Anadromous alosines are ecologically, commercially, and recreationally valuable fishes. Some populations of alosines are at historically low levels, as a result of overfishing, pollution and habitat change, including the presence of dams, which block access to historic spawning sites upstream and alter spawning habitat downstream. To aid in the restoration of alosine stocks, I evaluated several methods for spawning habitat identification and characterization and evaluated trap and transport as a method to give American shad Alosa sapidissima access to additional spawning habitat above dams in the Roanoke River, North Carolina and Virginia. The Roanoke River has four anadromous shads: American shad, hickory shad A. mediocris, blueback herring A. aestivalis, and alewife A. pseudoharengus. For all four alosines, spawning sites river-wide were most efficiently identified using plankton tows. Spawning habitat selection for hickory shad and river herring (blueback herring and alewife) could be evaluated using spawning pads, whereas American shad eggs were unsuccessfully sampled by spawning pads and spawning habitats were best examined by visual observations of spawning splashes. Unlike the other alosines in this study, very little is known about spawning habitat for hickory shad. Hickory shad eggs were collected at water temperatures from 10 to 23 ºC, and peaked from 11 to 14 ºC. Spawning generally occurred in water velocities â¥0.1 m/sec, over substrates free from silt. Standard USFWS and Bayesian belief network formats were used to develop preliminary habitat suitability models for hickory shad. Bayesian belief networks are a relatively new method for modeling habitat suitability for fishes, but could prove very useful in the future, especially for species such as American shad which have been the focus of more study and are in need of restoration. We evaluated movement patterns and spawning of sonic-tagged adult American shad transported to habitats above dams on the Roanoke River. Most transported fish spent relatively little time in the riverine habitat considered suitable for spawning and no eggs were collected by plankton sampling. American shad appeared to move more effectively through a smaller as compared to a larger reservoir, but migration was best when fish were released directly into riverine habitat. Low mortality resulted from downstream migration through each dam turbine, but many individuals were observed just upstream from a dam late in the season, suggesting that structures to increase downstream passage may be beneficial. We used data on behavior and outmigration of American shad adults and fry released above and below dams on the Roanoke River to develop a deterministic, density-dependent, stage-based matrix model to predict possible population-level effects of transporting American shad to upper basin habitats. The American shad population in the Roanoke River appears small compared to assumed values of carrying capacity in the lower river and would appear to benefit from transport only under optimal conditions of young survival and effective fecundity. The matrix model predicts that under present conditions, improvements to survival rates of young or adults would likely lead to greater improvements in the stock size of American shad in the Roanoke River.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-12102009-152753 |
| Date | 21 January 2010 |
| Creators | Harris, Julianne Elaine |
| Contributors | Joseph E. Hightower |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-12102009-152753/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dis sertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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