I had the pleasure to go on two dives with Mark Milburn of Atlantic Scuba on the ‘Stingray’ RHIB this weekend and last, leaving from Mylor Harbour (see photo above). The first dive was in the Helford Pool, a deep area in the otherwise shallow Helford river. Buddied up with Sue and Al, we descended to 18 meters to swim over a gravelly area covered with tunicates and sponges. This was a drift dive but we did not get all the way to the eastern end of the pool where some small maerl beds are located. Swimming crabs and Leach’s spider crabs were very common; there were not many fish though. One exception was a cute little John Dory Zeus faber. I was struggling to take any decent photographs, in part because I have not used my strobe much yet and because I should have two, not just one! Sue Barnes kindly let me use a photo she took of the John Dory for the blog; also added is a photo of a sponge, one of the few half-decent ones I managed to take: The dive today took us to the cannon ball site, roughly a mile from Pendennis Castle, and an area where many of the cannon balls fired for practice ended up. With buddy Alex we descended to around 16 m using a shot line. Again a flat ‘rubbly’ area with few fish. The seafloor was covered with Common brittlestars Ophiotrix fragilis. The viz was quite good, and it was much lighter than the previous dive. I also had *a bit* more luck with the strobe. Leach’s spider crabs were common, and we also saw some Sea lemons, Doris pseudoargus, a large seaslug. Up next three common species: a little Rock goby Gobius paganellus, the colonial Antenna hydroid Nemertesia antennina and the colonial sea squirt Aplidium elegans (thanks David Fenwick). I keep my eyes open for seaweeds too of course, there were some small red species and what I suspect is Desmarest’s prickly weed Desmarestia aculeata. I found out back on the boat that I completely missed a small octopus that Alex pointed out, argh! I was very happy though that I managed to spot an Imperial anemone Capnea sanguinea, which is an uncommon species. The photo of this all-white individual was taken without a strobe; I really should have taken more time to get a decent shot. A good reason to go back though, and maybe we can spot some cannon balls then too. The water is 13-14 degrees and so it is still doable to dive with a wetsuit.
I made some pics last weekend when low tide wasn’t very low, but since this weekend the tides hit record lows I will first post about these finds. First up, the sheltered estuarine conditions in Penryn river in Flushing, opposite Falmouth’s port. The conditions are silty, with lots of sponges, tunicates, variegated scallops, sea lemons, European cowries and enormous amounts of Squat lobsters (see also this old post). With the tide this low, we were able to see some other stuff as well. The water went as low as the Eelgrass:Shannys, Rock gobies, Rockling, Worm pipefish and (to a lesser extent) Butterfish are easy to find in Flushing. Today we saw for the first time two Connemara clingfish Lepadogaster candollei (first pic). Next a Rock goby Gobius paganellus. We also saw many large Tompot blennies Parablennius gattorugine which live subtidally and only now could be seen:
As the aquarium is currently in a state of limbo, I thought it would be fun to take a look at the critters that have been most rewarding to keep in the year or so I’ve had my aquarium. Based on my personal experience, I have made an, admittedly completely arbitrary, top 10 of animals for a Cornish (or North-Western European) marine aquarium. I picked animals that were both easy to collect (i.e. common), easy to keep (not requiring live food and resistant to water temperatures up to 25C) and fun to watch. Here goes with the first part of the list!
10: Netted dogwhelk Hinia reticulata
Not the prettiest of molluscs maybe, but very easy to find and very easy to keep. Burrowing in sand, and moving surprisingly fast over the bottom when smelling food. Their smaller (and prettier) cousins the Thicklipped dogwhelk Hinia incrassata never survived for long in my unchilled tank.
9: Common hermit crab Pagurus bernhardus
8: Shanny Lipophrys pholis (or Rock goby Gobius paganellus)
Shannies are probably the most common fish to find in rock pools. They are very easy to keep, their coloration is not particularly vivid but not dull either and they are quite active. The only downside is that they prey on molluscs and other small critters. Feeding them a bit more might prevent this, but especially the rock gobies are so voracious that I doubt that (one was so swollen I thought it was dying, until I realized that it had gorged itself on defrosted artemia…). Montagu’s blenny Coryphoblennius galerita is prettier and smaller than the shanny but much harder to find (see this post for experiences with other fish species).
7. Thicklip grey mullet Chelon labrosus
Most rock pool inhabitants live on or near the rocks, but it looks nice if the aquarium also have some fish swimming in the water column. Mullet are very common, and small individuals form nice silvery schools (which are almost impossible to photograph as you can see). They don’t really interact with the other tank inhabitants.
6: Painted top shell Calliostoma zizyphinum
One of my favorite local molluscs: a bright purple shell with an orange colored snail inside. Shells are never covered with algae as the snail wipes it clean with its foot (the shell can still be damaged of course as seen in this individual).
The next post will feature the top 5 of animals for the unchilled aquarium.
When it was very low tide last week, I decided to skip the ‘rock pools proper’ on my local beach in Flushing and to check out the zone just below where the rocks and the sandy bottom of Penryn River (an arm of the Fall Estuary) meet. All common rock pool inhabitants – winkles, top shells, edible crabs, worm pipefish and shannies – still live here, but some other organisms are more abundant here than in the rock pools.
In addition to sponges, I noticed quite a lot of the colony-forming ascidian Botrylloides leachi (see previous post). That explains why I could also find a couple of European cowries Trivia monacha, their predator. Also very common here are the Variegated scallop Chlamys varia and the Thicklipped dog whelk Hinia incrassata (top right picture). I am not sure what the slimy beige stuff is!
Very common were little Squat lobsters Galathea squamifera (no picture), rapidly swimming backwards to escape. Even more abundant were these little Hooded prawns Athanas nitescens:
Time for an update on the tank. Switching to two lamps instead of one looks good but has not brought the iridescence of the Bushy rainbow wrack back. I could not resist putting a new specimen in. Iridescence is defined as the property of certain surfaces to appear to change color as the angle of view or the angle of illumination changes. Left: viewed from below, right: viewed from above.
I noticed that the underside of the rock the weed was attached to harbored a nice little strawberry worm, but before I could photograph it, the large rock goby gulped it down. It is noticeable that the fish have full bellies after putting in a new piece of seaweed, which is no surprise as there is so much growing on and in it.I have seen the very cute amphipod Caprella acanthifera which looks like a tiny, marine cross between a praying mantis and a caterpillar, but since they did not come not near the glass I could not get a good shot. I have seen one Cushion star Asterina Phylactica as well, which looks nicer than the light grey Asterina gibbosa I have. I also noticed a couple of Cerithiopsis tubercularis (3-4 mm):
The tank is completely full of snakelocks anemones, hundreds maybe:
In the foreground an Idiotea isopod; there are many of these sitting on seaweed branches and occasionally swimming around, although most of them will probably be eaten by now. Finally, three seaweeds have started to grow from the pump outlets. Dudresnay’s whorled weed, a fine purple weed and a broadleaved red seaweed. I have placed adult plants of the latter species (30 cm or so) in my aquarium before, but these were quickly eaten. It is either a type of laver or dulse, but I am not sure. It has also settled on the glass, but seldomly grows ‘leaves’ on there. Growing in the water current protects the weeds from predation from shrimps, let’s see how big they can grow!
When looking for pictures of the squat lobster, I realized I have quite some neat old pictures to post. I should have started the blog when starting up the aquarium to keep things chronological, I will use the next couple of posts to get rid of this back log. First the fish. I have two Rock gobies Gobius paganellus in my tank. The big one is voracious and after a feeding session has a visibly distended belly. It is a curious fish that often comes to check me out when I am taking a picture. It is beautiful too:
However, I will attempt to catch it and release it, as I suspect it to be a bit too large (three inches) and rash. My worm pipefish Nerophis lumbriciformis are very shy and they might be bullied by large gobies and blennies. I actually suspect the big rock goby to have eaten my recently disappeared beautiful little Montagu’s blenny Coryphoblennius galerita, a species I have only found one time:
A worm pipefish Nerophis lumbriciformis. To replace the rock goby, I will try to catch some Two-spotted gobies Gobiusculus flavescens later. This species is also beautiful, but smaller and it spends more time in the water column which is nice. It is not a rock pool inhabitant though; it lives among seagrass. I have seen many last year when snorkelling. I need to look into a good net to catch them! I had two large Shannies Lipophrys pholis as well that I released again, I still have a small one left:
I also had three thick-lipped mullet Chelon labrosus in the tank. These fish are quite ugly as adults, but juveniles are nice, restless silver fish. All fish mentioned above are benthic (hang around the rocks rather than in the water column), whereas this species mostly swims at the surface and so really adds to the aquarium. I released these three when changing up the tank once and I now regret that. They are fast swimmers so quite difficult to catch (at least with the small aquarium net I use). Since they are so restless I did not manage to take a decent photograph. I have also added a Shore rockling Gaidropsarus mediterraneus and the cling fish the Cornish sucker Lepadogaster purpurea at one point. I should have known that these were mistakes as these are fish that mainly hide under rocks and I have not seen them since adding them to the aquarium. I will post some pictures of these fish in their natural habitat later.