Haley, N., J. Boreman, and M. Bain. 1996. Juvenile Sturgeon Habitat Use in the Hudson River. Pp. 1-18 in Final Reports of the Tibor T. Polgar FellowshipProgram. Hudson River Foundation, NewYork.Misho BorissovDr. Lin’s Seminar 475For Monday of April
Background (continued) • Oligohaline – intermediate freshwater/saltwater zone • Mesohaline – saltwater region
Historical Background • Atlantic Sturgeon • Acipenser oxyrinchus • Short-nose Sturgeon • Acipenser brevirostrum • Hudson River • History of the Hudson River
Experimental Background • Tappan Zee Bridge To Staatsburg, New York • Four Strata used • Wide Estuary • Highland Gorge • Wide River • Narrow River
Additional Background • Wide Estuary • Widest Section of the estuary. Channel of uniform depth • Highlands Gorge • Narrowest and Deepest section of the estuary. • Wide River • Widest, freshwater portion of the estuary. • Narrow River • Region consists of a straight, featureless channel. Channel and river width are nearly equal with very narrow subtidal banks along the shoreline.
Experimental Background(continued) • Nets placed @ each stratum • Three small nets in hopes of capturing juvenile sturgeon • Juvenile terms • Atlantic sturgeon • Less than 1200 mm • Short-nose sturgeon • Less than 510 mm
Results gathered • 57 Juvenile Sturgeon caught • 36 wild Atlantic sturgeon • 12 Short-nose juvenile sturgeon • 09 Stocked Atlantic sturgeon
Results(continued) • Total Length (mm) Weight (g) • Range Range • Short nose 404-584 300-1200 • Atlantic 272-1245 80-4940 • Stocked 306-659 120-2030
Sturgeon Distribution • Distribution amongst the four strata • Atlantic sturgeon - Distributed along all four strata • Short-nose sturgeon- distributed along all four strata. • Stocked sturgeon – found only in the Wide River and the Narrow River strata
Other experiments within this result • Wild Atlantic sturgeon with a length of less than 600 mm was used. • Scientists did because of the wide range of distribution between sturgeon • They compared the distribution of an Atlantic Sturgeon less than 600 mm with the distribution of the Short-nose and Stocked sturgeon.
Salinity • Saltiness measured with YSI model 5500 Salinity meter. • Short-nose Sturgeon • Found mostly in freshwater • Atlantic Sturgeon • Found mostly in salt water • Stocked Sturgeon • Found in three zones • Found in salty, sweet, and intermediate zones
Salinity Graph # 2 • Wild Atlantic Sturgeon • Different salinity and • temperature measure- • ments in HG to see if • seasonally-variable • characteristics are a factor • in surgeon distribution • and occurrence By following the red line At each strata, one would Notice that salinity levels Stayed nearly constant Throughout the summer
Salinity conclusion – All three exhibited different distributions in terms of the salinity level. • Distribution according to saltiness • Short-nose Sturgeon • As reported, short-nose sturgeons were found primarily in the freshwater region • Atlantic Sturgeon • These were found primarily in the saltwater region • Stocked Sturgeon • These were found in the intermediate zones
Silt, Sand, & Gravel • Silt • Rock and Soil • Sand • Gravel • Stone and Sand
Silt, Sand, & Gravel SUBSTRATE % of Effort SNS AS SS silt 80.4 11 34 9 sand 17.4 1 2 0 gravel 2.3 0 0 0 significance 1.03 4.61 2.20
Depth and Temperature • Temperature and Depth Measurement • Measured with YSI Model 5500 Temperature meter and depth Depth Temp. (July) Temp (Aug) Short-nose 17.3 24.2 27.5 Atlantic 22.8 27 26.6 Stocked 16.6 (around)26 26.9
Frequency of Occurrence • Sampled Depths to see in which range the sturgeon would appear. • Different depths were taken into consideration as well as which sturgeon was caught in that respective depth
Depth Frequency Graph SHORT NOSE ~~> WILD ATLANTIC ~~> STOCKED ATLANTIC ~~>
Finale • The Wild Atlantic Sturgeon were primarily in the Highlands Gorge stratum (deep salty region) • The Short nose Sturgeon were primarily found in the Narrow River stratum (freshwater zone) • In saltier regions, AS outnumber SNS by 10:1, while in freshwater regions, that ratio is reversed, thus concluding that freshwater/saltwater boundary may serve as an ecological barrier between these two species.