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Ashland NFWCO
 Midwest Region
 ***Dedicated To Tribal Aquaculture Programs***
      Fish Jumping
          **December 2008 ~ Volume 66****Coordinator:
                  Frank G. Stone 
                  (715-682-6185) Ext. 12
                  U.S. Fish and
                  Wildlife Service
                Email: [email protected]** Topics
  of Interest: MTAN ArrowAquatic Animal Drug Approval Partnership Program
  MTAN ArrowReplacing Traditional Sturgeon Diets with Commercially Formulated Diets
  MTAN ArrowQuestion for the Tribal Aquaculture Programs in the Midwest Region
  MTAN Arrow**NADF Walleye Project for 2007**
  MTAN ArrowEvaluation of Brook Trout Culture in a Water Recirculating  System   Updates from the Aquatic Animal Drug Approval Partnership Program (AADAP)
By MTAN American Fisheries Society (AFS) and AADAP publish an aquaculture   drug-use poster: The AFS’s Fish   Culture (FCS) and Fish Health Sections (FHS) have partnered with the AADAP   program to produce a Quick Reference Guide poster titled “Approved Drugs for Use   in Aquaculture.” The poster is intended to serve as a useful outreach product   that will hopefully minimize some of the confusion that typically arises   regarding what approved drugs are available to fisheries biologists, as well as   how and when they may be used. The poster has been made available to all FCS and   FHS members. The poster is constructed of a laminated heavy weight paper,   measures approximately 2 ft X 3 ft, and is designedfor use in, or in close   proximity to, fish rearing environments .
    The poster is also   being made available to non-FCS/FHS folks on a first-come/first-served basis.   Anyone who is interested in receiving a copy of the poster should contact Jim   Bowker at 
      406-994-9910 or [email protected]. Supply is limited so   don’t delay!
    **Aquaculture drug-use posters are also available on-line.**
  Alternative iodine and hydrogen peroxide treatement regimes tested for egg   disinfection: Utah's Division of   Wildlife Resources Fisheries Experiment Station reports on experimental trials   conducted on rainbow trout eggs. New oxytetracycline (Terramycin® 200 for Fish) supplemental approval   for Phibro Animal Health: Phibro Animal Health today (9 July 2008)   received official confirmation from FDA’s Center for Veterinary Medicine that   Phibro’s Supplemental New Animal Drug Application for oxytetracycline medicated   feed product has been approved for the additional claims of: 1) coldwater   disease in all freshwater reared salmonids, 2) columnaris in all freshwater   reared Oncorhynchus mykiss, 3) treatment   of salmonids for approved diseases at all temperatures (i.e., removal of   prohibition of treatments below 9°C). Congratulations to Phibro, CVM and all   others involved in bringing this to fruition. For more information on activities   regarding this supplemental approval see the most recent AADAP   Newsletter and the latest CVM update.  **Replacing Traditional Sturgeon Diets with Commercially Formulated Diets**By James Luoma, USFWS, Genoa National Fish Hatchery The Genoa National Fish Hatchery (NFH) has been involved in  lake sturgeon propagation since 1995 to support restoration efforts in Wisconsin, Minnesota and  Missouri.  In 2007, the Genoa NFH raised approximately  30,000 seven inch lake sturgeon using natural diets that cost many thousands of  dollars.  Using natural diets for feeding  sturgeon has several draw backs including: decreasing supplies and increasing  costs, labor intensive preparation and feeding requirements, potential chemical  contamination in the feed and possible disease transmission from the feed. Genoa NFH biologist Nick Starzl and maintenance worker Jeff  Lockington recently designed and constructed an experimental fish rearing  battery which has been put into operation to evaluate the suitability of replacing  natural food diets for rearing lake sturgeon with commercially formulated diets. The current study is evaluating a Rangen® semi moist diet and  an Otohime®  larval fish food diet  against the standard natural diet.  The  diets are being evaluated with three replicates each for a total of nine  tanks.  If a particular diet is found to  be promising future studies will refine its utility with the hope of converting  it to a production scale use.  The NADF Has a Question for the Tribal Aquaculture Programs in the Midwest RegionBy: MTAN Greg Fischer, Facility Manager ( Northern Aquaculture Demonstration Facility - NADF) asked the MTAN to relay a short message. He is would like to know what type of programs or training would be most useful for the tribal programs in the Midwest Region.
      Greg and the entire staff at the NADF are attempting to reach out to the tribal aquaculture community to assist them in resolving their training and aquaculture related needs. Perhaps you have a technical question or a concern as simple as locating literature to help you address a specific issue.
        Whatever your program may require, please consider
          making the NADF a primary contact for any
          of your fish rearing needs. 
        Facility phone number:  715-779-3461
  The mission of the Northern Aquaculture Demonstration   Facility is to promote and advance
  the development of commercial aquaculture in   a northern climate by:
  Demonstrating production-scale aquaculture.
    Conducting applied research.
    Providing outreach and extension services.
    Providing training, workshops and educational opportunities.
    Building & strengthening cooperative relationships among commercial   aquaculturists, tribal, state and federal agencies.
    Working with fish growers on fish health issues, assessments, training and   permitting.
    Developing best management practices for a sustainable and environmental   industry.  **NADF Walleye Project for 2007**
By Greg Fischer, Northern Aquaculture Demonstration Facility **NADF LogoIntroduction**From April through October, 2007, the UW Stevens Point Northern  Aquaculture Demonstration Facility (NADF) continued to cooperatively work with  the Lac Courte Oreilles Tribal Fisheries Program (LCO) providing approximately  203,450 fry, 76,053 fingerlings (1,082/lb), and 9,606 extended growth (8/lb)  walleyes for the tribes’ lake stocking program.   The information presented in this case study describes the methods used from  beginning to end in a “cookbook” style how the NADF incubated and raised the  walleyes in two 0.4 surface acre outdoor earthern ponds (520,740 gal.)(1,971,000  L) utilizing several types of organic and inorganic fertilizers, various  aeration systems and forage minnows. Implications of this years research in  walleye rearing and management suggests that you can produce approximately 500  pounds of extended growth walleye in a 0.4 acre outdoor earthern pond.  Size and number of fish will be determined by  time of harvest from the pond, initial stocking numbers, good water quality  parameters and proper feeding protocol.  The intent of this report is to provide  information to assist other aquaculture and hatcheries that are raising  walleyes and other coolwater fish. **Egg Collection and Fertilization Methods**Adult male and female walleye were collected by NADF and  WIDNR staff using fyke nets set in lakes on April 17 from Big  LCO Lake  near Hayward, WI.   Eggs were stripped by hand from female walleyes into plastic containers  and milt was added from several males utilizing both wet and dry methods.  More than one male was utilized for several  reasons; because milt from a single male may not be capable of fertilizing  eggs, and for maintaining genetic diversity. After eggs and milt are in the pan,  clean water was added and the combination stirred with a soft brush or  feather.  Stirring continued for several  minutes and a slurry of bentonite clay was added to the mixture.  Stirring the egg/clay mixture continued for  several minutes and additional clean water was added.  The egg/clay mixture was rinsed off with clean  water and placed into a larger bucket or cooler of clean water.  Water in the container was freshened periodically  to keep oxygen levels up and maintain water temperature during transport.  Water hardened eggs were transported to NADF  for incubation in the bell jar incubation system located at the facility. Due to fish health concerns (VHS) ovarian fluid was  collected for screening from female broodfish and several egg treatments were  field tested by NADF.  All ovarian  samples collected were negative for VHS.  The three egg treatments tested were: Untreated  Control
  100  ppm/Iodine mixed in w/milt and sterilized water during fertilization step and  then clayed on boat.
  100  ppm/Iodine/10 minute bath after water hardening in sterilized water. **Egg Incubation**Approximately 630,000 eggs were placed in McDonald style egg  jars for incubation on April 17.  Water temperature was maintained between  48-50°F throughout incubation. Temperatures were increased to 59°F (during hatch  out) to aid in hatching.  Initial water  flow through jars was approximately 0.4 gpm and then increased to 0.7 gpm once  eggs became eyed.  Dead eggs were removed  daily from the hatching jars through siphoning.   A modified chicken waterer with a 15 minute (1,600 mg/l) formalin drip  was used daily after egg eyeup to control fungus.  Formalin treatments were discontinued nearing  egg hatchout.  Fry hatched May 3 through  May 13.  Total average hatching  percentage was 61%.  Hatching percentage  results of egg treatments were: Untreated  Control:  63%
  Iodine  w/milt:  25%
  Iodine  after water hardening:  75% Strong swimming fry were stocked into two (2) prepared  17,600 (0.4 acre)(1,971 m3) outdoor earthen ponds on May 7-14.  Pond 1 was stocked with approximately 82,950  fry and pond 4 was stocked with approximately 96,100 fry.  Additionally, approximately 203,450 walleye  fry were provided back to the LCO Natural Resources Department and stocked into  local lakes for conservation purposes on May 10.  All fry numbers were determined  volumetrically. **Fingerling Pond Production**Two different types of organic fertilizer, soybean meal and  alfalfa meal, in conjunction with inorganic fertilizer were used in separate  outdoor rearing ponds at NADF to do some comparison evaluations.  The fertilizer type, cost, and application  rates are as follows: **Pond 1:** Pond number 1  was filled partway and prepared approximately one week in advance of filling with  400 pounds of alfalfa meal, 2.25 gallons liquid 28% nitrogen urea, and 1.0 lb. granular  0-45-0 phosphorous  fertilizer.  Granular phosphate was liquidfied with warm  water before application.  A total of 600  pds of alfalfa meal ($120.00), 3.0 gallons of 28% nitrogen ($18.00),  and 2.0 lbs. of 0-45-0 phosphorous fertilizer ($0.56) was added during  May-June to stimulate plankton blooms.  Supplemental  aeration was provided via the facilities main 5 h.p. rotary blower and two  round membrane diffusers. **Pond 2 & 3:**  Additional fertilizer was added to Ponds 2  and 3, after fingerling walleye were placed into them for extended growout, to  increase pond turbidity for decreased bird predation and to assist with  vegetation control.  The total extra  fertilizer added was 400 lbs of alfalfa meal ($80.00) and 1.5 gallons of  liquid 28% nitrogen urea ($9.00). **Pond 4:** Pond number 4  was filled partway and prepared approximately one week in advance of filling  with 400 lbs of soybean meal, 2.25 gallons of liquid 28% nitrogen urea, and 1.0  lb. of granular 0-45-0 p-phosphorous fertilizer.  Granular phosphate fertilizer was liquidfied  with warm water before application.  A  total of 700 pds. of soybean meal ($105.00), 3.38 gallons of 28% nitrogen  ($21.00), and 2.5 pds. of  0-45-0 phosphorous  fertilizer ($0.70) were added during May-June to stimulate plankton  blooms.  Supplemental aeration was  provided via the facilities main 5 h.p. rotary blower and two handmade pvc  airlifts. 
Pond water quality parameters were monitored on a daily  basis. **Fingerling Production Results**Walleye fry were observed around edges of the ponds in  daylight and at night with lights in May.   Plankton populations were average, but seemed adequate as sampled fish  condition was good.  Early fish sampling  in both ponds yielded good numbers of fish per seining attempt which hypothetically  meant good numbers in the ponds.  Pond  temperatures as well as the plankton populations increased in June. Small fingerling  walleyes from both ponds were sampled on a weekly basis to assess length,  weight, and fish 
  condition.  Length and weights varied for both  ponds.  Fish condition was excellent. in  ponds.  Ponds were 
  monitored daily  for temperature (oC), oxygen (ppm), pH and seechi disk readings(m) throughout  fingerling 
  production (Figures1  and 2).  
  Lowest oxygen  levels observed during fingerling production were in Pond 4 during May at 2.5  ppm.  Pond 
  2 oxygen levels  during fingerling production were not recorded lower than 5.0 ppm. during this  phase. The low 
  oxygen level  recorded in pond 4 may have been detrimental to the fish in the pond.  Fresh water was added at 
  this point to  alleviate the problem. On June 15 we moved approximately 8,076 fingerlings  averaging 24.9 mm (3,846 fish/kg)(1,748/lb) from pond 4 into pond 3 for further  rearing.  Pond 4 was fully drained on  June 20 and approximately 30,708 fingerling walleye averaging 32.8mm (2,222  fish/kg)(1,010/lb) were collected.  Fry  to fingerling production return in pond 4 was 40.4%.  An additional 8,620 fingerlings harvested  from pond 4 were placed into pond 3 bringing the total number of fish in pond 3  for further rearing to 16,696.  Pond 4  was left dry. On June 15, we moved approximately 11,686 fingerlings  averaging 32.4 mm (2,381fish/kg)(1082/lb) from pond 1 into pond 2 for further  rearing.  Pond 1 was fully drained on  June 19 and approximately 53,965 fingerling walleye averaging 37.5 mm (1,724  fish/kg)(784/lb) were collected.  Fry to  fingerling production return in pond 1 was 79.1%.  Pond 1 was left dry.  Average cost to produce the fingerling  walleye was $0.0032/fish not including labor or capitol costs.  A fish health assessment was performed on the  walleye fingerlings on June 14 during NADF Field Days by Dr Robert Smith of  Clayton Veterinary Care and a certified clean bill of health was provided. LCO Natural Resources picked up 76,053 excess fingerlings on  June 20 and 21 for stocking purposes. **Extended Growth Production Summary**Ponds 2 and 3 were initially stocked with 11,686 and 16,696  fingerlings respectively to investigate the capacity of 0.4 acre ponds in rearing extended growth walleye.   Ponds averaged four (4) ft (1.2 m) deep during extended growth  rearing.   Final pond volume was  approximately 520,740 gal. (1,971,000 L).  
Ponds were stocked periodically with a total of 539 gallons (4,312  lbs)(1,960kg) of forage minnows of various sizes ranging < 1”to 2” from June  through October.  Poundage ratio of  forage minnow to walleye was approximately 4:1. Walleyes from both ponds were sampled on a weekly basis to  assess length, weight, and fish 
  condition.  Fish condition was excellent.  Ponds were monitored daily for temperature,  oxygen, pH and seechi 
  disk readings  throughout advanced fingerling production   (Figures 3 and 4).  Aeration systems  were run at night 
  during days of  excessive heat to prevent pond temperatures from increasing.  Fresh groundwater was also added 
  periodically  during excessive heat periods to help control temperature in ponds.  No observed water quality 
  parameter issues  were apparent during this time period. Extended growth (E.G.) walleyes were harvested from the pond  2 and 3 on October 11 and 12 respectively.   Ponds were drawn down slowly through the use of gate valves and dam  boards located in the concrete funnel structure at the rear of the ponds. Fish  were collected and held in the external concrete collecting kettle with fresh  water and aeration. Approximately, 9,606 extended growth walleyes 1,151 lbs  (522 kg) were harvested from the two ponds (33.8% survival f).  The harvested walleyes averaged 7.3” (185 mm)  in length, average fish weight was 54.3g (8/lb).  No significant losses were recorded during  harvest.  The walleyes were hauled by the  Red Cliff Fish Hatchery and Bayfield State Fish Hatchery staff for LCO.  Fish were stocked by LCO Fisheries Department  into local lakes for conservation purposes.   All fish underwent a fish health assessment and were tested negative for  VHS before leaving the facility. Fish were stocked  by LCO Fisheries Department into local lakes for conservation purposes.  All fish underwent a fish health assessment  and were tested negative for VHS before leaving the facility. Total estimated cost to produce the extended growth walleye  was $16,143($1.68 per fish) which includes forage, fish health testing,  fertilizer, and miscellaneous expenses. No labor or capitol cost was included  in this estimate.  Due to fish health  concerns (VHS) extended growth walleyes were held for a longer period of time  than was anticipated.  This caused an  increase in cost of approximately $4,000 (VHS testing and minnow feed) and may  have reduced fish numbers in ponds due to cannibalism. **Discussion** We doubled the capacity of the ponds with this years harvest  of 1,151 pounds as compared to the harvests of 2005 (511 pds) and 2006 (507  pds).  But, due to the increased holding  time this year the total number of fish harvested (9,606) fell between 2005  (11,744) and 2006 (7,876) harvests.  The  2007 extended growth walleyes were larger and heavier than the previous  years.
  Implications of this in walleye rearing and management  suggests that you can produce approximately 500 pounds of Extended Growth (EG) walleye  in a 0.4 acre outdoor earthern pond.   Size and number of fish will be determined by time of harvest from the  pond, initial stocking numbers, good water quality parameters, and proper feeding  protocol.
  For 2008, we hope to replicate the poundage produced in each  pond but will harvest the EG walleyes earlier in the fall resulting in higher  numbers of fish to meet target quotas. **Acknowledgements** Special thanks go to Paul Christel  and Bill Nebel at LCO Natural Resources Department for working with us on this  project.  Also would like to thank the  WIDNR Tommy Thompson State Fish Hatchery for helping us collect walleye eggs on  behalf of LCO to start the project.  Carey  Edwards and Gervase Thompson from the Les Voigt and Brule River State Fish  Hatchery and Francis Cadotte from the Red Cliff Tribal Fish hatchery assisted  LCO with hauling the fish.  Mark Duffy,  Larry Deragon, and Shelly Gurnoe assisted with harvesting of fish.  NADF technicians Kendall Holmes and Dan Duffy  were assisted by college interns, Abby Purdee (UWSP) and Ryan Huber (UWSP) to  provide the necessary expertise monitoring ponds, sample counting and harvesting  walleyes to complete the project. **Questions or comments regarding this project can be directed  toGregory Fischer, NADF Facility Manager, at 715-779-3461** **Evaluation of Brook Trout Culture in a Water Recirculating  System**By: Gregory J. Fischer,  Christopher Hartleb, 
  James Held and Jeffrey  Malison **Abstract**Brook trout  (*Salvelinus fontinalis*) is an  important commercially raised coldwater species in Wisconsin  and the Midwest. Brook trout are raised by  private, tribal, state, and federal fish hatchery facilities in Wisconsin.  Approximately 10% of private coldwater  aquaculture operations are presently raising brook trout of various strains for  stocking uses and a limited amount for food markets.  Growing brook trout to a larger size, if they  can be reared in a shorter time span, may present a potential new sector for  the aquaculture market in the Midwest.  Researchers at the University of  Wisconsin-Stevens Point Northern Aquaculture Demonstration Facility (NADF) have  been raising Lake Superior strain (Nipigon) brook trout to evaluate hatchery  production attributes i.e., husbandry, growth, physiological condition, feed  efficiency, survival, water chemistry requirements and body condition factor of  brook trout in a recycle aquaculture system at an average temperature of 13° C.  The trout performed well in RAS and grew  faster (0.84g/day) than fish cultured in traditional flow-through tank culture  utilizing ground water at 7.6 °C (0.14g/day). Tank densities at harvest ranged  from 34-46 kg/m3 in RAS.   Final average weight of RAS fish was 260g, while the flow –through fish  averaged 65g.  Final tank densities for  the RAS was 40.4kg/m3 and flow-through  tanks was 31.2kg/m3.  Throughout the project period feed conversions  in the RAS ranged from 0.9-1.3 and daily growth rates averaged 0.61mm/day and  0.84g/day.  Daily growth rates in the  flow-through tanks averaged 0.35mm/day and 0.14g/day.   Measured total ammonia nitrogen (NH3+NH4)  and nitrite nitrogen (NO2-N) levels exiting the culture tanks in the  recirculating system averaged 0.059 mg/L and 0.090 mg/L respectively and ranged  from 0.0 - 0.4 mg/L throughout study. Calculated unionized ammonia (NH3-N)  levels did not exceed the “safe” level of 0.125 mg/L as recommended for most  species.  Measured dissolved oxygen concentration  in the culture tanks averaged 8.2mg/L and ranged from 5.5-14.0 mg/L throughout  the project. Baseline alkalinity was 80-120 mg/L, pH levels averaged 7.34, and  carbon dioxide concentration in the culture tanks averaged 30 mg/L and ranged  from 18-36 mg/L. The recycle system at NADF reared 1,379 kg of brook trout over  a 10 month period from fingerling (9g) to market size (340-454 g).  This translates to 36 kg/yr of brook trout  per 1 L/min fresh water added to the system. It does appear from this initial  research project that market size brook trout can be raised successfully in a  recycle system within a similar time frame as rainbow trout. **Introduction**Brook trout (*Salvelinus fontinalis*) is an important commercially raised  coldwater species in Wisconsin and the Midwest.  Brook  trout are not a true trout, but a charr, more closely related to arctic charr,  dolly varden, and other lake charr (Ryther, 1997).  Among the first and easiest of the salmonids  to be spawned and reared in captivity, hatchery reared brook trout have now  been distributed and released into brooks, streams, rivers, ponds, and lakes  throughout North America with suitable climate and environment (Ryther, 1997). 
  Brook trout are raised by private, tribal,  state, and federal fish hatchery facilities in Wisconsin.   Approximately 10% of private coldwater aquaculture operations are  presently raising brook trout of various strains for stocking uses and a  limited amount for food markets.  In Wisconsin, traditional  private coldwater production occurs in flow- through raceways, ponds or  fiberglass tanks at between 7 and 10 °C. One problem with raising brook trout  is that they normally grow slower than rainbow trout under these conditions. In  commercial aquaculture, faster growth in less time equals more total production  which leads to increased fish sales to the market. Thus, most of the commercial  trout production in the Midwest consists of faster growing rainbow trout,  although there does appear to be a unique niche market for brook trout, with  local sellers getting higher prices per pound (2006 pers. communication, Peter  Fritch, Rushing Waters Fisheries).  If  brook trout could be grown to a similar size as rainbow trout in the same  amount of time, it may prove to be  advantageous for a producer or seller and  could potentially expand the niche market for  brook trout in the Midwest. In the present study, researchers  at the University of Wisconsin-Stevens Point Northern Aquaculture Demonstration  Facility (NADF) raised Lake Superior strain  brook trout in a RAS maintained at 13oC.  The objectives of the study was to evaluate hatchery production attributes i.e.,  husbandry, growth, physiological condition, feed efficiency, survival, water  chemistry requirements and body condition factor under these conditions. The recycle  aquaculture system (RAS) was similar to one used for Artic char (*Salvelinus alpinus*;described by  Summerfelt et. al., 2004).  We used Lake Superior (Nipigon) strain brook trout for our trials,  because of reportedly faster growth rates.   Based on previous experience, this strain has other commercially positive  attributes including longer lifespan and later maturity. With stricter discharge standards  becoming a reality and high quality water resources in scarce supply, salmonid aquaculture  has begun to rely on water reuse and recirculation technology (Summerfelt et  al., 2004a;2004b).  A recycle system  provides an alternative method with less water usage and lower discharge  amounts for salmonid production compared to standard flow-through raceway  systems.  RAS systems also provide for a  more controlled environment resulting in better biosecurity and predator  exclusion.  
  The purpose of this study was to  document the production performance of Nipigon strain brook trout in a recycle  system operated at culture temperatures of approximately 13° C.  Estimates of this system’s operating costs at  NADF are also included. **Materials and Methods**Experiments were  conducted inside an 7,085 m2 steel construction building at the NADF site near Bayfield, Wisconsin,   USA.   
  Fish were  cultured in a 48,049 liter RAS (Figure 1) that was supplied by Marine Biotech  Inc. (MA).  The RAS contained six 5.7 m3,  5,693 L fiberglass tanks installed with side drain and bottom drain  configurations as described in Timmons et. al. (2002).  Mechanical filtration was provided by a microscreen  drum filter (Hydrotech Model 803, Water Management Technologies Inc., LA)  fitted with 30 micron screens.  Biofiltration  was provided by a 3.6 m3 fluidized sand biofilter (Cyclobio, Marine Biotech  Inc., MA) filled with 1.4 m3 silica sand.  A CO2 stripping column was stacked  above a Low Head Oxygenator (LHO), (PraAqua,   Canada).  Oxygen was supplied to the LHO by a permanent  station liquid oxygen tank (Praxair Inc, MN).  UV irradation was supplied by one 920 watt, 8  bulb unit (Model MWUV, Aqualogic,   CA) plumbed into the tank water  distribution line.  A custom fiberglass 8.0  m3 sump with pumping stations for one 4.0 hp biofilter pump and two 4.0 hp  distribution pumps (Model 4UMF3, Jacuzzi Inc.) together supplied >1,477 L/min  continuous water flow, as monitored by a pipeline mounted paddlewheel flowmeter  (Model 8550-1 flow meter, Signet Scientific Company, CA).  Pumping and water levels was monitored using a  SCADA system (LW Allen and Intellisystems Inc., WI), which also provides staff  notification (phone dialer) service in case of emergencies.  Tanks were insulated with aftermarket insulation  wrap (Nitron Inc., CA) and covered with black plastic netting to prevent escape  (Aquatic Ecosystems, FL).  Photoperiod  was controlled by timers (Model T103, Intermatic Inc., Ill.) to provide 12-16 hrs of daylight  throughout the study period.  Ground  water (7.6°C) at 46L/min (approximately 3% of total flow) was added to the RAS,  which maintained an average culture temperature of approximately 13°C. **System  operation summary (Figure 1):**  Water exiting the culture tank’s sidewall and  bottom drains was treated across a microscreen drum filter, then pumped from a  sump into a sand biofilter.  Water  gravity flowed from the biofilter into the aeration/stripping column where  carbon dioxide was stripped.  Water  exiting the stripping column flowed by gravity through an LHO where pure oxygen  supplementation took place before water was pumped back to the culture tanks  from the sump tank.  Excess water  overflowed the system at the pump sump.  A  CO2 stripping fan in the aeration/stripping column, used to lower CO2  levels in the system, was on full time when fish loads were high.  **Figure 1**. **The water  recirculating system at UWSP-NADF utilized for the brook trout study** The system above consists of six (6) 5.7 m3  “Cornell-type” culture tanks; drum filter; 8.0 m3 sump;  biofilter pump station; biofilter; carbon dioxide stripping column w/fan; LHO;  distribution pump station; flowmeter, and UV iridiation treatment unit (not  shown).  The CAD drafting was provided by  Marine Biotech Inc., MA. Nipigon strain brook trout were cultured from eyed eggs  obtained from the Red Cliff Tribal Fish Hatchery on January 13, 2006 at  approximately 714 temperature units (TU).   Incubation was continued at NADF utilizing a 16 tray vertical Heath  Stack Incubation System (MariSource Inc., WA) operated in a single pass using 7.6  ° C degassed and aerated ground water.   Eggs hatched between January 25 and February 11, 2006 (182-406 TU  respectively).  Newly hatched fry were  kept in heath trays for approximately 30 days.   Fry were then transferred to custom made, shallow (406 mm x 1219 mm) flow-through  fiberglass tank inserts (Gemini Tanks Inc., CO) and fed to satiation utilizing  belt feeders (Eagar Inc., Utah) with 52% protein, 14% lipid, 1% fiber, 9% ash  dry salmon starter (Nelson Silver Cup Inc., Utah) at approximately 5% BW.   Water temperature was maintained at 7.6 °C utilizing  approximately 20 L/min of degassed, aerated, single pass, ground water running  through the tank.  Tanks were cleaned and  monitored daily.  Mortality was recorded  and dead fish were removed daily. Fingerling  brook trout averaging 51.3mm, 1.25g were moved into 1,500 L fiberglass rearing  tanks (Gemini Tanks Inc., CO) on May 31 and June 1 with approximately 40 L/min  7.6 ° C degassed, aerated, well water flowing through the tanks. Approximate  density in the culture tanks was 2.2 fish/L.   Fingerling brook trout were fed a 48% protein, 14% lipid, 1% fiber, 9%  ash dry trout diet (Nelson Silver Cup Inc.,Utah) of appropriate size.  Feed rate was adjusted monthly based upon  trout growth and feed consumption.  Fingerling  trout were fed to satiation at between 3-5% daily body weight.  Belt feeders provided the fry and fingerlings  constant feed throughout the day. Brook trout  averaging 103.0 mm and 9.0 g were placed into the RAS tanks for rearing on October 4, 2006.  The fish were reared in the RAS unit until August 8, 2007.  Fish were fed a 42% protein, 12% lipid, 1%  fiber, 9% ash trout diet (Nelson Silver Cup Inc., Utah) or a 45% protein, 16%  lipid, 3% fiber diet (Aquamax grower 400, PMI International, LLC. MO) of  appropriate size throughout the grow-out period.  Automatic vibratory feeders (Model SF7, Sweeney  Inc.) set on feeder controllers (Model H1201, Aquatic Ecosystems Inc., FL)  dispensed feed at 2 hour intervals in an 8 hour daily time period.  Feed rates were adjusted monthly based upon  trout growth and feed consumption.
Brook trout length and weights were  measured monthly by obtaining 50 randomly sampled trout from each tank.  Dissolved oxygen (mg/L), temperature (oC), and total dissolved gases (%) were  measured daily in each tank (Common Sensing Model TBO-DL6F Gas Meter, Common  Sensing Inc., ID).  pH was also monitored  daily in each tank (Pinpoint pH meter, American Marine Inc, CT). Ammonia-nitrogen  (NH3-N), nitrite-nitrogen (NO2-N), and reactive phosphorous  (PO4) were measured (CEL 850 Hach Test Kit, Hach Inc., CO) once weekly  from samples collected in the RAS distribution water sump tank according to  standard water quality methods (APHA, 1989).  Total suspended solids (TSS) and carbon  dioxide (CO2) levels were measured as needed throughout the study period from  the same water samples collected above.  RAS system routine maintenance included; tank  cleaning and power washing of drum filter as well as monitoring flow rates and  sand filter biofloc removal as needed. Also, brook  trout from the same cohort group averaging 103.0 mm and 9.0 g were kept in two  (7.6 C), single pass, flow-through, 1,500 liter (1.4m3) fiberglass rearing tanks utilizing 20 L/min of groundwater per  tank.  Trout in the flow-through tanks  were fed a 42% protein, 12% lipid, 1% fiber, 9% ash trout diet (Nelson Silver  Cup Inc., Utah)  of appropriate size throughout the grow-out period. Feed rate was adjusted  monthly based upon trout growth and feed consumption.  Fish were fed beyond satiation at 1-5% daily  body weight depending on the size of the fish, i.e. larger fish were feed lower  % daily body weight.   Belt feeders were  utilized for constant feeding throughout an 8 hr day. Brook trout length and weights  were measured monthly by obtaining 50 randomly sampled trout from each tank.  Tanks were cleaned daily. Dissolved oxygen  (mg/L), temperature (oC), and total  dissolved gases (%) were measured daily in each tank (Common Sensing Model  TBO-DL6F Gas Meter, Common Sensing Inc., ID).   PH was also monitored daily in each tank (Pinpoint pH meter, American  Marine Inc, CT).   No data regarding  ammonia, nitrite, or phosphorous was collected from the flow-thru tanks as the  incoming flow of 20L/min of ground water was presumed adequate to prevent these  from accumulating to a level of concern.  **Results and Discussion** **Fish Performance**Nipigon strain brook trout performed well in the13oC RAS and grew faster than trout reared in  traditional flow-through tank culture utilizing ground water at 7.6 °C (Figure  2).  In the RAS, feed conversion rate averaged  1.1 and ranged from 0.9-1.3, daily growth rates averaged 0.61mm/day and 0.84  g/day (Figure 2).   Daily growth rates in  the flow-thru tanks averaged 0.35 mm/day and 0.14 g/day (Figure 2) and the feed  conversion rate averaged 6.7, due to planned overfeeding to not limit feed  availability for these fish.  Average tank  densities at harvest for the RAS tanks was 40.4 kg/m3 and was 31.2 kg/m3 in the flow-through tanks.  Density index (Piper et al., 1982) values at  the end of the study averaged 0.24 per RAS tank and 0.19 for the flow-through  tanks.  Cumulative mortality percentage  in the RAS tanks was 6% and <1% in the flow-through tanks.  **Figure 2**.  **Average brook trout length and weight increase  in coldwater RAS and flow-through tank systems** **RAS Performance** The removal of solid wastes or suspended solids in  recirculating systems is a primary goal due to the adverse impact solid wastes  have on fish respiration (Timmons et al. 2002).   Uneaten feed, fecal material, and additional solids constitute suspended  solids and can cause adverse fish health issues in fish rearing systems.  With adequate flow rates and adjustable water  inlet orifices, the RAS culture tanks were able to rapidly concentrate and  flush total suspended solids out of the tank and into the tank drain piping for  further removal by the drum filter.  The  water inlet orifices were adjusted to allow approximately 1 1⁄2 tank rotations  for feed pellets before being flushed down the bottom center drain.   Fecal material, being slightly buoyant, was  flushed faster into the bottom center drain.   The drum filter effectively removed the larger solids and flushed them  to an external settling basin. Daily flushing of the tank drain was simple and  efficient.  Biweekly cleaning of the drum  filter was done with a high pressure wash. Fish expel various nitrogenous waste products through gill  diffusion, gill cation exchange, urine and feces (Timmons et. al., 2002).  Biological filters are designed to aid in the  oxidation of ammonia to nitrite and then to nitrate, with eventual removal from  the  culture water.  Because trout and char require relatively  clean water and low levels of un-ionized ammonia, fluidized-bed biofilters  containing fine sands are commonly used in coldwater RAS systems (Summerfelt et  al., 2004b).  This study employed a  fluidized sand bed biofilter for a variety of reasons including space, water  temperature, and design attributes.    Measured total ammonia nitrogen (NH3-N) and nitrite-nitrogen  (NO2-N) levels throughout the study averaged 0.059mg/L and 0.090mg/L  respectively and ranged from 0.0 - 0.4 mg/L (Figure 3).  Calculated unionized ammonia (NH3)  levels did not exceed the “safe” level of 0.0125 mg/L as recommended for most  species in Meade et. al.(1989).   According to Lewis et. al. (1986), the published literature on nitrite  toxicity to fish shows the ratio of the 24-h LC50 to the 96-h LC50  with a median value of 2.0 mg/l and is fairly uniform across species. However,  presence of chloride, calcium, and other specific ions is known to reduce nitrite  toxicity.   Phosphorous levels averaged  1.56mg/L and were < 2.4 mg/L throughout the study (Figure 3).  **Figure 3.**  **Measured ammonia- nitrogen (NH3-NH4), nitrite-nitrogen(NO2-N),  and reactive phosphorous (PO4) in the 13o C RAS system** Fish production within any intensive tank-based system is  first limited by availability of dissolved oxygen (Colt et al., 1991) and,  depending on the species being cultured, can be limited by the density of fish  per unit volume of culture water.   Throughout the course of the experiment measured dissolved oxygen levels  in the RAS system averaged 8.21 mg/L and ranged from 5.5-14.0 mg/L and did not  appear to limit fish production (Figure 4).   Baseline alkalinity ranged from 80-120 mg/L, pH levels averaged 7.34 and  ranged from 6.0 – 8.5, and carbon dioxide levels averaged 30 mg/L and ranged  from 18-42 mg/L.  All water quality  parameters were within the acceptable range for brook trout and no adverse  health effects were noted.  **Figure 4**. Typical profile of tank temperature, pH and  oxygen levels measured once daily in the 13oC**RAS system at NADF during brook  trout project** Through the study period the flow-through tanks observed  water temperature averaged 7.9 oC, dissolved oxygen averaged 8.7 mg/L, and pH  averaged 7.9.  All water quality  parameters were within the acceptable range for brook trout and no adverse  health effects were noted. The UV  system on the RAS performed well after initial adjustments to the main power  supply box.  Fish health was not an issue  in the system, although at higher densities (46 kg/m3) some fin  erosion was evident that may affect consumer perception of fish quality.  Good et. al. (2008) reported caudal fin  erosion and fin quality issues in rainbow trout reared in a RAS operated at low  flushing levels, which may have been caused by water quality issues and not  densities. Summerfelt et. al. (2004) found  that a partial-reuse system was able to sustain an annual production level of  35-45 kg of rainbow trout for every 1 L/min of make-up water, which is approximately  6-7 times greater than the typical 6 kg of trout produced for every 1 L/min of  water reported in Idaho  serial-reuse raceways systems. Our recycle system handled 1,379 kg of brook  trout over a 10 month period from fingerling (9 g) to market size (340-454 g) and  appeared capable of handling greater densities.   This translates to 36kg annual production of brook trout per 1 L/min  fresh water added to the system which is approaching the value recorded for  rainbow trout in Summerfelt et. al. (2004a) and is approximately 5x greater  than the typical reported production value from Idaho serial-reuse raceway systems. The calculated system operating  cost during the 10 months trout were in the RAS    was  $10,840 ($1,084 month) based upon average commercial rates and estimated labor  (Table 2).  A total of 3,057 kg feed at  an average cost of $0.88/kg were utilized for total feed cost of $2,690.  Total estimated production costs, not  including capital costs, was  $13,530.  On May 3, 2007 approximately 5,564 brook trout (average  length 249mm) weighing 923 kg were moved out of the RAS to outdoor  raceways.  These fish were valued at  approximately $7,511 ($1.35 each).  The  remaining fish reared in the RAS until August 8, 2007 weighing 1,379kg were valued at  approximately $7,585 ($5.50/kg) in the round.   Total approximate value of brook trout produced in the RAS was  $15,096.  Average dressed weight yields  of 85% were noted by commercial processors.   The fish were processed and prepared in different ways such as dressed  (bone in), boned, butterfly fillet, and smoked.   Average cost of prepared brook trout was approximately $6.6/kg up to  22/kg, depending on preparation.  **Conclusion** Our study demonstrated that market size brook trout  can be raised successfully in a recycle system operated at 13oC within a similar time-frame as rainbow trout.  Additional research is needed to investigate the  extent to which brook trout production levels can be increased in a recycle  system, as well as brook trout marketability and cost comparisons. Table 2. Click here to view this pdf file.  **Acknowledgements** We thank Peter Fritch of Rushing Waters Trout Farm for his  involvement and interest in this project.   Jeff Taylor and Nate Wendt of  Star Prairie Trout Farms were also  helpful throughout this project and provided important information regarding  fish production and processing.  We would  also like to acknowledge the efforts of technicians Kendall Holmes, Dan Duffy,  and summer interns Abby Purdy and Ryan Huber at the UWSP Northern Aquaculture  Demonstration Facility for fish rearing and data collection.  Steve Summerfelt of Freshwater Institute  provided valuable review comments and technical assistance. This project was supported by NADF base funding. Mention of  trade name, proprietary product, or specific equipment does not constitute a  guarantee or warranty and does not imply approval to the exclusion of other  products that may be suitable. The views contained in this document are those  of the authors and should not interpreted as representing official policies of  UWSP or other state or federal entities.   **Return
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