4 October 2013

Clingfish, crabs and the best marine biology day I ever had

Gobiesox maeandricus (captive/staged)*

This is the northern clingfish, Gobiesox maeandricus. Are there (m)any divers who have met this species? I only met these clingfish while beachcombing 

Rock Bay at extreme low water.

On what would eventually became the best marine biology day I ever had, I woke up at 7.30. I had planned to make my first two dives in Rock Bay (Vancouver Island, Canada) that day. But when I stepped out of our RV, I noticed it was extreme low water. As landlubber (as contrary to a diver) this means rich pickings and hopefully some new species. So I took my gear and went beachcombing and photographing. After 30 minutes I decided to skip photographing and to collect. Because in that short time I found 5 species I had never seen before, like the northern clingfish. Partly on, but mostly hidden between and beneath rocks.

Again Rock Bay at extreme low water.

A lot of fish, crab, sea anemones, tunicates, sponges, worms and molluscs hide this way from the sun (against dehydration) and for protection against predators. So you just have to overturn rocks to find certain species. 

None of these new species did I see afterwards while diving! Maybe if I had made a night dive I would have seen a few. A lot of these creatures, especially crabs and lobsters, are very cryptic and are mostly active after dark. The crabs and the clingfish I present in this post are partly photographed in their natural surrounding, but all staged.

Petrolisthes eriomerus (staged)

This is the flattop crab, Petrolisthes eriomerus. Sometimes it is difficult, even impossible, to identify a species by means of a photograph. This crab was easy to identify because of its blue mouthparts. Its lookalike, Petrolisthes cinctipes, has red mouthparts. To 2 cm across carapace.

Petrolisthes eriomerus (staged)

It is an Anomuran and related to hermit crabs. 'True' crabs have 4 pair of walking legs. Anomuran crabs have 3 pair of walking legs. Their last, fourth pair of legs is very small.

Hapalogaster mertensii (staged)

Another Anomuran crab (count the walking legs!), the hairy crab, Hapalogaster mertensii. To 3.5 cm across carapace.
Compared to European waters, this part of the Pacific is very rich in Anomuran crabs.

Hapalogaster mertensii (staged)

Cancer oregonensis (staged)

The typical shape of its carapace with indentations that look like the rim of an apple pie, makes the genus of this crab easy to identify: a Cancer species. It is Cancer oregonensis, the pygmy rock crab. And a pygmy it is: to 5 cm across carapace. Other Cancer crabs can become huge, like the red rock crab, Cancer productus, up to 20 cm, and the edible crab, Cancer pagurus (NL: Noordzeekrab) over 30 cm.

Cancer oregonensis (staged)

I like Cancer crabs. Their locomotion is a bit clumsy and for me they look a bit like teddy bears. But look out for their claws, because they are extremely strong.

Lophopanopeus bellus (staged)

The black-clawed crab, Lophopanopeus bellus, is a crab that lives in the same habitat as Cancer crabs. They are smaller, but also have formidable claws, especially older male specimens. This (youngish) specimen has brown pincers. I don't think the pincers really colour to black, as its name suggests, but it is a bit atypical. As is its smaller right claw, which it has lost and is now regenerating.

Lophopanopeus bellus (staged)

Lophopanopeus bellus (staged)

These black-clawed crabs are more typical and you can see that the claws of the specimen at the right are relatively big. I am sure that is a male. Have big claws something to do with making an impression to the ladies? Very well possible because that seems to be the case with fiddler crabs. To 4 cm across carapace.

Hemigrapsus oregonensis (staged)

The yellow shore crabs, Hemigrapsus oregonensis, were abundant and I had seen a few while snorkeling. To 5 cm across carapace.

Hemigrapsus oregonensis (staged)

The typical angular shape of Grapsid crabs. Click here for my post about its relative, the purple shore crab, Hemigrapsus nudus.

Hemigrapsus oregonensis (staged)

Hemigrapsus species are not relying on their strength, but on their agility and speed.

At this low tide seascape I found the clingfish and crabs. It looks a bit chaotic, but I know where to look. The pinkish blob is a giant pacific chiton, Cryptochiton stelleri (more about this and other shells in one of the next posts).

Do not ever forget to return the rocks and do it cautiously. If not, the seaweeds on the rocks will perish because they need the sun and the current, and sponges, tunicates etc. will die because of the sun and predators. I have seen a lot of sites in France and the Netherlands destroyed, because people are not aware or simply do not care for the life on and under rocks. So spread the word!

Photo: Hetty van der Hoeven

I put the collected animals in a bucket with water and after some time I went back to the RV (just 50 mtr away). My first dive was due to begin in one hour time, so I had not sufficient time for photographing. Where could I put them to stay overnight? My suitcase looked watertight...

My wife is accustomed to such strange behaviour, the other guests of the camping site were not. But they already thought I was a bit strange.
With some effort of my wife to keep the suitcase filled with water and out of the sun, all survived (when it became dark I removed the seaweed). The next day I made photo's and returned all the animals within a few meters of the location I collected them.

Gobiesox maeandricus (staged)

Back to the northern clingfish. As you can see, it looks like a flattened tadpole. It can grow to 16 cm, which is quite large for a clingfish species. All clingfish have a large sucker on their belly: their pelvic fins are formed into an adhesive disc. They have no scales that are easily lost or damaged. Instead they have a slimy hide.

That makes it the top gun fish in shallow waters with heavy current and crashing waves: it simply clings itself against the rocks. Clinging in itself costs no energy; it is a vacuum. Only freeing itself will be a little effort.

Lipophrys pholis (captive, Kerpape, France)

And they have no competitors. In Europe the shore clingfish, Lepadogaster lepadogaster (NL: zuignapvis) and its relatives have competitors: about 20 species of blennies, like the shanny, Lipophrys pholis (NL: steenslijmvis). Shannies are agile, also have no scales and are adapted to breathing out of water. See the next photo of three shannies which I exposed after overturning a rock at low tide. No competition for the northern clingfish: in this part of the Pacific there is not one single blenny species to be found!

Lipophrys pholis (Zierikzee, The Netherlands)

The northern clingfish hides its entire life and I think its 'lebensraum' is quite small. Lamb & Edgell (1986) note that while diving it is very infrequently sighted. 'Beachcombers overturning rocks commonly encounter this clingfish clinging tenaciously to its shelter. Various small snails, worms and shrimp-like creatures sharing the rocky abode of this fish also form much of is diet.'

Gobiesox maeandricus (staged)

As I know of its European counterpart, the already mentioned shore clingfish, Lepadogaster lepadogaster, you have to slide him forwards, shoving a piece of seaweed under its sucker to free him from the rock. If you push him backwards, the vacuum gets stronger and you will injure the fish considerably.

At the camping site they told me they were called bullheads and every year they are sought after for one day by children. As a competition who can collect the most. Last year (2011) they had collected 80 bullheads, this year only a few. He suspected that they had almost died out because of the heavy rainfall that year, that made the salinity too low. I found five specimens.

Where the sea meets land (author unknown)

But why the best marine biology day I ever had? An hour after this magnificent beachcombing adventure (illustrated above) at Rock Bay I had my first dive here. Swimming in an underwater forest a dream came true and I saw the spotted ratfish. In between this and the next dive my wife yelled: orca's! We saw four killer whales, Orcinus orca, passing by. And after I had warmed up in the sun I had another wonderful dive.

* I would have preferred a more natural background, but contrary to the other photo's of the clingfish I wanted to make a photo of these clingfish in water. Especially to get rid of the reflections caused by the slimy skin. So the glass baking dish (provided with the RV) on a white table was convenient at the time. And it is better than my lyme coloured suitcase... Even so I still had to do some background photoshopping. Ofcourse the specimens themselves have not been altered in any way!