Date of Award
Master of Science
More knowledge about the spawning habits of the invasive silver (Hypophthalmichthys molitrix) and bighead (H. nobilis) carps in the United States could lead to a better understanding of how and where these fish are able to successfully reproduce and continue to expand their range. This study explored the possibility of combining multiple strategies (mobile tracking, catch-per-unit-effort [CPUE] of females, reproductive staging of females, and CPUE of larvae) to determine whether Asian carp were more likely to spawn in specific habitats. Additionally, I explored whether the timing of spawning was size-dependent for female Asian carp, and whether Asian carp larvae overlapped with those of native species in space and time. Adult females and larvae were collected weekly and transmittered adults were tracked generally monthly in Pool 26 of the Mississippi River during optimal spawning temperatures in 2011. Mixed model repeated-measures analyses indicated no effect of habitat on adult female or larvae CPUE. There were significant increases in Asian carp larvae CPUE on June 6 (t77 = 5.65, P < 0.001) and June 20 (t77 = 7.33, P < 0.001), indicating recent spawning bouts. Regression tree analysis found that the highest Asian carp larvae CPUE occurred at temperatures ¡Ý 22.5¡ãC and turbidities ¡Ý 163.5 NTU (0.50 larvae m-3). A multinomial baseline-category logit model suggested that there was a 0.83 probability of relocating a tagged fish in a backwater. Logistic regressions determined that 50% of silver carp females were mature at 688 mm total length and larger silver carp females had a higher probability of being spent earlier in the spawning season than smaller females. Asian carp represented 10% of all collected larvae and made up over half of the total larval catch on June 6, 2011. This study found little evidence suggesting that Asian carp are spawning in specific habitats. However, it is possible that the temporal collection pattern was too coarse to catch their potentially rapid response to spawning cues. Larger females may be contributing disproportionately to the population through early spawning, suggesting that population reduction could be increased by targeting these females.
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