Seven gill slits, one rear-set dorsal fin, and fossils deep in its past: the broadnose sevengill is the ancient apex cruiser of temperate kelp coasts worldwide.
Most sharks carry five gill slits a side. The broadnose sevengill (Notorynchus cepedianus) carries seven — a signature of one of the oldest shark body plans still swimming. It is a big, blunt-headed, beautifully handled predator of temperate coasts: kelp edges, sandy bays and estuary mouths from San Francisco to Tasmania to the Strait of Magellan. Long lived, slow breeding and fond of shallow water, it is also a shark whose fortunes track how well — or poorly — we manage coastal seas. Here is the profile.
| Scientific name | Notorynchus cepedianus |
| Family | Hexanchidae (cow sharks) — among the most ancient living shark lineages |
| Maximum size | Commonly to about 3 m and ~180 kg; larger claimed reports are poorly verified |
| Range | Temperate seas worldwide except the North Atlantic; in the Pacific from British Columbia to Chile, plus southern Australia, New Zealand, South Africa and Patagonia |
| Depth | Surface shallows to well over 100 m; strong association with bays and coastal shelves |
| Reproduction | Aplacental viviparity; large litters (dozens of pups) born in shallow nursery bays |
| Status | Listed as Vulnerable on the IUCN Red List; recovering or stable in some regions, pressured in others |
The cow shark family, Hexanchidae, is a living fossil gallery. Sharks recognisably of this plan appear in the fossil record on the order of a couple of hundred million years back, and the hallmarks have barely changed: extra gill slits (six or seven where other sharks have five), a single dorsal fin set far back over the tail, and a heavyset body powered by long, deliberate strokes.
Whether the northeast Pacific sevengills are exactly the same species as the Southern Hemisphere ones has been debated; some authors have split Pacific animals as Notorynchus pectorosus. The mainstream position treats them as one wide-ranging species, N. cepedianus, with regional populations. Either way, what you are looking at over a kelp reef off La Jolla or in a Tasmanian bay is the same archetype: a temperate-water apex cruiser with the design brief of an earlier ocean.
Identification is mercifully easy. Count the gill slits on one side: seven, and you're done — nothing else in its range shares that. Then confirm with the single, rear-set dorsal fin and the broad, blunt snout. Colour is grey to brownish above, pale below, liberally freckled with small dark spots and scattered white dots; the pattern is individual enough that researchers photo-identify sharks by it, and citizen-science programs have built catalogs off diver photographs in places like San Diego and South Africa.
Movement matches the build: unhurried, powerful, gliding. Divers often describe sevengills as calm to the point of indifference — but this is a three-metre predator with a mouthful of unusual teeth: hooked cusps up top for gripping, flat saw-edged combs below for shearing. Respect is the right register, not fear.
The broadnose sevengill is a creature of temperate coasts: cool, shallow, often murky water where most shark-watchers don't think to look for big sharks. It patrols kelp forest margins, sandy bays, channels and estuary mouths. It is absent from the North Atlantic but otherwise forms a near-continuous band through the temperate Southern Hemisphere — Chile and Argentina, South Africa's Cape coast, southern Australia and Tasmania, New Zealand — plus the northeast Pacific from British Columbia down through California and into Mexico.
Shallow bays are the system's nurseries. On the US west coast, San Francisco Bay, Humboldt Bay and Willapa Bay have been documented as pupping and nursery grounds, where young-of-the-year sharks ride out their smallest, most vulnerable phase in protected water. Tagging work has revealed strong site fidelity at multiple scales: individual adult sevengills return to the same bays and even the same ledges year after year, season after season — a habit that makes them wonderfully watchable and, unfortunately, easily targeted. The kelp forests of Tasmania and the Cape Peninsula hold some of the most reliable adult aggregations anywhere.
Sevengills eat broadly and ambitiously. The confirmed menu includes bony fishes — from salmon and anchovies to lingcod-sized reef dwellers — and a working knowledge of other cartilaginous fish: leopard sharks, spiny dogfish, bat rays and smaller sharks all appear in stomach contents. They scavenge readily; a carcass on the bottom will draw them in numbers.
At the top end of their ambition sits marine mammal prey. Off South Africa and Argentina, sevengills have been recorded killing and eating seals — with observations suggesting coordinated approaches by groups of sharks around hauled-out fur seals, a rare documented case of something like cooperation in sharks. This is an apex predator that scales its menu with its size.
Kelp forests figure in the story at the margins — literally. Sevengills cruise forest edges and sandy corridors where prey bunches and flees, and bays with kelp habitat hold the forage fish that young sharks cut their teeth on.
Reproduction is aplacental viviparity: eggs hatch inside the mother, and pups are born live, nourished by yolk, with no placenta. Litters are large by shark standards — up to around 80 pups have been reported, an unusually high count — and pups arrive at roughly 40–45 cm, ready to hunt small prey in the nursery shallows. Females return to sheltered bays to pup, which concentrates the next generation in exactly the waters most affected by coastal development, pollution and gillnetting.
The maths of shark life applies here in full: high litter numbers, but long gaps between breeding events, late maturity and slow growth, so the population's ability to absorb sustained removal is modest.
Sevengills have been through this before. San Francisco Bay supported an intensive targeted fishery in the 1930s and 1940s — for liver oil and meat — that stripped out the big sharks within a few years; the population there has taken decades to rebuild its adult structure. Sport catch, bycatch and shark-control nets have pressured populations elsewhere.
The global IUCN assessment lists the species as Vulnerable. The positives are real: the species breeds in protected bays, shows strong fidelity that marine protected areas can exploit, and in several regions — California, parts of South Africa, Namibia — targeted pressure has eased enough for numbers and diver sightings to climb. Modern monitoring leans on photo-identification, acoustic tagging arrays and, increasingly, environmental DNA, which can flag sevengill presence in a bay from a few litres of seawater.
For anyone working the kelp coasts — councils, dive operators, restoration programs — the sevengill is an emblem species: an apex presence you can actually see, whose return signals an ecosystem with its top story rebuilt. Our work at the forest edge, from reef structure to prey base, aims at exactly the kind of coast that can afford to keep them.
Are sevengill sharks dangerous to humans? Bites are rare. Sevengills are usually calm around divers, but they are large, powerful predators that can become assertive when competing for food or when bait is in the water. They have lunged at divers in baited situations. Treat them like any big wild animal: no baiting, no crowding, stay visible.
How do you identify a sevengill shark? Two checks. Count the gill slits — seven per side where other local sharks have five — and confirm the single dorsal fin set far back, almost over the tail. The body is heavy, the snout blunt, and the flanks grey-brown with dark and pale freckling.
Why do they have seven gills? They're members of the cow shark family, an ancient lineage that branched off early in shark evolution and kept the extra slits as part of its body plan. Their closest living relative is the sixgill shark; the feature is a hallmark of the group, visible in fossils hundreds of millions of years old.
Where do sevengill sharks live? Temperate coastal seas nearly worldwide except the North Atlantic: the northeast Pacific from British Columbia to Baja, southern South America, South Africa, southern Australia, Tasmania and New Zealand. They favour bays, estuaries and kelp-fringed coasts, usually shallower than 100 metres.
Can you dive with sevengills? Yes — some of the most reliable encounters anywhere: San Diego's kelp, Tasmania, and Cape Peninsula sites all have seasonal aggregations. Go with local operators, expect calm, curious passes, follow operator guidance, and enjoy one of the ocean's oldest designs at arm's length.
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