Category: Fish


Wolf-Eel – No Ugly Fish!

Filed under: Fish — 8 Comments
February 17, 2013
Mr. and Mrs. Wolf Eel on February 16, 2013 near Port Hardy. © 2013 Jackie Hildering

Mr. and Mrs. Wolf-Eel on February 16, 2013 near Port Hardy. © 2013 Jackie Hildering

Don’t say it, please don’t say it.

This is not an ugly fish.

It hurts when people say this about wolf-eels. Such is the way when there is misunderstanding and disrespect for something you love.

There is no ugly in Nature – only perfection.

If the features of an animal appear foreign to you, it is because it fulfils a role in Nature that is truly awe-inspiring; possibly even beyond your imaginings.

Mature male wolf-eel - about 2.2 m long. © 2008 Jackie Hildering

Mature male wolf-eel – about 2 m long. Can be 2.4 m.
© 2008 Jackie Hildering

I hope to make this point by sharing with you why the wolf-eel is “designed” as it is and how very wrong many of us are in our perceptions about this species.

The wolf-eel (Anarrhichythys ocellatus), which can be as long as 2.4 m, is not an eel. It is clearly also not a wolf. It is desperately misunderstood.

It is not dangerous nor “mean”. The opposite is true. They are reclusive, anything but ferocious, quite sedentary and slow moving.

The upper jaw of a wolf-eel. Impenetrable to even urchin spines! © 2005 Jackie Hildering

The upper jaw of a wolf-eel. Impenetrable to even urchin spines! © 2005 Jackie Hildering

Yes, the mature males have very large, fleshy, ossified heads and the species has sharp teeth but this is so they can do what so few marine species can – they can feed on spiny sea urchins, snapping them effortlessly into pieces without suffering a single puncture. They also feed on other hard-shelled animals like shellfish and crabs.

Even the roofs of wolf-eels’ mouths are impenetrable with ossified, tooth-like projections.

Each wolf-eel has distinct spots around their eyes which helps recognize them as individuals. © 2012 Jackie Hildering

Each wolf-eel has distinct spots around their eyes which helps recognize them as individuals. © 2012 Jackie Hildering

To my knowledge there has never been an attack on a diver UNLESS, and here comes the predictable thing, we choose to habituate them.

Wolf-eels spend a great deal of time on the ocean bottom in dens where, as divers, we have the enormous privilege of  ”visiting” the same spot and seeing the same individuals for years. It is not just their address that makes them recognizable as individuals. Each wolf-eel has a unique pattern of black spots near their eyes.

Mature male bearing the scars of battle. © 2011 Gord Jenkins.

Mature male bearing the scars of battle. © 2011 Gord Jenkins.

Some divers choose to feed them, leading to the wolf-eels associating us with food and that’s where accidents can happen and where the wild behaviour that lets animals survive, becomes compromised.

It also makes them tragically easy targets for any spear diver wanting to poach them. There is no legal fishery for this species but there is a demand for them in the Asian market which is why there are also attempts to farm wolf-fish i.e. aquaculture.

Not surprisingly, wolf-eels might also be defensive when accidentally caught by anglers. I found one account from 1959 where a commercial fisherman was bitten and “The teeth penetrated the hip-waders and broke the skin on both sides of the ankle.”

Juvenile wolf eel. © 2010 Jackie Hildering-

Juvenile wolf-eel. © 2010 Jackie Hildering-

The mature males do carry battle wounds supporting that they don’t just hang out in dens waiting for a snack to come by, but rather that they will occasionally duke it out with other male wolf-eels.  They do also sometimes need to do battle for den space with a giant Pacific octopus.  This is likely another driver for the male’s having such fleshy heads – they are better able to survive the wounds inflicted by such battles.

Another unique feature about this species is their eel-like body. They are the only member of their family that have this body shape. The long tail serves in locomotion, powering them forward with big, slow, s-shaped waves while being stabilized with the long dorsal and pectoral fins (see video below). Having a long tail also allows them to den-up, curling up and around in narrow spaces between rocks and . . . wait for it . . . it lets them hold onto their eggs.

Mr and Mrs Wolf-Eel tending their egg mass © 2005 Jackie Hildering-

Mated pair tending their egg mass. Note how much darker and smaller the female is. © 2005 Jackie Hildering-

Wolf-eels have long-lasting pair bonds, coming together when they are around 4 years old and having their first clutch when they are around 7. In aquariums, their life expectancy is known to be at least 28 years.

Both male and female juveniles are brownish orange and look even more eel-like, lacking the big head of the adults. As adults, the females are smaller and a darker brownish grey (both remarkably camouflaged for when they are in their rocky dens).

Grandpa Wolf-Eel on February 16, 2013 near Port Hardy. © 2013 Jackie Hildering

Grandpa Wolf-Eel on February 16, 2013 near Port Hardy. © 2013 Jackie Hildering

Mating apparently most often occurs between October and December, with the female releasing eggs after the male prods against her swollen abdomen. He then wraps around her to fertilize the 10,000 or more white to yellow eggs that she will mould into a ball shape. This mass does not need to adhere to anything because the parents will take turns wrapping their tails around the mass, holding and turning it for good aeration until the +/- 3.5 cm young hatch some 3 months after fertilization.

Statler the Muppet is cute and loveable. Ergo - so are wolf-eels. Case closed!!

Statler the Muppet is cute and loveable. Ergo – so are wolf-eels. Case closed!!

The juveniles do not settle into the adult sedentary lifestyle until around age 2. One juvenile is even known to have travelled a minimum of 1,000 km; having been tagged in Port Hardy, BC and found back in Willapa Bay, Washington two years later.

It was long thought that wolf-eels always mate for life but, this is not always the case. The males do compete for females who will sometimes opt to swap dens and go live with the competitor. Sound like any other species you know? Wonder if it happens at mid-life?

The wolf-eel is indeed akin to us in so many ways. It is a homebody that likes crunchy snacks and prefers that they come right by the front door; they are great parents and are docile unless fighting for home or partner. They invest in durable relationships and – they are only as strange looking as we terrestrial bipeds would appear to them.

Range: Sub-tidal to 226 m; Baja California (Mexico) to the Aleutian Islands (Alaska); west to Russia and south to the Sea of Japan.

Mr. and Mrs. Wolf Eel on February 16, 2013 near Port Hardy. © 2013 Jackie Hildering

Mr. and Mrs. Wolf-Eel on February 16, 2013 near Port Hardy. © 2013 Jackie Hildering

Me and a mature male wolf eel.

Me and a mature male wolf-eel. © 2012 Norris Colby.

Mature male wolf-eel. © 2007 Jackie Hildering

Mature male wolf-eel. © 2007 Jackie Hildering

Mature male wolf-eel. © 2007 Jackie Hildering

Mature male wolf-eel. © 2007 Jackie Hildering

For these and more images of the wolf-eel, please see my gallery at this link. 

Sources:

Lamb, Andy and Edgell, Phil. Coastal Fishers of the Pacific Northwest - Second Edition.

Love, Milton; Certainly More Than You Want to Know About the Fishes of the Pacific Coast – A Postmodern Experience; pp 467-468

Pers. communication Dr. Jeff Marliave, Vice President, Marine Science, Vancouver Aquarium.

http://www.racerocks.com/racerock/eco/taxalab/zaheerk.htm

http://www.nwdiveclub.com/viewtopic.php?f=1&t=890

http://www.fishbase.org/summary/Anarrhichthys-ocellatus.html

http://scrippsblogs.ucsd.edu/onboard/2011/03/24/wolf-eel-eggs-are-hatching/

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Grunt – So Happy to See You!

Filed under: Fish, Sculpins — 5 Comments
October 21, 2012

Grunt sculpin. Tiny fish. Giant attitude. ESPECIALLY the females. Photo: Hildering.

Meet the fish that so often has people exclaiming “It lives HERE?!”

Yep, the tiny grunt sculpin is a powerful ambassador for raising awareness about the depth of biodiversity hidden in the cold, dark, rich waters of the north east Pacific. 

We are programmed to associate warm waters with exotic-looking fish species but how’s this for being astoundingly adapted and mastering mimicry?:

  • Adapted to look like a giant barnacle! Huge thanks to dive buddy Natasha Dickinson for finding this one. Photo: Hildering.

    The species reaches only a maximum of 9 cm.

  • It is adapted to look like a giant barnacle (Balanus nubilis)!  When facing outward, its pointy nose looks like a closed giant barnacle and when the fish turns around, its tail looks like the foot of the barnacle that rakes in plankton.
  • This little fish has giant attitude. When not hidden away in a barnacle (or a cup, see photo), it can be highly territorial, hopping around on its pectoral fins in a strutting, jerky fashion. A lot of literature reports that the grunt sculpin is an “awkward swimmer” but I solidly disagree.

    If you can’t find an empty barnacle shell. A cup will apparently do! Photo: Hildering

    I once saw one flash away with lightning speed back to its hiding place. Yes, I was being an annoying photographer.

  • Ah and you probably think the males are the master strutters? Ha! The female is as fierce as can be. She will aggressively chase a male into a crack, an empty barnacle shell, or other place of no escape and guard him there until she is ready to lay her eggs. When she has laid them, the male is released to do his duty.

    Very young grunt sculpin. The red-gilled nudibranch in the upper part of the image is only about 2 cm long. Another great find by dive buddy Natasha Dickinson. Photo: Hildering.

    She watches him to ensure he fertilizes the eggs (up to 150 at a time) and then – she saunters off. Apparently she may return once in a while to take on a shift. For many members of the sculpin family, the males are the sole egg guarders.

    But wait, it gets even more remarkable, when the eggs are near hatching, the guarding grunt sculpin takes them into their mouth and spits them out into the open water. This causes the eggs to hatch and the little zooplankton are sent on their way. (Source: Aquarium of the Pacific).

  • The grunt sculpin’s pointy “bill-like” head is reflected in the species’ scientific name. Photo: Hildering

    With regards to classification, the scientific name Rhamphocottus richardsonii reflects the Greek “rhamphos” for the grunt sculpin’s bill-like snout. This makes some people think that the species looks like a seahorse but note that they are not closely related at all. The grunt sculpin is the only member of its genus. It is truly one of a kind.

  • Oh, and the name “grunt” sculpin? Apparently the species grunts when it is taken out of the ocean. You would too! Likely it also grunts when being defensive underwater. It is also the sound I make in my delight when I find one. It will be a very loud grunt indeed if I ever find one guarding eggs or with its tail-end extended out of a barnacle.

Grunt sculpin in a empty barnacle shell. Photo: Hildering

Another very fortunate find of a grunt sculpin in a empty barnacle shell. Photo: Hildering

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Plankton Got Sole!

Filed under: Flatfish, Plankton — 2 Comments
September 19, 2012

No, I have not mixed up my spelling of “soul” verses “sole”.

Planktonic sand sole.  Only 2.7 cm. 
Click image to enlarge. Photo: Hildering

This last weekend, while watching herring feed on krill in a tide line, I suddenly noticed a very small transparent fish.

Upon closer inspection, I saw that it was a larval form of some species of flatfish.

I was able to dip the little guy into my dive mask for a few pictures and, due to the size of the lettering in the mask, I know that the fish was only 2.7 cm.

I was in awe of how transparent s/he was; that I could see the bones and heart; and that this small, fragile planktonic stage could ever survive to grow into an adult.

These sorts of “finds” are as awe-inspiring to me as any sighting of a whale. The thick planktonic soup of our rich cold oceans is full of the larvae of so many species. Anemones, nudibranchs, sea stars, crabs, etc. – they all start off as zooplankton and the incidence of what sort of plankton are present often gives scientists an indication of what may be happening with the marine food web.

It is like a world of hidden secrets to me and of course I wanted to find out all I could.

What species of flatfish was this – halibut, sole, flounder?

Click image to enlarge.
Photo: Hildering

I do not have the expertise to know but, oh so thankfully, there are those out there willing to share their great knowledge.

Marie-Josée Gagnon of the Salmon Coast Research Station quickly steered me in the right direction, believing it was most likely a species of sole.

She connected me with zooplankton taxonomist  Moira Galbraith of the Institute of Ocean Sciences who confirmed that this was the larval form of a Pacific sand sole (Psettichthys melanostictus), a species that can grow to 63 cm. She also shared that the transparency of the larval fish serves as camouflage, reducing the chances of it being eaten before reaching the life stage where it settles to the ocean bottom and hides on and in the sand.

But wait, what are those two little zooplankton guys attached to the larval sole? They are copepods, but what kind of copepod?  What does their presence mean ?  Are they parasitic? And there I go down the marine id rabbit hole. 

One thing I know for sure though – and forgive me for the following pun because the emotion behind it is very sincere – how I hope this little planktonic fish will be a  . . . sole survivor.

Sources:

Update September 30, 2012:

  • This great item by Puget Sound Sea Life has been brought to my attention and includes the following: ” . . . within several days to weeks, depending on the species, the larva undergoes a radical metamorphosis. The right or left eye migrates from it’s normal position across the top of the head to the other side of the body changing some skull bones in the process . . . . After metamorphosis, the fish settles to the bottom on it’s left side, develops skin color on the right side and continues growth as a juvenile.  Adapting a bottom-dwelling life style allows flatfish to exploit a common habitat – flat sandy bottoms which are very common in the subtidal zone. Many fish avoid this habitat because of the lack of rocks or other features that would provide a hiding place. Flatfish can hide from predators by burrowing, leaving only their eyes above the surface. In addition the habitat is home to an abundance of prey such as worms and shrimp. With both eyes on the upper side they can use 3D vision to hunt and detect predators. There has been considerable controversy over the origin of flatfish, but recent discoveries of several fossil intermediate forms show that eye migration evolved gradually some fifty million years ago.”
  • With regard to the ectoparasites on the sand sole larva, Marie-Josée Gagnon and Moira Galbraith have again been very generous with their knowledge. It is impossible to know the species from my photo but, due to the size, it is likely a recent infection and could be (1) first stage Chalimus; (2) Lepeophtheirus bifidus – which, unlike most parasites of benthic marine species is host specific – only being found on the rock sole or possibly, (3) the isopod Gnathia.   I valued having affirmed too that adults and young live in different environments to eliminate competition for the same resources but also to provide a buffer or separation to prevent transfer of disease or parasites.
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Rockfish Barotrauma

Filed under: Fish, Rockfish — 5 Comments
July 22, 2012

Yelloweye rockfish that has died of barotrauma. Reduced water pressure causes the air in the swim bladder to expand and push out the stomach and eyes. Photo: Hildering. Click to enlarge.

Here’s another case of a photo being worth a thousand words.

It is of a yelloweye rockfish that has died from barotrauma aka “pressure shock”.

Many rockfish species are particularly sensitive to reductions in pressure since the air in their swim bladders expands substantially. The swim bladder is a buoyancy control organ and even when slowly reeled in from a depth of only 20 m (60’), a rockfish’s swim bladder can expand to three times its size, putting pressure on the fish’s organs.

As is the case with the yelloweye rockfish in the photo, the swim bladder can expand to the point of causing the fish’s eyes to bulge out of their sockets and its stomach to be pushed out of its mouth.

Other than this being a sight that may not enhance your appetite for your rockfish catch, the death of rockfish due to barotrauma wouldn’t be a problem were it not that there are grave conservation concerns for many rockfish species.

Colossal management errors were made with overfishing slow-growing rockfish. Many species are extremely long-lived, slow to sexually mature, and the big old females are the most fertile – producing the most eggs and hatching the largest number of healthy young.

For example, yelloweye rockfish are believed to have a lifespan of up to 118 years, don’t reproduce until they are at least 12 years old, and the old females can incubate up to 2.7 million eggs!

This means that species are very slow to reproduce whereby, if you catch lots, especially the big females, you can devastate populations very quickly.

Another nail in the coffin of rockfish is that many adults also have high site fidelity so that by fishing one area, you can wipe out a community of fish.

Therefore, there are relatively strict limits on fishing for some rockfish species but of course you see dilemma. You may not be allowed to keep a rockfish but what if you reel one in, or if they are bycatch in a fishery, and their eyes and stomach are distended due to barotrauma?

There are studies that prove that if you were to quickly recompress the fish, it would stand a very good chance of survival, even where it appears dead at the surface (see video below). The fish could be brought back to depth with barbless weighted hooks, commercial “fish descenders”, or even by inverting a weighted milk crate over the fish. 

How wonderful it would be if more people would undertake the effort to recompress the fish, knowing how dire the situation is for many rockfish species. Imagine the further positive impact if people would choose to return the depleted species to depth even when they haven’t reached their catch limit, especially the big, highly productive females.

But, even if there was to be such enlightenment, many rockfish populations are so depleted that they need far more protection.

This is why there are Rockfish Conservation Areas (RCAs). These should be areas known to be the territory of depleted rockfish populations. As these are no-fishing zones, there is no chance of barotrauma and the rockfish populations that live in the area are given the time to rebuild to have more sexually mature fish and more big old super mamas.

Long live rockfish!

For how to save a life – a rockfish life – see this entertaining video by fish guru Milton Love with a rap song by Ray Troll.

Links:

Fantastic video showing how rockfish that appear dead at the surface due to barotrauma fully can revive at depth! From the Coastside Fishing Club.

Video showing how well a “fish descender” works to save rockfish that have suffered barotrauma. 

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Very Rare Fish Find: King-Of-The-Salmon (Trachipterus altivelis)

Filed under: Fish, Other species — 2 Comments
April 28, 2012

Here’s a finding to enhance your sense of wonder about the sea and how little we know about its inhabitants.

Darren Rowsell with the king-of-the-salmon found on March 23rd, 2012. Photo Joanne Rowsell.


On March 23rd, 2012 Darren and Joanne Rowsell found this dead specimen on the beach at Lady Ellen Point, Port McNeill, British Columbia, Canada. When the photos landed in my inbox, I almost fell off my chair recognizing how rare a find this was. It’s a king-of-the salmon (Trachipterus altivelis). The adults feed in the open ocean at depths of 900+ m (3,000 feet) so they hardly ever wash ashore and I have never seen one before. 

Easy to see why the king-of-the-salmon belongs to the ribbonfish family. Photo Joanne Rowsell.

The king-of-the-salmon belongs to the ribbonfish family (Trachipteridae). You’ll note from Joanne’s photos that the species is indeed very ribbon-like. It is extremely thin and reaches lengths of up to 1.83 m (6 foot). The long, high, crimson coloured dorsal fin is also very reminiscent of a ribbon, tapering down the full length of the fish’s back. These fish move in a snake-like fashion, undulating their long bodies.


King-of-the-salmon. Photo Joanne Rowsell.

The unique common name of the king-of-the-salmon originates from Makah First Nation legend. This fish was believed to be the “king” that would lead salmon back to their rivers to spawn. To kill one was believed to bring bad luck, causing the death of the salmon.  The Makah, like other fisherfolk, must occasionally have caught one on their lines or in their nets.


King-of-the-salmon’s dorsal fin extends all the way down its back. Photo Joanne Rowsell.

When one of these very rare and unique fish does wash ashore, it usually draws a lot of attention. The fish that the Rowsell’s found is relatively small. See the image below of the one found in 2006 near Salem, Oregon. It was 1.83 m (6 foot) long and the head was about 23 cm (9 inches) wide.


The species range is believed to be from the Gulf of Alaska to Chile.

King-of-the-salmon’s head. Photo Joanne Rowsell.

Smaller king-of-the-salmon do feed closer to shore and their diet is known to include copepods, annelid worms, fish scales, and  fish larvae. Larger individuals feed on copepods, krill (euphausids), small pelagic fish, young rockfish, squid, and octopus. I presume that stomach content studies have allowed science to determine that the predators of the king-of-the-salmon include the bigeye thresher shark (Alopias superciloosus), and the longnose lancetfish (Alepisaurus ferox).


And that appears to be all that is known about the king-of-the-salmon – yet another one of our remarkable marine neighbours.

Sources:

King-of-the-salmon found near Salem, Oregon in 2006. 1.83 m (6 foot) long and the head was about 23 cm (9 inches) wide.
Source: Salem News; July 23, 2006; “Strange Fish Found on Beach Near Seaside”
Click the image to read the story.


Plankton life stages of the king-of-the-salmon. http://access.afsc.noaa.gov/ichthyo/LHDataIll.cfm?GSID=Trachipterus!altivelis
Credits:
A: Matarese, A.C., and E.M. Sandknop. 1984. Identification of fish eggs. In H.G. Moser, W.J. Richards, D.M. Cohen, M.P. Fahay, A.W. Kendall, Jr., and S.L Richardson (eds.), Ontogeny and systematics of fishes. Spec. Publ. 1, Am. Soc. Ichthyol. Herpetol., p. 27-31. Allen Press, Lawrence, KS, 760 p.
B: Charter, S.R., and H.G. Moser. 1996.Trachipteridae: Ribbonfishes. In H.G. Moser (ed.), The early stages of fishes in the California Current region. CalCOFI Atlas 33, p. 669-677. Allen Press, Lawrence, KS, 1505 p.
C and D: Matarese, A.C., A.W. Kendall, Jr., D.M. Blood, and B.M. Vinter. 1989.
Laboratory guide to early life history stages of Northeast Pacific fishes. NOAA Tech. Rep. NMFS 80, 652 p.

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Buffalos Mating . . . Underwater!

Filed under: Sculpins — 4 Comments
April 1, 2012

That’s right, it’s mating season for buffalos   . . .  buffalo SCULPINS that is!

Male buffalo sculpin guarding eggs. April 1, 2012. Photo: Hildering

Now that I’ve lured you to this posting with the procreation of a huge, shaggy terrestrial mammal on your mind  . . . let me show you the spawn of this wondrous fish.

The buffalo sculpin –  Enophrys bison – has earned the association with buffalo/bison due to the horn-like spine found on each gill plate (operculum). The species can be up to 37 cm long.

As is the case for many species in the sculpin family,  male buffalo sculpins guard the eggs from predators and fan them with their pectoral fins.  Sometimes they guard the eggs laid by multiple females. When you consider that a female can lay between 19,000 and 32,000 eggs, the males have a lot of fertilizing and guarding work to do!  Their guard duty lasts 5 to 6 weeks until the eggs hatch. 

A cascade of eggs below this brilliantly coloured male buffalo sculpin’s chin, April 1st. Still guarding the eggs on April 21st, see image below. Photo: Hildering

The photos in this blog – all taken on April 1st, 2012 – show you the males with their flat heads directly upon a cascade of eggs. The clusters of eggs allowed me to find this incredibly camouflaged fish much more easily than I normally could. When I saw a golden, orange or greenish shiny mass of eggs, I knew a male buffalo sculpin had to be very near by. The bright colour of the eggs suggests that they might be toxic to many species, further protecting them from predation. 

As you can see, the buffalo sculpins’ red, brown and pink colouration makes them very difficult to discern from the similarly brilliantly coloured life around them.  They will remain absolutely still so as not to give away their presence. Their relative, the red Irish lord, has the same survival strategy. (See this previous blog item for photos and information on the red Irish lord.) 

The camouflage, in addition to reducing the risk of predation by bigger fish and harbour seals, allows the buffalo sculpin to be a very successful ambush hunter of shrimps, crabs, amphipods and small fish. It has been suggested that they eat mainly algae since this has so often been found in their gut but I am willing to bet that the algae ends up in their stomachs as a result of the buffalo sculpins grabbing prey ON the algae!

Another male guarding eggs. If you look carefully, you will see the horn-like spines on the fish’s right gill plate. It is these horn-shaped gill protrusions that led to this species getting both its scientific and common name. April 1, 2012. Photo: Hildering

April 1, 2012. Photo: Hildering

The two differently coloured egg masses suggest that this male is guarding the eggs from two different females. April 1, 2012. Photo: Hildering

April 1, 2012. Same male as above photo. Photo: Hildering

Same male guarding eggs 3 weeks later. April 21st. Photo: Hildering

Same male with a new egg mass – May 6. Checked in on him on May 20th and he was no longer guarding eggs. Photo: Hildering

Range: Monterey California to Kodiak Island, Gulf of Alaska. Most often found to a depth of 20 m but have been found to 227 m.

Spawn: February and March. 

Source: Oregon Department of Fish and Wildlife – Biological Synopses of Nearshore Fishes 

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Sharks Among Us #4 – The Salmon Shark

Filed under: Sharks — 6 Comments
December 1, 2011

Salmon shark found dead on Port Hardy beach on November 23, 2011. Photo: Mandy Norrish.

This is a salmon shark (Lamna ditropis) that washed up dead on a beach in Carrot Park in Port Hardy, B.C. on November 23rd. 

Local Department of Fisheries and Oceans staff conducted an external examination and collected the unfortunate shark so that a full necropsy could be done at a later date.  Although salmon sharks are common in the North Pacific, examining the body may allow science to find out more about the species and how this individual died. 

The dead salmon shark was just over 1.5 metres (length from the nose to fork in the tail = fork length). The species can be 3.7 m and weigh up to 454 kg.

Cut in the pectoral fin. Suggesting it may have been entangled in a net. Photo: Mandy Norrish.

Salmon sharks are of no threat to humans, however, the species does suffer impacts from humanity. 

The Port Hardy salmon shark had external injuries that suggest it may have been caught in a fishing net and possibly even shot.  It had a large cut on its tongue and on one of its pectoral fins and there was a circular hole behind the dorsal fin.  Many shark species suffer the threat of  by-catch in nets since they are targeting the same species we humans are fishing for.  

If it is determined that this shark indeed was caught in a net, this may be particularly interesting since I believe there are no openings for net fisheries at this time of year. 

Cut also found on the shark's tongue. Photo: Mandy Norrish.

Although the salmon shark feeds on many species of fish,  it is indeed a very successful predator of salmon.

Salmon sharks can regulate their body temperatures to be higher than the temperature of the surrounding water. The salmon shark, in fact, has a higher body temperature than any other shark species. Apparently, even when the water is 2 °C, their internal temperature can be 16 °C.

This ability to thermoregulate is why, in part, salmon sharks can be incredibly fast. The US Navy has recorded speeds of up to 80 km/hr.  

I was heartened by the response of the majority of people to the death of this shark. It seems society might be moving beyond the “Jaws Effect” where we demonized sharks because we have bought into their fictitious portrayal.  

Many of us now seem to embrace shark fact rather than fiction, realizing that sharks pose little threat to humans; that they have been shaped by some 200 million years of evolution; that globally they are struggling to survive; and that they have an essential role in marine ecosystems.

Hole behind the dorsal fin. Photo: Mandy Norrish.

Sharks, as top-level predators, strongly shape food webs.   Loss of such predators has proven to have profound effects on the number and diversity of other species.   

The unenlightened are still out there though. It may be an inevitability that sharks get caught in fishing nets but they need not then be shot or butchered. Locally, I have seen evidence of both. 

[Update: December 22nd, 2011 - The necropsy revealed that this was a female shark. It is also now known that the shark was caught in a hook and line sable fish fishery and that the hole behind the dorsal was the result of a hook. It is rare that there is shark bycatch in this type of non-net fishery.]

For further information on salmon sharks, please refer to the natural history information from ARKive below.

Click here for two ARKIve videos showing salmon sharks hunting.

Skin parasite (ectoparasite). I have no expertise here but had suggested that this a copepod from the Caligidae family.

Click here for the petition to ban shark fin products in Canada and here for video by astounding 18-year-old Madison Stewart about the vilification of sharks and the atrocities of shark-finning . . . 73 million sharks killed/year for their fins = 190 sharks killed/minute.   

Click here for video of the shark found on the beach in Port Hardy.

Click here to follow tagged salmon sharks in our waters. 

Click here for a scientific paper reviewing the biology of salmon sharks and evaluating their “status” as predators of salmon.

 

Salmon shark image from ARKive site. Click image for two ARKive videos of salmon sharks hunting. Credit: BBC Natural History Unit.

Salmon Shark Information
from ARKive

Description

A formidable hunter, the salmon shark (Lamna ditropis) is sometimes mistaken for the white shark (Carcharodon carcharias), but can be distinguished by its shorter snout and the dusky blotches that mark the white abdomen of adults (3) (4). The rest of the salmon shark’s stocky, spindle-shaped body is dark bluish-grey or blackish, with white blotches around the base of the pectoral fins. The first dorsal fin is large, while the second dorsal and anal fins are tiny and are able to pivot. Its crescent-shaped tail gives it impressive propulsion through the water (2) (3), while its large, well-developed eyes enable it to spot potential prey (2), and its large, blade-like teeth are well suited to gripping slippery fish(2) (3).

Range

The salmon shark occurs in the North Pacific Ocean. From Japan, North Korea, South Korea and the Pacific coast of Russia, its distribution extends east to the Pacific coast of the U.S.A., Canada, and probably Mexico (3).  See this species on Google Earth.

Habitat

The salmon shark is a coastal and oceanic shark, inhabiting waters between 2.5 and 24 degrees Celsius, generally from the surface down to depths around 152 metres, although one individual has been recorded at 255 metres (3).

Biology

Occurring singly or in schools of several individuals (3), salmon sharks are long distance, high-speed predators (2), occasionally seen at or near the surface in some areas. They can maintain their body temperature well above that of the surrounding cold water of the North Pacific, and may have the highest body temperature of any shark (3). This allows them to maintain warm swimming muscles and internal organs, so they can still hunt effectively in cool waters (2).

The salmon shark is considered to be one of the main predators of the Pacific salmon, and its voracious feeding on this fish has earned it its common name (3). However, it is an opportunistic feeder that consumes a wide variety of fish that also includes (amongst many others) herring, sardines, pollock, Alaska cod, lanternfishes and mackerel. It also feeds on some squid and is sometimes attracted to by-catch dumped back into the ocean by shrimp trawlers (3).

After spending the summer in the north of their range, the salmon shark migrates south to breed. In the western North Pacific they migrate to Japanese waters whereas in the eastern North Pacific, the salmon shark breeds off the coast of Oregon and California, USA. The young are born in spring after a gestation period of around nine months (3). The salmon shark is ovoviviparous (young hatch inside the female; they are nourished by their yolk sac and then ‘born’ live), and oophagy (when the growing embryos eat unfertilized eggs to gain nutrients) has been recorded in this shark (4). Most litters contain between two and five young. Male salmon sharks are thought to mature at about five years and live to at least 27 years; females reach maturity at eight to ten years and are known to live to at least 20 years (3).

Threats

The salmon shark is often caught as by-catch in Japanese, United States and Canadian fisheries. When caught, often just the fins are taken for shark fin soup and the rest is discarded, although sometimes the flesh may be sold for consumption in Japan and the United States (4). Many fishermen view salmon sharks as pests, as they often damage fishing gear, making them more likely to be killed if captured (4). In addition to the threat of by-catch, some recreational fishing for this shark occurs in Alaskan and Canadian waters (4), and some commercial fishing has taken place in the past, such as in Prince William Sound, Alaska (5).

Conservation

In 1997, the Alaska Board of Fisheries closed all commercial shark fishing in state waters and implemented strict regulations in the state sports fishery for salmon sharks (4). Measures such as these are vital in protecting this species’ future, until further research can determine the conservation status of this magnificent predator.

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Holy Mola!

Filed under: Fish — 5 Comments
October 24, 2011

Chad Chrighton, the pilot who found the Mola mola near the seaplane base. Photo credit: Mike D'Amour (North Island Gazette).

Something very unexpected landed near the Port Hardy seaplane base on October 20th – a dead Mola mola. This is the largest of the world’s ocean sunfishes and looks like a cartoon character rather than a relatively fast-moving, deep-diving fish whose design has been perfected by millions of years of evolution.

This fish species is aptly named since Mola means “millstone” in Latin and indeed this fish looks like a huge, flat, gray circle and has rough skin.  It appears to have no body, only a giant, round, flat head with a small beak-like mouth. It is propelled by two pointy fins (dorsal and anal) and is steered by a wide, rounded, rudder-like tail. 

Photo credit: Erika Grebeldinger.

Mola molas are found in all temperate and tropical seas and are relatively common in the open ocean off our coast; often getting misidentified as sharks. They were believed to be passive drifters who travelled only at the surface, wherever the current took them. However, satellite tracking studies have revealed that they dive deeper than 600 m and travel an average of 10 to 20 km per day, the same distance traveled by open-ocean shark species. 

Matthew Drake measuring the Mola mola. To give you get a sense of size, Matthew is almost 2 m tall (6.5').

They are certainly a rarity on the inside of Vancouver Island however and I greatly appreciate that Matthew Drake let me know about this find and that he undertook a necropsy of the giant together with Louisa Clarke and Natasha Dickinson. (I only recall there being a similarly sized one on the beach in Port Hardy in 2005). 

This Mola mola measured 2.00 m wide, from beak to tail fin, and 2.06 m long, from the tip of one pointy fin to the other. It may have weighed more than 200 kg. Remarkably, this is small for its kind. Mola molas hold the record for being the largest bony fish on earth with an average mass of 1 tonne. The largest Mola molaever recorded was 2,235 kg and 3.10 m by 4.26 m (it was struck by a boat near Australia in the early 1900s). Note that the whale shark can be more than 9 times bigger than this but, it is not a bony fish. 

Mouthparts. Photo credit: Mandy Norrish.

Matt and the team concluded that the Port Hardy Mola mola was female which meant that she could have up to 300 million eggs in her one ovary. This is another record for the species: having more eggs than any other animal with a backbone.  Another astounding fact is that the larvae could grow to be 60 million times their weight at hatching.

The investigation also revealed partially digested jellyfish in her gut, which is the typical prey of Mola molas. Their diet also includes small fish, eelgrass and crustaceans and they are able to spit out and pull in water and food with their unique mouthparts. As with all species that feed on jellies, a conservation concern is that they mistake plastic bags for their food. However, there was no evidence for this being the cause of death for this particular Mola mola.  

Maybe parasites were a factor in her death? The team found lots of skin and intestinal parasites! Some of the round worms in the guts were even still alive. Parasites are common for Mola molas. In fact, it is now believed that the behaviour of “sunning” at the surface (hence, ocean “sunfish”) might be so that birds can feed on the skin parasites and that jumping more than 3 m out of the water might help dislodge some parasites too. Mola molas are also found associated with drifting kelp patches, where small fish can clean away the pests.  

HOLY MOLA you never know what you are going to find in our amazing marine backyard. 

All the information collected will be reported to oceansunfish.org and the mouth parts will end up on display in Telegraph Cove’s Whale Interpretive Centre. 

 

Beware!  Fabulous Mola mola parasite pictures below! 

Advance only if you are NOT about to eat lunch and/or if you a biology-type like me who can view these kinds of photos in rapturous fascination anytime!

Sources: 

Her intestines were an astounding mass of worms. Likely the species include the parasitic flatworm, Nematobibothrioides histoidii which is thread-like but can grow to be over 12 m (40'). No one apparently knows just how long they can become, in part because dissections/necropsies on Mola mola are rare events. Photo credit: Natasha Dickinson. Click image to enlarge.

Parasites near the eye. Photo credit: Mandy Norrish. Click image to enlarge.

More great ectoparasites. Photo credit: Matthew Drake. Click image to enlarge.

Her single ovary. Can have 300 million eggs. Photo credit: Natasha Dickinson. Click image to enlarge.


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

Filed under: Sharks — Leave a comment
September 29, 2011

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 diver observation can help research. 

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

Filed under: Sharks — Leave a comment
August 13, 2011

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 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 15 sightings of basking sharks since 1996. So what happened?

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

Click here for the annotated basking shark colouring sheet by Romney McPhie. She's not only a shark scientist - she's an artist and very skilled presenter and educator!

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 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 15 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.

Blade on the bow of the "Comox Post" from "Popular Mechanics" November 1956. Click image to link to this edition of the magazine.

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.

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. 

See:

Basking Sharks – The Slaughter of B.C.’s Gentle Giantsby 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

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. 

 

 

 

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