Title page for ETD etd-06082010-020440


Type of Document Master's Thesis
Author Blythe, William G
URN etd-06082010-020440
Title Induced maturation and spawning of striped bass, Morone saxatilis, exposed to 6-, 9-, and 12-month photothermal regimes
Degree Master of Science
Department Fisheries and Wildlife Sciences
Advisory Committee
Advisor Name Title
Helfrich, Louis A. Committee Chair
Beal, W. E. Committee Member
Hallerman, Eric M. Committee Member
Heath, Alan G. Committee Member
Keywords
  • Striped bass
Date of Defense 1992-03-05
Availability restricted
Abstract
This thesis was partitioned into three studies. In the first study, striped bass, Morone saxatilis, (n = 16) were monitored over a 13 month period to examine the efficacy of ultrasound to determine sex and to monitor sexual maturation. Four observers reviewed all ultrasound images (n = 208) of striped bass and were able to sex male and female striped bass with 99 and 95% accuracy, respectively throughout an annual reproductive cycle. Egg diameter was highly correlated with average (r = 0.89) and maximum (r=0.92) ovarian diameter as measured by ultrasound. Spenniating males exhibited larger maximum testicular diameters (23.5 mm) than non-spermiating males (13.1 mm). Fully mature female and male striped bass exhibited maximum ovarian diameters > 30 mm and testicular diameters > 20 mm as measured by ultrasound. The results of this study indicate that ultrasound is an effective and non-invasive method that aquaculturists can use to quickly scan, sex, and assess the sexual maturation of adult male and female striped bass year-round.

In the second study, photothennal manipulation was used to induce spawning out-of season and to increase the frequency of spawning in striped bass, Morone saxatilis. Forty adult striped bass, held in five environmental chambers, were exposed to compressed 6- and 9- month cycles and a 12-month reference cycle. Maximum egg diameters increased with cycle length, averaging 845 urn, 946 urn, and 1,073 um for females held on the 6-, 9-, and 12-month cycles,respectively. Females held on the 6-month cycle had smaller ovarian diameters (19.6 mm) than those held on the 9-month (27.4 mm) and 12-month (24.5 mm) cycles. Ovary diameter was highly correlated with egg diameter (r = 0.91). Spawning success (percent of females spawning) increased with cycle length, averaging 38%, 86%, and 100% in the 6-, 9-, and 12-month cycles, respectively. However, no differences in latent times, fecundity, or fertility were detected between cycles or between tank-spawned and strip-spawned females. Males held on the 6-month cycle had smaller testicular diameters (16.2 mm) than those held on 9-month (23.6 mm) and 12-month (19.2 mm) cycles. Testicular diameter ofspenniating males (15.7 mm) was significantly larger than that ofnon-spenniating males (6.9 rnrn) in all cycles. Mortality increased with cycle length, averaging 28%, 38%, and 88% for fish held on the 6-, 9-, and 12-month cycles, respectively. Maturation and spawning were advanced by five and three months for fish held in the 6- and 9-month cycles, respectively when compared to a natural 12-month reference cycle. Fish held on the 6-month cycle matured twice within a year. However, the relatively low number of spawning females and diminished egg, ovarian, and testicular diameter of fish held on the 6-month cycle suggest that an abbreviated cycle length « 9 months) may inhibit maturation and constrain spawning success.

Files
  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
[VT] LD5655.V855_1992.B597.pdf 5.18 Mb 00:23:57 00:12:19 00:10:47 00:05:23 00:00:27
[BTD] next to an author's name indicates that all files or directories associated with their ETD are accessible from the Virginia Tech campus network only.

Browse All Available ETDs by ( Author | Department )

dla home
etds imagebase journals news ereserve special collections
virgnia tech home contact dla university libraries

If you have questions or technical problems, please Contact DLA.