413,714 1,617,189

Market size (lb) 1.6 Aug. 803,238 107,232 677,313 453,813

FCR 2.0 Sept. 849,942 113,467 0 0

% satiation 100 Oct. 1,286,401 171,735 0 0

% bodyweight/day 2.5 Nov. 1,821,959 243,232 0 0

Dec. 2,419,135 322,955 1,431,491 959,099

TOTAL 14,760,277 1,970,497 6,935,092 4,646,512 2,676,014

Table 1. Summary sheet for the catfish growth and feeding spreadsheet.

Table 2. Effect of varying feed priceand percent satiation of feeding on net returns above feed cost.

Percent satiation of feeding Feed price

$267/ton $285/ton

100% satiation $2,676,014 $2,543,172

75% satiation $2,335,483 $2,244,342

Values to change Feed fed Fish sold Net returns above feed cost

feed all their fish to satiation. Howshould a farmer manage ponds if capi-tal is lacking? Our catfish growthspreadsheet can demonstrate theeffects of satiation feeding of selectedponds but restricted rationing of otherponds. For the example used above, iffeed were severely limited, at only3,000,000 lb for the same time period(20 percent of satiation feeding), netreturns would be negative, at -$38,025.However, by targeting full feedingrates to those ponds with fish close tomarket size, and feeding others atlower, maintenance rations, a positivenet return of $15,508 was obtainedeven at this highly restrictive feed

limit. By raising the feed limit to6,000,000 lb, net returns of $96,472were obtained from spreading feedequally across all ponds. Then, byusing the spreadsheet to allocate feedmoney to the ponds with fish close tomarket size, net returns wereincreased to $503,258. Feed fundingcan be assigned to individual pondson the EXCEL spreadsheet, and theeffect on net returns viewed immedi-ately. Thus, for farms with limitedmoney to spend, the best feedingschedule can be determined.

The values from these spread-sheets can be entered into the cashflow budget to further consider how

the best feeding pattern affects cashflow, including loan payments. Forcopies of these spreadsheets, contactCassandra Hawkins-Byrd at (870)575-8123 or email her atcbyrd@uaex.edu. For further explana-tion of financial analysis on catfishfarms, contact Dr. Carole Engle, at(870) 575-8523, or email her at cengle@uaex.edu. For technical assis-tance with the catfish growth spread-sheets, contact either SteevePomerleau at (870) 692-3709, oremail him at spomerleau@uaex.edu orDavid Heikes at (870) 489-1083, oremail him at dheikes@uaex.edu.

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The catfish hatchery at the UAPB AquacultureResearch Station is a small unit capable of handling onemillion eggs and raising them to 21-day fry. The unit useseight 10'x2'x10” troughs to hatch and raise these fry. Twoof the troughs are standard configuration paddlewheeltroughs with baskets for holding the egg masses.

Due to the small area allocated to the unit, de-stickingcatfish eggs and moving to McDonald egg jars for hatch-ing has been considered. Past experience has shown verylittle disease potential and iodine or any other prophylaxishas not been used for five spawning seasons. In theinstance of occasional fungal infection, eggs from theinfected baskets have been removed and de-stuck usingsodium sulfite solution and then put in a McDonald jar.This process allows the heavier eggs to roll on the bottomof the jar while the lighter fungal globs are caught in thecurrent and moved out of the jar. Sometimes the fungalglobs do not exit the jar, but simply float over the eggs.Although never quantified, the fungi never seemed tospread down to the rolling eggs. Additionally, this separa-tion allows the fungus to be siphoned out of the jar.

This spring a non-replicated comparative study of thetwo different incubation systems was completed. Thehatching troughs hold six baskets. Catfish fry were hatchedin six baskets and six McDonald jars loaded to the samedensities. See Table 1.

Forty-four catfish spawns were collected and weighed.Each spawn was divided in two with half going to a basketand half going to a McDonald jar. All weights were takenbefore any sodium sulfite was used.

The egg masses were divided in two, and each halfwas weighed in a bucket until approximately the sameweight of eggs was present in each bucket. One bucket ofeggs was placed in a standard hatching basket and the sec-ond bucket of eggs went into a hatching jar. Before movingto these assigned hatching units, the bucket of jar eggs wasdrained of water and one gallon of sodium sulfite solutionadded to those eggs. All volumes were measured after de-sticking of the eggs with sodium sulfite. Sodium sulfitesolution was prepared in one gallon batches at the rate of57g sodium sulfite per gallon of water. During the sodiumsulfite bath, the bucket of basket-bound eggs remainedundisturbed in their original weighing water. When the jar-bound eggs were de-stuck, they were volumetrically mea-sured in a graduated pitcher and loaded into a McDonaldjar. Then the basket eggs were loaded into the basket. Thissequence was repeated for each basket and jar pair.

Sodium sulfite caused high pH fluctuations, whichwere monitored but not controlled. See Tables 2 and 3. Allbuckets with egg masses exhibited a pH of about 7.4 afterweighing. During de-sticking in sodium sulfite solution thepH rose to 9.2. Basket masses remaining in their bucketwaiting for the jar masses to de-stick had a pH of 7.4.

When those eggs were moved to the basket in the trough,the pH was 7.3. When fresh water rinsed away the sodiumsulfite solution from eggs in the jar, the pH was 7.3. Ingeneral, jar eggs had a pH of 7.3 at time 0, when eggswere sorted into buckets but no sodium sulfite was yetadded. The pH was about 9.2 at 5 minutes after addingsodium sulfite. The pH dropped back to about 7.3 aftercompletion of the 10 minute bath and 5 minute rinse infresh water.

All eggs were collected May 22, 2004. The first eggshatched May 25 from baskets, and on May 26 from jars.Well water was used to hatch the eggs in both systems.Water temperature was approximately 76˚F.

No preventative chemical baths were used on anytreatments this year and a much higher than normal rate offungal infection was experienced in the baskets. In con-trast, almost no fungus was observed in the jars. On theoccasion that fungus was observed in a jar, it seemed togrow only on bits of egg mass matrix that were not flushedout, rather than on the eggs themselves. No attempt wasmade to treat any fungus in this study.

Fry were counted after they turned gray. Fry countswere volumetric. Three counts of 5ml of fry were made todetermine the average number of fry per milliliter. Frywere then placed in a graduated pitcher, the volumerecorded and the number calculated. On May 30, the fryfrom the basket-hatched trough were collected and quanti-fied and 188,150 fry were recovered. On May 31 and June1, the fry from the jar-hatched trough were collected andquantified and 361,900 fry were recovered. About twice asmany fry were recovered from the jar hatch method as thebasket hatch method.

Jar Hatching of Catfish - A Good AlternativeBauer Duke, Aquaculture Research Station Manager

After de-sticking 5 pounds of eggs are held in each jar.

Continued on page 4

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Important points:

1. Two McDonald jars can fit in thesame hatchery space as one hatchingbasket.2. Hatching rate from the jars wasalmost twice that of the baskets.3. Given 1 and 2, the jar methodmay render four times as many fry as

the basket method when no prophy-lactic chemicals are used.4. Prophylactic chemical treatmentsdid not appear to be necessary withthe jar-hatched eggs.5. The newer the eggs at collection,the longer the time needed in the sodi-um sulfite bath for proper de-sticking.6. Eggs were checked twice per day,at 7:30 a.m. and 4:30 p.m.7. Moving the new fry to a rearing

trough from a jar is easier thansiphoning from a hatching trough.

Previous experience indicates, byobservation only, that fry hatched injars survived better if they werepoured from the jar after they turngray than when they are still pink, asthey are when they fall through thebasket mesh.

Continued from page 3

Table 1. Weights and volumes of eggs used after splitting spawns in half.

Group Basket weight (lbs) Jar weight (lbs) Jar volume (ml)

1 4.77 4.74 21002 4.66 4.68 17503 4.90 4.92 20004 4.93 4.98 21005 5.02 4.98 22006 4.67 4.72 2000

Table 2. pH changes in the eggs destined for jars after weighing in the bucket, during the sodium sulfitesolution bath in the bucket and after 5 minutes of rinsing in the McDonald jars.

Jar number pH after weighing pH during sodium pH 5 minutes after(eggs in weighing water) sulfite bath rinse in McDonald jar (time = 0) (time = 5 min) (time = 15 min.)

1 7.8 9.3 7.22 7.0 9.2 7.43 7.4 9.2 7.24 7.4 9.1 7.45 7.3 8.9 7.36 7.4 9.2 ?

Table 3. pH changes in the eggs destined for baskets after weighing, while waiting for jar eggs to de-stickand after loading into the basket.

Basket number pH after weighing pH during sodium pH in the basket trough (eggs in weighing water) sulfite bath (eggs still (time = 15 min)(time = 0) in weighing water)

(time = 5 min)

1 7.8 7.4 7.22 7.0 ? 7.33 7.3 7.3 7.24 7.4 7.3 7.45 7.2 7.4 7.36 7.4 7.4 ?

[5]

Now that the spawning season isapproaching, how did your hatchinggo last year? Did you obtain satisfac-tory hatching rates? If not, it wouldbe good to consider making somechanges in the hatchery.

Disinfecting eggs daily toimprove hatch by reducing fungusand bacterial infections is a recom-mended practice. Research hasshown that a number of compoundsare effective disinfectants, but farm-ers are restricted to those chemicalsin the FDA approved or “low regula-tory priority” categories: povidoneiodine, formalin (approved brands)and hydrogen peroxide.

Iodine is commonly used as a dipfor eggs before they are placed introughs. Formalin is effective (Rachet al. 1997) but produces a strongsmelling noxious gas. OSHA recom-mends handled formalin in the work-place as a potential occupational car-cinogen (Lee and Radtke 1998) withprotective gear required during han-dling. Hydrogen peroxide, H2O2, isan attractive alternative because it isodorless and breaks down into oxy-gen and water. A 3 percent hydrogenperoxide solution is widely used inhomes for treatment of minor woundsor as a gargle. It is also relativelyinexpensive. Stock solutions come as35 - 50 percent hydrogen peroxide,and adequate care must be taken inhandling and storage. Stock hydrogenperoxide is a strong oxidizer. It willburn you, on contact! Protective gearis required. See the label and MSDSsheet.

Research by Brian Small of theARS Catfish Genetics Research Unit,Thad Cochran National WarmwaterAquaculture Center (Small 2002,Small and Wolters 2003) has shownthat daily 15-minute baths of hydro-gen peroxide at a rate of 250 ppm areeffective at improving the hatchingsuccess of channel catfish eggs.Alternatively, hydrogen peroxide canbe added all-at-once to in-flow end ofthe hatching troughs, as a flow-through treatment, at 70 ppm. Rach

et al. (2004) found that a 15 minuteflow-through treatment of hydrogenperoxide at 500 to 750 ppm waseffective for controlling fungus oncatfish eggs. This was true whetherthe eggs were still within the gelati-nous matrix or sodium sulfite-treated.Water temperature during the studywas 79 to 84˚F (26 to 29˚C).

Before treating with hydrogenperoxide, it is critical to consider twoimportant factors: water temperatureand exposure time. Hydrogen perox-ide is more toxic at higher tempera-tures and a lower rate should be used(Rach et al. 1997, Small 2004). Evena minor temperature change makes abig difference. Small found thathatching success at 75˚F (24˚C) wasgreatest when eggs were treated with250 - 500 ppm hydrogen peroxide(15-minute bath). At 82.4˚F (28˚C),hatching success was best at 100 to250 ppm. At this higher temperature,the hatching rate decreased for eggstreated with 500 ppm. The toxicity ofhydrogen peroxide is also greater atlonger exposure times, so be sure torespect the time limits on the bathtreatments. Before adopting a hatch-ery-wide program, first test hydrogenperoxide on small batches of eggs todetermine a suitable concentration ofhydrogen peroxide for your particularhatchery's conditions (Small 2004).

Previous work (Rach et al. 1998)on hydrogen peroxide for egg treat-ments was done in cooler water.Channel catfish were treated at 72˚F(22 ± 2˚C), lake sturgeon, paddlefishand common carp at 63˚F (17 ± 2˚C),and northern pike, walleye yellowperch and white sucker eggs at 54˚F(12 ± 2˚C). Mean hatch for eggs of avariety of fish species was greatestwhen treated daily for 15 minutes at1,000 ppm.

Hydrogen peroxide can also beused to treat baitfish eggs during jarhatching. No formal studies havebeen done on eggs of these species asyet. Based on the typical range ofincubation temperatures for goldenshiner and goldfish eggs, an effective

and safe rate is probably 1,000 ppm(at 65˚F) and 250 ppm (at 75˚F).Because baitfish eggs are only about1 mm in diameter, hydrogen peroxidetreatment will cause some eggs tofloat, buoyed by the temporaryattachment of small bubbles. Jarsmust have a fine screen installed, ofless than 1,000 microns, or eggs willbe lost from the hatching jar.

Factors other than disease canresult in poor hatch. Low dissolvedoxygen or high ammonia levels aresometimes the cause. Mechanicalshock and temperature shock can killeggs as well, so eggs must be treatedwith care (like the babies they are) onthe way to the hatchery.

Lee, S., and T. Radtke. 1998. Exposure toformaldehyde among fish hatchery workers.Case Studies. Dawn Tharr, Column Editor.Applied Occupational Environmental Hygiene13(1):3-6.

Rach, J. J., G. E. Howe, and T. M. Schreier.1997. Safety of formalin treatments on warm-and coolwater fish eggs. Aquaculture149:183-191.

Rach, J. J., T. M. Schreier, G. E. Howe, and S.D. Redman. 1997. Effect of species, lifestage, and water temperature on the toxicity ofhydrogen peroxide to fish. Progressive Fish-Culturist 59:41-46.

Rach, J. J., M. P. Gaikowski, G. E. Howe, andT. M. Schreier. 1998. Evaluation of the toxic-ity and efficacy of hydrogen peroxide treat-ments on eggs of war- and coolwater fishes.Aquaculture 165:11-25.

Rach, J. J., J. T. Valentine, T. M. Schreir, M. P.Gaikowski, and T. G. Crawford. 2004.Efficacy of hydrogen peroxide to controlsaprolegniasis on channel catfish (Ictaluruspunctatus) eggs. Aquaculture 238:135-142.

Small, B. 2002. Treating channel catfish eggswith hydrogen peroxide can improve hatchingsuccess. Thad Cochran NWAC News, 5(2):6-7.

Small, B., and W. R. Wolters. 2003.Hydrogen peroxide treatment during egg incu-bation improves channel catfish hatching suc-cess. North American Journal of Aquaculture65:314-317.

Small, B. 2004. Accounting for water temper-ature during hydrogen peroxide treatment ofchannel catfish eggs. North American Journalof Aquaculture 66:162-164.

Treating Eggs with Hydrogen PeroxideNathan Stone, Extension Fisheries Specialist

Fish Farming Trade ShowFebruary 3-4, 2005. Regional trade showand conference. Annual event.Washington County Convention Center,Greenville, Mississippi. The event issponsored by Catfish Farmers ofArkansas, Catfish Farmers of Mississippi,Alabama Catfish Producers and LouisianaCatfish Farmers Association. ContactMike McCall, (601) 714-5327.

Mid-Continent WarmwaterFish Culture WorkshopFebruary 7-9, 2005. Blue Springs,Missouri. The workshop is primarilyintended for public fish hatchery employ-ees. It will be held in conjunction with theMissouri Aquaculture Association AnnualMeeting, which will take place onFebruary 9, 2005. For more information,go to http://www.moaa.pond.org/newsletters/4.4/volume4_issue4.htm or contactTommie Crawford at (660) 438-4465.

Arkansas Baitand Ornamental Fish Producers February 10, 2005. Lonoke AgriculturalCenter, Lonoke, Arkansas. Annual educational meetings. For more informa-tion contact Hugh Thomforde at (501) 676-3124.

Texas Aquaculture Association AnnualConference and Trade ShowFebruary 8-11, 2005. Texas A&MUniversity, Corpus Christi, Texas. Formore information go to http://www.texasaquaculture.org/id3.htm or call MichaelMasser at (979) 845-7473.

Arkansas Chapter of the American Fisheries SocietyFebruary 23-25, 2005. Arkansas TechUniversity, Russellville, Arkansas. Jointmeeting of Arkansas AFS, TWS, SAF andthe USFS. Days two and three of thismeeting will feature presentations on avariety of fisheries, wildlife and forestrytopics. Day one will focus on the pro-posed ten-year plans for the Ouachita andOzark-St. Francis National Forests. Forfurther information contact Joe Stoeckelat (479) 964-0852.

Catfish Farmers of America Annual ConventionFebruary 24-26, 2005. Renaissance ArtsHotel, New Orleans. For hotel reserva-tions call (800) 468-3571. Contact MikeMcCall for more details, (601) 714-5327.

Upcoming Events

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The essence of the CatfishResearch Verification Program is toprovide intensive monitoring of com-mercial ponds in which research-based management recommendationsare implemented. The program wasinitiated in April 2004 and will end inthe fall 2005. The program focuseson the traditional multiple-batch cat-fish growout. The main recommenda-tions are stocking fingerlings, largerthan 5 inches, at a density of 6,000head/acre, and feeding daily to satia-tion. Research conducted at UAPBclearly indicated that stocking small-er fingerlings or feeding every otherday negatively influenced net returns.The UAPB in-pond grader is used tograde fish at harvest to reduce thenumber of sub-marketable size cat-fish sent to the processing plant.

There were five verificationponds monitored, in Ashley andWoodruff Counties. Results of twoponds for which the recommenda-tions were best followed are present-ed here. See Table 1. More resultsand details of the recommended man-agement practices are available onthe Catfish Research Verification website at www.uaex.edu/aquaculture.

The average feeding ratesincreased from 19 and 24 lb/acre/dayin April, to 108 and 117 lb/acre/dayin August, and started decreasing in

September. See Table 2. The totalmonthly aeration levels ranged from56 to 100 hp-hour/acre. One hp-hour/acre of electric aeration is theequivalent of one hour of aeration forone 10-hp paddlewheel on a 10-acrepond. One harvest was conducted ineach pond. Fish averaged 2 lb and thepercentage of fish smaller than 1.25-lb averaged 9 percent by weight and17 percent by heads. See Table 3.

Three aeration efficiency ratioswere estimated. See Table 4. Monthlyelectric aeration was 77 to 258 hp-hour per ton of feed. The ratio of fishproduction over electric aeration was10.6 and 12.0 lb of fish per hp-hourof aeration. The monthly cost of elec-tricity for aeration ranged from 0.7 to2.2 cents/lb of fish production.Catfish farmers are encouraged tocalculate those efficiency ratios fortheir own farms and compare resultswith the verification ponds, and con-sider what you could do to improveperformance.

The catfish verification commit-tee is considering modular manage-ment strategies in which fingerlingsare raised to stocker size beforetransfer to growout ponds. If you areinterested in being a cooperator in the2005 program, contact SteevePomerleau at (870) 692-3709.

Catfish Research Verification Program UpdateSteeve Pomerleau and Jeremy Trimpey,

Research Associates (Aquaculture Verification)

Table 1. Inventory and stocking at the start of the program

CHARACTERISTICS UNITS Pond A1 Pond A2

INITIAL INVENTORYDate 04/06/04 04/07/04Weight lb/acre 1,008 1,367Number heads/acre 1,209 2,140Average size lb/fish 0.8 0.6

STOCKINGDate 04/23/04 04/20/04Number heads/acre 5,986 5,192Size lb/1,000 fish 43 88Length inches 5.7 6.6

Table 2. Monthly feed and aeration inputs.

Average Feeding Rate Total Electric Aeration 1 Total Tractor Aeration(lb/acre/day) (hp-hour/acre) (tractor-hour/acre)

Month Pond A1 Pond A2 Pond A1 Pond A2 Pond A1 Pond A2

Apr 19 24 0 0 0 0May 25 31 100 56 3 0Jun 49 67 122 102 1 0Jul 78 89 148 102 0 0Aug 108 117 140 140 3 1Sep 97 112 199 199 4 2Oct 49 37 84 75 0 0Nov 2 2 0 0 0 0Dec 0 0 0 0 0 0

1 One hp-hour/acre of aeration is the equivalent of one hour of aeration for one 10-hp paddlewheel on a 10-acre pond.

[7]

Table 3. Harvests

CHARACTERISTICS Pond A1 Pond A2

Harvest Date 08/30/04 10/21/04Total Weight (lb/acre) 1,837 4,821Average Weight (lb) 2.1 2.0Under-sized Fish (< 1.25 lb)

Weight 5% 12%Heads 10% 23%

Over-sized Fish (> 4.00 lb)Weight 14% 9%Heads 6% 4%

Table 4. Electric aeration efficiency estimates.

Aeration per unit of feed Production per unit of aeration1 Electricity Costs2

(hp-hour/ton of feed) (lbs produced/hp-hour) (cents/lb produced)Period Pond A1 Pond A2 Pond A1 Pond A2 Pond A1 Pond A2

Apr 0 0 - - 0.0 0.0May 258 117 3.5 7.6 2.2 1.0Jun 167 103 5.3 8.7 1.4 0.9Jul 122 74 7.3 12.0 1.1 0.6Aug 84 77 10.6 11.5 0.7 0.7Sep 137 118 6.5 7.5 1.2 1.0Oct 111 129 8.0 6.9 1.0 1.1Nov 0 0 - - 0.0 0.0Dec 0 0 - - 0.0 0.0Annual 123 93 7.2 9.5 1.1 0.8

1 Assuming a feed conversion ratio of 2.252 The energy consumption of a 10-hp aerator was estimated at 8.47 kwh/hour, and electricity cost was $0.09/kwh. Fish productionwas estimated assuming an FCR of 2.25.

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Dr. Hugh ThomfordeExtension Aquaculture SpecialistTechnical Editor County Extension Agent

FDA considers salt a “low regulatorypriority” drug. Salt is frequently used inholding vats and transport tanks to mini-mize fish stress. Some salt contains theanti-caking agent yellow prussiate ofsoda, or YPS, also known as sodium fer-rocyanide decahydrate. The FDA permitsthe use of YPS as an additive in foodgrade salt and in animal feed and drinkingwaters at a level not to exceed 13 partsper million (ppm). Road salt used for de-icing typically contains the additive YPSand/or prussian blue (ferric ferrocyanide).

An article in Arkansas Aquafarmingin the early 1970s warned against use ofsalt containing YPS, based on the reportof an unexpected kill in Lonoke of fish ina salt bath. Nevertheless, in other cases,salt with YPS has been used on fish withno ill effects. Why the difference? RobinCalfee and Edward Little of the USGS

Columbia Environmental Research Centerconducted research on fire-retardantchemicals containing YPS as a corrosion-inhibitor. They found that the ultravioletlight in sunlight transforms YPS into toxicforms of cyanide. Cyanide is quite toxicto fish even at very low concentrations. Areview by Ronald Eisler of the U.S.Geological Survey indicates fish dierapidly from free cyanide concentrationsabove 200 parts per billion, or 0.2 mg/L,and long exposure to 50 - 200 ppb islethal to sensitive species. As little as 10ppb impairs the ability of some fish toswim.

Salt is normally used for fish as anindefinite bath treatment at 1 - 3 parts perthousand (ppt). If YPS were present at themaximum allowable level (13 ppm), a 3ppt salt treatment would result in 0.039ppm of YPS (39 ppb) in the water. Only a

certain fraction of this would become freecyanide, depending upon the amount ofsunlight and other factors. Thus undertypical indoor vats conditions and treat-ment levels, it is unlikely that enoughYPS is present to cause a fish kill.Nevertheless, there are sublethal effectsfrom cyanide exposure, and it would seemwise to avoid salt containing YPS, espe-cially in outdoor facilities.

Calfree, R. D., and E. E. Little. 2003. Theeffects of ultraviolet-B radiation on the toxicityof fire-fighting chemicals. EnvironmentalToxicology and Chemistry 22(7):1525-1531.

Eisler, R. 1991. Cyanide hazards to fish,wildlife, and invertebrates: a synoptic review.U.S. Fish and Wildlife Service BiologicalReport 85(1.23), Patuxent Wildlife ResearchCenter, Laurel, Maryland.

Salt Containing Yellow Prussiate of SodaNathan Stone, Extension Fisheries Specialist