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A fascinating World under Water
NORWAY
Part two
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Pictures and text by Erling Svensen
Many fish spend part or all of their lives in the Laminaria zone. On
such is one of Norway’s most beautiful fish, the Norway bullhead,
Taurulus lilljeborgi. Is has a mottled body colour which changes to
match the background to maintain its camouflage. Reds, browns and
yellows are among the predominant colours. It relies on the colouring
to get its prey. It lies motionless, unseen until its food swims
within range when it lunges forwards and takes the fish into its
cavernous mouth. Even the cod, which often hunt in the kelp beds, can
change their colour to some extent. Those living among the red algae
are redder than those in the green algae. Cod over sandy bottoms tend
to be yellower than those over rocky areas.
Crustaceans are well represented here. The edible crab Cancer pagurus
occurs in large number in the crevices, lobsters inhabit other hollows.
In winter, as the temperature approaches zero, both the lobster and
the edible crab retreat to the warmer, deeper water. The anomuran
crustaceans (which include the hermit crab and the squat lobster) are
regarded as the most beautiful, but even though they are common, they
are rarely seen as they are nocturnal. The squat lobsters Galathea
strigosa and Munida rugosa are found under deeper rocks all the way up
to shallow water. Living amoung the kelp holdfasts are many species of
malacostracan crustaceans. Probably the most interesting are those in
the genus Caprella wich appear in abundance in the winter. The
resemble small marine praying mantises, waving their food into their
mouth. Often they are so abundant that there is one each square
centimetre of substrate. The females of these transparent glass
shrimps have a brood pouch on the abdomen in which the eggs are
carried.
Depending on the clarity of the water at some 25-30 m deep the kelp no
longer grows as there is not enough light to enable the spores to grow
into young plants.
Sandy plains
Between the outermost islands and the shore there are sand plains. Life
here is very different from that found in the kelp beeds. Down in the sand
there are many polychaete worms and molluscs. The polychaetes are an
important source of food for the fish that live over the sandy areas.
Some polychaetes burrow, some live in tubes whilst otheres are free
swimming. They have seperate sexes and fertilization takes place in the
sea. Of the stranger dwellers in the sand are the burrowing sea-urchin of
which the heart shaped Echinocardium is one of the best known. This animal
burrows through the sand using its fine spines in the manner of oars to
prograss and to eat small particles of organic matter. It takes in sand
grains at the front, digests any food particles and voids the inedible
waste at the rear. Their function in the sand ecosystem is rather like
that of worms in the garden soil. Large numbers can be seen on the surface
of the sand in midwinter when they come to the surface to spawn.
Many fish live on the sandy areas, some permanently. In this catagory
are the flatfish who live on, or just under the surface with only their
eyes showing. Some flatfish are the chameleons of their world with an
astonishing ability to change their body colour to match that of the
background. Particularly adept at this skill are the plaice (Pleuronectes
platessa), the dab (Limanda limanda), and of course the smallest European
represenative, the colourful Phrynorhombus norvegicus. Flatfish are almost
worldwide in distribution but all go through the same developmental
stages. When the young hatch from the egg they are like all other fish
with an eye on each side of the head. As they grow one eye moves to join
its partner on the other side of the head and the fish comes to lie on its
side. The side on which the fish comes to lie varies with the species, but
exceptions are occasionaly found i.e. a right sided individual will
sometimes turn up when the rest of the species are left sided.
The dragonet (Callionymus lyra), a small elongated fish with a broad head,
burrows as well. Its capicious mouth is highly protrusible and the eyes
are set high on the head so that it can see its prey while it is burried
in the sand. Looking more like fish from a coral reef than from the floor
of the north Atlantic they have a colour pattern of bright yellow and blue.
The male’s colour is more intense than that of the female and he has a
large flag-like first dorsal fin which he waves in the water to attract
the female.
The peculiar little pogge (Agonus cataphractus) also lives in the sand. It
has bony scutes in its otherwise scaleless skin which gives it a rather
prehistoric look. On the flat underside of the scutes there is a bush of
sensory tentacles that it uses to locate its food.
Innermost in the Egersund is the brigde that goes over to Eger Island.
Here the strong current surges through the channel and sand is washes out
over the fjord.
Read part
three
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