Dedicated To The Tribal Aquaculture Program
 |
March 1995 - Volume 11 |
| Administrative
Coordinator:
Frank G. Stone
(715-682-6185) Ext.12 |
Edited By: Elizabeth W. Greiff
(715-349-2195) |
Topics Of Interest:
Aquaculture - On Line and On Screen
By: MTAN
Yes it's true, the time has finally come to drop that pocket calculator and make way for the new "Information Highway". This new technology to the sky has many forms. It may just be a more enlightened use of the many software programs now available for aquaculture professionals, or a it could be a "In-Your-Office" trip to the other end of the planet. Using a computer modem permits many exciting opportunities for people who are interested in aquaculture not only to share information with other professionals, but also to learn from them so we can better insure that our programs have the same levels of success. The MTAN has been gathering information on both the various types of aquaculture software now available plus a skyward path you may wish to take as you travel along this new Information Highway.
So buckle those seat belts, the posted speed limit is only as finite as your computer system's operating speed or your own imagination.
Let us first begin with the "Internet" because it's the true backbone for the information superhighway. The Internet is a network of thousands of other networks linking millions of people worldwide through their computer modems. Besides being a method of exchanging electronic mail (e-mail), the Internet provides access to databases, computer programs, card catalogs, electronic forums (listservs) and much more. Electronic forums provide a way for hundreds of users to exchange information, discuss issues, and find solutions to common problems. An electronic forum is like a mailing list; every message sent to the list gets forwarded to every other member on that list. There are electronic forums on almost any imaginable topic.
If you have access to the Information Highway, you can also retrieve information from the Aquaculture Network Information Center (AquaNIC). AquaNIC (http://ag.ansc.purdue.edu/aquanic) is a gateway to the world's electronic resources in aquaculture. AquaNIC is maintained at Purdue University in West Lafayette, Indiana and is supported by the Libraries of Purdue University, Purdue University Cooperative Extension Service, University of Illinois Cooperative Extension Service, the Illinois-Indiana Sea Grant Program, and the United States Dept. of Agriculture Extension Service.
AquaNIC is a multi-branched system containing a wide variety of information. Most documents can either be viewed on your computer monitor, downloaded via modem, or a copy sent to your e-mail address. AquaNIC also contains an image directory that holds hundreds of pictures, short videos, and slides in a variety of common image formats. A long-term AquaNIC objective is on-line interactive media that can be used by Cooperative Extension Service or Sea Grant county staff.
One of AquaNIC's unique features is that it is linked to other aquaculture databases on the Internet. These links are established for you when another aquaculture database is selected. AquaNIC's gateway searching capability allows users to individualize specific search criteria. If a user does not have direct access to the Internet, there are several commercial carriers that will help you to link up with AquaNIC, including America On-Line, DELPHI, and Prodigy, which do charge a user fee.
If the Information Highway can go no further then the back of your computer, several options still exist to connect your hatchery program with the expertise from other professionals. Several stand alone computer programs and spreadsheet/database worksheets are available which provide a fantastic means of quickly organizing and calculating information. These programs can also be specifically tailored to meet your needs. Often the initial time to setup the worksheet may test your tolerance level, but once the format has been established and the worksheet has been tested, you will quickly see what time savers these programs can truly be.
The MTAN has collected some information on a few of these stand alone programs and worksheets which may help your aquaculture program. If you feel these may have some application to your facility you should contact the originator of the application to obtain a copy of the program. These programs use accepted formulas for calculations involving cool and cold water fish culture. For those programs involving the application of chemicals, the user should use the program at your own risk and always apply the necessary precautions before application.
Stand Alone Program
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SamCalc (V2.1)
Written by Joe N. Fries, 500 E. McCarty Lane, San Marcos, TX. 78666 512-353-0011
The Following Menu Items Are Included:
Fish-hauling, Static Treatment, Flow-through, Length-weight, Contingency Table (2x2), Analysis of Variance, Experimental Design, Dissolved Oxygen Solubility, Injection Calculations.
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Fish Hatchery Mathematics (1986)
Written by Darryl Bathel, French River Coldwater Hatchery, 5357 No. Shore Dr., Duluth, MN. 55804 218-723-4881
The Following Menu Items Are Included:
Weekly Feed Rate, Treatments, Raceway Capacity, Piper's Density and Flow Indices, Feed Order For Production Fish, Length of Salmonid Incubation, Daily Temp. Unit Calculator, Gas Supersaturation, Condition Factor (C), Distribution Tank Loading Guidelines, Descriptive Statistics.
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Aquadec (1989)
Written by Chuck Adams and Rom Alderman
University of Florida, Institute of Food and Agricultural Sciences, Bldg. 120 Room 203, P.O. Box 110340, Grainesville, FL 32611-0340 904-392-7853.
Aquadec is a budgeting and financial analysis software package that can provide information to the financial decision-making process of an aquacultural (commercial) business. A wide range of financial statements and other related information can be gathered by Aquadec for a one to five year period. Sensitivity analyses can also be performed on key management and market parameters.
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AquaSoft
P.O. Box 853, Gresham, OR 97030
AquaSoft has developed three aquaculture software packages for professionals who are their own "expert systems" and see microcomputers primarily as tools for increasing personal productivity.
Aquacalc: This program allows the user to enter simple, language-like phrases to calculate the amount of chemical to add to produce a specific concentration, or convert from one unit of measure to another. The language-like interface provides easy access to over one hundred fifty conversion factors for over fifty commonly used units of measurement. Version 2.0 (PC compatible only) allows the definition and storage of up to twenty conversion factors and units.
CARPplusl1: Computer assisted rearing projection takes another step forward with this newly enhanced level of CARPplus. This fish growth and feed projection program works for any species of fish, under any conditions, with user specified units that can be changed at any time. Six units of fish size make it possible that you may never again have to refer to a manual of fish culture to convert from length to weight. Three units for describing fish mortality, four units for growth, and three units for feed output combine to give the user tremendous versatility. Spreadsheet like input screens add to the ease of use.
CARPplus: For not much more than you would spend for "free" public domain software you can have a copy of this second generation program for computer assisted rearing projection. CARPplus calculates required amounts and estimated costs of feed for any species of fish. CARPplus also schedules fish harvests, calculates feeding rates, and estimates amounts of space and water needed for groups of fish.
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Levee
Mississippi Cooperative Extension Service, Mississippi State Univ., Mississippi State, Miss. 39762
Levee calculates volume of earth to be moved during pond construction. User enters levee width, wet and dry slopes, finished elevation, survey elevations and length of levee segments. Output is in the format used by the Soil Conservation Service.
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Fishpond Construction Planning Templates
Texas Agricultural Extension Service, Extension Computer Technology Group, Special Services Build. Rm 105, College Station, TX 77843
This program lists some of the considerations in initial construction planning of fish ponds and allows estimation of excavation and dam volume (cubic yards) required for construction. Pond excavation volumes can be estimated for one pond or a series.
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AQUA MEDIC
North Systems, 4443 Nalani Court SE, Salem, OR 97302 503-364-3829
AQUA MEDIC is a diagnostic program specifically designed to aid in the differential diagnosis of fish diseases. AQUA MEDIC allows veterinarians, fisheries professionals and scientists to enter a set of symptoms, physical findings, and water quality information. The program will then list the diseases associated with those attributes (in ranking order) according to the number of symptoms in common with each disease. Additionally the program allows the user to display a complete list of attributes and symptoms for any disease in the data base.
Symptoms are entered quickly and easily by the first three letters of the name, by a code number, or by its classification. A listing of all of the diseases and attributes is included in the manual, and a new listing may be printed at any time after modifications or additions to the data base have been made by the user. A record form, including a complete listing of all attributes in the AQUA MEDIC data base, accompanies the program and enables users to input and analyze attributes efficiently.
Spreadsheet/Database Worksheets
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Broodstock Egg Take Calculator
Lotus 123 Worksheet
Written by Lee Peterson, Peterson State Fish Hatchery, Rt. 1 Box 85A, Peterson, MN 55962 507-875-2625
Lee has developed a very easy to use worksheet to determine the number of broodstock (male and female) needed to insure you will always have the correct number of eggs for any given year. For those fish hatcheries who need to continually adjust broodstock densities to maximize rearing space and to satisfy established egg production levels, will find this worksheet to be very useful.
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Carrying Capacity of Tanks
Lotus 123 Worksheet
Written by Steve Roberts, Washington Dept. of Game
This worksheet calculates water inflow and space requirements based on pounds and numbers of fish. It also calculates pounds and numbers of fish based on water inflow and space. The formulas used in the worksheet are based on Piper's flow and density indexes.
OXYGEN INJECTION BACKUP SYSTEM
By: Gregory J. Fischer
Hatchery Manager, Red Cliff Tribal Fish Hatchery
The Red Cliff Tribal Fish Hatchery is now rearing Lake Trout and Coaster Brook Trout. This hatchery facility has been in the works for many years and is still not fully completed due to budget constraints. One of the hatchery's main goals is to establish a reliable and accessible source for Coaster Brook Trout eggs via a broodstock supply. To accomplish this goal the hatchery has two electric powered fifty horse submersible pumps capable of pumping between 500 to 1000 gallons of water per minute.
Last fall (1994) as the hatchery was nearing operating capability, it was evident that we were not going to be able to afford a backup generator in case of an electrical power failure. Due to the remote location of the facility and the history of power failure in years past, some type of backup had to be designed and installed. After speaking with many other hatchery professionals on our dilemma, we decided to set up an oxygen injection backup system.
The oxygen injection system has many qualities Red Cliff's facility was looking for:
1) It is relatively cheap and easy to install. 2) It is portable and easily relocated throughout the hatchery. 3) It is easy to operate at 2:00 a.m., when most power outages always seem to occur. 4) The system can be used to inject oxygen into tanks to increase productivity at a later date. 5) The system provides additional oxygen to fish in a standing body of water (raceway) when they need it most.
This system also has some disadvantages:
1) Does not remove harmful gases from the water, such as ammonia, during the power outage.
2) Requires bottles of oxygen which must be bought, rented, or leased and refilled as necessary. 3) Only a temporary solution for a relatively short period of time depending on build-up of other gases in the system.
Red Cliff ordered our oxygen system from Eagar Inc. of Utah (1-800-423-6249). They were extremely helpful and were able to custom design a system for treating a small number of tanks (<10) at a low cost of $300. This system consists of a flowmeter and regulator, 1 x 4 manifold with valves, aquapor diffusing hose, air hose and all the necessary fittings. Oxygen bottles were rented at a local supplier of welding materials. Installation was simple and completed in about one hour.
In case of a power failure or pump shutdown, hatchery personnel are notified via an alarm system (MTAN Dec. 1994). After getting to the hatchery and assessing the situation, the oxygen backup system hose is lowered into the raceways and the oxygen is turned on. Oxygen flow is adjusted for each raceway depending on the amount of fish. Our tanks hold between 130 to 160 pounds of fish and the folks at Eagar felt that one liter per minute per raceway would be sufficient to sustain the fish. At that rate, one large oxygen bottle can sustain 10 tanks for approximately 10-12 hours. Of course, each facility is different depending on water conditions and species of fish, so it is advisable to contact Eager Inc. and other professionals before hooking up a system. Also, Red Cliff hatchery personal plan on monitoring the dissolved oxygen levels at the front and rear of the raceways during the use of the oxygen backup system and adjust the flow accordingly.
Remember, this is only a short-term, low-cost remedy to a power outage and is not the solution. Red Cliff Tribal Fish Hatchery has plans to have a backup generator installed this summer, until then the oxygen injection backup system has given us a little more security and "piece of mind".
Maximize Your Hatchery's Budget To Train Your Staff
By: MTAN
How often do you find yourself faced with the dilemma of having insufficient revenues to spend on your hatchery program? How frequently do you wish you had the opportunity to find good affordable training for your hard working staff? The MTAN would like to offer one option which may save your hatchery program training dollars that could be channeled to other areas.
Fish hatchery supervisors from state and federal hatchery systems are excited about sharing information with Tribal hatchery workers. One of the ways this exchange is taking place is through an "On The Spot Hatchery Experience." If you feel that your staff would benefit from a training visit to one of these hatchery facilities, please give a call to the MTAN so we can help to made the arrangements. Depending on your specific needs, this kind of training could be one or several days in length and could even be spaced out over a broad cross section of the fish rearing cycle. The only expenses incurred to your program would be for travel, meals and lodging.
Evaluation of Tank Shape and a Surface Spray for Intensive Culture of Larval Walleyes Fed Formulated Feed
By: Alan Moore and Margaret Prange
Iowa Dept. of Natural Resources, Rathbun State Fish Hatchery, Rural Route
2, Moravia, Iowa
And Robert Summerfelt and Richard Bushman, Dept. of Animal Ecology, Iowa
State University, Ames, Iowa
(From
the Progressive Fish-Culturest 56:100-110,1994)
The objectives of this study was to examine the effects of different tank
characteristics on intensive culture of larval walleyes reared on only formulated feed.
To improve reliability and success of maintenance stocking of walleyes, many natural resource agencies are giving more attention to large fingerlings (> 100 mm, typically 100-150 mm, total length) as an alterative to stocking yolk-sac larvae or small fingerlings. Currently, a tandem procedure involving pond culture first, then tank culture, is used to rear almost all large fingerling walleyes. Typically, fingerlings are reared from fry in a pond environment to total lengths of 35-50 mm, then harvested and transferred to tank or raceway (i.e., intensive culture) facilities, where they are trained to eat formulated diets and reared to total lengths of more than 100 mm. Because of the mortalities that occur in pond production and when the pond-reared fingerlings are trained to formulated feed, totally intensive culture is an attractive alternative. Intensive culture efforts to raise larval walleyes on formulated diets, however, have met with limited and inconsistent success.
Failure of gas bladder inflation in larval walleyes is considered the key factor in poor survival to 20 d posthatch. Noninflation of the gas bladder usually results in mortality before 30 d posthatch. Fry with uninflated gas bladders swim poorly and expend extra energy to maintain position in the water column. These weakened fish become stressed easily, and mortality is high when they are moved between tanks or transported for short distances in bags. Fry with uninflated gas bladders probably are more vulnerable to predators and less capable of capturing prey after stocking. Tank design is regarded as important to survival and gas bladder inflation of walleye.
Walleyes are assumed to inflate their gas bladders by gulping air at the air-water interface. Larval walleyes go through a stage of pushing their snouts upwards against the surface film, presumably to gulp air. Walleyes reared in tanks with a surface exit for oil and debris (at the surface film) have higher gas bladder inflation rates than do walleyes reared in tanks with only a subsurface outlet.
The present study was an effort to advance the technology for intensive culture of larval walleyes, especially by finding ways to improve gas bladder inflation. Experiments were performed to compare rearing success of larval walleyes held in a cuboidal tanks (T-1) and of those held in a deep cylindrical tanks (T-2). These differently shaped tanks also differ in flow pattern. The cuboidal tanks have an upwelling water circulation pattern that resuspends feed to maintain a high feed particle density. We modified the screen of the original design to create a surface drain. The cylindrical tanks have a circular flow pattern. Both tank types were equipped with surface sprays as a means to clear the surface of oil, feed, and debris. A preliminary evaluation of the role of surface spray in gas bladder inflation was also undertaken (T-3).
Results
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Comparison of Cuboidal and Cylindrical Tanks:
In experiment T-1, survival and viability were significantly greater for walleyes reared in cuboidal tanks than for those in cylindrical tanks. The gas bladder was inflated in 100% of the fish in the cylindrical tanks and in 86.7% of the fish in the cuboidal tanks, but this difference was nonsignificant. Fish reared in cuboidal tanks were significantly longer than those reared in cylindrical tanks.
The 11.4% difference in survival between cuboidal tanks and cylindrical tanks in experiment T-2 was not statistically significant, but gas bladder inflation (GBI) and viability were significantly greater for fish reared in cylindrical tanks than for those in cuboidal tanks. Fish reared in cylindrical tanks were significantly longer than those in cuboidal tanks.
In experiment T-3, survival, GBI, and viability were significantly higher for walleyes reared in cylindrical tanks with surface sprays than for those in cuboidal tanks with surface sprays. Differences in mean length of fish between the two tank designs were not statistically significant.
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Comparison of performance in tanks with and without a surface spray:
Differences in survival, viability, and mean length for fish in tanks with and without surface sprays could not be statistically compared because of the lack of replicates. However, in cylindrical tanks, survival, GBI, and viability were substantially greater in the two tanks with surface sprays than in the one tank without a surface spray. In the cuboidal tanks, survival and viability also were substantially greater in the two tanks with surface sprays than for the one without a surface spray, but GBI was slightly greater in the cuboidal tank without a surface spray.
Discussion
Zitzow reported higher survival and GBI rates for larval walleyes reared to 29-32 d posthatch in cylindrical tanks than for those in cuboidal tanks. Viability calculated from their data on survival and GBI was only 23.9%, whereas viability was 60.8% in the same tanks in experiment T-3 of the present study. In the present study, GBI and viability were considered the critical measures of performance, and performance was better in the cylindrical tanks in two of the three experiments (T-2 and T-3).
In the present study, survival of larval walleyes to 15-25 d posthatch ranged from 3.8 to 68.2% over all three experiments, compared with an average of 17.5% in prior studies. The GBI in the present study ranged from 71.5 to 100.0% in the three experiments. Survival was significantly higher in the cuboidal tanks only in experiment T- 1, when a feed bridging problem in both the cylindrical and cuboidal tanks kept feed from being dispensed at the desired times. The upwelling flow pattern in the cuboidal tanks, however, maintained higher particle densities and thus made more feed available to fish. Therefore, the higher survival in the cuboidal tanks in experiment T- I may be attributed to the greater starvation of fish in the cylindrical tanks as a result of the feeder problem. Survival was higher in the cylindrical tanks in experiment T-2 and significantly higher in these tanks in T-3.
The results of this study represent improvements over previous efforts to rear larval walleyes on formulated feed. If these results can be repeated, they will represent a substantial advancement in the intensive culture of larval walleyes. Other investigators have used live food (brine shrimp nauplii or zooplankton), formulated feed, or combinations thereof. We think that the surface spray influenced the success of the present study. In the cylindrical tanks (T-3), all performance values were greater in the two tanks with a spray than in the one tank without a spray; however, in the cuboidal tanks, GBI was greater in the one tank without a spray than in the two with a spray (although viability and survival were higher in those tanks with a spray).
TANK CULTURE TECHNIQUES FOR REARING WALLEYE FINGERLINGS
By: Eric E. Moodie, Department of Biology, University of Winnipeg,
Winnipeg, Manitoba, R3B 2E9 Canada 204-786-9435
The system is based on the idea of growing walleye from egg through to
fingerling size or larger entirely inside a hatchery.
Our research group has been developing a commercially feasible walleye culture system for the past several years. This kind of culture offers several advantages; the fish can be reared in a disease-free environment, the operators rather than Mother Nature control environmental conditions, ideal year-round rearing temperatures can be maintained, the fish are reared on prepared feed throughout their lives so feed conversion problems are avoided, and the fish never need to be moved from a pond to a tank at any point in their lives.
The main obstacles to successful walleye culture have been mortality resulting when hungry larvae cannibalize each other and problems due to poor swim bladder inflation. (For a report on swim bladder inflation problems in walleye see the article by Kindschi and Barrows in the March, 1994 issue of the MTAN Newsletter.) We have been able to reduce cannibalism to an acceptable level by supplying plenty of high quality feed (BioKyowa B400 and C700) in carefully controlled quantities. We make sure there are always at least 100 food particles per liter of tank water. Normal swim bladder inflation depends on good water quality so we reduce the level of recirculation and increase the supply of new water while inflation is taking place.
We feel that good hygiene is another important factor in successful intensive culture. At the start of each culture cycle we disinfect the entire system with a 10% solution of Prepodyne. After the eggs are fully hardened they are disinfected with a 10 minute immersion in a 1% solution of Iodine before being placed in the incubation jars. Our water supply is drawn from a deep well which also reduces the risk of disease organisms getting into the tanks.
During the hatching period we let the larvae accumulate in a 600 L holding tank after they leave the incubation jars. The outlet of the holding tank is provided with a removable screen with a mesh size of 500u and an area of 2200 cm2. When hatching begins we increase water flow through the jars and the holding tank to help move larvae out of the jars and to flush away oils and other wastes. Larvae stay in the holding tank until about 1 day before the yolk is used up. We siphon out empty egg shells and dead larvae once or twice a day during this period. The outlet end of the tank is darkened to encourage the larvae to avoid that region and simplify cleaning the screen and removal of dead larvae and egg shells.
Larvae are transferred from the holding tank in a small 125u mesh nylon net. Groups of about 1,500 larvae are caught and gently poured through a funnel into a 50 ml graduate cylinder. We estimate larval numbers volumetrically by draining most of the water from the netted larvae. We determine the number of larvae occupying 2-3 ml of a 10 ml graduate cylinder by actual counts of several samples. Appropriate quantities of larvae are then placed in the rearing trough which is at the same temperature as the holding tank. After the larvae are moved to the rearing trough the temperature in the trough is raised to 20 C over the next 48 hours.
The rearing trough has a capacity of 2.6 m3. Until the larvae begin to feed, the rate of water flow in the trough can be low (77 L/minute [1.8 exchanges/hour]) because the larvae are small and water quality is easy to maintain as long as no food is entering the system. After feeding begins, we increase the flow rate to 123 L/minute (2.8 exchanges/hour). This produces a velocity of about 8 cm/second at the surface which is enough to delay the sinking of food and maintain adequate water quality. The trough is designed to keep the food where the larvae can make use of it. Walleye larvae will not take food from the bottom or from the water surface. We get around this problem by pumping water into the trough through a perforated pipe running along the bottom. The flow of water from the perforated pipe lifts sinking food so that the larvae can "capture" it. Water leaves the trough via screened outlets along the back of the trough. The screen has a mesh size of 500um which is sufficient to keep the larvae and most of the food inside the trough. The boxes are removable and can be opened for cleaning. It might seem to make sense to use a slightly larger mesh in order to allow uneaten food to escape, however, that would just mean having to provide more food (which is very expensive) to supply the density needed to keep cannibalism under control.
Waste water from the trough flows by gravity to a particle separator which removes fish and food wastes which pass through the outlet screens. Water is then pumped to an inline heater and on to a down-flow submerged gravel biofilter. After filtration the water goes to an aeration tower consisting of a 2 m length of 30 cm diameter PVC pipe. The tower was built on-site and contains a series of internal baffles which break up the water as it falls down the pipe. The tower restores the oxygen content of the culture water to about 94% saturation or an oxygen concentration of about 8.4 mg/L at 20 C. Water from the tower collects in a small reservoir from which it is pumped back to the rearing trough. Pumping is necessary at this point in order to generate the water pressure which drives the water circulation in the rearing trough.
These components together with additional tanks are also used for juvenile grow-out after 30 days. The rate of water flow to the rearing trough is critical to its successful operation; we keep it under 70 L/m. The upwelling flow which is necessary to prolong the suspension of food has to be managed carefully because excessive current is harmful to the larvae. We think surface water velocity should be under 10 cm/second. This velocity can be achieved by changing the angle at which water is ejected from the perforated inlet pipe and by adjusting a valve on the main supply line to the trough.
Interruptions to the food supply and drops in the dissolved oxygen resulting from component failures can quickly kill large numbers of larvae. To limit this possibility, the system is backed up by alarms triggered by high temperature, low water levels, or a pump failure. Compressed oxygen is available if electricity or water flow can not be restored immediately.
The system requires a maximum flow rate of about 7 m3/day. We maintain water temperature at 20C during the 30 day culture period. We keep dissolved oxygen concentration close to the saturation level or at least over 65% of saturation. Un-ionized ammonia concentrations are held below 0.1 mg/L. Total ammonia concentrations do not exceed 0.7 mg/L. These oxygen and ammonia levels are easy to maintain at the larval and feed densities we use. Declining oxygen levels can be corrected by more cleaning, backwashing of the filter, and flushing of sludge in the trap of the particle remover.
During the period when the swimbladder is inflating we supply new water at a rate of 6.3 m3/day. This high level which is equivalent to 2.5 exchanges of the entire system volume per day, reduces the accumulation of surface oils and films which inhibit swim bladder inflation. For the remainder of the larval culture period the new volume is reduced to 0.7 m3/day (equivalent to an exchange of the system every 2.5 days).
We used to begin supplying feed shortly before the larvae would accept it. Now we think swim bladder inflation occurs very soon after the yolk is consumed and that the process is completed quickly under ideal conditions. Better swim bladder inflation may result if feeding can be delayed until the level of inflation reaches 80%. We feed the larvae BioKyowa B-400 feed for the first 7 days. Larvae remain on B-400 feed longer if necessary to ensure all individuals are ready to shift to larger (C-700) feed. This gives smaller fish a chance to catch up in size to larger ones and may slow down the growth of larger ones, so that size variation will be reduced. The automatic feeders we use are custom built and capable of reliably releasing about 0.06 g of B400 food per delivery. Five to ten feeders per trough will ensure even food distribution. If ten feeders are used, each will need to deliver at about 2 minute intervals to maintain the correct food particle density in the water. The larvae are held under continuous illumination and fed day and night to reduce cannibalism resulting from food deprivation which occurs if the lights and feeders are shut off during the night.
The food ration is based on supplying enough to maintain a density of at least 100 particles/L. We monitor food particle density regularly and adjust the output of the feeders as necessary to maintain the correct food density within the trough. The same procedure applies after the diet is changed to C700 food. It is important to note that we base the feeding rate not on the number of fish present, nor the density of fish, but rather on maintaining approximately 100 particles per liter in the water column at all times.
Most of the labor involves cleaning. The system relies on supplying an excess of food which must eventually be siphoned from the trough at least once or twice a day. The exit screens also have to be removed and cleaned once or twice daily. By the time the fish are receiving C700 the sides and bottom of the trough need to be brushed or wiped to remove films which build up there (solid kitchen scrub pads are perfect for this job). Sludge traps in the particle remover and elsewhere in the system also need to be drained every 2-3 days. A major objective of our research has been to reduce the labor requirements which make up a large portion of aquaculture production costs. We have therefore tried to develop a system that is easy to operate. The system I have described requires 5 hours of labor per day.
Other routine chores involve monitoring water quality, swim bladder inflation, feed supply and particle density, level of feeding, growth rate, general well-being of the larvae, and the extent of cannibalism.
We have produced from 23,000 to 33,500 thirty day old juveniles from starting densities ranging from 19 to 56 larvae/L. Once the juveniles reach the age of 30 days, their survival rates improve tremendously and their culture becomes relatively straightforward. We have released over 20,000 6 inch fingerlings into several lakes in Manitoba and have successfully held others in the hatchery for 5 years. The modular design of the system makes it possible to scale up production for larger numbers simply by adding additional troughs and associated components.
Pond Production of Fingerling Walleye at Garrison Dam National Fish Hatchery
By: John E. Call, U.S. Fish & Wildlife Service, P.O. Box 530, Riverdale, N.D. 58565
The Garrison Dam National Fish Hatchery, located in central North Dakota, has been operated by the U.S. Fish and Wildlife Service since 1964 for the production of sport fishes. Up to 10 million walleye fingerlings are produced annually. Northern pike, saugeye, bass, paddlefish, trout, and salmon are also cultured. The hatchery is situated below the dam of Lake Sakakawea, which serves as its primary water source. There are sixty four 1.5 acre (0.61-ha) ponds. All ponds are equipped with outside kettles.
Walleye eggs are obtained from wild stocks at Devils Lake and Lake Sakakawea in mid-April. The hatchery water supply at this time of year is approximately 35 F (2 C), and must be heated by boilers to provide more suitable water temperature for egg incubation. Manipulating water temperatures enables us to control the egg incubation period length and double crop some rearing ponds, producing both northern pike and walleye fingerlings in the same rearing ponds. This is possible because northern pike spawn earlier in the year than walleye, and northern pike fingerlings require a relatively short rearing period. Fry survival from eggs incubated over 40 days may be reduced, but it's a small price to pay for enabling us to double crop ponds.
Pond filling and egg hatching are coordinated by using a spreadsheet which predicts hatching dates based on cumulative temperature units. Pond filling begins approximately May 6, at which time the water temperature is near 50 F (10 C) and prolonged periods of cold weather are normally past.
Pond fertilization is based on information gathered by trial and error over 30 years. For many years alfalfa hay was chopped and added to the ponds. It performed well as a fertilizer, but was labor intensive to handle and spoiled quickly in storage. In 1992, after several years of testing, we switched to alfalfa meal. The small particle size allows rapid decomposition and it does not plug screens during pond draining. Additionally, because it is stored in a bin, there is no spoilage. A grain box mounted on a trailer is used to transport the alfalfa meal to the ponds. The meal is broadcast into the pond by an auger projecting out over the pond water as the truck is slowly driven along the dike.
Fertilization begins immediately after pond filling using 133 lbs/acre (60 kg/ha) of alfalfa meal per application. Ponds are fertilized once every 3 days. Fertilization is discontinued 7 days before the anticipated draining date. Pond fertilization schedules are generated by a computer program and dissolved oxygen levels are monitored closely. If dissolved oxygen levels fall below 5 mg/l at sunrise, when measured 1 ft(30 cm) above the pond bottom, fertilization ceases until oxygen levels recover.
The maximum amount of organic fertilizer that can be safely used without oxygen depletion will be influenced by many factors, such as water temperature, natural soil fertility, cloud cover and the amount of phytoplankton present. No attempt is made to adjust fertilization based on plankton tows, pond color or other criteria. Cost of alfalfa meal for pond fertilization is approximately $75.00/acre ($185.00/ha).
Walleye fry, 24 to 48 hours old, are stocked 9 days after the pond has started to fill with water. Fry are enumerated by water displacement (220/ml) and are transported to the pond in 5 gal. buckets which are equipped with a stone diffuser through which oxygen is bubbled during transport. Stocking rate varies from 166,000/acre (410,000/ha) to 200,000/acre(494,000/ha). The culture period for walleye fingerling is normally 29 days, but abnormal water temperatures can alter this period by as much as seven days.
As the anticipated draining time approaches, fish are sampled by seining to determine fish size and condition. When fish reach 1.25 inches (32 mm) total length, the pond is drained. If successive sampling 3 days apart indicate that the fish have not grown, a food shortage probably exists, and the pond is drained before fish condition deteriorates. We believe that survival after distribution is determined as much by fish condition as it is by fish size.
Average production for the last 3 years has been 136,000/acre (336,000/ha) of 1700/lb fingerlings. Average survival for the same period was 76%. As the pond bottom is exposed during the draining process, it is seeded with annual ryegrass using a broadcast seeder at the rate of 33 lbs/acre. This is done to increase soil organic matter and to help control soil erosion.
Information gathered during the growing season is stored in a computer database file as it occurs. We have found this to be a convenient way to not only record information but to later analyze the data we collected.
ENVIRONMENTAL GILL DISEASE
By: Terrence Ott, La Crosse Fish Health Center, La Crosse, WI
This is not a new disease, but a very common bacterial problem experienced by many culturing fish in a closed or open system. The disease more commonly known as Bacterial Gill Disease or simply "BGD" is most devastating to fry and fingerling fish.
Environmental gill disease is a complex disease in which more than one type of filamentous bacterium may be involved. Diagnostic cases of environmental gill disease have isolated Flexibacter sp. and Flavobacteria sp. from the gills of infected fishes. These opportunistic soil and water born bacteria are present in most waters which harbor fish. The only way to eliminate these facultative bacteria from a water source would be by a process called ozonation. Water entering a facility would pass through a machine emitting ozone at levels appropriate to kill these microorganisms, before they made contact with the fish. A costly process and one that is not always 100 percent effective.
All freshwater species of fish are susceptible to environmental gill disease. However, various species of fishes differ in resistance to this disease. Cultured salmonids are especially susceptible to this disease and the disease becomes of great economic importance in salmonid culture.
Environmental gill disease develops when gill irritants are present in the water source at concentrations high enough to damage gill epithelium (skin covering the gills). Gills which become irritated produce a condition called hyperplasia. This occurs when epithelial cells (skin cells in the gill) increase in number in response to the irritant. These excess cells are not lost as rapidly as they are formed, so a thickening of the gill membrane develops at the distal end of the gills. As the gill surface increases in size it obstructs flow of water between them so that hemoglobin in the blood cannot be oxygenated.
Overcrowding of fishes, especially when accompanied by reduced water exchange, is one of the major causes of gill irritants. Another very common gill irritant occurs during this time of year when fry are being fed fry feeds. These fine particulate feeds can irritate and clog gill membranes encouraging the development of environmental gill disease.
Salmonids affected with environmental gill disease are usually lethargic and refuse food, "ride high" in the water and orient toward the incoming water supply. They may also be spaced equidistantly from one another, have labored opercular movements, and gills will appear excessively slimy with whitened tips.
Clinical signs, behavior, and bacterial isolation can be used to diagnose environmental gill disease. Measuring the water chemistry parameters to determine the source of gill irritant may also be helpful in the diagnosis.
Treatment of environmental gill disease should be initiated as soon as possible. The longer the delay before starting a chemical treatment can result in extensive gill hyperplasia and high fish mortalities. The disease is best controlled by eliminating the cause of gill irritants in the water column and treating the fish with the low regulatory chemical sodium chloride containing no anti-caking agents at a 2% concentration. A dip or standing bath treatment for 15 to 30 minutes and repeated daily for 3 to 4 days should eliminate the bacteria buildup on the gills of the fish.
Hatchery Tip
By: MTAN
Now that we are approaching the electrical "power outage" season, you may want to consider how you would maneuver within your hatchery facility should the lights go dim.
One solution that works for the MTAN is to install a rechargeable flashlight just inside the entry door to your hatchery. We're referring to the kind of flashlight that you keep plugged into a wall electrical outlet. The flashlight will continue to be fully charged and readily available when you need it. Should you choose to adopt this same safety measure for your home use, be sure to instruct the kids to always return the light to its recharging station (good luck with that one).
Product and company names mentioned in this publication are for informational purposes only. It does not imply endorsement by the MTAN or the U.S. Government. |
