Evaluation of Brook Trout Culture in a Evaluation of Brook Trout Culture in a

Water Water RecirculatingRecirculating SystemSystem

Gregory Fischer, Chris Hartleb, James Held & Jeff MalisonGregory Fischer, Chris Hartleb, James Held & Jeff Malison

HistoryHistory

�Brook trout 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 for stocking and food fish purposes.

�Unique niche market for brook trout, with local sellers getting higher prices per pound than traditional species such as rainbow trout.

�Traditional coldwater production occurs in flow- through raceways, ponds or fiberglass tanks at between 7 - 10 °C.

�Issues of brook trout growing slower than other species and possibility of rearing in RAS systems at slightly higher temperatures.

�� The purpose of this study was to evaluate Nipigon strain The purpose of this study was to evaluate Nipigon strain brook trout hatchery production attributes in RAS.brook trout hatchery production attributes in RAS.

�� Nipigon strain brook trout were selected due to faster Nipigon strain brook trout were selected due to faster growth rates, longer lifespan, and delayed maturity.growth rates, longer lifespan, and delayed maturity.

�� Experiments were conducted Experiments were conducted

inside main 7,085 minside main 7,085 m²² Aquatic Aquatic

Barn at NADF in Red Cliff, WI. Barn at NADF in Red Cliff, WI.

Materials and MethodsMaterials and Methods Materials and MethodsMaterials and Methods

�� 48,000 L Coldwater RAS @ 1348,000 L Coldwater RAS @ 13ooCC

�� Six 5.7 mSix 5.7 m33 (5,693 L) round (5,693 L) round

fiberglass tanks with side & fiberglass tanks with side &

bottom drains.bottom drains.

�� System components included System components included microscreenmicroscreen drum filter, drum filter,

sand filter, LHO w/oxygen, COsand filter, LHO w/oxygen, CO22 stripper, UV irradiationstripper, UV irradiation

�� Average system water flow was 1,477 L/minAverage system water flow was 1,477 L/min

�� 7.67.6ººC groundwater added @ 46 L/min or 3% of total flow to C groundwater added @ 46 L/min or 3% of total flow to

maintain system temperature.maintain system temperature.

��Two 1.4 mTwo 1.4 m³³ (1,500 L) (1,500 L)

flow thru tanks.flow thru tanks.

��Single pass water usageSingle pass water usage

��20 L/min groundwater 20 L/min groundwater

@ @ 7.67.6ººC or 100% of C or 100% of

total flow per tanktotal flow per tank

Materials and Methods

� Brook trout were cultured from eyed eggs in Heath Stack Incubation System using 20 L/min of 7.6 °C degassed & aerated ground water.

� 30 day old fry were transferred to shallow (406 mm x 1219 mm) flow-through fiberglass tank inserts. Fed using dry salmon starter at approximately 5% BW. Water temperature maintained at 7.6 °C at a flow of 20 L/min.

� When fingerling brook trout averaged 51.3 mm (1.25 g) they were moved to 1,500 L fiberglass rearing tanks. Flow-rate was 40 L/min of 7.6 °C. Density was 2.2 fish/L. Fingerling trout were fed to satiation at between 3-5% daily body weight.

Materials and MethodsMaterials and Methods

Materials and MethodsMaterials and Methods(RAS)(RAS)

�Brook trout averaging 103.0 mm (9.0 g) were placed into the RAS 5.7m³ tanks for rearing for 308 days (approx.10 months).

�Fish were fed a commercial trout diet of appropriate size throughout the grow-out period utilizing shaker style feeders.

� Feeding occurred 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 from the same cohort group averaging 103.0 mm (9.0 g) were kept in two (7.6 oC), single pass, flow-through 1,500 liter (1.4 m³) fiberglass rearing tanks utilizing 20 L/min of groundwater per tank for 308 days.

� Fish were fed commercial trout diet. Feed rate/feed size was adjusted monthly based upon trout growth and feed consumption.

�Belt feeders were utilized for constant feeding throughout an 8 hr day.

Materials and MethodsMaterials and Methods(Flow(Flow--thru)thru)

Materials and MethodsMaterials and MethodsMonitoringMonitoring

��DO (mg/L), temperature (DO (mg/L), temperature (ººC), pH and total C), pH and total dissolved gases (%) were measured daily in dissolved gases (%) were measured daily in each tank. Mortality was recorded daily and each tank. Mortality was recorded daily and mortsmortswere removed and sampled.were removed and sampled.

��AmmoniaAmmonia--nitrogen (NHnitrogen (NH33--N), nitriteN), nitrite--nitrogen (NOnitrogen (NO22--N), reactive phosphorous (PON), reactive phosphorous (PO44), carbon ), carbon dioxide(CO2), and total suspended solids (TSS) dioxide(CO2), and total suspended solids (TSS) were measured once weekly from water samples were measured once weekly from water samples collected in the RAS sump.collected in the RAS sump.

��No data regarding ammonia, nitrite, or No data regarding ammonia, nitrite, or phosphorous were collected from the flowphosphorous were collected from the flow--thru thru tanks as the incoming flow of 20L/min of ground tanks as the incoming flow of 20L/min of ground water was presumed adequate to prevent these water was presumed adequate to prevent these from accumulating to a level of concern.from accumulating to a level of concern.

��Brook trout length and weights were measured Brook trout length and weights were measured monthly by obtaining 50 randomly sampled trout monthly by obtaining 50 randomly sampled trout from each tank. from each tank.

80-120 mg/L80-120 mg/LAlkalinity

na1-3 mg/LTotal suspended solids

na<0.0125mg/LCalculated Unionized nitrogen

na0.09 mg/LNitrite nitrogen

na0.059 mg/LTotal ammonia nitrogen

na30Carbon dioxide

7.97.3pH

8.7 mg/L8.2 mg/LDissolved oxygen

7.6 C13.0 CTemperature

Flow Thru TanksRAS Tanks

Average Water Quality Parameters

0

50

100

150

200

250

300

350

10/4/06

10/18/06

11/1/06

11/15/06

11/29/06

12/13/06

12/27/06

1/10/07

1/24/07

2/7/07

2/21/07

3/7/07

3/21/07

4/4/07

4/18/07

5/2/07

5/16/07

5/30/07

6/13/07

6/27/07

7/11/07

7/25/07

8/8/07

date

length in mm

weight in g

raslen

raswgt

fllen

flwgt

average 0.61mm/d

average 0.84g/d

average 0.32mm/d

average 0.19g/d

ResultsResultsBrook Trout Monthly Growth in RAS & FlowBrook Trout Monthly Growth in RAS & Flow--through Tanksthrough Tanks

ResultsResultsRAS System CostsRAS System Costs

�� $542.00 monthly electrical charge for $542.00 monthly electrical charge for

system pumps based on average system pumps based on average commercial electrical rate of $0.08commercial electrical rate of $0.08

�� Average oxygen use of cost $142/monthAverage oxygen use of cost $142/month

�� Average labor costs for feeding, cleaning, Average labor costs for feeding, cleaning, monitoring = $400/monthmonitoring = $400/month

��Total monthly operating costs for RAS Total monthly operating costs for RAS

was $1,084 plus feed/chemicals. Does not was $1,084 plus feed/chemicals. Does not

include capitol costs for equipment or include capitol costs for equipment or building.building.

ResultsResults

ProductionProduction

�� RAS system successfully raised 1,379 kg (3,000 lbs) in RAS system successfully raised 1,379 kg (3,000 lbs) in

approximately 10 months from fingerling (9 g) to filet market approximately 10 months from fingerling (9 g) to filet market

size (454 g) and appeared capable of rearing greater densities.size (454 g) and appeared capable of rearing greater densities.

�� Annual production of 36 kg (80 lbs) of brook trout per 1.0 Annual production of 36 kg (80 lbs) of brook trout per 1.0 LpmLpm

replacement water (5x greater than typical reported flow replacement water (5x greater than typical reported flow

through production values).through production values).

�� Average head on/gutted dressed Average head on/gutted dressed

weight yields of 85% noted by weight yields of 85% noted by

commercial processors.commercial processors.

ResultsResults

��Total estimated system production costs, not including capital, Total estimated system production costs, not including capital, was $13,530.was $13,530.

��Average sale price of prepared brook trout was approximately Average sale price of prepared brook trout was approximately $6.60/kg $6.60/kg -- $22.00/kg ($3 $22.00/kg ($3 -- 10/lb) depending on preparation.10/lb) depending on preparation.

��Total approximate value of all troutTotal approximate value of all trout

produced = $15,096.produced = $15,096.

ConclusionConclusion

• Our study demonstrated that market size brook trout can be raisedsuccessfully 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 troutproduction levels can be increased in a recycle system, as well as brook trout marketability and cost comparisons.

AcknowledgementsAcknowledgements

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-NADF 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.

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