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ponds to a length of 12 inches (- 300 mm) TL before they are stoccked into the Middle Green River. The fish will be reared on zooplankton and should be able to convert to other, larger natural food organisms after they are released into the wild. Reasons for stocking razorbacks at 12 inches TL include: (1) they will be easier to sample during monitoring efforts, (2) they are expected to survive at a higher rate, and (3) they are expected to become mature and spawn for the first time in the Year 2001. Increased numbers of razorback sucker larvae in the river will allow better evaluation of survival related to enhancement/restoration of flooded bottomland habitats (i.e., levee removal evaluation). Number of Fish to be Stocked. In 1995, approximately 200 fish from five family lots of captive-reared razorback sucker were stocked into the Middle Green River. To prevent genetic swamping in the wild stock, the numbers of captive-reared razorback suckers will be equalized by stocking about 200 fish from each of 25 family lots. Surviving razorback suckers from wild larvae will also be stocked into the Middle Green River, provided that they are genetically similar (based on DNA fingerprinting) to the wild stock. The number of razorback suckers that can be reared from natural spawning is dependent upon the effectiveness of the collection of wild larvae. Time of Release into the Green River. The fish will be PIT-tagged, characterized through DNA fingerprinting, and released into the Green River in either September or October. The intent is to release the fish with sufficient time to acclimate to the riverine environment before the water temperatures decrease during late fall. Also, the streamflows are lowest at that time of the year so fish reared in ponds or bottomland habitats will not subjected to high streamflows that are characteristic during the spring runoff. Location of Release. Surviving razorback sucker will be released in a five mile section of the Middle Green River beginning and extending downstream from the Split Mountain boat ramp. Experience has demonstrated that stocked endangered fish disperse downstream shortly after their release. By releasing the fish in the area of Split Mountain, the fish will disperse downstream and be able to select low velocity habitats that they encounter through the broad valley in the Jensen-Ouray reach of the Green River. Although it has been documented that razorback sucker have fidelity to certain spawning sites, it is unknown if the fish actually imprinted to the site or if it is a learned behavior. Increased thyroid activity occurs during the egg and swimup stage of the razorback sucker that may indicate the time of imprinting (Scholz et ale 1993). Therefore, wild larvae will have already been imprinted to the spawning site (e.g., Razorback Bar) or captive-reared fish that have been exposed to a synthetic chemical from egg through the swimup stage will be used in the augmentation stocking efforts. This is a conservative approach in the event that the ongoing research study demonstrates that razorback suckers imprint to spawning sites. If imprinting occurs in the razorback sucker, wild larvae will already be imprinted to the site where they were spawned. Captive-reared fish will be exposed to 6