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Distinct Shark Species Confirmed in Puget Sound
Researchers from Oregon State University (OSU) have achieved a significant milestone by scientifically confirming the presence of two distinct shark species in Puget Sound, one of which is critically endangered.
The identification of the broadnose sevengill shark and the endangered soupfin shark in this region—the southern segment of the Salish Sea—suggests notable ecological changes in an area recognized for its economic, cultural, and ecological importance. The Salish Sea, which separates northwest Washington from Vancouver Island in British Columbia, covers approximately 6,500 square miles and extends into Washington as Puget Sound. The sharks were captured near Olympia, close to the southern tip of the sound.
Oregon State’s Taylor Chapple, an assistant professor in the College of Agricultural Sciences, along with graduate students Jessica Schulte and Ethan Personius, documented their findings in research papers published in Frontiers in Marine Science. They collaborated with NOAA’s National Marine Fisheries Service and the Washington Department of Fish and Wildlife to establish that the broadnose sevengill shark, an apex predator capable of reaching nearly 10 feet in length, is now residing in the heavily urbanized areas of South Puget Sound.
“Understanding the presence of the sevengill shark in this new habitat is essential for grasping the food webs in the Salish Sea. It underscores the necessity for ongoing monitoring and research, particularly regarding its interactions with other species at risk, like salmon,” stated Schulte, who is the lead author associated with the sevengill research.
The broadnose sevengill shark is distinguishable by its unique anatomical feature of having two additional gill slits compared to most other shark species. This species preys on a diverse range of marine life, including fish, crustaceans, and marine mammals. Broadnose sevengills are distributed in temperate waters globally, with habitats along the west coast of North America extending from southern Alaska to Baja California.
Prior to 2021, only one sevengill shark had been recorded in the Salish Sea, located at Point Roberts, Washington, near the Canadian border. However, in August 2021, anecdotal sightings suggested that several of these sharks had been caught in South Puget Sound.
During field research conducted over a span of 10 days in 2022 and 2023, the team captured nine broadnose sevengills, marking a substantial 190-mile extension from previously recorded habitats. Among these, eight were males, with the largest measuring nearly 7 feet, while the female measured about 4 feet 6 inches.
“Ongoing research on the sevengill species in Oregon and Washington waters will enhance our understanding of its ecological role in these important marine ecosystems,” Schulte noted.
The soupfin shark, highlighted by Personius, the lead author on that particular paper, is the largest of the hound shark family, capable of growing up to 6.5 feet. Its name is derived from its historical use as a key ingredient in shark fin soup.
“During the 1930s and 1940s, soupfin sharks were heavily targeted, not just for their fins but also for their livers, which are high in vitamin A. Despite a reduction in fishing pressure, the species has struggled to rebound and is currently under consideration for federal protection under the Endangered Species Act,” Personius explained.
Like the broadnose sevengill, the soupfin shark thrives in temperate waters and serves as a top predator, consuming cephalopods and various fish species. They are known to be strong swimmers and are capable of migrations exceeding 1,000 miles.
In a parallel field study, the researchers also captured one soupfin shark, a male measuring just over 5 feet. Personius pointed out that the Salish Sea has undergone significant shifts in species distribution and composition due to industrialization and habitat degradation. The increasing presence of soupfin sharks may be linked to climate change and variations in prey populations.
Following the extreme marine heat wave event from 2014-2015, known as “The Blob,” a surge in anchovy populations in the Salish Sea has been observed, as they became a dominant prey species. Since soupfin sharks are confirmed predators of anchovies, this could explain their recent appearance in the area.
Graduate student Maddie English contributed as a co-author on the soupfin shark research, collaborating with scientists from NOAA and the Washington Department of Fish and Wildlife. Research associate Alexandra McInturf also played a role in the sevengill shark study.
More information:
Jessica M. Schulte et al, Advancing the ecological narrative: documentation of broadnose sevengill sharks (Notorynchus cepedianus) in South Puget Sound, Washington, USA, Frontiers in Marine Science (2024). DOI: 10.3389/fmars.2024.1430962
Source
phys.org