Laserfiche WebLink
4 <br />3. Larger fish can be permanently marked with PIT tags and implanted <br />with radio transmitters. Razorback sucker smaller than 75 mm can <br />neither be safely PIT tagged (Burdick and Hamman 1992) nor be <br />radiotagged. <br />4 <br />Time of Year to Stock <br />An important consideration is the time of year razorback sucker should be <br />stocked. In the lower basin, reintroductions of hatchery razorback sucker <br />were hampered by predaceous fishes (Marsh and Minckley 1989). Juvenile <br />razorback sucker reintroduced in the summer and fall were heavily preyed upon <br />by centrarchid and ictalurid fishes. Based on the failure of juvenile <br />razorback sucker reintroduced in the summer and fall in the lower basin, Marsh <br />and Brooks (1989) recommended stocking razorback sucker in late winter to <br />allow razorback sucker time to acclimate while predation intensity was at its <br />yearly low. If adult razorback sucker are released in the upper Colorado <br />River upstream of Government Highline Diversion Dam, predation would probably <br />not be an important consideration. . <br />There are merits to releasing fish either prior to, during, or following <br />runoff. Osmundson and Kaeding (1989b) recommended stocking adult fish in <br />early summer to allow adequate time for them to acclimate to the river <br />environment before the rigors of winter occur. This may also reduce the <br />chance of fish being transported downstream by high runoff flows and minimize <br />undesirable dispersal. On the other hand, releasing fish in early spring <br />(March) may allow an adequate acclimation period before runoff. It may also <br />enable the stocked adults to exhibit spawning behavior and possibly spawn the <br />first year of release (May-June). A third option would be to release fish <br />into flooded areas during runoff and allowed to move into the river, rather <br />30 <br />4