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

Posts tagged ‘shark’

Sharks Among Us #3 – Meet the gang – From Rat Fish to Sixgills! (Video)

Great thanks to Rendezvous Dive Adventures for sharing this video with me! 

It’s a fantastic (7.5 minute) interview with Dr. Chris Harvey-Clark of the University of British Columbia and the Greenland Shark and Elasmobranch Education and Research Group (GEERG).

He discusses the shark species found in our cold-rich waters in the Pacific Northwest: “We have some of the largest species of sharks in the world swimming in these waters”.

Great video of sharks and I particularly appreciated Dr. Harvey-Clark’s explanation of the ecological link between rat fish and bluntnose sixgill sharks and, related to this, the latest research on the “ocean wanderings” of sixgills. 

I learned too about the Shark Observation Network where divers’ observations can help research. 

Basking in History – The Story of B.C.’s Basking Sharks

Photo by Chris Gotschalk (Wikimedia Commons)

It’s a first. Canada has acknowledged the endangerment of a marine fish species – the Basking Shark (Cetorhinus maxiumus). 

Basking Sharks used to be common in the coastal waters of British Columbia.  As the second largest fish species in the world, they could be half the size of a city bus (12 m and 4 tonnes) and could be seen at the surface of the ocean, “basking” there to feed on plankton. It’s a long-lived species too, believed to be able to reach 50 years of age.

However, even the most seafaring fisher is now unlikely to ever see one off the B.C. coast. There have been less than 25 sightings of Basking Sharks since 1996. So what happened?

We slaughtered them.

These sharks were put on the Canadian fisheries “Destructive Pests” list in 1949, and from 1955 to 1969 there was a federal eradication program directed at these benign, plankton-eating giants. In these years, the federal fisheries patrol vessel, the Comox Post, even had a blade mounted on its bow, designed specifically to slice basking sharks in half.

This species of shark has only the tiniest of teeth and does not compete for a commercial fishery like the sea lions, seals and Killer Whales that were also culled in that time period. The motivation for the “pest control” of these gentle giants was that they got trapped in gill nets, causing damage to fishing gear.

Click here for this annotated Basking Shark colouring sheet by Romney McPhie who is not only a shark scientist but clearly also an artist (and very skilled educator)!

Who we used to be. Blade on the front of the Comox Post. Source: Popular Mechanics 1956.

As an indicator of how far we have come since then, imagine the social outrage today if a magazine celebrated the ingenuity of the Comox Post’s blade, illustrating how the executioner’s tool was used accompanied by the text “Huge 30-foot basking shark is almost cut in two by sharp-edged ram. The sharks, floating lazily near the surface of the water, are no match for this skillfully handled vessel, which heads directly into a school and catches an individual shark before it is aware of its plight”.  November 1956’s edition of Popular Mechanics featured just that and the June 22,1955 front page of the Victoria Times included a photo with the text “This is a basking shark, basking and leering. But the smirk will soon be wiped off its ugly face by the fisheries department, which is cutting numerous sharks down to size” (from The Slaughter of B.C.’s Gentle Giants by Scott Wallace and Brian Gisborne).

Basking Sharks survived as a species for at least 30 million years but have been pushed to the brink extinction in B.C. by just a couple of decades of human intolerance, misunderstanding and mismanagement.

But as a testament to how quickly human social evolution can occur, we have gone from being executioners to acknowledging the species’ endangerment in just over 40 years.  In February 2010, the Pacific population received legal protection by being listed as “endangered” under Canada’s Species at Risk Act. The Recovery Strategy was finalized at the end of July, 2011. 

Only history will tell if our evolved enlightenment is enough or if it came too late for the basking shark and many other marine species. The fact that you care enough to read this blog item is every reason for hope.

If you ever see a Basking Shark in British Columbia: call 1-877-507-4275 (1-877-507-4275).

Above: Basking Shark sighting July 17, Caamano Sound, BC. Video by Archie Dundas of the GitGa’at Guardians via Fisheries and Oceans Canada.

Sources:

Basking Sharks – The Slaughter of B.C.’s Gentle Giants by Scott Wallace and Brian Gisborne 

How BC Killed All the Sharks – Hysteria and a knifelike ram helped us slaughter the benign basking giants by Scott Wallace and Brian Gisborne

David Suzuki Foundation blog; April 2014; What’s bigger than a bus but has prey smaller than a grain of rice

Final Recovery Strategy for the Basking Shark (Cetorhinus maximus) in Canadian Pacific Waters (2011-07-26)

Photos of basking sharks

Species at Risk Act (SARA) Species Profile– summary of natural history, threats, etc. 

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.


Sharks Among Us #1 – The Blue Shark

The image below is of a Pacific blue shark (Prionace glauca) being rescued by Lindsey Pattinson of Tiderip Grizzly Tours on July 15th in Glendale Cove, British Columbia.

Lindsey Pattinson rescuing a blue shark. Photo: Nick and Sue Spiller.

Many British Columbians are unaware that we have at least 12 species of shark among us, ranging from the smaller species such as the spiny dogfish up to the 6-gill shark (5 m+) and the very, very rare basking shark (9 m+). The beautiful blue shark reaches a maximum of 3.8 meters and is distinct in its deep blue colouration and slender shape.

The blue shark is common in B.C. and is, in fact, extremely far ranging and widespread. It is found from Alaska to Chile in the Pacific but is also present in the Atlantic and Indian Oceans.  It has been found in waters from 7 to 16°C, latitudes of 60°N to 50°S and from the shallows to depths of 350 m (being more often at depth in warmer waters).

In researching the species after Lindsey’s find, I discovered that blue sharks undertake very large migrations, reportedly up to 9,200 km, moving north in the summer months.  More females than males move to the higher latitudes.

But, of course a sighting like this in Glendale Cove is an enormous rarity. Even with the blue shark being common in B.C., they are more often oceanic, on the continental shelf . . . not on the beach in Glendale!

For whatever reason, the animal stranded there and Lindsey cared enough to do what he could to save it.  Many shark species need to keep swimming in order to have oxygen-rich water pass over their gills. Knowing this, Lindsey moved the stranded shark back and forth in the water, forcing water over its gills and indeed, he revived it. He and the tourists he was guiding on the Grizzly Bear (and shark) watching trip had the joy of watching the animal swim to depth.

Thanks to Lindsey, this blue shark will be able to have more days of feeding on anchovy, mackerel, salmon, hake, dogfish, crustaceans and squid. It may also scavenge here and there and even feed on aggregations of krill by straining the water in the way a baleen whale would.

I suspect the Glendale Cove shark was a female and with blue sharks being a very prolific species, now saved, she could go on to bear 25 to 50 pups at a time (apparently even as many as 135)!  These young would grow inside her as the blue shark is “viviparous”, meaning they bear fully formed young. The pups are 35 to 44 cm at birth.

I was fascinated to learn that blue shark females can apparently “get pregnant” up to 20 months AFTER mating. They can store sperm packets in special glands in their reproductive tract called “shell glands” (aka nidamental glands) and pass their eggs through these glands to get fertilized.

If the rescued blue shark was indeed female, she may not have been able to feel much of Lindsey’s caring touch since the females are up to 3 times thicker skinned that the males! This adaptation is believed to allow the females to deal with the males since there is a lot of biting during courtship.

Unfortunately, the fate of blue sharks can also be to become the bycatch of longline and driftnet fisheries. One source reported that in one year alone (1990) “it is conservatively estimated that by-catch of blue sharks taken by the Japanese squid fleet in the North Pacific totaled 700,000.”

Further life history: Males sexually mature at 4–6 and females at 5–7 years. Believed to live to age 20.

For more photos of the blue shark rescue, click here.
Great thanks to Nick and Sue Spiller for sharing these photos.

Sources include: