Modeling the Effect of Environmental Parameters on Feeding Ecology of the Shortnose Sturgeon in the Saint John River, New Brunswick

Abstract

We examined the effects of spatial, temporal, and environmental parameters on the feeding habits of the shortnose sturgeon Acipenser brevirostrum. We sampled sturgeon gut contents using colonic flushing, a new, low-impact technique. We found that heavy feeding continued until at least November, when water temperature reached 8 • C. In all seasons, foraging shortnose sturgeon used shallow water (2-8 m); however, in late fall this trend was even stronger, when 50% of the sturgeon were captured in less than 3 m depth. Over 60 families of prey items were identified from 166 colonic samples collected at four points between spring and late fall from seven locations throughout the lower Saint John River, New Brunswick. Samples from freshwater sites contained mainly Gastropoda, Sphaeriidae, Chironomidae, and Gammaridae. Samples from saline and brackish environments contained mostly Gammaridae, Corophiidae, softshell clam Mya arenaria, Cyathura polita, and Chironomidae. We used sensitivity analysis to determine the number of shortnose sturgeon required to obtain a representative sample of the diet. We found that 20-40 gut samples from sturgeons in both brackish and freshwater environments would suffice for a general description of the diet but that complete knowledge of the sturgeon diet and a comparison among several sites would require the sampling of hundreds of fish. The digestibility of prey varied from 77% of the ingested volume in a saline environment to only 6% in freshwater samples. Shortnose sturgeon from freshwater sites had higher ingested volumes and more prey per ingested volume than did those from brackish sites, which indicated further differences in feeding efficiency between the environments. Salinity was a significant parameter in the redundancy analysis of ingested prey items. In freshwater sites the significant factors were season, sturgeon length, ingested volume, number of ingested prey, and number of ingested taxa. In saline sites the significant factors were season, location, ingested volume, and the number of ingested prey. Our findings identified the spatial and temporal gradients in shortnose sturgeon foraging and provided insight into foraging efficiency in this species.Studying a species' foraging ecology is critical to understanding their movements and habitat requirements. Sturgeon diets have been previously studied in several species, e.g.

Effects of nutritional deprivation on juvenile green sturgeon growth and thermal tolerance

“…The recent colonization and domination of the SFE benthos by Corbula amurensis Schrenck, 1861 (the Asian overbite clam) (Feyrer et al 2003;Cloern and Jassby 2012) has displaced many of these prey species (Nichols et al 1990;Gilbert et al 2011;Greene et al 2011;Cloern and Jassby 2012). Other sturgeon species have been shown to successfully adjust their diet to altered prey availability (Brosse et al 2000;Usvyatsov et al 2012), and the Asian overbite clam has been identified as a major component of the diet of the sympatric white sturgeon (Kogut 2008). However, in sturgeons, manipulation of diet ration or nutritional content has been shown to affect growth, energetic status (Hung and Lutes 1987;Cui et al 1997;Hung et al 1997;Deng et al 2009;Han et al 2012;Haller et al 2015) and the cellular response to heat stress (Deng et al 2009;Han et al 2012;Wang et al 2013).…”

Acoustic Telemetry and Benthic Habitat Mapping Inform the Spatial Ecology of Shortnose Sturgeon in the Hudson River, New York, USA

“…For instance, Usvyatsov et al. () found that freshwater bivalves were less digestible to Shortnose Sturgeon than softshell clams in saline waters of the Saint John River, New Brunswick, Canada. During spring on the Hudson River, the salt front is common in the Haverstraw Bay/Peekskill region, with the modeled salt front occurring north of Peekskill on average 61% (SD = 34%) of the time during the study period (Georgas and Blumberg ; Urban Ocean Observatory at Davidson Laboratory ).…”

“…Shortnose Sturgeon are opportunistic suction feeders, exploiting deepwater channel habitats (Dadswell ; Carlson and Simpson ; Bain ; Usvyatsov et al. ). Within this 75‐km stretch, tagged fish were mostly detected in channel habitats (>5 m) comprising mud and sand sediments.…”

Life history and status of Shortnose Sturgeon (Acipenser brevirostrumLeSueur, 1818)

“…Riverine habitats typically used by juveniles and adults follow: sandy to hard‐mud bottom; water depth – highly variable from channel to shoals, with night‐time foraging often in water <1 m deep; but no diel pattern of water depth use by CR SNS (Kynard et al., ). However, SJohnR SNS have a seasonal difference in foraging depth where the shallowest depths are used in the fall (Usvyatsov et al., ). Thus, GOM and northeastern SNS are highly flexible for foraging depth with fish probably going wherever forage is most abundant.…”

“…Juveniles and adults are characterized as benthic cruising predators with a broad diet, foraging opportunistically on a wide variety of invertebrates like benthic insects, crustaceans, mollusks, and polychaetes (Taubert, ; Dadswell et al., ; Kynard, ; Usvyatsov et al., ). Forage items vary widely depending on their abundance in space and time.…”