The Potential for Vessel Interactions with Adult Atlantic Sturgeon in the James River, Virginia

Abstract

In 2012, all populations of Atlantic sturgeon Acipenser oxyrinchus oxyrinchus were listed as either threatened or endangered under the U.S. Endangered Species Act. During 2007–2010, researchers documented 31 carcasses of adult Atlantic sturgeon in the tidal freshwater portion of the James River, Virginia. Twenty‐six of the carcasses had gashes from vessel propellers, and the remaining five carcasses were too decomposed to allow determination of the cause of death. The types of vessels responsible for these mortalities were not explicitly demonstrated. Most (84%) of the carcasses were found in a relatively narrow reach that was modified to increase shipping efficiency. To explore the number of Atlantic sturgeon being hit and their horizontal and depth distributions in relation to vessel draft, we conducted telemetry experiments on three living fish (all males) and six dead specimens. While staging (holding in an area from hours to days, with minimal upstream or downstream movements), the adult male Atlantic sturgeon spent most (62%) of the time within 1 m of the river bottom. Assuming that behavior is not modified by vessel noise, adult male Atlantic sturgeon in the James River would rarely encounter small recreational boats or tugboats with shallow drafts; instead, mortalities are likely caused by deep‐draft ocean cargo ships, which have drafts that coincide with the distribution of the tracked adult males. Dead specimens (n = 6) drifted with the current for several hours to almost 4 d before beaching at distances ranging from 0.5 to over 50 river kilometers from the point of release. We estimated that current monitoring in the James River documents less than one‐third of vessel strike mortalities. A better understanding of Atlantic sturgeon behavior in the presence of vessels will aid in restoring this federally endangered species. Received February 20, 2012; accepted July 19, 2012

Characterizing watercraft‐related mortality of sea turtles in Florida

“…For some aquatic vertebrates, this can be done easily. The floating carcasses of Atlantic sturgeons (Balazik et al ), Florida manatees (Lightsey et al ), and North Atlantic right whales (Campbell‐Malone et al ) tend to float upside down. Therefore, a VSI in the dorsal surface indicates an antemortem occurrence, whereas a VSI in the ventral surface indicates injuries were likely postmortem.…”

“…Many large fishes that feed near the surface have been documented with scars from a vessel‐strike injury (VSI) including whale sharks ( Rhincodon typus ; Speed et al , Ramírez‐Macías et al ), manta rays and devil rays (Mobulidae; Couturier et al ), basking sharks ( Cetorhinus maximus ; Kelly et al ), and ocean sunfish ( Mola mola ; Porcasi and Andrews ). The Atlantic sturgeon ( Acipenser oxyrinchus oxyrinchus ) spends most of its time near the bottom but lives in shallow areas and is also prone to vessel strikes (Balazik et al ). The propellers of vessels kill small fishes (Killgore et al ) and larval fishes (Killgore et al ), and this could represent a substantial mortality that is not well documented (Whitfield and Becker ).…”

Estimated Survival of Subadult and Adult Atlantic Sturgeon in Four River Basins in the Southeastern United States

“…Our survival estimates imply a range of 0.14-0.25 for the total instantaneous mortality rate (Z D ¡log e [survival]). Given that there is no legal harvest of Atlantic Sturgeon, these Z-estimates likely reflect a combination of true M (e.g., due to predation, disease, or senescence) and mortality due to anthropogenic sources, such as degraded habitat, vessel strikes, or bycatch mortality in ocean, estuarine, or inland waters (Collins et al 1996(Collins et al , 2000aSecor and Waldman 1999;Stein et al 2004;Oakley and Hightower 2007;Simpson and Fox 2009;Brown and Murphy 2010;Balazik et al 2012). The Z-estimates could also be biased upward by permanent emigration from any of the areas with receiver coverage.…”

Downstream Passage of Lake Sturgeon through a Hydroelectric Generating Station: Route Determination, Survival, and Fine‐Scale Movements

“…Stationary manual tracking indicated that the remaining three tags were moving more than 30 d after downstream passage. Given the swiftly flowing nature of the Winnipeg River between the Slave Falls GS and Scots Rapids, it was assumed that a Lake Sturgeon carcass (with tag still inside) would tend to drift downstream over time following mortality, as has been observed in the morphologically similar Atlantic Sturgeon A. oxyrinchus (Balazik et al 2012). Of the other three fish, one subadult (#4059) was consistently located approximately 1.5 km downstream of the Downloaded by [Umeå University Library] at 02:34 20 November 2014 a Fish were too large to fit through the 10-cm trash racks on the turbine intakes.…”