British Coldwater Marines

by Andy Gordon of England, and Michelle Stuart of Ontario Canada
Reprinted, with permission, from their web site Fishtanksandponds.net
Aquarticles

Bullrout                                  Photo by Andy Gordon

Here in the UK no one lives more than 2 or 3 hours from the sea. Which means there are loads of fish for free just waiting to be found. But first there are a few rules to do with safety and preservation which should be thought about in advance. Most of them just basic common sense.

If you stick to rock-pools with easy access, keep an eye on the tides, and wear sensible footwear able to cope with the sometimes slippery rock surfaces. Your safety shouldn't be compromised. Secondly, if you turn over any stones or lift seaweed, make sure you return it to how it was before moving on.

I don't know of any laws that are in force in the UK that make it an offence to collect a few specimens for your own aquarium but it might be a good idea to check, since the National Trust owns more and more of the beaches now.

One final point, make sure you know what it is you are collecting. There are a lot of large fish that use rock-pools as nurseries. When I lived in Cornwall for a while I kept a very nice little fish that I had caught in a rock-pool. It was 2 ins. at the time of capture, but it turned out to be a Corking Wrasse and within a few months it became far too big and was released. Since I only lived a few minutes away from the sea this wasn't a problem, but if you took one home from holiday it might well be one. There are also a few fish that you should avoid because they have a very potent sting - the Lesser Weaver fish is one example. If you get stung by one of these it will really hurt for 48 hrs. and you will need medical attention, so make sure you know what you are doing in advance.

The Fish
Shanny, Lipophrys pholis. This is a very common little fish, found in and around rocks and never in the open or over sand. It is a member of the blenny family. It eats almost any meaty food and is particularly fond of shellfish and small shrimps.
They grow to about 7" and can spend quite a time out of water without harm, in fact they sometimes do this voluntarily and bask on a rock above the water surface. I have also found them living in small damp crevices at low tide but well above the water line. They should be provided with a cave (for each specimen) a large shell is ideal for this. And they should be kept in a group. A word of warning: although they are quite small they do possess strong jaws and sharp teeth, and will not hesitate to use them. They are easily capable of drawing blood with their bite too (personal experience).

Rockling, Ciliata mustela. Grows up to 8".  I recommend that you do not try to keep this fish. I have caught two specimens (they look like eels with large whiskers) and each time the fish died within 24hrs., even though every care was taken and the tanks were fully mature and with a stock of healthy fish already present. No noticeable bullying occurred and the water parameters were all acceptable.

Fifteen Spined Stickleback, Spinachia spinachia. Grows up to 6". I have only ever seen two wild specimens of this fish and I have never kept them because they will only accept live food and require feeding several time per day. They will eat daphnia, tubifex, etc., so it is still easily possible to keep them. It should also be kept in a species tank because it is a fin nipper. This is one of the few species that if you can manage to feed and keep healthy it is very likely to spawn in captivity.

Bull Rout, Myoxocephalus scorpius. Grows to 12". This is another one to treat with caution. The books say, although not unanimously, that this fish is not poisonous. But if you get stung with one of the spines the wound will be very painful and it will swell. I would not risk touching one myself because they look like they are dangerous, so if it's one of nature's bluffs it works on me. They do make great subjects for the aquarium though. At first they tend only to accept live food, but with patience they will learn to take dead food so long has it moves, i.e. falling through the water. It eats small fish, so only keep it with larger fish. They are found in seaweed at the edge of rockpools.

Rock Goby, Gobius paganellus. Found in S.W. England. Grows up to 4.5". This is a very dark, almost black fish. After a while mine would eat flake food. A little bit secretive but easy to keep. There is a light orange tip to the first dorsal fin of the males. It is pale yellow in the females. You will have noticed that I said the first dorsal fin. Gobies have two dorsals one behind the other, and blennies have one long dorsal - that is how the two can be told apart at a glance.

Care
To keep the fish you should set up a tank in the same way you would for any marine fish, with the obvious exception of a heater. The starter units for the fluorescent lighting should be kept away from the tank too, because these are coldwater fish and will suffer at high temperatures. Although having said that, they are more tolerant of small changes in conditions than are most marine fish. They have to be, because when in a rockpool a sudden heavy shower can reduce the salinity of the rockpool water, and temperature can also quickly drop if they are in full sun in summer one minute, and dark shade and raining the next.

Ammonia - 0
Nitrite - 0
Nitrate - < 10 pH - 8.2 to 8.4
SG - 1.021 to 1.025
Temp < 65F
Stocking level - 1 inch of fish to 4 gal.
Water changes - 25% every two weeks

Stocking Level
I have suggested a really low stocking level due to the water being cold. The normal biological breakdown of waste takes much longer at lower temps, so the tank should be very well maintained and the use of a skimmer is very highly recommended.

Feeding
Almost without exception these fish require a diet high in protein. They will do well on a diet of proprietary frozen food intended for their tropical counterparts.
Mysis shrimp, lance-fish,  krill,  chopped mussel,  red plankton. In some cases marine flake.

As mentioned previously, it is vitally important that all uneaten food is removed from this system because at low temperatures the biological processes occur only very slowly, and any excess load will reduce the water quality.

Fish, Tanks and Ponds 2002 - 2004 All Rights Reserved