Diving Thoughts

A pod of around 400 short-beaked common dolphins have been seen in the Moray Firth, which is better known for bottlenose dolphins. This is much further north than they would normally be found. Scientists at EarthWatch are claiming that this is further evidence of global warming causing animals to move beyond their normal range.

I saw large pods of dolphins in New Zealand several years ago which were very impressive, but nothing as big as this.

The photo above comes from a story on the BBC website.

According to the SCMP, a great thick-knee (Esacus recurvirostris) was seen at Mai Po last Wednesday. This bird is native to south and south-east Asia and is common in Vietnam but doesn’t normally travel long distances.  There is speculation that recent winds have brought it here.

The above photo by Michelle and Peter Wong is taken from the SCMP’s story.

Whales off the coast of Argentina have a new persecutor to worry about. Not the Japanese whaling fleet, but flocks of seagulls. The gulls are landing on the whales and pecking away at their skin and blubber. This behaviour has not been seen elsewhere. It was first reported 35 years ago, but has not been seriously studied until recently. Nowadays up to 78% of the whales in the area are being attacked annually, with mothers and calves being particularly tormented. Unfortunately the area where this is happening is an important breeding ground for the endangered southern right whale. The whales are not feeding in the area, so they should be conserving their energy, but the gulls are making it difficult for them to do that.

Doesn’t it make you glad that there aren’t any seagulls around Hong Kong?

There’s some great photos from the BBC’s website.

The International Union for Conservation of Nature (IUCN) has listed 64 species on their first ever red list for oceanic sharks. These include hammerheads, giant devil rays and porbeagles. Overfishing is getting the blame, and it is particularly problematic for sharks which produce few young and take many years to mature.

Scalloped hammerheads have been categorised as globally endangered. In some parts of the world their numbers have declined by 99% over the last 30 years.

Conservationists are calling for limits to catches and enforcement of strict bans on finning, where a shark’s fins are chopped off before the shark is thrown back to die.

There is a lot more information in an article on the Guardian’s website.

Sand goby males look after the eggs from multiple females, which then go off looking for more mates. The eggs are buried safely in the sand and the males keep a careful eye on them, however in some circumstances they will eat their offspring. Research by Ashley Chin-Barstaard (an unfortunate name which sounds as though it ought to apply to the cannibal fish rather than a researcher), of Purdue University, has been investigating the circumstances that causes the cannibalism.

Her research has shown that the trigger appears to be the presence of an egg predator such as a brown shrimp. This causes the male goby to eat the eggs before the shrimp has a chance to get at them. There is a long summer breeding season for the gobies, so it looks as though they eat their eggs to recoup some of their investment in them in the form of food, knowing they still have time to breed again.

Smaller males, who presumably need all the energy they can get, were found to be more likely to eat their eggs than larger males. However sickly males were less likely to eat their eggs, which may be because males with eggs are more likely to attract females.

There is an article on this on the New Scientist website.

Delegates at the International Whaling Commission annual meeting in Madeira have agreed to continue with reform talks that started a year ago, despite fundamental differences between pro and anit-whaling countries.

Animal welfare groups have recently issued a report claiming that whale watching would generate tourism revenue of around USD 2.1bn, considerably more than the tens of million dollars that are currently brought in by commercial whaling.

Despite all this, Japan, Norway and Iceland are showing no signs of giving up whaling, so the anti-whaling countries are trying to find a compromise. This might involve greater oversight of hunting, a reduction in the total number of whales killed, and reform of the scientific whaling clause under which any country can set its own quotas.

Japan has apparently agreed not to include humpback and fin whales in its annual Antarctic hunt, and to reduce the number of minke whales targeted from 935 to 600. But they won’t give up the principle that each country can set its own quotas for special permit catches.

More detail from the BBC website.

A pod of orca are hunting near Auckland’s Tamaki Drive, attracting crowds of onlookers. Two adult orcas and 3 – 4 juveniles are believed to be hunting stingrays, which they are throwing into the air and eating.

New Zealand orcas are the only known group that eat stingrays as a staple food. This often means they come into shallow waters, which may be a reason that they have the highest rate of beachings in the world.

The story is from the New Zealand Herald, which also has some subscriber photos.

The BBC have an article on the strategies that great whites use when hunting seals. The sharks identify a location, an anchor point, and then search the surrounding area for prey. Researchers found that this anchor point did not necessarily offer the best chance of intercepting prey, but did provide the optimal balance between finding it and catching it.

Apparently this suggests a premeditated hunting strategy akin to that used by human serial killers. The team of researchers did consult a specialist in geographically profiling criminal acts such as those committed by terrorists and serial killers.  Such profiling is used to identify the criminals’ anchor points. But the researchers were using the profiling to analyse the attack patterns and identify location points, not to suggest that sharks are serial killers.

Personally I think the BBC have just taken the opportunity to play up the “sharks are serial killers” angle. In fact when I originally spotted the article yesterday the article title said something like “sharks use same tactics as serial killers” (I don’t remember the exact wording). It’s good to see they’ve now changed it to something less dramatic and more accurate. Sadly Yahoo (“Great white sharks hunt just like Hannibal Lecter“), Bloomberg (“Great White Sharks Said to Hunt Like Serial Killers“) and the LA Daily News (“Great white sharks: serial killers of the sea“), among others, have stayed with exaggeration and hyperbole.

As far as I can what the sharks are doing is adopting a sensible hunting strategy, to wait where you’ve got the best chance of catching what you want. Yes, you could argue that is the same thing that serial killers do. But it’s also what most of us do on a daily basis. If I want to catch a bus, I generally find that the best strategy is to wait at a bus stop. If I want to catch a train or an MTR, then waiting at a station tends to give best results. But sadly headlines such as “Great White Sharks use Same Strategy as Commuters” is presumably not sensational enough for journalists and editors. Instead they take the easy option and continue to villify sharks.

The above photo comes from Neil Hammerschlag and is shown on the BBC website, where you can read the article.

WWF are saying that pollution has pushed the freshwater dolphins of the Mekong to the brink of extinction, with only 64-76 Irrawaddy dolphins left.  The Mekong flows through China, Laos, Cambodia, Thailand and Vietnam and the pollutants that are affecting it are widely distributed, which means it would take a cross-border effort to help the dolphins.

Since 2003 there have been 88 deaths of which over 60% were calves less than 2 weeks old. These were mostly killed by a bacterial disease which the WWF argued would not have been fatal if the dolphins’ immune systems had not been suppressed by environmental contaminants. The calves had toxic levels of pesticides such as DDT and contaminants such as PCBs. Some of them also had high levels of mercury.

For more there is a story on the BBC website.

Fish apparently use their gas-filled swim bladders to sense the pressure changes associated with sound waves, so can hear relatively well. Cephalopods don’t have gas-filled chambers, which has tended to suggest that they could not hear or at least not well.

However Hong Young Yan of the Taiwan National Academy of Science in Taipei has been looking at another organ, the statocyst. This is apparently a sac-like structure containing a mineralised mass and sensitive hairs. Previous research has shown that fish also use this to detect sounds and so do prawns.

Yan looked at the common octopus Octopus vulgaris and the Bigfin reef squid Sepioteuthis lessoniana. He found that the octopus hears sound between 400 and 1000Hz, whereas the squid can hear from 400 up to 1500Hz. This discrepency could well be explained by the environment in which they live. Squid tend to be free swimming, whereas octopus live along the seabed among rocks and coral. Sounds above 1000Hz would have a wavelength of over 1.5 metres, which would mean they would be deflected by rocks and coral, making them irrelevant to octopus. Both species hear best at frequencies of 600Hz.

The next question is to find out what they are listening for. Is it sounds of predators, or of prey, or are they also making sounds to allow them to communicate amongst themselves.

The photos on this article as well as a full story are on the BBC website.

With a forecast of heavy rain and squally thunderstorms following on from a week of heavy rain, I wasn’t expecting a great deal from Saturday’s dive. In fact the Underwater Club had cancelled their Sunday dive because of the weather and apparently Mandarin Divers abandoned their plans too.  So were we keener, tougher, or just less smart? Whichever it was, we were also considerably luckier, as there was no rain, no thunder, no squalls, just a very pleasant day with 2 metre vis which was much better than we all expected.

Just for a change, I decided to dive twins. I had a twin tank wing which I picked up remarkably cheaply from someone who’d won it in a raffle. It looked in good nick, but when I tried to fit it to my backplate, I found the holes didn’t line up with the bolts on my twin tank adapter. There were 2 pairs of 3 holes at top and bottom, so I did the best I could but it wasn’t attached all that smoothly. Also I need to replace the inflator hose  and I will have to service the kidney dump valve because it was sticking closed. But apart from that, well it was cheap!

I fixed the tanks and regulators, and warned Marcus L. that my sinuses were playing up. We agreed I’d lead the descent down the anchor line so I could stop if I was in pain. Then he’d take over and lead the rest of the dive as practice before he starts a Dive Leader course. The anchor was in 12-13 metres, but we came off at about 7 metres and headed inshore because I couldn’t get any deeper than that. Gradually my sinuses improved and we were able to head down the steep slope to 15 metres. Not  a lot to see, but certainly much better than I’d been expecting. Quite a lot of schools of apogon, rabbitfish and damsels, plus a nice goatfish. Quite a lot of urchins too, one of whose spines is now securely lodged in my knee.

Marcus got us back to the boat where we came across Catheryn doing a rescue assessment with Andreas as instructor and Rita as a rather noisy victim. The de-kitting didn’t go too well, so Andreas wanted them to redo it. As Rita jumped back in her weight belt came adrift and plummeted to the depths. I shouted for Marcus to fetch a weight belt and, once I’d managed to impress on him the urgency, he gave me my own weight belt. Unfortunately it only had 2 lbs on it so I scrounged a 3 lb weight and gave it to Catheryn to lower down as a shot with a dSMB fixed to the top. David and Joerg were next in so they did a circular search from the hastily improvised shot, and within 5 minutes they’d found the weight belt and brought it back to the boat. A successful demonstration of the skills learnt on the search and recovery course.

Meanwhile the Kiss boys, Brian and Andy, had finished a deep (for Hong Kong) dive using trimix. They’d encountered vis of less than 0.5 metre and Andy was taking a bit of persuading that he really wanted to do a second dive. In LS’s absence, Mike and Marcus S. took the prize for worst navigation when they surfaced with a long swim back.

Then a speedboat appeared out of nowhere and tried screaming between us and the shore. The ABC boatmen responded immediately and started blowing the horn and waving the speedboat off. The speedboat crew didn’t seem to be aware that they should keep well clear or travel at slow speed. Sadly this is pretty typical of boats in Hong Kong waters, in fact we had the same problem with a squadron of jetskis, 2 weeks earlier. The ABC boatmen phoned in a report about this speedboat although whether anything will happen as a result is uncertain.

For the second dive Marcus and I decided on the same arrangement as on our first dive, I’d lead the descent to make sure my sinuses were OK, then he’d take over at the bottom. This time I had less trouble and we made it to the bottom of the anchor line before heading off deeper. We got down to 17.5 metres where it seemed a lot darker, but we hit some patches of really good soft coral and some nice whips. There was a particularly big scorpion fish, plus the smallest moray I’ve ever seen. This was turning out to be a much better dive than the first one. We got back up to 9 metres and Marcus sent up a dSMB. I then checked my dSMB was still in place as I’d replaced the bungee earlier in the week. It was now held by only one of the two bungee cords, so I decided I might was well deploy it rather than risk dropping it as I got back on the boat. So I put a puff of air into it to make it easier to control, then felt for my spool, only to find that it had mysteriously disappeared leaving just the double ender behind. Since I’d not bothered to carry my reel on this dive, I was left with no choice but to finish the safety stop and ascent with a dSMB looped over my arm. Marcus who hadn’t realised the problem thought I was mad. I did try and signal to him what was going on, but I was laughing so much that my mask kept filling up with water.

Most people were impressed with the soft coral that was down below 15 metres and we had some surprisingly good dives with quite a lot to see.  Back on board, beers and champagne were opened. It seems we were celebrating a number of things:

1. Catheryn passing her Dive Leader practical assignments
2. Brian and Andy doing a 50 metre dive, which we believe is the deepest  by the Club in Hong Kong
3. Brian’s last dive with SCDC in Hong Kong before his departure next month after 29 years (although perhaps “celebrating” is the wrong word in this context!)

Oh and we should also mention Mike making it out on the boat which is always a bit of a rarity.

All in all a good day out.

In addition to the basking shark video, the BBC has a few others that are worth a look. Specifically:

• Shark tagging off the west coast of Scotland
• Rare prickly shark captured off California. This is only the second time one has been captured. The video was shot during the shark’s 15 hour stay in Monterey Aquarium. It has now been tagged and released.
• Testing the great white shark’s bite.
• Tagging whale sharks in the Maldives.