Dedicated To Tribal Aquaculture Programs
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December 2008 ~ Volume 66 | |
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Topics of Interest:
Aquatic Animal Drug Approval Partnership Program
Updates from the Aquatic Animal Drug Approval Partnership Program (AADAP)
By MTAN
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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 jim_bowker@fws.gov. Supply is limited so don’t delay!
Aquaculture drug-use posters are also available on-line.
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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.
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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 Region
By: 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: 715-779-3461The 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
Introduction
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 to
Gregory 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 ½ 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.
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