Dedicated To The Tribal Aquaculture Program

December 2001-Volume 38

Topics Of Interest:

Aquatic Plant Control

2000 Tribal Fish Hatchery Production

Walleye Spawning Operations at Bonny Reservoir

Hatchery Tips

Aquatic Plant Control (A Power Point Presentation)
By:  Gregg Raisanen, Alexandria Technical College, 320-762-4618 

(Please click on the images below to view each picture).

Conclusion

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2000 Tribal Fish Hatchery Production
Data submitted by the Bureau of Indian Affairs (Midwest Region).  Table generated by the Great Lakes Indian Fish and Wildlife Commission.

Fish hatcheries play an important role in co-managing interjurisdictional fishery resources. Midwestern tribes have responded to the modern day challenges of multijurisdictional resource management in their unique role as users and managers on over 900,000 acres of reservation inland lakes, treaty ceded territories and the Great Lakes. There are currently fifteen tribal fish hatcheries and or rearing components in the 1999 Midwest Region. Red Lake and Lac du Flambeau are the oldest, being established in 1929 and 1936, respectively.  These reservations in serving tribal subsistence and commercial needs are also contributing significant fish stocks to reservation waters fished by over 95% non-Indian anglers.  The U.S. Fish and Wildlife Service and state Departments of Natural Resources also play an active role in stocking fish as a management tool in reservation waters.

2000 Tribal Hatchery Fish Stocking By Species

Walleye Spawning Operations at Bonny Reservoir, Colorado
By:  Charles O. Benneft and James L. Melby~ Colorado Division of Wildlife, 2126 N. Weber, Colorado Springs, Colorado 80907

Bonny Reservoir is a 1,924-acre plains reservoir constructed and operated by the United States Bureau of Reclamation. The Colorado Division of Wildlife and Colorado Division of Parks and Outdoor Recreation own the conservation pool and manage fish, wildlife, and recreation. It is located on the South Fork of the Republican River in Yuma County, northeast of Burlington, Colorado.  Walleye spawning at Bonny historically starts on or about March 20. Thirty to 45 million walleye eggs are collected annually from wild captured broodfish. Average hatching rate is 65-75 %.

A two-slip boat house in a protected cove adjacent to the dam is modified for walleye spawning. A floor is constructed over one boat slip that contains four, 4 x 4 x 4 ft x 1 in mesh holding nets, a 100-gal holding tank for receiving broodfish, a spawning table, and an oblong shallow (50 gal) tank for floating egg boxes during the egg hardening process. A submersible electric pump provides water for all phases of the spawning process. Overhead PVC pipes and valves deliver water where needed.

Standard neutral buoyancy 2.5 inch bar mesh gillnets, 6x200 ft are used to capture brood size walleye. Nets are deployed daily at sunset parallel to the dam riprap and in sand/rack rubble shoreline areas. Net placement is in 3-6 ft deep of water. Gill nets are checked at 7am by a boat crew of 3-5 people. Two crew members pull the nets while 1-2 personnel remove broodfish. The sex of a netted fish is noted before removing, because removal techniques are different due to average size and body shape differences between sexes. Males are usually removed from the nets head first, while females are backed out of the net to minimize egg loss. Standard net picks are used and additional care is given when in the opercular area to prevent gill damage.

Gravid females that are expelling eggs while in the net are held tail up or on their back, and the vent is blocked with a finger to prevent further egg loss while handling. Brood fish are placed in a 100-gal tank containing lake water and supplied with 1-2 L oxygen/mm dispensed with airstones. Fresh water is supplied as necessary with a 12 volt pump. A burlap tank cover is used to reduce potential stress from bright sunlight. The standard project boat is 18 ft long, powered by a 150 hp outboard engine. The size and power of this equipment is deemed necessary due to payload, distance from the boathouse and potential foul weather conditions.

Broodfish are returned to the boathouse when the carrying capacity of the tank is reached. The actual number of broodfish in any haul varies due to fish size and sex ratio, but generally 25-50 fish can be held safely in the tank. Fish are transferred to a holding tank inside the boathouse. The tank is supplied with recirculating lake water and provided with 1-2 L oxygen/min. An overhead counter-weighted submersible pump is lowered to empty and refill the boat tank for additional trips to the nets. Broodfish are sorted by sex and ripeness. Males are placed in a 4x4x4 ft holding net (1-in bar mesh) suspended through the floor of the boat house. "Green" females are held in a similar holding net. They are checked each morning and ripe fish are stripped. Fish that are still green are marked with a hole punch in one lobe of the caudal fin and held back another day. Females that have not ripened after two such marks are released. Males as needed are placed in a tub with oxygen and recirculating water on the spawning table.

The dry method of spawning is used in Colorado. A female and the spawning pan is wiped dry and eggs are extruded from the fish into the pan by firm pressure to the abdomen. We have found that wearing rubber surgical and/or wool gloves and using a closed finger rocking motion from the tips of the fingers to the back of the hand is an effective method for stripping eggs. This technique is thought to be less harmful to the fish. Less scale loss and mucus production is observed compared with other techniques that have been used. However, personnel with small bands may have difficulty using this technique. Large females (8-15 lb) are always handled by the head and tail rather than by the tail only. Handling a large fish by the tail can only result in skeletal damage.

Fresh semen from two males is used to fertilize the eggs. Extended semen is used when males are in short supply. Fertilized eggs are covered with water and stirred for 90 s with a feather. Water is then decanted from the eggs. This step is done as quickly as possible, and can require additional repetitions if blood or fecal matter is present.

Egg clumping will occur if too much time is spent cleaning the eggs.

After fertilization and cleaning, a mixture of Fullers Earth and water (3-4 cups Fullers earth to 1 gal of water) is added to the eggs and stirred for an additional 90 s to remove the sticky matrix that causes eggs to clump during incubation. The mud solution is decanted and the eggs are washed with clean water to remove residual mud and blood. Eggs are then poured into a Saran cloth (32x32 mesh/in) covered egg box. Each box is capable of holding 2 -3 million eggs. The boxes float in a shallow oblong tank that is supplied with oxygen and lake water. Minimum water hardening time is 1 h. After the eggs are water-hardened, they are dipped from the egg boxes and placed into an appropriate sized cooler. Coolers should not be filled more than two-thirds full. Additional egg swelling can exceed the cooler capacity and oxygen depletion can result in substantial losses. Fresh water is added to completely fill the containers and lids are secured. The coolers are then transported to the hatchery for tempering, enumeration, and jar incubation in well water.

Hatchery Tips
By:  MTAN

Are you having problems keeping small fry and debris off your tail screens?  The folks at the Lac du Flambeau Reservation have developed an air bubbling system that eliminates this problem.  The system involves a flexible air line inserted into a section of copper pipe.  The pipe is cut to a length that covers the entire tail screen (or stand pipe) area.  Holes (1/16 inch) are drilled into the copper pipe that will produce large air bubbles.  The air line has a valve that allows the operator to adjust a level of air flow to provide water currents where fry are floated away from the tail screen area.  Another benefit of this system is that additional oxygen is added to your rearing tank.

The MTAN recently had the opportunity to use the new microbubble oxygen diffusers that are now on the market.  Water Management Technologies is just one of many outlets for this fine product.  These diffusers produce a cloud of extremely fine bubbles (100 to 500 microns).  The smaller the bubbles, the more efficiently the gas will be absorbed into the water.  The end result is healthier fish due to a higher oxygen absorption rate.