Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) Behavioral Responses to Vessel Traffic and Habitat Use in the Delaware River, USA
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Abstract
The Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus), a large, long-lived, anadromous species, experienced rapid population declines in later part of the 19th century due to overfishing and habitat loss. The Atlantic Sturgeon was listed under the U.S. Endangered Species Act (ESA) in 2012. Vessel strikes and habitat destruction, along with water quality degradation and bycatch mortality, were listed as major threats to the recovery of the species in the ESA determination.
My study was conducted to further understand behavioral responses of Atlantic Sturgeon to vessel traffic and to indicate habitat preferences within an area of presumed spawning and foraging within the Delaware River. During the spring and summer of 2013 and 2015, I used a VEMCO Positioning System to monitor fine-scale movements of telemetered adult and subadult Atlantic Sturgeon.
I used sturgeon spatiotemporal positions together with, commercial vessel traffic tracking data to observe possible differences between movement types, defined by using trajectory analyses for my first objective. Telemetered adult Atlantic Sturgeon exhibited several behavior types although I found no evidence that these behaviors were influenced by commercial shipping. For my second objective, I modeled habitat use of Atlantic Sturgeon in relation to Delaware River sediment types to observe whether sturgeons selected different proportions of the sediment than available. While subadults were shown to avoid muddy and sandy sediment, adults preferred course grain sediments (e.g., gravel) and avoided soft sediments (mud and sand). These results support the findings of previous studies which proposed that the study area was likely used for spawning/staging by adults during the early summer months.
My findings suggest that Atlantic Sturgeon exhibit no behavioral responses to vessel presence and that individuals select areas of occupancy based on available sediments. This has direct implications in species conservation due to the continued alteration of sediments to support an increasing vessel traffic through maintenance dredging and channel deepening. If vessel avoidance is not occurring, managers must consider alternative ways of avoiding vessel strikes (e.g., seasonal restrictions such as limits to speed, draft depth, and passing zones) while also considering issues of continued sediment (i.e., habitat) alteration in critical areas of the river.