Dedicated To The Tribal Aquaculture Program

 

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Topics Of Interest:

Hatchery Operations

Hatchery Security System

Broodstock Isolation Facility

Cotton Wool Disease On Fish Eggs

Early Mortality Syndrome

Old Generator Finds A New Home

Hatchery Tip

The Last Word (Two Important Notices)

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FISH HATCHERY OPERATION

By: Pam May, Red Lake Natural Resources Dept., Red Lake, MN 218-679-3959, EGG CARE DURING INCUBATION

As the hatching jars are put on the battery water flow rates should be adjusted to circulate the eggs high in the jar. As eggs are put into the jars, label each jar with the date the eggs are taken. The eggs should be rolled high in the jar for 1 or 2 hours, then the water flow can be reduced to a level where all eggs are gently rolling. Gently is a key work, as too much rolling increases egg mortality.

Several hatching jars on each battery should be left empty for use as hospital jars while the eggs clean up. All hospital jars should be placed on the bottom row of the battery. This helps to prevent fungus spoors from entering other jars. During the incubation process, and before eye-up, the eggs are very sensitive. Extreme care must be used in handling the eggs during this period. Do not disturb the eggs any more than absolutely necessary.

EGG ENUMERATION

In order to determine egg take, an egg rate (number/quart) must be obtained. The rate depends on egg size and will vary for each stripping site and size of fish collected. An egg rate chart converts the number of eggs which can be placed into a 6 inch Von Bayer metal trough, into eggs per quart.

When measuring eggs, four counts should be made so an average rate per quart can then be determined. Egg rates should be checked on the 2^nd, 4^th, and 6^th days of egg take. An average rate should be determined for the spawning run from these figures. Since fish size and egg expansion rate can vary from day to day, this procedure will reduce error. Eggs incubated less than 24 hours should not be measured. Eggs should be measured fairly dry since any excessive water will tend to spread the eggs. A toothpick can be used as a wick to absorb water while rolling eggs into the trough.

WALLEYE and NORTHERN PIKE SPAWNING TEMPERATURE REQUIREMENTS

WALLEYE: The optimum temperature ranges for fertilization, incubation, and fry survival are 43-54 degrees, 48-59 degrees, 59-70 degrees, respectively. If unusually cold weather occurs after the fry hatch, fry survival may be affected. Feeding of fry may also be reduced when temperatures are low.

NORTHERN PIKE: Water temperatures should not drop during the spawning season. Temperatures near an optimum of 54 degrees are recommended in northern pike management.

FACTORS AFFECTING EGG DEVELOPMENT

Three major factors that affect the development of the embryos are light, temperature, and oxygen.

LIGHT

Direct light may have an adverse effect on developing fish eggs. The most detrimental rays are those in the visible violet-blue range produced by cool white fluorescent tubes. Pink fluorescent tubes, which emit light in the yellow to red range, are best suited for hatchery use.

The best practice is to keep eggs covered and away from direct light. In general, embryos of fishes subjected to bright artificial light before the formation of eye pigments will suffer high mortality at all stages of growth.

Daily Temperature Units (D.T.U. = water temperature(F) minus 32 F). Walleye eggs start hatching approximately 14-18 days after spawning (300 DTU), depending on water temperature. Eggs and fry of walleye tolerate rapid temperature fluctuations. Approximately 390 daily temperature units are required for eggs to hatch in fluctuating water temperatures, while only 230 daily temperature units are required at more constant temperatures.

OXYGEN

Hatching jars provide a fresh water supply with oxygen, dissipate metabolic products, and protect developing embryos from external influences which may be detrimental. The best conditions for the optimal development of embryos and fry are at or near 100% saturation. As the egg develops, oxygen availability becomes increasingly important. Walleye fry do not survive well in water containing 3 ppm dissolved oxygen or less. The desirable range is above 5 ppm.

TROUBLESHOOTING DEBRIS IN WATER

A water intake in shallow water lakes can suck debris into the line during strong winds. The debris can slow or stop water flows to the jars and injure the eggs.

Debris can be eliminated by placing a screen box beneath the water inlet to each battery.

Brass screening similar to that used in egg cradles is preferred because it is durable, however plastic screen can also be used.

AIR BUBBLES IN WATER

A sudden increase in water temperature can cause air bubbles to appear in the hatchery water. This is a problem prior to the eyed stage because the eggs are still quite light and can float out of the hatching jars. To counteract this, the water temperature should be kept as low as possible. This is done by keeping the air temperature in the hatchery cool with fans and closing doors. Water should be run slowly through the jars and the top row of jars should not be used for hatching if possible. New green eggs can be left in tubs and water siphoned over them for a day, then jarred and put on battery. The water to each jar with older eggs may be shut off while a small amount of thin bentonite-water solution is added. After adding bentonite, gently stir the water with a feather to disperse the air bubbles. Recoating the eggs with bentonite can reduce bubble problems for several hours. If possible, the hatchery water can also be agitated to remove dissolved gases before circulation in the hatching battery.

FUNGUS CONTROL

It's common for dead eggs to develop fungus during incubation. If not controlled, the fungus can spread to live eggs and reduce hatching success. A formalin drip at the water inlet, which delivers 1 part of 37% formaldehyde to 600 parts of water for 15 minutes will control fungus. Don't wait for fungus to develop, start treating eggs the second day they are in the hatchery. With well water you can treat every 2-3 days. If you use surface water you may need to treat daily.

Don't treat eggs that are within 3 days of hatching as it will cause a premature hatch and death of the fry. Also, don't allow the formalin to directly contact fry as it will also kill them.

During incubation, it will be necessary to remove dead eggs from the hatching jars. This is done by siphoning the dead eggs and fungus balls from the jar. Higher water temperature accelerates egg decomposition and fungus growth, increasing the amount of siphoning needed to control fungus. Generally, siphoning is not required until after the eggs are jarred. Dead egg removal may have to be done each day until about 15 days after jarring (eyed egg stage).

The siphon is a heavy wall inch gum rubber hose about 15 feet long attached to a inch goose-necked copper tube. Tape is wrapped around the copper tube before stretching the hose over it to form a tight seal. A hose clamp is used to hold the hose onto the tubing. A 3 ounce weight is attached to the hose which sits in a tub to hold it in place while siphoning.

Siphon the bad eggs from the top of the hatching jar into the tub. Often, some live eggs will also be sucked into the siphoning hose. Movement of the siphoning tub is much easier if it is placed on a wood or angle iron frame which has a handle and casters. A 2" by 8" piece of window screen should be placed on each side of the tub below the top rim. This allows excess water to drain off when siphoning.

The water and bad eggs should be poured from the tub with care. The tub used to siphon eggs should not be dragged or scraped on the floor since this is a shock to the eggs. After removing the bad eggs, live eggs should be measured into hospital jars and incubated on the bottom row of the battery.

EGG HANDLING

Egg handling should be minimal between the green and eyed stages. Sometimes, the eggs will clump in a hatching jar and it is necessary to remove the clumps by screening the eggs. A 3/16 inch screen in a round wooden frame should be used over a tub half filled with water. The round frame keeps eggs from packing in the frame corners. Do not use inch screen, since each egg must drop through which may cause injury. A inch screen is used for sucker eggs but do not use it for walleyes because it will allow funguses egg clumps to drop into hospital jars. If an oil slick appears on the tub water, the eggs are being handled too roughly and the egg shells are rupturing.

RE-JARRING EYED EGGS

When the eggs are cleaned up and fully eyed, they should be removed from the battery and re-jarred. The jars must be washed before the eyed eggs are placed in them. No more than 2 quarts of eggs are put in each jar. To re-jar the eyed eggs take the hatching jars from the battery and pour out about half the water in the jar. Put 3 or 4 inches water in a clean tub and pour eggs into the tub until it is approximately half-full of eggs. It may be necessary while adding eggs to pour off water from the tub. Dip eggs from the tub, keeping about 1 or 2 inches of water over the eggs. Pour the eggs into a hatching jar containing 5 or 6 inches of water. If the jar does not have quart markings a measuring stand can be used. Pour excess water off, only 1 inch of water should be over the eggs when measured.

In order to reduce premature hatch at this stage, the eggs should be handled with great care. Some years the eggs do not fully clean up by the time they are eyed. Under these conditions, it is necessary to re-jar them with a small allowance for further cleanup (additional eggs).

Each of the batteries should have about an equal amount of eyed eggs so when the fry hatch, they will not be too heavily loaded in one fry tank. Never wait until the last minute to re-jar eyed eggs; this may result in loss from premature hatch.

FRY TANKS

At egg eye-up, all fry tanks should be cleaned and made ready for the hatch. Fry tank screens should be put in channels and sealed to prevent fry from escaping. A piece of soft foam rubber, 9/16 inch thick and 1 inch wide should be placed in the screen channel at the bottom of each fry tank. When the screen is pushed down on the foam, it forms an effective seal to prevent escape of the fry. After putting the screen in place, the side channels should be caulked. Silicone works well for caulking but must be removed each year by heating. Rope putty and manila rope also seal well and may be easily removed. Tail screens that have air bubblers injected on the front side of them will keep fry and egg shells from clogging up the holes.

EGG HATCH

If the eggs are within 3 days of hatching, a severe disturbance such as a thunderstorm can cause premature hatching. If a thunderstorm is forecast, additional people should be placed on standby to help if a premature hatch occurs. As the eggs hatch, both the egg shells and fry are carried into the fry tank. In order to maintain correct water flow through the tank and prevent the tank from flooding over, it may be necessary to clean the egg shells away from the tank screens. If this is not done it is possible to have all the eggs hatch and lose the fry because they were washed out of the fry tanks onto the floor.

Before cleaning the screens, the fry must be concentrated towards the center of the fry tank. Fry can be diverted away from head and tail screens by using a flood light to attract them to the center of the tank. Also, if air bubblers are injected in front of the tail screen the bubbles will slowly help to move fry away from the screen towards the center of the tank. Turn off the air injection system so egg shells and dead fry can be siphoned from the tank. You may wish to use a brush on the screen to remove egg shells. Do not allow turbulent air flow in the fry tank as it will kill fish.

If the eggs hatch very quickly, a large number of fry and egg shells may be carried into the fry tank. This can also cause screen plugging and make cleaning very difficult without losing a lot of fry. As the screens plug, the tank water level rises and water may begin coming over the bottom tank on the hatching

battery. In this situation, siphon boxes must be used to drain the water and relieve pressure on the tank screens so they may be cleaned.

The siphon boxes are 16 inches square, made with 2 inch by 2 inch lumber and covered with screen or cloth mesh fine enough to prevent entrance by walleye fry. A inch hose is used to siphon the water and three or four hoses may be used in each box. The water is siphoned onto the floor since the screen prohibits entrance of fry. Five or six boxes may be needed in each fry tank depending on how many fry and egg shells are coming onto the tank screens. The siphon boxes should be tied in place in the tank to hold them down.

The egg shells should be removed with a siphoning hose from the bottom of the fry tank. A 3 foot section of inch conduit pipe with 4 feet of gum rubber hose can be used. Siphoning is done into a tub and the eggs shells are allowed to sink to the bottom. Fry captured during siphoning are poured back into the fry tank or stocked out. This is best done when you can see the egg shells building up in the fry tank. If the water is too dark to see the egg shells, the fry can be concentrated at the center of the tank and then the egg shells siphoned near the tank screen.

When a large number of fry are present in one location of the tank, the water must be paddled to move the fry from the bottom or they will suffocate. Paddling should be done at 10 minute intervals and directed to move the fry from the tank screen towards the center of the tank. Fry should be distributed to lakes within 3 days and no longer than 5 days after hatching. If this is not done, the fry will absorb their yolk sac and become cannibalistic. This is evident when "chaining" occurs. This is when a walleye fry will grab onto another fry's tail and attempt to eat it.

FRY MEASUREMENT FOR DISTRIBUTION

Three methods of fry measurement have been used. When measuring fry, they should be placed in a container and taken to the lake for stocking. Do not attempt to transfer fry between fry tanks by using just a net. The stress of the handling will kill the fish.

One method for taking fry measurements is from displacement. This is accurate but difficult to use with large quantities of fry. Fry are added to a large graduated cylinder and the change in volume is recorded. There are approximately 5,440 fry per once (displaced volume). Fry measurement is then calculated by fry/ml. There are approximately 250 fry/milliliter (ml). Keep in mind that the size (displacement value) of fry will change with each passing day. Another method of fry measurement is by weighing them on an appropriate scale. Fry weights can very from year to year depending on time needed for hatching and from day to day after hatching. It appears that a normal hatch will produce about 100,000 fry per pound.

In order to get exact rates, a fry sample must be weighed on a gram scale. The fry sample is dipped out of the tank and strained through fry net webbing to remove excess water. A dry, empty petri dish is weighed on the scale and weight recorded. The fry are then rolled off the webbing into the dish. The edge of a paper towel is used to wipe up excess water. Care must be used so that the fry are not touched and the yolk sac broken. When the water is removed, weigh the fry and dish. Subtract weight of the empty dish to get net weight of fry. Count the number of fry in the sample. Four weights should be taken and averaged to get number of fry per pound. Number of fry per sample can be converted to fry per pound using the formula listed below:

If 10gr. (sample weight) divided by 454 = (X)

Number of fish counted divided by weight (X) = fry/pound

Once the fry rate per pound is determined, a platform scale can be used for weighing large quantities of fry and hanging scale with bucket for weighing small amounts of fry. With a 100 lb. platform scale, put a tub of water on it and balance to 50 pounds. A scale's accuracy is generally highest near the midpoint reading. Scoop a small number of fry from the tank and roll them side to side in net webbing to remove any excess water. Place the fry into the tub on the platform scale and record the weight. Be careful not to grab to large a net of fry as this may result in excessive stress and higher mortality.

DISTRIBUTION

Fry can be distributed in a number of ways depending on lake location and the number of fry to be released. Listed below is a loading rate guide we use for fry distribution:

Standard distribution tank (130 gallons of water)	1,000,000 fry
Oxygen bags (1,000 ml of fry plus 2,000 ml of water)	250,000 fry
Garbage can (very short hauls only of 15 miles or less)	5,000 to 10,000 fry
96 gallon stock tank	1,000,000 fry

Prior to loading fry onto trucks for distribution, oxygen should be released and regulated in the distribution tanks. All agitators should be covered with muslin or similar material before loading. When removing fry from the truck for distribution, they should be dipped in small lots with a net at least 18 inches square and having a slight bag. The fry net should be lifted from the distribution tank with care so the fry are not crushed and injured. Dippers of water should also be used to wash any remaining fry from the net. If a stock tank is used in a barge, fry can be gradually distributed over the center of the lake by siphoning them out with a 1 inch hose.

The fry may be placed in small stock tanks, tubs or garbage cans for distribution in the lake. The container should be at least full of water and lightly loaded to avoid fry suffocation. All fry should be stocked in open water near the middle of the lake but towards the lee side to protect them from being washed ashore. It may be necessary to distribute fish in several locations on a large lake.

If possible, fry should be stocked when water temperatures are rising and a good plankton population is present for best survival. There may be considerable variation in lake water temperature during fry stocking. If possible, lakes with lower water temperatures should be stocked either at the end of fry hatch or early in the morning when hatchery water temperatures are generally lowest and the least temperature difference can be obtained.

OXYGEN BAGS

Place 1,000 ml of fry per oxygen bag to reduce mortality. Add approximately 2,000 ml of water to bag, add fry, force all air out of bag and fill with bottled oxygen. You may want to use double bags in case one breaks or has a leak. To temper oxygen bags to lake temperature, float the bag in lake water for 10-30 minutes, then slowly add lake water inside the bag.

Oxygen bags are hauled in coolers (use square bottom oxygen bags, with square bottom corners to avoid crushing fry) to the stocking site. If traveling a long distance put ice on top of each oxygen bag to keep water and fry cool.

Keweenaw Bay Hatchery Security System

By: Michael Donofrio, KB Biological Services, Keweenaw Bay Indian Community, L'Anse, MI 906-524-5757

The Keweenaw Bay Indian Fish Hatchery recently completed the installation of a security system to protect our fish, submersible pumps, and generator. Our water supply originates from two deep water wells. Sometimes, we only have one pump operating, but most of the time both pumps are delivering water to the tanks. Our hatchery is located 10 miles from the nearest town.

The first aspect of the system was the installation of a three way switch to control our pumps. The switch is either in the on, off, or standby position. The standby mode is only used when one pump is operating. Therefore, one pump is switched on while the second pump is in standby. In the event the operating pump fails, the other pump will automatically start. If the first pump were to start again, the other pump would shut off and return to standby mode. This standby feature insures that one pump is always running. These three way switches were professionally installed for less than $50.

Electronic boxes (to protect the submersible pumps) are the second aspect of our system. We have three phase, 480V power at our hatchery. Power companies are known to have problems supplying the correct voltage in our area. We felt it necessary to install a Motor Saver unit (Model 520CP @ $375 ea) for each pump. The Motor Saver device protects and ultimately extends the life of our submersible pumps. These units monitor the incoming power for: overcurrent, undercurrent, single phasing, reverse phasing, and current unbalance. In the event of a problem, the Motor Saver will shut off the pump and try restarting the submersible every 60 seconds until the pump resumes normal operation. Each Motor Saver has an LED display to indicate the current operating amperage of the motor or a code to signify a problem with the pump.

The final aspect of the system was the installation of a security system. We installed a conventional burglar alarm, but changed the system from burglary to pump, power, and generator monitoring. The alarm system we chose is manufactured by Moose Products Inc. (Model Z1100). The unit was installed by a security company at a cost of $900. The security system can monitor 8 different relays, but we are presently using only five relays. Our security system monitors: generator operation, power transfer (between power company and generator), pump failure, and failure of generator to start. Our generator also has a series of fault relays which indicate why the generator didn't start or isn't running properly. These fault relays include: overspeed, overcrank, high engine temperature, low oil pressure, low engine temperature, low fuel and ruptured fuel tank. A problem with a fault relay is the fifth aspect of the security system.

The security system is monitored 24 hours a day. We pay a security company $27/ month to monitor our system. One of the hatchery staff must wear a pager at all times, so one person is on call during off duty hours and weekends in case the security system is activated for various reasons. If a problem occurs, we instructed the security company to call a series of phone numbers until contact is made with hatchery personnel. The pager system works for a radius of 100 miles from the hatchery.

We periodically test the system to make sure the alarm is functional and the system is being monitored properly by the security company. We'll shut off a pump, manually start the generator, or even shut of the incoming power source. The system has been functional for 4 months without any problems. The system is fairly compact and only needs about 2'x 2' area on the wall. As I mentioned before, the system is expandable to monitor other aspects of the hatchery operation. As the budget permits and need requires, we'll enlarge the system to further protect the fish and hatchery operation. We analyzed several options and this system was most feasible for our location. Other types of security systems are probably available in your area, but this system is meeting our present needs. All hatcheries should have some type of security system to protect your investment during the more critical aspects of the rearing process. Or maybe you just like digging holes to bury your fish.

Keweenaw Bay Indian Community Joins Efforts With the U.S. Fish and Wildlife Service To Restore Great Lakes Fishery

By: MTAN

The MTAN is pleased to announce the signing of a cooperative agreement between the United States Fish and Wildlife Service and the Keweenaw Bay Indian Community. This cooperative project will include the operation of a lake trout broodstock isolation facility at the KBIFH and the production of 100,000 lake trout at the Iron River National Fish Hatchery (which will serve to support KBIFH fish stocking priorities).

This agreement will foster the continued integration of fish health and fish genetics into our captive broodstock program. KBIFH will initiate this two year cooperative program in September of 1995. The success of this plan is dependent on the ability to capture and spawn mature fish of native wild stocks and transportation of fertilized eggs. Once a pathogen free disease history has been established (this includes three inspections over a two year period), the fingerlings will be distributed from the KBIFH to other fish hatcheries within the Great Lakes region.

COTTON WOOL DISEASE ON FISH EGGS

By: Terrence Ott, La Crosse Fish Health Center, La Crosse, WI

Cotton wool disease or Saprolegniasis is a ubiquitous component of freshwater ecosystems in the Great Lakes region. Any body of water capable of supporting fish will also support this fungus.

Species of the genus Saprolegnia are often considered secondary invaders following mechanical injury, but once they start growing the lesions usually continue to enlarge and may cause death unless medication is provided.

Saprolegnia grows on many types of decomposing organic matter, and the resulting asexual reproductive spores are almost universally present in water supplies to egg incubation trays or jars. Fungi often attack dead fish eggs and soon encompass adjacent live eggs, killing them. Fungus therefor constitute one of the most important egg diseases of cultured fish.

Dead fish eggs which are white in appearance are a fertile medium for the growth and disease of saprolegniasis. A single saprolegnia zoospore can initiate growth on a dead fish egg. As the disease progresses, a whitish fungal mesh, which looks like cotton wool, appears at the infected egg site. The mycelial mass extends out from the egg into the water thus surrounding more eggs. The partially suffocated eggs around the fungal mesh die when invaded by the fungi. The suffocating effect is spread (domino effect) until all eggs in the incubator tray are killed.

Rapidity of fungal growth on susceptible fish eggs is related to environmental temperatures. Most of the saprolegnia identified in fish cultural environments have an optimum growth temperature between 15 and 30C.

The wide distribution and general occurrence of saprolegniasis have been responsible for the development of many therapeutic procedures over the years for control of the disease. There are two effective methods in controlling cotton wool disease on fish eggs. One is mechanical, the other is chemical.

Mechanical control is effected by removing dead and infected fish eggs from the incubator tray two to three times per week. This is a time consuming procedure, but very important when incubating fish eggs, especially walleye eggs.

The chemical method is simpler, and certainly more efficient when using formalin as the chemotherapeutant. The U.S. Food and Drug Administration (FDA) has allowed fish culturists to use this chemical only on salmonid and esocid eggs. Prophylactic treatments of 1000 to 2000 ppm (based on 100% active ingredient) for 15 minutes a day or when needed is the recommended standard. Do not expose fry to these concentrations of formalin. They are lethal.

Fish culturists stop giving formalin treatments to their eggs 2 weeks prior to hatching.

A Side Note From MTAN:

[Elizabeth Greiff (St. Croix Tribal Nat. Res. Program) has used 4,000 ppm formaldehyde every 48 hours throughout the entire incubation period, including holding fry and has not experienced excessive fry mortality.]

Information provided by the National Fisheries Research Center at La Crosse, Wisconsin has led the FDA to conclude that hydrogen peroxide is a low regulatory priority drug when used at levels of 250 to 500 ppm to control fungi on all species and life stages of fish, including eggs.

The ruling has allowed fish culturists to use hydrogen peroxide as a fungicide on any species of fish eggs however, caution must be used when giving prophylactic treatments to walleye eggs. At Genoa National Fish Hatchery, Genoa, Wisconsin, hatchery staff experienced that walleye eggs will float to the top of the hatching jar when treated with the chemical (Todd Turner, USFWS, Genoa, WI, personal communication).

Fish culturists may obtain hydrogen peroxide from many commercial sources; however, vendors who advertise the product for use in aquaculture must meet certain FDA requirements. The La Crosse Center used a 35% solution obtained from Eka Nobel, Inc., Marietta, Georgia. The 35% formulation is suggested for use due to availability and safety.

Fish culturists now have the option to use hydrogen peroxide as a fungicide on eggs as well as formalin. Estimated costs for fungicidal use of hydrogen peroxide are comparable to those of formalin.

Early Mortality Syndrome: Nutrition, Contaminants, or Genetics?

By: Leslie TeWinkel, Re-printed from "FORUM", Great Lakes Fishery Commission Winter 1994/95

Hyperexcitability, anemia, spiral swimming patterns, dark coloration, deformities, and emaciation. Collectively, these clinical signs characterize a disease syndrome that strikes Great Lakes salmonids - Early Mortality Syndrome (EMS).

As the name implies, this syndrome manifests itself most dramatically as an increased mortality in recently hatched salmonid fry (but mortality also occurs in eggs). EMS has only been observed in eggs and fry that are progeny of wild broodstock. Researchers throughout the basin have begun to investigate the syndrome by searching for causes and cures. While an immediate remedy for high hatchery mortality is needed, it is also critical that researchers identify the root of the problem and broaden their field of focus to include changes within the Great Lakes ecosystem that may be causing the syndrome.

Overview of the Syndrome

EMS-like signs were first observed in lake trout in the Great Lakes between 1979 and 1981. Research began in earnest on the syndrome following a dramatic increase in hatchery mortality in the late 1980s in Lake Michigan. Research since then has shown that the syndrome cannot be readily explained by environmental, husbandry, or infectious-disease causes. Some researchers have noted similarities between EMS and other diseases of early-life stages including blue-sac, coagulated yolk, and white spot. Yet, while these diseases had some signs which overlapped with EMS, none of them mirrored the complete suite of clinical signs or caused mortality solely between eye-up and first feeding.

The puzzle of EMS is confounded by its nonuniform distribution in the Great Lakes, both in terms of geography and species. While the syndrome has been observed in Skamania-strain steelhead, lake trout, and chinook salmon, coho have been the most severely affected species. However, not all coho have been influenced. EMS has not been observed in coho or any other species in Lake Superior. In Lakes Erie, Ontario, and Huron, managers have observed the syndrome to some extent. But it is Lake Michigan populations that have been the hardest hit. Estimates of hatchery mortalities for coho in Lake Michigan have increased from 18% in 1985 and 1986 to 64% in 1992 and 1993. This increase in mortality threatens the coho fishery in Lake Michigan, a lake where the chinook salmon fishery has already seriously declined.

High hatchery mortality has prompted scientists to investigate possible cures for the syndrome. Experiments on a variety of compounds showed that one of the B vitamins, thiamine, produces dramatic results. Thiamine treatment including egg immersion and fry injection significantly reduces EMS signs and mortality. Other research has indicated that thyroxine, a thyroid hormone, also reduces mortality. The results of these experiments are extremely useful for managers concerned with decreasing mortality in hatcheries. However, the root of the problem is still undetermined. Three factors have been postulated as potential causal agents of EMS:

• nutrition

• contaminants

• genetics

Possible Causes

One of the leading hypotheses for EMS at this time is a nutritional deficiency. Given that thiamine treatment produces a significant decrease in mortality, it follows that a thiamine deficiency may be causing EMS. Other research has shown that eggs taken from salmonids in Lakes Ontario and Erie have lower levels of thiamine than those taken from a domestic broodstock, and fish from this domestic broodstock do not exhibit EMS. Furthermore, treatment with other B vitamins, and Vitamins A, C, E, and astaxanthin does not reduce EMS. Yet, successful treatment of EMS with thyroxine brings a thiamine deficiency theory into question. It is possible that EMS is the result of another problem - one which is masked by treatment with thiamine. Problems with contaminants in the Great Lakes throughout the past two decades suggest the second potential cause of EMS.

However, an important element missing in a contaminant theory is a contaminant which is known to have increased or been introduced into Lake Michigan in the early or middle 1980s. If such a contaminant existed, it would provide rationale for the appearance of the syndrome in the late 1980s. Although Great Lakes managers are not aware of a contaminant with this profile, one could still be present. For this reason alone, contaminants can not be dismissed as a possible cause. A third possible cause relates to population genetics. Current hatchery practices emphasize efficiency and production with less concern given to the genetic pressures that these practices may exert on salmonid populations.

Inadvertent artificial selection could conceivably result in inbreeding or outbreeding depression which is manifested as EMS. However, given that EMS occurs across species, a genetic hypothesis is unlikely. Thus, at this time, managers are favoring thiamine deficiency, contaminants, or a combination of the two as the cause of EMS.

Plan for Action

In order to further evaluate these potential causes and develop a plan for action, a workshop was held under the auspices of the Commission's Great Lakes Fish Health Committee. Participants recognized the need to devise both a short-term plan to decrease hatchery mortality and a long-term research plan to investigate the root causes of the syndrome in the Great Lakes ecosystem.

Workshop participants agreed that the methodology for the short-term plan should be based on previous research which showed that thiamine is an effective remedy. A plan for long-term action was not as obvious. Many research needs were identified including baseline nutritional analysis for both adult salmonids and eggs, investigation of the interaction between thiamine and contaminants, determination of possible contaminants which are increasing in the Great Lakes, and examination of broodstock for contaminant status. The answers to these questions and others may be necessary before the syndrome can be fully understood and a long-term solution can be developed. At that time, Great Lakes natural resource managers can begin to address the ecosystemic changes that are causing EMS. Until then, only the symptoms of this syndrome can be treated.

A report on the EMS workshop is in preparation. For more information on EMS, contact:

Al Sippel, Chair, Great Lakes Fish Health Committee 519/824-4120, ext. 3819.

John Hnath, Coordinator, Thiamine Treatment Studies 616/668-2132.

Sue Marcquenski, Coordinator Long-term Research Needs 608/266-2871.

Congratulations To The St. Croix Band For Winning The 15KW Generator "Quick Pick"

The U.S. Fish and Wildlife Service recently received a 15KW diesel generator from government surplus. The MTAN and the Service were surprised by all the interest shown by Tribal hatchery programs desiring to have such a unit. The only fair way to decide which program was to receive the generator was through a random selection.

The luck of the draw favored the St. Croix Tribal Band. This power system will be a welcome addition to the St. Croix hatchery. Once installed it will help to insure the continued electrical power needed for developing eggs and fry.

The MTAN will continue to attempt to locate additional generator systems. We're sorry that we were not able to offer one to all those hatchery programs that responded to our inquiry.

Hatchery Tip

The sound of rushing water can be very serene at times, but for hatchery workers subjected to extensive levels of rushing water, this can result in a very distracting working environment. Greg Fischer (Hatchery Manager from the Red Cliff Band) came across an interesting way to decrease the "sucking" sound heard from rearing tank discharge pipes. The technique involves attempting to break up the water flow pattern as it exits the top of the tank's stand pipe. The solution involves drilling two holes (") about three inches below the top of the pipe. This will cause an interruption in the flow pattern which also eliminates that nasty sucking sound common to water discharge pipes.

Another solution to eliminate the sound of water as it exits rearing tanks, is to change the manner in which it enters the discharge drain. This problem is initially caused when the discharge water is allowed to splash directly with the water already in the drain channel. The MTAN has found that a 45 angle attached to the end of the drain pipe which is then attached to a straight section of pipe that leads into the drain channel, will help to reduce most of these annoying sounds.

The Last Word

The MTAN has just been reminded of a proverb we once heard as a small tadpole growing up in the big pond of life. The lesson of reality we're referring to is the one that goes something like this: "Be careful what you wish for, you may just get it."

In the last issue of the MTAN we presented information on how to access the information super highway via your computer modem. One of the features we discussed was an "Internet" connection with the Aquaculture Network Information Center (AquaNIC).

Apparently the MTAN was overheard because we are now connected to the Internet and have begun to access AquaNIC. The MTAN has much to learn on how to retrieve information but at least the learning curve has begun. The MTAN would like to offer its help to Tribal hatchery programs who may be thinking of accessing the many features of AquaNIC. Just give us a call at the Ashland FRO (715-682-6185) and ask for Frank.

The Last Last Word

The MTAN would like to take a new direction and offer to our Tribal hatchery programs the opportunity to advertise (without any fees) within the pages of the MTAN. We feel that Tribal programs have much to offer to all the other Tribal programs that receive the MTAN. If your Reservation produces a product of any kind and you would like to spread the word to other Tribal programs, please call Frank at the Ashland FRO to discuss the details.

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Last updated: November 19, 2008

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