Broadnose Sevengill Shark.
A large bodied cow shark with a short, rounded snout. Seven gill slits. Six fairly broad, sawlike teeth on each side of the lower jaw. Single dorsal fin. Dorsal origin level with (or anterior to) free rear tips of pelvic fins. Caudal fin has an indistinct lower lobe. Upper caudal lobe deeply notched. Dorsal coloration grey or grey-brown with many scattered dark grey spots and blotches and a few white spots and blotches. Spot pattern may be quite dense completely absent. Ventral coloration may be light grey or mottled white and grey.
Maximum length 296cm. Size at birth 34-45cm.
A temperate water species inhabiting kelp forests and sandy or rocky bays. Found from the surface to at least 136m but usually in shallow water.
The broadnose sevengill shark is wide ranging along temperate coastlines. It is found along most temperate coastlines in the southern hemisphere. In the northeast Pacific it has been recorded from British Columbia to Baja, and the northwest Pacific from Korea to Taiwan including Japan. Records from Sri Lanka and India are probably misidentifications. Absent from the North Atlantic.
DATA DEFICIENT GLOBALLY
NEAR THREATENED REGIONALLY
The broadnose sevengill shark is targeted for its meat, and it is also taken in some areas for its hide and liver oil. Intensive commercial and sports fisheries in San Francisco Bay targeting it for its fine meat caused a marked local decline in numbers during the early 1980s. It is utilised in China for its skin and liver. Pollution may be a possible threat to inshore bays which are nurseries.
Although wide ranging in temperate waters and moderately common where not heavily exploited (e.g., southern Africa), this large shark has a limited inshore bathymetric range in heavily fished temperate waters and is often concentrated in shallow bays. This exposes it to intensive inshore bycatch and sometimes targeted commercial, sports and semi-commercial fisheries over most of its range, particularly off China, California, Argentina, Namibia and South Africa (Compagno in prep. a). Catch statistics are not reported, except for the west coast of the USA, which show a peak in landings of 1.55 t in 1981 with a sharp decline to less than 0.1 t in 1986 (Compagno in prep. a).
Citations and References
Compagno, L.J.V. 2009. Notorynchus cepedianus. The IUCN Red List of Threatened Species 2009: e.T39324A10200310. https://dx.doi.org/10.2305/IUCN.UK.2005.RLTS.T39324A10200310.en. Downloaded on 15 October 2020.
An aplacental viviparous species. Litter size poorly known but clearly very large; one specimen contained 82 near term embryos.
Feeds on sharks and rays, bony fishes and marine mammals (pinnipeds). In turn, sevengill sharks predated upon by orcas and white sharks.
A slow moving species that patrols kelp forests, rocky reefs and mud flats. Sevengills in Humboldt Bay, California have been observed foraging on shallow mud flats before dawn, returning to deeper channels at sunrise.
In False Bay, South Africa, many sevengills (often juveniles) remain in the kelp forest. As well as providing an abundant supply of food, the forests likely act as cover from great white sharks; a species that rarely ventures into kelp. However, in False Bay I have also seen sevengill sharks far away from the forest, on a baited camera left on open sand at ~50m.
At one particular kelp stand in False Bay where sevengills were especially abundant, in 2018, a sevengill carcass was found on the sea floor with tooth marks that indicated an attack by orcas. Since that time, sevengills have been mostly absent from that specific area.
Reaction to divers
When encountered in kelp forest, broadnose sevengill sharks often seem oblivious to divers until they are extremely close (1-2m away), at which point they usually explosively accelerate, but soon resume their normal slow swimming speed. It is tempting to think they don’t see divers but as apex predators that consume seals and fast moving sharks, they probably have excellent eyesight.
CAUTION: In baited situations, sevengills usually become very aggressive. Not only will they persistently turn towards divers and attempt to bite, but they also approach from above and below, making the process of redirecting them rather difficult when multiple sharks are present.
There are a number of places where broadnose sevengill sharks are regularly encountered by divers.
Historically, Millers Point in False Bay, South Africa, was an excellent spot to see sevengills until a predation event (probably from an orca) took place a few years ago. Since then the sevengills have been thin on the ground but they still show up on occasion. During our (Big Fish Expeditions) South African Endemic Shark Diving Expeditions, we always conduct a few lightly-chummed dives either in the kelp forest or within the harbour at Simonstown. Invariably, sevengill sharks show up, so the sharks are clearly still in the area.
In the eastern Pacific, Divers at La Jolla Cove near San Diego, often encounter sevengills patrolling the kelp forests. The encounters are hit and miss but a few days of diving in mid/late summer will likely be rewarded with an encounter. La Jolla Cove is a very popular shore diving spot, so arrive early to avoid a very long schlepp with heavy dive gear!
In Bahia Bustamente in Patagonia, kelp harvesters regularly encounter sevengills within the kelp forest. There is a hotel at the ‘kelp farm’ but no diving infrastructure, so divers will need to drive down from Puerto Madryn with all personal equipment and a supply of tanks.
Further south at Ria Deseado, a hotel owner told me that he also sees sevengills while diving but this area is even further away from the nearest diving infrastructure.
Sevengills are also seen on occasion by divers around the south island of New Zealand. A 2015 Shark Week ‘documentary’ entitled Sharks of the Shadowlands sensationalized the encounters where sevengills have apparently harassed divers that were removing invasive kelp from local reefs.
Bluntnose Sixgill Shark Differentiated by having six gill slits instead of seven, and lack of significant markings. Although sevengills have been recorded in BC where sixgills are found in shallow water, there are no records of sevengill encounters by divers that far north.
Sharpnose Sevengill Shark Differentiated by it’s small size (<1m), pointed snout, much larger eyes, and lack of spots. This species rarely enters shallow water.
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