8026 - Laserfiche WebLink

Home Browse Search

a very potent mortality factor. Predation in Terry Pond was so intense that 2625 squawfish may have been entirely eliminated in a matter of twc or three weeks. Fish Chalet Pond also had low survival during the first stocking attempt and yet it is a bass-free pond. Over-winter mortality is suspected on account of the relatively high survival there during the summer months. Squawfish experienced their highest rate of survival with the fall plant at Pabco Pond. Over- winter mortality was apparently not a problem there and bass preda- tion must have been lessened by cold temperatures and the availabil- ity of buffer prey species. In contrast, the summer stocking of squawfish at Pabco resulted in their almost complete annihilation within two months. In that situation, there were more bass present than before, the water was warmer, and possible buffer prey species like fathead minnows and mosquitofish were no longer present. Results from T + F Pond are difficult to interpret. The number of bass present was low and the abundance of buffer prey fish high. One would expect predation to not be a major mortality factor there. Survival, however, was negligable after both stocking attempts. The parasite Larnea was found on 85/ of the summer-stocked squawfish in T + F Pond, with infections averaging five active lesions per fish. This and stress during winter may be the main causes for high mortal- ity there. Judging from the survival and growth data, it appears that there is no advantage to stocking squawfish in fall rather than in spring. Winter stress exacts a heavy toll on squawfish numbers and no growth occurs during the winter months. The best, results for pond stocking would likely be produced by stocking during spring in a predator-free pond like Fish Chalet, where spring-spawning carp provide an abundant food source. 8. Laboratory Studies Three of the four bass food preference experiments were completed in 1984. Bass did not display a preference for one prey species when offered both fathead minnows and young squawfish together (Tables 11 and 12), indicating that fatheads may serve as a buffer to bass predation. They definately prefer squawfish over green sunfish when offered that choice, however (Tables 13 and 14). Small bass greatly prefer eating small squawfish rather than larger ones. Medium-sized bass tended towards the smaller squawfish also. However, the large bass, although eating higher numbers of small squawfish, had a diet comprised by weight more of larger squawfish (Tables 15, 16, 17, and 18)p Thus, the smaller the squawfish - the more will be eaten to satiate a bass, and the more size ranges of bass it will be available to. 1985 WORK PLANS The fourth and last bass prey preference experiment (red shiner squawfish) will be completed in Febuary. In April, removal seining will recommence at the ponds so that estimates of survival for the fall 1984 stocked squawfish can be made. Limnology data will continue to be collected until May. Coded microtags will be decoded in the lab to determine size-related survival and the remaining bass stomach contents will also be analysed. 18