Marine
Life Society of South Australia Inc.
Newsletter
September
2005 No.
325
“understanding, enjoying & caring for our
oceans”
Next Meeting
This
will be held at the Conservation Centre, 120 Wakefield Street, Adelaide
on Wednesday
21st September commencing at
7.30pm.
Our
speaker will be Lauren
Johnston who will be talking about Featherstars.
Contents
Sharks Galore
Is Not A Bore - II (David Muirhead)
Rock Pool
Danger Concerning Blue Ring Octopus (Steve Reynolds)
Some Terms for
Fish Genders and Gender Changing (Steve Reynolds)
This Month’s
speaker - Lauren Johnston (Steve Reynolds)
2005
Journal
At present I
have only one article. One more is promised but this is not really enough to
warrant the production of a Journal this year.
So it is up to
YOU!!
Articles please, or
the possibility of no Journal this year.
2006
Calendar
This
is now available. AUS$8 to members and AUS$10 to non
members. Please buy as many as possible and also sell to anyone who
is interested.
We almost sold every
2005 calendar! A wonderful
effort.
People
who have seen the new edition say it is our best yet.
This
Newsletter
The hardcopy of the Newsletter is in black and white as usual. If members prefer a colour PDF version then please email me.
Sharks Galore Is Not A Bore - II
(Part II of Ben and
Dave’s legendary encounter at Encounter Bay.)
by David Muirhead
Upon slipping
nervously beneath the sunlit surface of the shark enclosure I took a hasty
inventory of the marine life as follows (all sizes are
‘guesstimates’):
1) One other
fine example of homo sapiens (this being Ben Brayford -
surely readers didn't think I’d get in first?!)
2) Three (or
four) bronze whalers - one undoubtedly the star of the show, being ~ 7’ (~ 2.2
m) another under 5ft (~ 1.5 m) and a 3rd little sprat being surely
less than 2ft (~ 0.6m) long and looking very lithe and trim. Though more wary
than its already quite stand-offish larger kin, this baby bronzie got my vote
for the cutest critter in the aquarium, not just for its diminutive stature but
because it looked leaner, sleeker, more streamlined and somehow ‘racier’ than
its stablemates. Ben told me that he and his brother Joe suspected the biggest
bronzie might be pregnant, and (?)she certainly had a
midriff bulge (older MLSSA members may remember that unflattering term from the
early days of TV ads for ladies' supportive undergarments) but I scarcely gave a
thought to trying to ‘sex’ any of the sharks during our dive, there were too
many distractions to really focus on such things until afterwards. This baby
bronzie stirred memories of a slightly longer one, probably still under 1 metre,
that came to check me out while I was spearfishing at Corny Point circa 1971
(our generation really pushed our luck in those halcyon days -just ask any
‘real’ spearo from that era, such as Rodney Fox).
To this day my
dominant recollections of my bronzie are of being struck by its sinuous beauty
and its timid but curious nature. For these traits to be so transparently
apparent to me even then, a lone spearo on a lonely shore with a lively
imagination and a head filled with images from ‘Blue Water, White Death’ (my two
spearo mates were already back on the rocks), is surely an indication of the
trustworthiness of one's primal instincts in the fleeting moments of such
encounters.
The little
bronzie in the floating cage instinctively knew about risk minimization, for it
seemed to spend most of its time in the upper½ of the available water
column, perhaps away of maximizing the value of its stealth bomber-like
‘photo-spectral mergence’. Please interpret this pseudoscientific double-speak
as my way of saying how difficult these sharks’ dull dorsal colouration and
contrasting pale, almost white ventral colour makes them to actually see from
above or below. Alternatively my few misguided and petty-minded detractors may
see this as the nearest they'll ever get to an admission by me that, try as 1
might, I failed to get any decent photographs of bronzies despite having at
least 3 as a captive audience, in an enclosure only a bit larger than your
average backyard swimming pool! (but considerably
deeper).
In plain
language, its by evolution and not by accident that they’ve got bronze backs and
white bellies, so they can get closer to their prey before being seen,
especially if the prey is on or near the surface, while being hard to spot from
below - a survival mechanism that must be particularly important for the very
young bronzies, which, I'm sure, would be legitimate prey for any
self-respecting adult wobbegong.
And a passing
thought – there’s been publicity recently about declining wobbegong (and other
bottom-dwelling shark) numbers in the Eastern states, particularly NSW where
they are heavily fished (the NSW Fisheries Department has detected a 60% decline
in the commercial catch of Spotted Wobbegong and the species is now listed as
Near Threatened regionally and globally), yet it seems to me SA’s may well have
suffered a comparable decline.
Sadly,
although such anecdotal impressions as mine are justifiably next to meaningless
to the scientific, let alone commercial fishing communities, they are often all
the ‘evidence’ we're going to get about population densities of
noncommercial species so I encourage any divers, snorkellers, or ex-spearos
(or even spearos, but I'm absolutely sure their numbers have declined
since my youth, thankfully, and even a brace of shark shields wouldn’t give me
the courage to spearfish nowadays, were I ever foolhardy enough to consider
resuming this dangerous blood sport) to write down the main species they see on
each dive or snorkel, no matter how common they seem at the
time.
Looking back,
spearfishing could at best be justified as the entry door to an appreciation of
our fantastic marine life, for many spearos eventually swapped spear for camera
and became passionate conservation advocates. But let me assure you, from my own
spearfishing experience and that of others, if your favourite inshore reef seems
suddenly devoid of larger territorial reef fishes and spearos were recently seen
in the area, then I'll bet you an angry wombat to a sawtooth pipefish that the
spearos caused the problem. I recall, usually with only 1 or 2 mates, hammering
certain Fleurieu Peninsula reefs repeatedly during the school holidays and being
surprised at how quickly even the best spots became unproductive and how long it
took them to recover. But, in my defence, I was only a small-time pretender as
far as spearos go, and we did eat the catch. And I can boast that I never
speared a wobbegong or ray myself, but this was more from fear, justified if the
many stories of the day were anything to go by, of the wrath of an injured
wobbegong, than from lack of opportunity!
For all the
negatives that followed that initial cluster of white pointer attacks on spearos
over four decades ago, we should not overlook at least one positive outcome -
they scared all but the most committed, brave or foolhardy spearos out of the
water, or onto scuba courses and thence lobster hunting and photography, for by
then, fortuitously, it was already illegal to spearfish using SCUBA, and so
virtually a whole generation of spearos began to seek other outlets for their
energies and marine life interests.
Before that
Blind Freddie (whom I knew then as Dudley Squat - no, I'm not Deadly Earnest!?)
attests to this group’s great impact, over just those few decades, on our
inshore reef fish populations. Accessible parts of the Fleurieu Peninsula such
as Noarlunga, Aldinga, Myponga, Carrickalinga and Second Valley suffered (again
anecdotally) the worst losses, and I can assure readers that within only a few
years of, respectively, Noarlunga, Aldinga and Second Valley’s main reefs
becoming reserves, their biomass of larger reef species increased dramatically,
despite the fact that line fishing was still allowed in most reserves, and
despite the fact that declining water quality due to stormwater discharge,
sewage and other pollutants was already damaging Noarlunga and Aldinga
reefs.
Anyway, all
this is very stale news, so I’ll return to my main theme - sharks! I’m sure I
saw more Wobbegongs, also rays, as a spearo all those years ago, than in the
last few decades. I only rarely saw other spearos showing off ‘trophy’ wobbies,
but quite a few smaller rays came to grief, usually left to rot on the beach,
and even some big (but harmless by nature of course) eagle rays, and yet my
impression nowadays is that I see as many and varied rays as I ever did, but far
fewer wobbies! Whether this is the result of fishing (including inshore
set-netting, now fortunately on the way to the history books here in S.A), or
perhaps other factors such as declining lobster and octopus numbers, I can only
guess. Again, where was I? Oh yeah, that legendary encounter at Encounter Bay...
Can readers handle a Part III? Let’s wait and see....!
Cleanup Dive at the Screwpile
Jetty
by Steve
Reynolds
Several
Society members participated in our clean up dive at the Screwpile Jetty on
Sunday 6th March. These were Kevin Smith, Neville Skinner, Chris
Hall, Maggie Williams, Tim Woonton, Tim Cuthbertson and myself. Two of Chris Hall’s friends also came along to watch
proceedings. We all met at the boat ramp car park close to the Granite Island
causeway. Everyone’s dive gear was loaded into my trailer for the long trip
across the causeway. Kevin’s car towed my trailer across the causeway to the
Screwpile Jetty. Most members sat on the trailer to ride across to the island.
Halfway across the causeway though Maggie opted to run the
rest of the way to the jetty. Once that we arrived at the jetty we
checked it out for entry and exit points for divers. The three landings on the
jetty made entry easy enough but the low tide coupled with the lack of any
ladders meant that exits would be impossible. It was decided that the divers
would have to swim back to the nearby sandy beach close to the kiosk to exit
from the water. I nominated myself to act as the ‘top person’ needed to take all
of the rubbish collected from the divers. There were to be just six divers –
Kevin, Neville, Chris, Maggie and the two Tims. After
they had all geared up, Chris’s friend Ann took a couple of photos of our group.
Three pairs of divers were soon on their way into the water with clean up bags
in hand. I got busy preparing ropes on the jetty. Divers soon returned to hand
over the first lot of clean up bags. Full bags were swapped for fresh empty bags
and the divers disappeared back into the murky water. There were so many bottles
down there that they soon returned with full bags again. I told them to only
half fill the bags so that I could handle them on the jetty. I also spent much
of my time returning lots of chitons, seastars, shells, fish, etc.. to the water. There wasn’t much time to think about things.
Kevin surfaced to say that it was ‘raining’ chitons
down there. I suggested that they were just a new species of swimming chiton. Sometimes the divers took a long rope to the bottom
so as to tie it to heavy bags for lifting to the surface. A small outboard motor
was also hauled out from the bottom. A large transistor radio and a diver’s
compass were some of the unusual finds. Dive times went beyond the planned 60
minutes. The divers then made their way to the little beach nearby before
trudging back to the trailer on the jetty. Once the divers had changed back into
dry clothes we loaded the trailer up with all of the wet dive gear on top of all
of the rubbish.
Picture taken
by Steve
Reynolds
There were
some 17 bags of rubbish plus the outboard motor and transistor radio. A few
fishing knives and other bits of fishing gear had been collected. Neville had
been unable to locate the owner of the diver’s compass that he found so he held
on to that, plus an old dive knife that he also found. Kevin towed the trailer
back to the mainland whilst we (most of us?) walked back. Dive gear was
transferred back to people’s cars at the car park. We then had lunch on the
nearby reserve. Kevin and I had to leave early to take the trailer-load of
rubbish to the recycling depot out of town on the other side of Victor Harbor.
It was a bit of a long trip there. We disposed of all of the rubbish in the
trailer and headed off home as soon as we could get away from the friendly
workers there at the depot. It was a long drive back home but we stopped off at
Peter Gilbert’s home to drop off my computer for repairs. Peter wanted us to
stay a while for a chat but we wanted to be back home by tea
time.
Picture taken
by Ann
Williams
The one good
thing for me was that I didn’t have to wash out my dive gear at home. There was
still paperwork to do for Clean Up Australia after the
dive though. I had some forms to fill out for returning to CUA. At our March
General Meeting I tabled a certificate of thanks for MLSSA from CUA. I also
presented certificates to Neville, Chris and the two Tims. Tim W took one for Maggie who was an apology for the
evening and I took one for Kevin who was another apology. My
thanks again to Kevin, Chris, Neville, Maggie and the two Tims for their efforts.
Rock Pool Danger Concerning Blue Ring
Octopus
by Steve
Reynolds
In May 2005 I
saw Dr Kirsten Benkendorff speaking during Channel 7’s “Australia’s Deadliest
Destinations” program. Dr Benkendorff is a lecturer in marine biology at the
School of Biological Sciences at Flinders University. She had been the guest
speaker at our August 2004 General Meeting. Her topic was “Medicinal use of
molluscs”. On “Australia’s Deadliest Destinations” Dr Benkendorff reported how
she had once been affected by a blue-ringed octopus with eggs found in a rock
pool. I asked her to tell me more about what happened. She told me that she had
not heard of anyone who has had a similar experience to the one that she had.
Here is her story (in her own words): - “What happened was that I was
undertaking a molluscan biodiversity survey at North
Wollongong reef over low tide and I picked up a fairly large boulder ~60x 40cm
that was in a relatively deep rock pool ~ 1m deep. I turned the boulder over as
per usual and underneath was a (female) blue-ringed octopus carrying a bunch of
eggs in her arms and flashing blue like crazy! I also noticed one side of the
boulder seemed to be coated in a great mucus (but I can't be sure now that this
wasn't a colonial ascidian) but I did notice it at the
time which makes me suspect it was more of an unusual sighting (i.e. mucus from
the blue ring). Anyway, I basically replaced the boulder straight away but then
almost immediately started to feel a tingling in my left arm. I was instantly
terrified and shouted for my research assistant and made my way to a more stable
part of the reef. The tingling and numbness spread to just above my elbow and
the arm was noticeably colder than my right arm (at least 5 degrees but could
have been more). As time passed I didn't show any further symptoms and after
~2hrs the numbness started to subside - although it remained colder with some
residual tingling until very late that night. My take on this is that I probably
absorbed a low dose of the toxin through my skin - the localised reaction suggests that the venom didn't get into
my blood stream and that, along with the fact that I didn’t get more severe
symptoms, makes it unlikely that I was bitten. Furthermore, I didn’t see or feel
the octopus approach my hand (although no one ever feels these guys bite!). But
I suspect that either:
1) The mucus I
saw on the boulder was impregnated with some venom
or
2) The female
released some venom into the rock pool and I absorbed some of this.
Either way, it
makes sense that the female would defend her eggs indirectly by releasing some
anesthetizing venom in the face of threat, rather than having to rely on biting
the victim. This is because she had her arms full of eggs and thus would have
restricted access to the flesh and could potentially damage some of the eggs in
the process. This is the only aggressive encounter I have ever had with a blue
ring - they mostly just try to disappear as quick as
possible when I expose them! But suffice it to say, I always try to remind
myself to wear gloves when I'm turning boulders these days! I still wonder how I
managed to survive...
Cheers,
Kirsten”
Kirsten later said
that she would be interested to hear if anyone else has had a similar
experience.
Blue
Ring picture supplied by Dennis Hutson
Some Terms for Fish Genders and Gender
Changing
by Steve
Reynolds
‘Protandry’ is a biological term which means ‘change from
male to female’. The opposite to protandry (change from female to male) is ‘protogyny’. Both of these two terms are explained in my old
biology dictionary. “A Dictionary of Biology” explains both ‘protandrous’ and ‘protogynous’ in
relation to both flowers and animals. In the case of animals, ‘protandrous’ means ‘producing first sperm, and then eggs’,
whereas ‘protogynous’ means ‘producing first eggs, and then
sperms’.
In her article
“Gender benders” in Scuba Diver Australasia August-September 2002, Danielle
Johnson says that some species of flathead and gobies are ‘protandrous’ (males become females) and some species of
wrasse are ‘protogynous’ (females become males). She
also says that aeolid nudibranchs are ‘protandrous’ (males become females) and that Sea Bream
change sex in both directions. Another term that Danielle used in her article is
‘gonochoristic’. She says that ‘gonochorists’ are creatures which do not change sex (or
gender). Then there is ‘hermaphrodism’. Danielle says
that ‘hermaphrodites’ are creatures which have “complete sets of sexual
equipment for both genders”. She says that “Among the hermaphrodites, there are
species which function alternatively as one gender then the other, and others
who operate as both sexes simultaneously”. She also says that “There are those
(hermaphrodites) who produce both sperm and ova in separate gonads and those
where both are in the same gonad”. Danielle’s article discussed wrasses quite a
bit, especially in regard to many wrasse species starting out as females. She
talks about the colour phases of adult wrasses, saying that adult females all go
through an initial colour phase, referred to as the initial phase. She says that
some “Other wrasses and parrotfish can have both mature females and males in the
initial phase” but, it seems, some males have a terminal colour phase. (I found
this part of the article difficult to follow.) Danielle went on to talk about
secondary males and primary males (in parrotfish). She said that protandrous parrotfish males (sex-changed males, those that
had changed from female to male) were termed ‘secondary’ males. Gonochristic parrotfish males (unchanged males) were termed
‘primary’ males. This was all explained further in a separate section where
Danielle said that male wrasses “can originate two ways: either they are born
that way (primary males) or they were born female and changed sex somewhere
along the line (secondary males). Secondary males all have terminal phase
colours. . . Primary males are found in both initial . . . and terminal phases,
meaning they change phase, but not sex”. Neville Coleman wrote in his book
“Australian Fish Behaviour” that “some wrasses are hermaphroditic with both male
and female sex organs. These fish function in the role of practicing females
during their early adulthood, and then after a number of years, develop into
males for the rest of their lives”. When discussing wrasses in his book “Coastal
fishes of South-eastern Australia”, Rudie Kuiter said “There are usually various
and distinct colour-forms within species between juveniles and sexes. Juveniles
are usually female first and adults are referred to as the initial phase; as
males derive from females this form could represent either sex. Fully developed
males usually become very colourful and very different from the initial phase,
and are referred to as the terminal phase. Most males dominate a harem-like
group of females and are territorial towards other males. If the male disappears the most dominant, usually largest, female takes
over and changes sex”. When discussing parrotfishes in the same book, Rudie says
“Most species have different-coloured stages as juvenile, initial phase and
terminal phase. The latter has usually a mixture of brilliant contrasting
colours”. In “Australian Fish Behaviour”, Neville Coleman says that “Sexual
dimorphism is the term used to describe the difference in size and shape”
between the sexes and “sexual dichromatism refers to
the differences in colour, or pattern of males and females within the same
species”. He then goes on to say that “fishes such as wrasses (and parrotfishes)
have specific sexual dimorphic and sexual dichromatic characteristics”. Also
found in Neville Coleman’s book “Australian Fish Behaviour” are some comments
about hybrid fishes. Neville mentions that “hybrids (the result of breeding
between closely related species) in nature are usually infertile”. He then goes
on to mention that “two species of bream, Acanthopagrus australis & Acanthopagrus buthcheri, landlocked in lakes in south eastern
Australia have interbred and produced fertile hybrids”. And remember that
Danielle Johnson said that Sea Bream change sex in both
directions.
Now here is a
recap of many of the above terms: -
Protandry means ‘change
from male to female’
Protogyny means ‘change
from female to male’
Gonochoristic means ‘does
not change sex’
Hermaphroditic
means ‘have complete sets of sexual equipment for both
genders’
Primary males
means ‘males that were born that way’ (haven’t changed
sex)
Secondary
males means ‘males that were born female and changed sex somewhere along the
line’
Terminal phase
colours is what all secondary males have
Initial phase
colours are those of a protogynous (females become
males) adult female
Sexual
dimorphism is the difference in size and shape between the
sexes
Sexual dichromatism is the differences in colour, or pattern of
males and females within the same species
Hybrids are
the result of breeding between closely related species
REFERENCES:
“Gender benders” by
Danielle Johnson in Scuba Diver Australasia August-September
2002.
“A Dictionary of
Biology” by Abercrombie, Hickman & Johnson, Penguin Books,
1970.
“Australian Fish Behaviour” by Neville
Coleman, published by Neville Coleman’s Underwater Geographic P/L,
1993.
“Coastal fishes of South-eastern Australia” by
Rudie Kuiter, published by Gary Allen P/L, 2000.
This Month’s Speaker - Lauren
Johnston
by
Steve Reynolds
In April I approached
several people from the SA Museum about speaking at one of our forthcoming
meetings. I soon received replies from a couple of them agreeing to talk to us
soon. I was quite impressed with the following response from Lauren Johnston:
-
“Hi Steve,
I would be happy to talk about my work for a MLSSA
meeting. . . . . . . I am currently
working as a research assistant for Greg (Rouse) on several projects focusing on
relationships of feather stars and developing an online guide for recreational
divers to the feather stars of Australia. My major project, from honors, has
been to determine the number of species within, and evolution of, a family of
tiny, brooding, feather stars that are only found in the southern waters of
Australia. Out of work, I am also a keen diver getting out almost every week
with the Adelaide Uni Scuba Club and have been diving
in Hawaii, Vanuatu, East Timor and plan to dive the Red Sea in July.
Thank
you for the invitation . . . . . ..
Lauren”
A second email gave
more details as to the talk.
“Hi Steve,
I would like to talk generally about my research and
role as a research assistant. I am involved in fieldwork, our museum collections
and laboratory work and my main focus is using DNA to study feather star
relationships and evolution. So I will focus on my work with Aporometra
and the results of that study. I will be submitting ‘part one’ of my findings on
Aporometra for publication over the coming weeks. I have a degree in
Biotechnology and graduated with Honours in 2002. My thesis subject was ‘The
phylogeny and systematics of the feather star
Aporometra (Echinodermata:Crinoidea)’. I do not have to dive very deep for my
work, most feather stars can be found at less than 20 metres, but most are in
the tropics which makes them an even better group to
work on occasionally. I have ventured into 13ºC waters for my work though, and
I’m sure you’re familiar with winter diving in South Australia. My up coming
trip will be a holiday that will take me to Washington DC and then various stops
in Europe, but I am most excited about getting down to the Red Sea for a week
during that time.
Best wishes,
Lauren”