Join me in the cold, dark, life-sustaining NE Pacific Ocean to discover the great beauty, mystery and fragility hidden there.

Sharks Among Us #2 – The Bluntnose Sixgill Shark

4.2 m female sixgill shark.

The awe-inspiring images here are of a pregnant female bluntnose sixgill shark (Hexanchu griseus) that was found dead on a beach in Alberni Inlet on low tide. She was necropsied by Department of Fisheries and Oceans staff on February 11th and there were no obvious indications of how or why she died.

The information has been generously shared by federal shark biologist with the Pacific Biological Station, Romney McPhie (click images to see at larger size).

This female sixgill was 4.2 metres and was estimated to weigh 569 kg (1254 lbs).  As a viviparous shark species, she carried her embryos through the entire 12 -24 month gestation period (species does not lay eggs / egg cases).  She may have given birth to some prior to her death and still had 28 pups inside her.  If she did indeed give birth, these pups would likely survive.

Romney McPhie, DFO shark biologist examining pups.

Examination of the pups in one uterus. Yes, 6-gill sharks have two uteri.

Sixgill sharks have been reported to be up to 4.8 metres in length with females being larger than males and reaching sexual maturity only between age 18 and 35. It is believed that they may reach 80 years in age.

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) 2007 assessment report on the bluntnose sixgill puts into perspective how rare an opportunity it is to learn about a pregnant six gill.  It relates that the number of pups carried by females is known from only three previous credible accounts (ranging from 47 to 70 pups of size 61 to 73 cm).

The bluntnose six gill is an extremely cryptic species that can dwell at depts up to 2,500 m.  So little is known about them and (sigh)  they are “near threatened” globally and are a species of “special concern” in Canada.

I have had the incredible privilege of seeing a bluntnose six gill shark while diving and felt like I was in the presence of greatness. They are living fossils, perfected by 200 million years of adaptation. They are amazingly graceful with large, luminous and intensely green eyes.

They are of absolutely no threat to humans and, like all sharks, have an essential role in marine ecosystems.  As top-level predators, sharks strongly shape food webs and the loss of such predators has proven to have profound effects on the number and diversity of other species.

The unique teeth of bluntnose six gill sharks. Photo by Romney McPhie.

 

We however are a threat to them.  It is reported that in just three years (2006 to 2009), 1,341 sixgills were by-catch in longline fisheries. There is no information on the survival rates from by-catch nor is population size and reproductive rate known for this species.

Please read more about the biology and conservation of bluntnose sixgill sharks in the Species at Risk Public Registry. Click here.

See the Alberni Valley News for coverage on this sixgill. 

 

See the Draft Management Plan for the bluntnose six gill shark and tope shark in Canada for natural history information and a summary of threats. 

Sixgill shark eye. This one died as a result of longline by-catch and was brought into Alert Bay in July of 2007. It was rumoured to be one of 12 sharks caught by only one local fishing boat. Photo: Jared Towers.


12 Responses to “Sharks Among Us #2 – The Bluntnose Sixgill Shark”

  1. The short one

    if we don’t know anything about them we shouldn’t be fishing them and we should be questioning fishing methods that allow for bi-catch of unknown species…or is it a time of year thing? Like the dragger’s hauling up pregnant lingcods this time of year….or quillbacks spewing eggs as they are hauled in..or or the rec fishermen retaining berried prawns or or or…maybe to much coffee consumed this morning ;-0

    Reply
    • jackiehildering

      Nope Cold Feet – not to much coffee but sheer lucidity. The attitude to by-catch appears to be “we can’t help it” and too it seems to be “oops – their pregnant – who knew” (insert the voices of government regulators here NOT fishers). We KNOW the seasonality of reproduction for species like lingcod and quillbacks!!!! We know as divers but fish observers who report to government know better and this knowledge would inform sustainable fisheries. Keep up the good fight!

      Reply
  2. Fran

    Hi Jacqui!

    About all those pups inside the six gill…..would she have that many pups at one time? I would have thought only one at a time. Enlighten me please!

    Reply
    • jackiehildering

      Over a matter of days I think Fran but inseminated at the same time so at “full-term” at the same time. Up to a two-year gestation with a very late reproductive age = must have many young at one time for species to survive.

      I thought Gord would also be very interested in this find of the pregnant six-gill. I’ll never forget his euphoria at having seen one while diving.

      Reply
  3. Wes Blow

    Last week I caught one of these sharks while fishing that we estimated was 12 feet long. Just curious how much the one that was found weighed.

    Reply
    • jackiehildering

      Hello Wes,
      I don’t believe they had an opportunity to weigh this female. The largest record I was able to find for this species is 590 kg.
      It would be valuable if you could share where you caught the six gill; at what depth; what fishing method, etc.
      Greatly appreciate it.

      Reply
      • Wes Blow

        We were fishing out of Virginia Beach VA around the Norfolk Canyon. It is about 65 miles off the coast we were in about 600 feet of water. I was fishing with Ken Neill who has been been deep drop fishing that are for about 7 years I think. I have been fishing with him a couple years now. Just about every trip we have had an encounter with something we could not get up and would break a rod or line. I lost two last year and the day I got the six gill to the surface, I had something on for about 30 minutes before loosing it. I was using a rig I made out of 300 pound mono leader with one light on it, large spinner blades and cut fish for bait. Ken takes lots of pictures if you want any,

      • Wes Blow

        Yeah, that was us in the Sea Monster report. We let the shark go. We were actually fishing for grouper. We catch and eat plenty of fish but I have no desire to kill something like that. I just enjoyed catching it except for the last 15 minutes when I thought it was going to win over me and my back.

  4. Ken Neill

    That is Wes’ fish. Not a targetted catch at all. We were fishing for golden tilefish and snowy grouper. The shark was released and seemed to be fine, swam away strong.

    Reply
    • jackiehildering

      Hello Wes and Ken,
      Thank you so much for your responses. I can only imagine what it would be like to try to get a six gill to the surface! As a diver, I’ve been mindblown to see how, what first appears to be a slow moving giant, can power away.
      With so little known about these species, it is great to know that (thanks to your ethics) this one continued on to live its mysterious life at depth.
      Awe-inspiring photos!
      Jackie

      Reply
    • jackiehildering

      Awe-inspiring photos.
      Here is the copy of my email to Wes (and his sore back)!

      Hello Wes and Ken,
      Thank you so much for your responses. I can only imagine what it would be like to try to get a six gill to the surface! As a diver, I’ve been mindblown to see how, what first appears to be a slow moving giant, can power away.
      With so little known about these species, it is great to know that (thanks to your ethics) this one continued on to live its mysterious life at depth.
      Awe-inspiring photos!
      Jackie

      Reply

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