Posts Tagged ‘diving’

Benthic Natural History In Cowlitz Bay, Waldron Island.

Monday, February 4th, 2013

Passing into deeper water from the eelgrass beds found in the shallow nearshore environments of many embayments of the American San Juan Islands, the highly organic muddy sand substrate is typically replaced by a less organic or “cleaner” mixture of sand and silt.  Such a transition is certainly the case in Cowlitz Bay of Waldron Island.  I can verify that the silty-sand substrate continues to, at least, a depth of 50 m (165 feet).   Except for emergent rocky outcrops, this habitat type is likely characteristic of all the deeper water of Cowlitz Bay and the nearby San Juan Channel and Boundary Passages.

The tidal ranges that distinguish this region, coupled with its geography, mean that high tidal currents are the norm, and the volume of tidal water movement is immense.  All of this, added to the dense, rich plankton found in those waters creates a habitat that is probably nearly optimal for suspension feeders.  As a result, virtually all of the hard subtidal real estate is occupied some sort of organism specialized to grab food or nutrients from the water moving past them.  Subtidal rocky substrates are often characterized by dense populations of suspension-feeding epifaunal sea cucumbers.  And, although it may seem unlikely, some of the unconsolidated, silty-sand, habitats are also dominated by dendrochirote holothurians, albeit in this case these cases they are infaunal, not epifaunal.  Infaunal sea cucumbers dominate the subtidal Cowlitz Bay benthic environment below 10 m.    

0 - Pentamera cf populifera 11vii77 6m Cowlitz Bay, Waldron Id. 01 Juveniles

Pentamera individuals extending from the bottom of Cowlitz Bay, 11 July, 1977.  The abundance of the adult animals exceeds 20,000/m2 (about 0.2 m2) is visible.

Pentamera sp. indivdiual with some of the many juveniles in the sediment circled.  Taken 11 July, 1977.

Pentamera sp. adult indivdiual with some of the many juveniles in the sediment circled. Taken 11 July, 1977.  The juveniles become evident in the sediments in early summer, indicating spawning likely occurs in the spring.

Although a few other species are rarely found, the vast majority of these suspension-feeding, infaunal cukes belong to a few species of Pentamera.  The individuals belonging to the different species are relatively similar in size, shape, and coloration making them effectively indistinguishable in the field by non-specialists, so I will refer to them all as Pentamera.  Living buried in the sediments they feed by extending a small portion of the oral end of the body above the sediments.  This exposes just a bit of the animal, primarily the mouth, and its surrounding crown of highly-branched feeding tentacles.   

White, and only about 2 or 3 cm long, these relatively small sea cucumbers are often found in beds so very dense that in the summer, the benthic sediment appears snow-covered due to the many tentacles visible.  In the clear water of the late autumn and winter plankton-free periods, these holothuroids do not feed.  Presumably quiescent, they remain buried under the sediment surface.  During these seasons, the habitat looks relatively barren; with only scattered larger animals, such as individuals of tube anemones, Pachycerianthus fimbriatus, orange sea pens, Ptilosarcus gurneyi, snake-skin stars, Luidia foliolata, sunflower stars, Pycnopodia helianthoides, or weather-vane scallops, Patinopecten caurinus being evident to the casual observer. 

Patinopecten caurinus, the Weather Vane Scallop, about 15 cm (6" in) in diameter. Photographed in the Summer (June, 1977).  Note the visible Pentamera cukes.

Patinopecten caurinus, the Weather Vane Scallop, about 15 cm (6″ in) in diameter. Photographed in the Summer (June, 1977) on the benthic subtrate of Cowlitz Bay; note the abundant Pentamera cukes.

Patinopecten caurinus.  Area as before, except it was photographed in the ealry winter (December, 1976).  Note the lack of visible cukes.

Patinopecten caurinus. Area as before, except it was photographed in the ealry winter (December, 1976). Note the lack of visible cukes.

With beginning of the diatom bloom starting in February, smaller life “returns to”, or more correctly, becomes evident again on the benthos.  The sediment becomes covered completely with a thick and rather ugly, dense dark brown film, consisting of several species of microalgae, primarily diatoms and dinoflagellates. 

Unidentified Polyclad Turbellarian, photographed in April, 1983.  The "black material" is the diatom film that is found in this area in the spring.

Unidentified Polyclad Turbellarian, anterior end to the left, photographed on April, 1983 on the substrate in Cowlitz Bay.  The “black material” is the diatom film that is found in this area in the spring.

By early March, many turbellarian flatworms of several visually distinctive types are commonly found gliding over the brown algal film and sediments.  These small worms, each only a few millimeters long, may be distinguished by their differing shapes and color patterns.  Although common, at least in the spring, virtually nothing is known of their natural history.  Shortly after the worms become common, small caprellid amphipods, otherwise known as “skeleton shrimp”, seem to appear out of nowhere and are soon found covering the diatom film.  These small, about a centimeter (0.4 inch) long, animals reproduce rapidly and soon reach abundances around 1 animal per square centimeter, or a density of 10,000 animals per square meter.  As they become common, pelagic predators, such as ctenophores and chaetognaths, may be observed grabbing copepods off the bottom and swimming back up into the overlying water.

A Sagitta (planktonic chaetognath carnivore) photograph near the bottom, hunting for caprellids.

A Sagitta (an almost completely transparent planktonic chaetognath and a predator normally on zooplankton) photographed near the bottom, where I have seen other individuals grab caprellids.

 By the middle of March, the spring plankton are in full bloom and the Pentamera are beginning to feed.  By moving up and down in the sediment, the resulting bioturbation soon destroys the diatom film, and the sediment becomes relatively clean again.  Snake-skin stars, Luidia foliolata, are common in this habitat where these sea cucumbers are their principal prey.  Caprellid amphipods, Caprella gracilior, and small hermit crabs are often seen on the aboral surface of the stars.  The Luidia-sized, star‑shaped, feeding depressions, along with the small piles of regurgitated remains attest to the star’s feeding habits.  Pycnopodia helianthoides is also commonly found in these beds and may also feed on the sea cucumbers.  Some aspects of the natural history of Luidia in this habitat will be discussed in subsequent post.

 Individuals of the large, up to 15 cm (6 inches) in diameter, weathervane scallops, Patinopecten caurinus, rather rare elsewhere in the San Juans, are found not uncommonly in these cucumber beds.  They are found lying in shallow, somewhat bowl-shaped, depressions probably created over time by the scallops’ feeding currents which might gently displace and excavate the sediments.  Eaten by the sunflower star, the scallops will swim in response to being touched by the predator.  They are not particularly vigorous swimmers, however, nor do they seem to start swimming immediately, thus they could be captured relatively easily.  Their shells are a common feature in this habitat, so presumably some predators are capturing them.  These large shells, either living or dead, provide about the only hard substrate in these habitats, and are often covered with barnacles, algae, or occasionally attached bryozoans or hydroids. 

Maroon more pachycerianthis

Both color varieties or “morphs” of  Pachycerianthus fimbriatus found in the benthos of Cowlitz Bay.

The tube-dwelling anemone, Pachycerianthus fimbriatus, is particularly common in this habitat, and becomes very abundant just below the dense Pentamera beds in the more silty habitats of the steeply sloping areas.  Pachycerianthus individuals may be colored either gray or a dark brown to maroon.  These do not appear to represent separate species, and the different colors have no known significance.  Close examination of the anemones will show some very small epifaunal, possibly stenothoid, amphipods visible as small dots moving over the anemone’s body and tentacles.  During the spring and early summer periods of dense plankton, it is possible to watch the Pachycerianthus catch copepods, and other small crustacean zooplankton, with their long tapering, thin, tentacles. 

An ectoparasitic or commensal stenothoid amphipod on a Pachycerianthus tentacle.  Assuming the tentacles are about the same size (and they are) compare this amphipod to the hyperiid amphipod captured as food by a different tube anemone (next illustration).

An ectoparasitic, or commensal, stenothoid amphipod on a Pachycerianthus tentacle.  Assuming the tentacles are about the same size (and they are) compare this amphipod’s size to that of the hyperiid amphipod captured as food by a different tube anemone (next illustration).

A small Pachycerianthus fimbriatus with a captured planktonic hyperiid amphipod (arrow).

A small Pachycerianthus fimbriatus with a captured planktonic hyperiid amphipod (arrow).

 These slightly deeper habitats where Pachycerianthus is most common, ranging downward from about 10m (33 feet) in depth, have a silty sand substrate.  Pentamera are found in these regions, they are just not as abundant as they are in the dense assemblages in shallower water.  Individuals of the orange sea pen, Ptilosarcus gurneyi, are well represented in these deeper habitats, and although they are not as abundant here as they are in the dense sea pen beds of the lower Puget Sound region, they are nonetheless found relatively frequently.  Occasionally, a different type of pennatulacean, a sea whip, may be found.  In the genus Virgularia, these whips are narrow pennatulaceans, with short “leaves”.   At least two species within this genus found in our waters and they are not terribly difficult to distinguish in the field.  The species found in Cowlitz bay is small, tan to whitish, with small “leaves” and is seldom over 15 cm (6 inches) in height.  The feeding zooids often appear to arise from directly from the central stalk.   The other species, found in other areas, such as Lopez Sound, is larger and more robust, pink to orange, and often reaches heights of 50 or more centimeters.  This species has larger relatively distinct “leaves” with the gastrozooids on them. 

A small, about 8 cm (3.5 in) high, pennatulacean, probably a species of Virgularia.

A small, about 8 cm (3.5 in) high, pennatulacean, probably a species of Virgularia.

 Several nudibranch species are also found in these areas, most of which are probably preying on the cnidarians.  The largest and most evident of these are individuals of Dendronotus iris.  These are amongst the largest local snails; in this area they often reach lengths exceeding 25 cm (10 inches) which is probably due to the high abundances of their preferred prey, the Pachycerianthus anemones.  They approach the anemones by slowly crawling under the tentacle crown, to where the anemones extend from their tube.  They, then, reach up rapidly, bite, and hang on to either a mass of tentacles or even the anemone’s column.  Generally, the Pachycerianthus rapidly withdraws into its tube when it is bitten, and in these cases, it often pulls the predator in with it.  Sometime later, the Dendronotus iris often crawls out of the now empty tube, and may set off in search of another anemone.  The nudibranch may, at times, lay its loosely coiled egg masses attached to the Pachycerianthus tube, bits of shell, or just bits of the sediment.

0 - Dendronotus iris Cowlitz Bay, Waldron Id. -7m 11vii77 WA 01

A 10 cm (4 inch) long Dendronotus iris in Cowlitz Bay. Photographed at a depth about 7 m. This large nudibranch reaches over 30 cm (12 inches) in length, and eats Pachycerianthus. 

Other nudibranch specimens are found in the area, and they can be relatively common at certain times of the year.  Dendronotus albus specimens will be found occasionally, preying on those few hydroids that are found attached to the shell fragments or other hard substrata present on the sediment surface.  These nudibranchs are slender and may reach lengths of about 10 cm.  The basic ground color is white, but the tips of the branched cerata are tipped in orange.  Individuals of another dendronotid, Dendronotus albopunctatus, are often abundant in the spring.  These animals are brown to pink and freckled with small light dots.  They only reaches lengths of 2 to 3 cm (up to about 1.5 inches), but they are recognizable by their somewhat “oversized”, relatively large, “front” cerata, which are often about a centimeter in length.  Little is known of the natural history of this species, although it is likely a predator on small cnidarians.

Dendronotus albus.

Dendronotus albus is a not uncommon, small, about 3 cm, (1.2 inches) long, nudibranch in habitats such as those found in Cowlitz Bay.  It eats hydroids, as this individual was doing when photographed

0 - Dendronotus albopunctatus Cowlitz Bay, Waldron Id. -9m 28iv83 WA 01

Dendronotus albopunctatus, about 3 cm (1.2 inches) long on the sediment of Cowlitz Bay.  It also has been seen to eat hydroids.

0 - Acanthodoris brunnea, Cowlitz Bay, Waldron Id.,  -9m, 13v86  WA 01

Acanthodoris brunnea, about 2 cm (0.8 inch) long, photographed on the sediment of Cowlitz Bay.  Reported to eat bryozoans, this dorid species is found on muddy-sand, a habitat notably lacking in bryozoans.  In this region and habitat, it is likely eating something other than bryozans.

Acanthodoris brunnea is another nudibranch species that is somewhat common at times in this habitat; little is known of its natural history.  These animals are small dorids, roughly the same size as Dentdronotus albopunctatus, reaching lengths of 2 to 3 cm (up to about 1.5 inches).  Their basic coloration is brown; the individuals are covered with distinctive relatively large papillae on the back.   This species is considered to be predatory on bryozoans, but that is unlikely in this region as bryozoans are exceedingly rare in this habitat.

Also found in these areas are pennatulid-eating nudibranchs in the genus Tritonia.  The most abundant of these are individuals of the small white Tritonia festiva, described in the earlier post on sea pen beds.  Here, as well, T. festiva individuals seem to prey on Ptilosarcus.  Individuals of the larger, orange nudibranch, Tritonia diomedea, are also occasionally seen in these areas.  They seem to prefer the larger Virgularia as prey.  

Large shelled gastropods are relatively rare in this particular habitat, although several smaller species can be very abundant.  Perhaps the largest commonly found gastropod, and certainly one of the most beautiful, is the wentletrap,  Epitonium indianorum.  These animals are often found buried near to the bases of the tube anemones upon which they feed.  As with most snails, wentletraps have a feeding organ called a radula; unlike the “classic” gastropodan radula which functions something like a rasp, filing off pieces of tissue, the wentletraps’ radulae are highly modified and look like an inverted thimble lined on the inside with sharp teeth.   A wentletrap crawls up to the anemone and pokes the anemone with its radula everting the “thimble” in the process.  This turns the radula inside out, which in turn, carves a circular hole in the tissues on the side of the anemone.   The lacerated tissues are eaten, and the snail extends its proboscis which has the radula on its tip through the hole and proceeds to use the radula to cut up and eat other internal anemone tissues.  These snails reach lengths of 3 cm or more, and don’t seem to move much once they have found an anemone to feed on.  It is recognized by the distinct axial ribs, the rounded aperture, and the relatively high spire.

 One cephalopod can be relatively common in the lower slope areas, the Pacific Bob‑Tailed Squid, Rossia pacifica.  This small benthic squid lives buried in the bottom during the day.  If a diver is careful, they can sometimes see the slight depression that the Rossia occupies, and then can make out the eyes watching him.  The hole for the siphon is generally visible and if approached carefully, one can see the regular breathing movements of the mantle.  Rossia pacifica reaches lengths of about 10 cm, and seems to live about a year or eighteen months.  They have an interesting, stereotyped, escape response which I have described, briefly, in a previous post.  This small squid preys on small shrimps, crabs, and fishes, and is a nocturnal hunter.

Well, that’s enough for now… :-)

More later,

Cheers, Ron

 

 

 

 

 

Ecological Observations From Northeastern Pacific Subtidal Habitats – Sticky Post #3.

Friday, August 24th, 2012

Series Introduction.

All things must have a beginning, and putting these brief words prior to the beginning of my “series” about my subtidal ecological/natural history observations and “reflections”, is probably as good a place as any to put them.  I hope to add to these tales from time to time, and I hope “the times to times” are more frequent than they have been previously in my blog.

Exiting the water on the south shore of Alki Point in Seattle, Washington.

Here I am exiting the water on the south shore of Alki Point in Seattle, Washington in October, 1982, after doing a dive examining the sea pea bed that was found offshore of that beach (R. Fredrickson image).

That is the plan at least.

If I can do it, I hope to add in this series many of my unpublished and, prossibly, unpublishable, observations made while diving over the period when I was actively doing subtidal natural history research; roughly the period from 1971 to 1993.  There are a lot of reasons for writing this now, but suffice it to say, I am definitely not getting younger and it is possible that some of this material may be of interest to a few other people.  At the very least, they, and the rest of the readership, should get a good laugh out of considering that I would think that it could be useful. :-)

Nonetheless, I think it would be nice, if it simply did not disappear with my demise.  Perhaps, as well, what I write here will serve as an historical record of what occurred prior to any future wholesale habitat destruction due to climate change or some more directly local human activity.   Of course, the fact that many of the presumed untouched Puget Sound and Pacific NW subtidal habitats had previously been messed up seems to have escaped the notice of many people, researchers and divers alike, working in the region.  I will try to point out some of these communities when the need arises.

On the other hand, maybe all I am doing, however,  is just putting down the garbled memories of an old man.  I guess you get to choose.

I will add these tales, or studies (depending on how seriously one wishes to take them), in no particular order over no particular time frame.  Rather I will add them as my muse allows.  Those readers who have previously read my ramblings will realize I know how fully well that my writing depends upon my personal muse  and how she feels about each topic I try to write about.  If she doesn’t like it… nothing good will be written.  If she loves it… well, maybe the writting will still contain nothing good, but if so, there will be a lot of it!  When she likes the topic, though, my good gawd, how the writing flows.  The gorgeous litle blue-green minx (= my muse)  has been known to change her mind in the middle of an article as well.   That has NOT been a fun experience, but it occurs.  As I am writing here to just enjoy the process, I think she will be the helpful creature she truly can be.

If anybody that reads these pages is a scientist, I will add the advice of “not to hold your breath waiting for any of this to appear in the peer-reviewed journals”.  Trying to publish most natural history information and observations in such venues is a serious waste of time and effort.  And if you have gotten this far, you have read the first paragraph and realize that I feel don’t have that much time to waste.   So…  On with the show!

To examine these posts/articles/essays in this “series” as a group:

Please click on the blog “Category” (listed at the top of the column to the right) titled:

 

“Ecological Observations From Northeastern Pacific Subtidal Habitats”.

 

 

Sky Sharks And SCUBA

Sunday, December 19th, 2010

Hi Folks,

My wife and I got treated to quite a show yesterday.  For several hours, a male prairie falcon was cruising around our yard hunting doves.   These latter birds are Eurasian collared doves, one of several introduced pest birds (think large white/gray/tan pigeons) found locally – thesea are  probably descended from birds released by some non-thinking idiot who decided it would be cool to release doves symbolizing something or other at a ceremony somewhere near here.  Anyway, said skyrats appeared about four years ago, and have been doing well here.

Eurasian Collared Dove

Periodically, though, a truly native sky shark comes by to thin the herd a bit, and that is what happened yesterday.   It was great entertainment to watch the falcon, though I doubt the doves thought so. :-)  I saw him miss his target by inches on one pass; the dove was surprisingly agile in the air when the situation warranted!   The falcon was around for a while, and then vanished.   I hope he finally got dinner and settled down near by to enjoy his repast.

Almost exactly a year ago, we had a similar opportunity to watch a goshawk for a few days, and the second picture, below, shows the final outcome.  The first picture was taken a few days before the second one, and it appeared to be the same animal.  In the second image, the hawk is standing over his plucked prey that he has been eating.

Sharp-shinned Hawk in the poplar outside my office window.

Sharp-Shinned Hawk and Dinner

It was an amazing show.

Of such events, are the sciences of behavioral biology, or ethology, and ecology, made.  And people who study these things in terrestrial environments truly lose out.  I used to tell my students that one of the very neat things about being an ecologist who worked subtidally using SCUBA was that one got to see a lot more interactions than one’s terresterially-bound counterparts.

If you think about it, how many times have you seen a predatory animal in nature around you (excluding those events caused by humanity or human pets ) actually kill and eat a prey organism?  I would wager that the total sum of those events witnessed by anybody is pretty small; I know it is with me, and I look for them.  It is possible to calculate some sort estimat of the odds of seeing such an interaction at any given moment.  For example, if a person is 35 years old, that person has been alive about 1 billion seconds.  If each second is a discrete a moment of observation, the rough, back-of-the-envelope odds of having seen such an event through that person’s lifetime are easy to work out.  First, assume that about of the third of the time has been spent sleeping, so subtract a third of the billion away, phffftt!, and now there 667,000,000 million potential moments of observations.  Then assume that for the first third of the persons’s life she or he was effectively unaware of the world (childhood, teen-aged years, and so forth), so subtract a third of the previous remains and now there about 444,700,000 million potential observational moments.  Now, drop out a another third for meals, and other daily mindless activities, and now there about 296,400,000 million observational times.  Being generous, let’s say our victim subject was outside observing nature 1/10 of each day (and I think that will be a vast over estimate for most folks, but, what the hey, let’s go with it), so now there are 29,640,000 potential moments of observation.  And if that person witnessed 10 natural events wherein one animal killed and ate another (and I suspect that would an overestimate), that means our subject’s odds of seeing such an event were 10 in 29,640,000, or 1/2,964,000, or (very roughly) 0.0000003.

Pretty slim odds (!) of seeing some interesting natural event such as predation.

Back to my point about working underwater in the marine world, I could see animals kill and eat other animals many times during a hour’s dive, and often did so.   Below are a couple of images  recording some of those times (and be sure to click on the sculpin image to see the shrimp’s antenna).   Obviously, the moral of the story, of course, is that one must dive to really observe and understand nature.

A Buffalo Sculpin, Enophrys bison, that has just eaten a shrimp, note the antenna visible protruding from the mouth.

A red rock crab, Cancer productus, eating a scallop.

Yeah, sure!!!

But the point that visible large animal to animal interactions are more evident in the marine environment is, I think, a valid one.

Behavior and Marine Aquariums

Thinking about the point made above, and making a not-so-tortuous connection to marine aquaria, those boxes of water full of critters may be (depending, of course, on how the boxes are set up, and what’s in them) quite reasonable analogues to a natural environment.  And that means, any aquarist with such a tank should expect to see predatory (and other “natural” ecological or behavioral) events occurring with some reasonable frequency in their systems.

And, of course, all of us aquarists (or at least of us who observe our systems) do see these events.  Everytime we feed some live animal to our livestock, we see predation, albeit those are staged events, but with suspension-feeding animals, corals for example, within the staged event, the actual feeding behavior on the part of the coral, is likely essentially the same as when the “real thing” occurs in nature.  But even if those “wo/man-made” events are factored out, all aquarists have seen unintened predation occur in our systems, and sometimes rather frequently, as when when a newly-observed acoel flatworm on the aquarium wall is seen to capture and eat a copepod.  In fact, by observing some of these types of events any aquarist worth their artificial (sea)-salt can – for some animals, at least – see interactions that have never been seen in nature, and depending on the interaction – such as with the flatworm and copepod example – such events may be exactly what occurs in the real world, or a mimic so close that the difference is immaterial.

So, folks, on this cold winter, while the snow outside blankets the northern hemisphere, those of you with coral reef aquaria kick back and relax and enjoy the tropical world in your living room.

It’s a world of your making and if you have done your job, properly, it is a VERY real world.

For the rest of you, it is time to shovel snow!

Until later,

Cheers,

It Happened One Night

Saturday, April 3rd, 2010
    
It Happened One Night…2nd Edition.

This is the second version of this essay, the first one was destroyed when my blog had to be wiped as a result of being hacked, see the previous post for details.  I did not keep a record of the images that I had placed in the previous version, so if you read the previous version and had a favorite image, and it is not here, please contact me and I will see what I can do about inserting it. 

A couple of squid near the breeding assemblage

About 25 years ago I was teaching Marine Invertebrate Zoology at the Bamfield Marine Station (the name has been since changed to the Bamfield Marine Science Centre), a university-run marine teaching and research laboratory facility.  This facility is located on the shores of Bamfield Inlet, a small embayment on the south side of Barkley Sound near the southwest corner of Vancouver Island.  That particular year the course ran from late April until early June and was supposed to be a total immersion course – the students lived, breathed, ate, slept, and dreamed about invertebrates.  In this year, by late May, I was casting around for something of special interest for the students to work on, something above and beyond the “standard” course offerings.   

For about a week, we had been seeing a few squids swimming near the water’s surface next to the dock.  This was unusual, so I decided to go diving and see if I could see what they were up to.  These animals were Loligo opalescens, the “Pacific Market Squid” harvested in huge numbers near Monterey, California for calamari.  At the time, the southern populations were pretty well known, but not much was known about the northern populations. The local lore was that the squids, occasionally, would spawn in the inlet.  If spawning was to occur, I thought it would be nice to document this for a couple of reasons.  First – it would be ultimately cool to be in a squid spawning aggregation.  Second – I thought I might get some nice images that I could use in lectures.  Third – I thought I might be able to interest a few of the students in doing some actual research on some small aspect of the spawning.  All-in-all, if I could carry it off, it would be a win-win-win situation.  The only problem was trying to predict when the  animals would spawn, and then coming up with a scientifically valid short research project.   

Prior to this one particular morning, we had been seeing a few scattered squids near the surface in the inlet.  These surface-swimming animals were fully-grown, about 30 cm (1 foot) long, and bright white, so they were quite evident in the dark water of the inlet.  About 10 o’clock, after my lecture for the day was over, I wandered down to the dock, and noticed that the squids were present in larger than “normal” shoals, maybe up to 30 to 50 animals in each fast moving school, so I thought this would be worth a look.  I asked around and found a dive partner and dock tender, and we plopped ourselves in the water about 30 minutes after 10 AM.  To document our dive, I took along my underwater camera system, which consisted of an Olympus OM-2 in an Ikelite housing, with two strobes attached; one triggered by the camera and the other slaved to the first one.  The film was Kodachrome-64, my film of choice for underwater photography.  

Solitary Loligo opalescens

Dropping down to the bottom, at a depth of about 17m to 18 m (55-60 ft), we found a small mass of squids in a frenzy of activity.  As a result, I started my personal frenzy of activity taking some images.  It soon became evident that a couple of individuals were spawning, but that most of the animals were just “interested” observers, squid voyeurs, I guess.  I documented a solitary female spawning and depositing her egg capsules.  I presumed copulation had already taken place, as I saw no obvious mating activity.  I had seen movies of some squid spawning aggregations, and it was obvious that what we were watching was not a normal spawning event.  However, I thought it might be a precursor to the “real” action.       

Solitary Female Loligo opalescens Spawning. Note The Extruded Egg Capsule Between Her Arms.

Solitary Female Ovipositing. Note Egg Capsule Between Her Arms.

Same Individual As In The Previous Figure. Note The Egg Capsule.

Egg Capsules Deposited By The Single Female Over The Course Of Her Spawning

Egg Capsules Produced By The Single Female Over The Course Of Her Spawning.,

For about a week the people of the village of Bamfield had been catching squid by jigging for them near the government-owned docks in town.  So, after seeing the events off of the laboratory dock, I thought that there might be a small mass spawning event occurring near the dock in the upcoming evening.  It would be a “small” event simply because the area was constrained.  The inlet was not wide and was relatively shallow, about 18 m (60 ft) deep at its maximum in that area.  I arranged for another dive buddy and boat tender and we went down to the town docks about 10:30 pm to do our dive.  As usual, I took my camera system along to document interesting “happenings.”   

When we arrived at the scene, the fishermen already there said that jigging was “slow.”  Squids were visible, but sparse, and not many had come into the area where the fishermen were.  To avoid upsetting the fishermen, we dove well away from them.  This also prevented us from being “jigged.”  Having a sharp squid jig tear open and flood one’s (very) expensive dry suit can really ruin the experience of the moment!   

When we first got into the water, few Loligo were around, but within a couple of minutes they started to aggregate around us, probably attracted by our diving lights, and the large pile of rocks on the bottom nearby.  At first there were just a few solitary individuals, then a few doublets, and then quartets, and then … large groups; Too large and too fast to count.  All of a sudden the action began.   

Although the spawning aggregation appeared terribly chaotic, with thousands – yes, thousands – of Loligo jetting around from all directions and bumping into each other and us, after a bit of observation, it became clear that what appeared to be an unruly affair was really quite well “choreographed.” 

From the outside in…   

The animals approached the spawning site alone or in small groups of up to about ten individuals.  As they approached they had normal coloration; brown to reddish brown tones predominated on the bodies and the arms’ outer surfaces.    

A Squid Pair Above The Main Spawning Site

A Quartet Of Squid Approaching The Spawning Site.

At the outermost region of the spawning site, about 5 to 6 m (15 to 20 feet) above it, the individuals were actively fighting with one another to find a mate.  Females were “attacked” by males that wished to mate with them, and often two or more males fought each other for each female.  This was a brutal, winner-take-all, competition!  Skin was ripped off and the combatants used their beaks to rip pieces of flesh from their opponents.  The females were NOT passive participants in this rough foreplay; they were actively fighting as well.  Presumably, the strongest, most fit male prevailed.  During this activity, both males and females were white.  They did not flash or change colors.   

Mating/Foreplay Damage Making the mate choice - maybe... Lots of action here.

Foreplay - but getting near the final choice of mates. Note the bite damage on the male (lower animal).

Precopulation - "Foreplay" - Two Males and One Female

Loligo opalescens foreplay or copulation well above the egg deposition site

 As the combat continued, the participants got closer and closer to the bottom, and eventually one male prevailed.  He got into the oviposition position; holding the female from behind and below, with his eight arms wrapped around her.  Copulation, the transfer of a spermatophore (sperm packet) from the male to the female, occurred once this posture was stabilized.  The animals were now about 3 m (10 feet) above the bottom.  Once he was securely holding his mate, the male’s color pattern changed from pure white all over, to having a white body and reddish-brown tentacles.  The female remained totally white.  Once this color pattern was established all other males avoided the pair, and ceased jostling the resident male for possession of his female.  I suspect the color pattern change was THE signal that mating had occurred and that this particular female was no longer available.   

Mated Pairs Depositing Egg Capsules.

After the male’s color changed, he did all of the subsequent swimming for the pair.  He moved the female to the oviposition site and began to push her into the mass of egg capsules that were already at the site.  As they approached the site, the female extruded and formed an egg capsule which was held in her arms.  Once the male pushed her into the egg capsule mass, or onto any other acceptable area, the female wrapped the distal, adhesive and ropelike, end of the egg capsule around anything, such as other egg capsules, a sunken twig, a rock, a diver’s mask strap, which would hold it in place.   

The egg deposition frenzy, overall there were hundreds of pairs of squid at this one small site.

Egg Capsule Deposition

Frenzied action a couple of meters above the main egg capsule mass

Spawning pairs and the main egg capsule mass.

  When first formed, these egg capsules were about the size of one’s little finger, but they became larger as they absorb water.  From subsequent studies, part of the project we later did, I found that each egg capsule in this region contained about 150 eggs, sequestered within a series of protective – and toxic – membranous coverings.  I was unable to count the number of egg capsules produced by any specific single female, the situation was just too chaotic for that.  In the California areas other studies found that each female produced about 20 capsules.  If the same number was produced by these northern Loligo, each female would deposit about 3000 eggs in her one night stand.  

Newly deposited egg capsules

Egg Masses The Day After Spawning. The Masses Are About A Meter Thick.

After the final capsule was deposited, the male released the female and they both slowly departed the area.  The males seemed to be a bit more active and I surmised that at least some of them might try to mate again, as each one produces numerous spermatophores, and they only use one per female.  However, the action was so frenzied that I was unable to follow any given squid more than a few seconds, so it is possible that one shot was all the males had.  The females appeared to be totally spent; they swam erratically and weakly.  They often travelled only a short distance prior to settling to the bottom and dying.  The males probably swam a few more hours, at best, but they, too, don’t survive long.  Individuals of both genders are badly injured by the experience.   

New Egg Capsules, The Day After Deposition, My Dive Partner For Scale.

During the flurry of spawning activity predators made their appearance.  In the area where I was diving these predators were seals and California sea lions which would come blasting through the spawning masses biting up squid as they went.  Fortunately, they decided big ugly divers in rubber suits didn’t match their search image of calamari.  In other areas, larger sharks, such as blue sharks, will also come into the spawning squid schools, but, blissfully, I didn’t see any of those in the aggregations I dove in. 

After the spawning was over, the bottom was littered with egg capsule masses and dead or dying squid.  Over the week following the spawning, some of my associates and students and I did some diving to make measurements of the squid egg masses.  Scattered all over the bottom, from just below lowest low water to beyond diver depth, were small individual egg capsule aggregations.  Each of these covered about 0.3 square meters, (about 3 square feet) and there were about 1.3 of them per square meter (10 square feet).  I collected some of these aggregations, and found that each contained, on the average, about 1,940 capsules.  Each capsule contained about 150 eggs, meaning each capsule mass was the result of 194 squid pairs, and contained 291,000 eggs.   

Dead squid the morning after the spawning event.

Mass of dead squid, the morning after.

 We did diving surveys to determine the extent of the night’s spawning activity.  This particular night’s spawning aggregation extended along about 11 km (7 miles) of the southern edge of Barkley sound.  The largest egg mass we found in a quantitative survey area was 69 square meters or 742 square feet, however, we saw some much larger egg masses.  Unfortunately, these were seen during the spot surveys for determining the whole area covered by the spawning aggregation, and we could not return to them.  We estimated the largest measured spawning aggregation was result of 24,000 spawning pairs of Loligo, and based our quantitative measurements of small egg mass abundance we estimated that during that one night of spawning, in the Bamfield area, over 64,000,000 squids spawned!   

Urticina corieaca, a sand dwelling anemone, and squid corpses. It normally would eat squid, but was sated the next morning.

 Loligo opalescens eggs take about six weeks to hatch in that region, and some of the egg masses were followed for that length of time.  After hatching, the remnants of the membranous egg coverings were still noticeable on the bottom for another several weeks in places.  As long as the egg capsule membranes were intact, nothing was seen eating the eggs.  Stupidly, I did not wear gloves during my initial examination of the egg capsules and the eggs when I was tearing and cutting open the egg capsule membranes.  After a few minutes of handling the membranes my fingers lost feeling, and a few minutes after that my hands became numb and immobile.  The area of numbness continued to expand until finally my arms became numb up to the elbows.  It took about 2 to 3 hours before the feeling slowly returned to my arms and hands.  Obviously, whatever is in the membranes would be effective at deterring predation.  In over 100 diver hours of examining the capsule masses, no animals were seen eating the eggs, although we saw many animals positioned on or in the masses.  If egg capsules were torn or cut open underwater, red rock crab individuals, Cancer productus, rapidly approached and started eating the eggs or developing embryos, further illustrating the protective function of the capsular membranes.  The long decay period for the membranes after the squids had hatched also indicated that the membranes contained either or both antifungal and antibacterial agents.   

A sunflower star, Pycnopodia helianthoides, on an egg capsule mass. The star was not eating them.

Old egg capsules, near hatching. They absorb water and are about three times the size they were when deposited.

During the several weeks it takes them to hatch, other animals in the area seem to consider the toxic egg capsules as "just part of the habitat."

 Reference:   

Shimek, R. L., D. Fyfe, L. Ramsey, A. Bergey, J. Elliott, and S. Guy.  1984.  A note on the spawning of the north Pacific market squid Loligo opalescens(Berry, 1911) in Barkley Sound, Vancouver Island, Canada.  Fishery Bulletin.  82:445-446.