Critical Habitats of Atlantic Sturgeon
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GRANT NUMBER:  NA77FD0063            NMFS NUMBER:  96-SER-007

REPORT TITLE:  Critical Habitats of Atlantic Sturgeon

AUTHOR:  Mark R. Collins, Theodore I.J. Smith, and William C. Post

PUBLISH DATE:  March 25, 1999

AVAILABLE FROM:  National Marine Fisheries Service, Southeast Region, 9721 Executive Center Drive, St. Petersburg, FL 33702-2432 .   TELEPHONE:  (727) 570-5324


With the assistance of former sturgeon fishermen, large-mesh gillnets were deployed at historically productive fishing locations in Combahee, Edisto, and Cooper Rivers, SC, and limited sampling was conducted in the Savannah River, GA/SC.  A total of 42 adult Atlantic sturgeon Acipenser oxyrinchus (136-234 cm total length) was caught.   No adult or age 1 juvenile Atlantic sturgeon (the two indicators of presence of a population) were captured in the Cooper River. Pectoral fin spines were taken for ageing, a tissue sample was taken(for a molecular genetics study), the fish were tagged (PIT and dart), a gonad biopsy was taken when possible, and radio and acoustic transmitters were surgically implanted in 30 individuals (1 in the Savannah River, 29 in the Combahee and Edisto Rivers). Ages were 7-20. Of the 20 Combahnee/Edisto fish for which sex was definitively ascertained, 17 (age 7-15) were male and 3 (age 15-20) were female. Ripe males and females were captured in both Spring and Fall.  Directed upriver movements of over 100 miles by two fish in October also support the hypothesis that there is a Fall spawn. Continuous tracking of one fish for 36 hr.  Suggested active, extensive use of shallow areas (oxbows) at night followed by relative inactivity in a deep portion of the main river during the day. Two fish ascended both the Combahee and Edisto Rivers. It is likely that spawning occurs at several locations in the Comabahee and Edisto Rivers. A ripe female (hydrated eggs) that was likely in the process of spawning was captured in Spring at River Mile (RM) 34.7 in the Edisto River, which is an area of limestone outcrop, and another was captured there in Fall.  Hard substrates (rock or gravel) were also found at RM 30.8 in the Edisto river and RM 34.2 in the Combahee River. However, spawning may also occur in areas without rocks (e.g., Edisto RM 65 and 118), as sunken trees probably provide an adequate for egg adherence. Summer habitats, which may be essential for survival of southern sturgeons, were diverse and included the lower and upper estuary (RM 6, 17), tidal freshwater (RM 25), river (RM 40-45, 56-65), and probably the ocean because some fish left the system entirely. Two fish recaptured, one after a year, confirming that surgical (and other fish handling) procedures were effective and that males can be in spawning condition (running ripe) in consecutive years.

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