Historically, adult river herring (<I>Alosa pseudoharengus, Alosa aestivalis</I>) and American shad (<I>Alosa sapidissima</I>) fisheries were economically important in Albemarle Sound. Stocks of these species are currently in decline while stock estimates for striped bass (<I>Morone saxatilis</I>) have increased 10-fold for the Albemarle Sound-Roanoke River stock since the early 1990s. The primary goal of this study was to quantify the diet, prey selectivity and the predatory impact of age-1 striped bass on juvenile river herring and American shad in 2002 and 2003. Similar estimates were produced for juvenile yellow perch (<I>Perca flavescens</I>), a species with an expanding fishery. Striped bass and prey samples were obtained from 443 beach seine and 171 purse seine hauls from May through October in 2002 and 2003. Age-1 striped bass were primarily piscivorous from May onward in both years. <I>Alosa</I> spp. were a small component of age-1 striped bass diet in summer months but dominated diet in early fall months. Age-1 striped bass fed randomly with respect to <I>Alosa</I> spp. abundance during the summer and selected for them during early fall months. During summer 2003, selectivity for yellow perch decreased with concomitant decreases in importance as a prey item. Field estimates of consumption rates ranged from 3 to 8 % body weight per day while bioenergetics model estimates of consumption ranged from 4 to 12 % in 2002 and 3 to 10% in 2003. Age-1 striped bass density, diet, prey sizes eaten, and consumption rates were used to calculate loss rates due to predation and were compared with total loss rates from catch curves. There was interannual variation in the effects of predation. Age-1 striped bass predation had a marked effect on juvenile American shad densities in 2002 but had little influence on their numbers in 2003. Conversely, age-1 striped bass predation explained none of the loss in juvenile yellow perch in 2002 but accounted for nearly all of the loss in 2003. Thus, predation by striped bass may explain at least some of the variability in year class strength for these species. In most cases, age-1 striped bass predation did not have a strong influence on juvenile alewife numbers. Juvenile blueback herring were preyed on but the relative predatory impact could not be determined because of apparent emigration into the study area. To better understand striped bass impacts on <I>Alosa</I> spp., future work should address movement of juvenile <I>Alosa</I> spp into and out of Albemarle Sound estuary.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-12142004-132232 |
| Date | 14 February 2005 |
| Creators | Tuomikoski, Jack Esa |
| Contributors | Kenneth H. Pollock, Joseph E. Hightower, Jeffrey A. Buckel |
| 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-12142004-132232/ |
| 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, dissertation, 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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