Wolf-eel life cycle and biology

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John Rawlings
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Wolf-eel life cycle and biology

Post by John Rawlings »

Wolf-eels simply intrigue me.....they always have. A dive becomes special the moment I spot one!

Calvin and Nailer have recently posted some great footage and a still photo of a juvenile wolf-eel. You can check it out here:

http://www.nwdiveclub.com/viewtopic.php?t=885

I posted another shot of a juvenile wolf-eel on the club gallery that appears here:

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Calvin asked me a question regarding wolf-eel "parenting" after hatching. It struck me that the best means of answering his question would be to post the text of an article I wrote regarding wolf-eel biology and life cycle. A longer article appeared in Advanced Diver magazine (ADM) issue # 14. I scaled it down for publishing in Northwest Dive News (NWDN), in which it appeared in the August 2005 issue.

Here is the text from the NWDN article:

The Ugly Old Man of the Sea: The Wolf-Eel
By John Rawlings

Get any group of divers together in the Pacific Northwest and ask them what makes a really GREAT dive, and invariably one of the things they will agree on is that a wolf-eel will somehow be involved. There’s something about the ugly face of an adult wolf-eel staring at you from its den that will turn an ordinary dive into a great one – poor visibility, terrible weather, rotten currents…..all will be forgotten once a Wolfie appears. Divers travel from around the world to glimpse these fascinating creatures, and hope that they, too, will be able to say that they “Danced with Wolfies”.

Actually a wolf fish, not an eel, wolf-eels can be found as far south as San Diego and northward to the Aleutian Islands. Its scientific name, Anarrhichthys ocellatus, comes from both Greek and Latin - Anarrhichthys comes from the Greek Anarhichas, a Greek fish that the wolf-eel resembles. The second half, ocellatus, is Latin for “eye-like spots”, a perfect description of the wolf-eel’s skin. The popular name, “wolf-eel”, comes from the large frontal canine-like teeth that they use in seizing prey, mainly hard-shelled crustaceans and invertebrates. Growing up to 8 feet in length, these massive fish are thought to live up to 10 years, although documentation of longevity is lacking.

Throughout history, wolf-eels have been deeply respected by the peoples of the northern Pacific – In some tribes the tasty wolf-eel was a ritual food eaten only by the tribal shaman. In Washington the wolf-eel is a protected species in both Puget Sound and Hood Canal, not because they are endangered, but because their value as a living resource to divers and photographers far exceeds whatever commercial value the species could provide. Some dive sites, such as Sunrise Wall near Tacoma, are well known as locations where wolf-eels interact with divers and can be part of a unique photo opportunity. In both the American Pacific Northwest and in British Columbia, Canada, the prevailing attitude among divers regarding wolf-eels is both affection and protection.

Studies by Marine Fish Biologists with the Washington Department of Fish and Wildlife have revealed much new information regarding the life cycle of wolf-eels and debunked a few myths. In the past it was “well-known” that wolf-eels mated for life. This “fact” was the result of studies in aquariums and on casual observations in the wild in which individual fish weren’t clearly identified. New research reveals that wolf-eels do appear to be loyal mates, but only on a seasonal basis rather than for life. With some mated pairs, even this isn’t ironclad, with the occasional female abandoning the loser of a fight to share a den with the victor. Adult wolf-eels mate between October and April, although research shows that most nests will appear from December to March within the greater Puget Sound area. It is speculated that spawning is timed so that the eggs will hatch around the same time as the major plankton blooms in the Spring.

Approximately 24 hours prior to mating, the female’s abdomen becomes noticeably distended. The male will butt his head against the back of her abdominal region. This appears to stimulate physiological activity and a series of waves moves through the female’s body from her head to her tail, particularly pronounced in her abdomen. The male then wraps himself around her with their heads side by side and their genital areas adjacent to each other. In this position the female releases the eggs, usually between 5,000 and 10,000, and the male fertilizes them as they appear. Following fertilization, the female coils about the eggs, molding them into a ball-like cluster. The eggs are apparently adhesive to each other, but not to the walls of the den. Both parents will then coil themselves about the egg mass, sometimes together and at other times individually, tending the eggs and ensuring that they are rotated so that a good flow of water passes through them. The primary role of the male during this time appears to be guarding the nest from intruders. Males do make occasional forays out of the den, but it is yet to be ascertained if they bring food back to the female.

Following incubation of approximately 13 weeks (+ or -, variation probably due to water temperature and/or other environmental conditions) the eggs will begin to hatch. In the Puget Sound area this normally occurs from February through the end of April. Larval wolf-eels are approximately 1 inch long and are born hungry. From birth they are voracious predators and strike at their planktonic prey much like a coiled snake will strike at a mouse. Constantly in search of prey, larval wolf-eels lead a pelagic existence, free-swimming with the plankton, for as little as one month to as long as two years, the length of time presumably based on the availability of food and habitat. They then will settle to the bottom, searching out nooks and crannies in which to dwell when not hunting.

The change from a pelagic to a bottom dwelling existence spawns physical changes in the wolf-eel. Juveniles begin to change from a brownish or bright orange color pattern to the distinctive spotted pattern of an adult. Males and most females will turn light blue/gray, although often females will retain their brownish color. Males also begin to develop a puffy face, enlarged jaws, huge bulbous lips and a powerful sagital crest at the top of their heads to support the increased muscle mass as support for the jaws. With the exception of the frontal canine teeth, the teeth in the rear of the mouth become flattened molars designed to crush the hard-shelled crustaceans and mollusks that make up the majority of their diet. Favorite prey items will differ based on location, with the most abundant food source usually the most preferred. For example, wolf-eels in Puget Sound appear to favor sea urchins, those off the northern Olympic Peninsula apparently prefer the hairy triton, while those off Monterey, California apparently prefer sand dollars and graceful crab.

The giant Pacific octopus, Enteroctopus dofleini, is the wolf-eel’s primary competitor and will often force a wolf-eel, even a mated pair, out of a den and take it for its own. Wolf-eels and octopuses occupy the same habitat, hunt the same prey, and value the same type of den sites. Competition can be fierce! Once an octopus of even moderate size has made up its mind that it wants to occupy a particular den there is not much that a wolf-eel can do to prevent the take-over because, as many a diver can attest, when an octopus has established itself in a den getting it to come out when it has no interest in doing so is a virtual impossibility. Other species, however, seem to be able to share dens with wolf-eels as benevolent “roommates”, or even as partners. Ling cod have been observed sharing the same crevice with wolf-eels, the egg masses of both within close proximity. It is unclear whether the relationship is competitive or cooperative, but both ling cod and wolf-eels have been seen apparently acting jointly to ward off intruders. Copper rockfish, brown rockfish, sailfin sculpin, and several species of shrimp have also been observed sharing wolf-eel dens, apparently with no threat being perceived by either party.

I regularly dive with Marine Biologist Tony Parra, who, along with other Washington Department of Fish and Wildlife Biologists, has been conducting an extensive biological study of wolf-eels over the past few years. Few people know as much about wolf-eels as Tony and I enjoy tapping into his knowledge as well as meeting his “Wolfie” buddies from the study “close up and personal”. In one dive at Sunrise Wall in late October we excitedly expected the wolf-eels would be beginning to pair off to breed, giving us the opportunity of photographing that behavior.

Descending into the rich emerald green depths, we soon found ourselves gliding down the wall, covered with bright pink swaths of coralline algae interspersed with clumps of shining white and orange plumose anemones. Fall was at hand and the bull kelp that graces the wall in the Summer had decayed away to virtually nothing – small brown stalks all that was left of the once mighty carpet seen earlier in the year. Orange and purple seastars dotted the seascape as they slowly inched along the rocks searching for prey, while multi-colored red Irish lords and buffalo sculpins peered at us from their ledges. Not visible until they moved, tiny hermit and decorator crabs scuttled here and there. The remains of shellfish lay in heaps before numerous holes in the rocky reef – a sure sign of at least past occupancy by either wolf-eels or giant Pacific octopuses. Within seconds of arriving at the bottom, Tony flashed his light at me and pointed out our first “clients” – a pair of mated wolf-eels sharing a den, nestled side-by-side. The male was quite a monster, with a gnarled and puffy head like a slightly deflated basketball. As his mouth opened and closed we could clearly see his huge set of teeth, blunt and square, worn away from many years of feasting on the armor of urchins and other shellfish. Next to him his mate looked almost toy-like, despite the fact that she, too, was clearly an adult. His body pale with age, her darker gray body stood out as she lay beside him in the entryway. We later estimated the huge old male as between 7 feet and 8 feet in length.

Tony attempted to lure the pair out with a proffered treat of raw chicken, but neither of them appeared to be the slightest bit interested. Prior to entering the water, Tony had explained that once a male has enticed a female into sharing a den, he becomes extremely reluctant to leave it and will not allow her to do so either, undoubtedly concerned that a “bachelor” male will attempt to take his place. Nearby we noticed another male, unusually out in the open. He had a huge raw wound in his forehead - probably from a battle with another male. He circled around the den site, his eyes gleaming brightly with an intensity bordering on desperation. He reminded me of a teenager who had just had his girlfriend lured away by the high school football star. Obviously, he was a recent loser in the “game of love” and possibly he was the reason our mated pair refused to budge.

Moving southward down the wall we encountered two other mated pairs, who also refused to leave their dens. Along with the wolf-eels we also discovered 6 giant Pacific octopuses. Like the mated wolf-eels they also refused to come out to play. Still, they were only too happy to accept bits of our chicken, which they eagerly hauled into their dens with an extended arm.

Toward the end of our dive we found what we were seeking, a single male in his den by himself and still interested in such mundane things as food! Tony extended his hand, holding out a bit of chicken as an invitation. No sooner had he done so than the wolf-eel shot out of the den like a torpedo! Swirling about Tony’s arms, the wolf-eel chomped down on the treat while Tony rubbed his chin and petted his head like he would a friendly dog. A beautiful purplish-gray, the dark spots on the flanks of the wolf-eel stood out in my viewfinder as my camera clicked away. Chunk after chunk was eaten as copper rockfish, striped seaperch and sculpins darted in to snatch up the tiny bits scattering about as the big Wolfie fed, the sound of his huge jaws clearly audible through the water. Soon the bag was empty and suddenly Tony became MUCH less interesting. With a swirl of his sinewy tail the male turned and plunged back into his hole, where he busily began enlarging it in anticipation of attracting a feminine housemate - sand, small rocks and shells swirling out in a cloud as he twisted and turned.

As we swam back toward the anchor line we again came across our friend with the open gash in his forehead, still wandering about in search of a female not yet spoken for, the look on his fleshy face still every bit as intense. His glare seemed to say, “What the HELL are YOU lookin’ at?!!!” as we passed by and he continued on with his mission. As we slowly made our way up the anchor line toward the surface I found myself wondering if he would eventually achieve success. Perhaps another dive will provide the answer – a wolf-eel with a bite out of his forehead shouldn’t be THAT hard to recognize! Later, as our boat sped eastward toward the boat launch and home, Tony and I talked about what conclusions we might draw from the behaviors we had observed and photographed. It had been a marvelous and entertaining experience, one that we had shared with the “Ugly Old Man of the Sea” – the wolf-eel.

The original article in NWDN can be viewed along with photos on their web site. Here's the link:

http://www.nwdivenews.com/

To get to the .jpg file of the article, click on the "back issues" link at the center left of the home page. Next, click on file page 9. Then click on the cover of the August 2005 issue. the article appears on pages 16 through 19.
Last edited by John Rawlings on Thu Oct 26, 2006 7:00 am, edited 2 times in total.
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DiverDown
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Post by DiverDown »

Thanks for that John.. Before the construction at the T-Dock there was 2 juvies there. It was fun to catch a few shrimp to entice them out with..
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Post by Cera »

I actually read this article when it was originally published and was disappointed you didn't talk more about divers touching them with gloves on and wiping away the slime coating that protects them. I am constantly disappointed with all the photos of divers holding wolf eels with gloves on or against their wetsuits; especially dive shops actually use these photos as advertising. I think education( and setting a good example) is the best way to get the word out on the subject. I did enjoy the article on one of my favorite sea creatures!
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Post by sparky »

John :

grate story john I think I rember seeing this one when it ran in NW Diveer News

now I am going to have to check my stack of mags and see if I still have that one or not


thanks

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Tom Nic
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Post by Tom Nic »

Great story John! Well written as usual, and a delightful revisiting of a critter that we all love. Thanks for the journey!
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Post by Pinkpadigal »

Last March, I was diving at Sunrise and came upon the smallest, and youngest wolf eel I had ever seen. It was approx 18 inches long and was still dark brown, just starting to turn orange. My buddy and I went wild. It was just out, swimming around. It was amazing.
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Post by Tangfish »

Terrific article John, thanks for sharing. I was quite surprised too to read about the feeding and petting of the wolfie. Maverick, Dave and I have a great video of us interacting with a pair of wolfies, feeding them herring at Sunrise with the wolf eels wrapping themselves around us and generally having a good time.

I was so thrilled about the experience that I showed the video with pride to Janna during my Fish ID class. She laughed uneasily and then proceeded to tell me about the negative effects of such an interaction. I definitely felt like a kid who was proudly showing mom a window I broke, and realizing at the same time that it wasn't a good thing. With my tail between my legs, I apologized and swore not to do such a (fun) thing again. :pale:
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John Rawlings
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Post by John Rawlings »

Calvin Tang wrote:I was quite surprised too to read about the feeding and petting of the wolfie. Maverick, Dave and I have a great video of us interacting with a pair of wolfies, feeding them herring at Sunrise with the wolf eels wrapping themselves around us and generally having a good time.

I was so thrilled about the experience that I showed the video with pride to Janna during my Fish ID class. She laughed uneasily and then proceeded to tell me about the negative effects of such an interaction. I definitely felt like a kid who was proudly showing mom a window I broke, and realizing at the same time that it wasn't a good thing. With my tail between my legs, I apologized and swore not to do such a (fun) thing again. :pale:
I guess that all I can say is "opinions vary".

You will note that in the article I was diving with a degreed full-time marine biologist whose particular specialty is wolf-eels. The population we were diving with in the story is one that he has personally studied closely for many years, observing their entire life cycle and documenting how the population changed and developed over time. It appeared to me that some of them recognized him and he obviously cares deeply for the species and individuals within it.

If you ask anyone involved in marine biology in the Pacific Northwest who THE expert on wolf-eels is - Tony's name will be certain to be brought up. I would never believe for an instant that he would knowingly do anything to cause harm to these animals, and I doubt that he is ignorant of this particular controversy over feeding and touching them.

- John
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Post by Tangfish »

Well, there is a HUGE difference between a marine biologist doing research and interacting with his subjects and a few idiot yahoos (my dive buddies and I) doing the handling. :book:

I'm sure you and Tony didn't do anything negative to the Wolfies, but I'll probably end up in hell for being so ignorant and playing paddy-cake with them, not knowing anything about the effects.
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Post by Maverick »

great writting john, and reminds me of the dive clavin spoke of. lots of wolfies.

z's reef is also a great one as far as wolfies are concerned,
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Post by jlehigh »

lol Don't fret too much Calvin. Virtually all marine fishies have slime coats which serve two primary functions (so we think). One is to protect them from parasitic vulnerability, the other is to assist with osmoregulation (regulating the salinity in their bodies). Whereas stripping the slime coat can use some energy, it should not introduce high risk to healthy animals. It really becomes an issue when capturing and removing animals from their native habitat that the impact are compounded and a stressed animal is already working overtime to adapt to the rapid changes (netting, transport, re-acclimation).

I do endorse the practive of not handling animals without a better reason than fun, but Wolfie still loves ya ;)
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Post by Old Crab »

Some fish literally drown when the slime is removed because their bodies begin to absorb water and they can't excrete it or expell it fast enough and it overloads the heart which causes death.

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Post by diver-dad »

John -

Fascinating article!

Thank you for listing it here for us.
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