SOME STRANGE NURSERIES
As a rule, nests or nurseries are unknown in the world of fishes. They lay their eggs and leave them; and the young ones have to fight their own battles, in a sea full of fierce and hungry enemies. Indeed, it often happens that a parent fish is eager to make a meal of its own children!
The Codfish lays about nine million eggs! You would hardly expect the female Codfish to make a nursery for such a family! She would be much worse off than the "old woman who lived in a shoe." As a matter of fact, the eggs are laid in the open sea; and the Cod shows no interest in them, but leaves them to become food for many a roving enemy.
Those cousins of the Shark,--the Skate and the Dog-fish,--are more careful of their eggs. Have you ever found their empty eggs on the sea shore? Children call them "mermaids' purses." But they are more like little horny pillow-cases than purses.
When first laid, the Dog-fish's egg has a very long string or tendril at each corner. As the fish lays the egg, she winds these tendrils round and round a sea-plant; thus the egg is fixed firmly until the young one is ready to escape from within [(see p. 49)].
The Skate's egg is much the same, only there is no tendril, but a curved hook at each corner. These hooks, of course, serve as anchors to hold the egg: no doubt they catch in weeds and stones. One fish, you see, ties her eggs with strings, the other uses anchors. These large "purse eggs" are like cradles, and the baby Skates do not slip out of them until they are quite ready to look after themselves in the ocean.
There are fish in the sea which take great pains to save their eggs and babies from harm; they will even defend them at the risk of their own lives. Of course these careful parents do not have huge families, like the Cod. No; the fish that care for their young have small families, but the babies have a much better chance of living than the baby Cod. It is one of Nature's wise laws.
Our common Stickleback--"Tiddler," or "Red-throat," as boys call him--builds a nest in ponds. He has a seaside cousin, the fifteen-spined Stickleback, who is also a nest-builder. This little fish is fairly common round our coasts, living in weedy pools by the shore, where it devours any small creature unlucky enough to come near. It is about six inches long, this sea Stickleback, with a long snout, and its body is very thin near the tail.
To build his nest, this little fish chooses a quiet corner, then gathers pieces of green and purple seaweed. He takes the pieces in his mouth, pushing them about until the shape is to his liking. Having got his nursery to the right size and shape, the little builder next fastens it together. How can he do this? What mortar can he find in the sea? It is quite simple. He uses threads, which come from his own body. He swims round the nest, again and again; and, each time, a thread is spun, binding the clump of weed into a safe, tight nest for the eggs. When the task is done there is a weed-nursery about the size of your fist. Now all is ready for the eggs to be laid by the female Stickleback. You would expect them to be kept in a hole amid the nest, would you not? Instead of that, they are tucked a few here, a few there, in the weed.
Let us look at another nest-builder--the Sand Goby, or Spotted Goby, He is common enough in the pools at low tide, but not easy to find. You can look at him, yet not see him! For he takes the same colour as the rocks and sands of his home. Amid the glinting lights and shadows of his rock-pool, with a background of sand, rock, and weed, this little fish is nearly invisible. Of course it is a dodge, and a useful one, to escape the eye of the enemy!
Perhaps you will not think the Spotted Goby so clever at nest-building as the Stickleback. He likes to use a "ready-made" house, whereas the Stickleback finds his own "bricks and mortar." In the pools of the shore there is no lack of houses to let, the empty homes of shell-fish are there in plenty. So the little Goby, when nesting time comes, hunts round for the empty shell of a Cockle lying with its hollow side to the sand.
This shell is to be used as the roof for the nursery. The Goby's next task is to make a hole beneath the shell. He sets to work and, by scooping out the sand, makes a hole about as large as a marble. To keep the sand from tumbling in, he smears the hole with slime, which soon binds hard like mortar. Now the nursery is nearly ready; but a passage-way is made, passing under the edge of the shell, and then, to make things quite safe, the whole roof is covered with sand: it then looks more like a bump in the sand than a fish-nursery.
The female Goby enters the nest, and leaves her eggs in it; and then the little father fish is left in charge. He rests on the sand, near the entrance. When the little ones appear, he seems to think he has done his duty. So away, he swims, not staying, like the father Stickleback, to guard the youngsters. Again we see that the father, and not the mother, is the builder and nurse.
That very strange creature, the Pipe-fish, has the most peculiar nursery of all. He uses no building material! No made-up nest of weed or sand for him! No, he prefers to carry his eggs in his pocket. To be more exact, there is a small pouch under his body, and there the eggs are kept until they hatch. Meanwhile, the Pipe-fish goes about his affairs in the pool as if nothing particular had happened. You will see more about this funny little fish when we come to our lesson on "The Fish of our Rock-pools."
EXERCISES
1. What are the eggs of the Skate and the Dog-fish like? 2. How does the Sea-stickleback build his nest? 3. Where would you find the Sand Goby, the Pipe-fish, and the Sea-stickleback? 4. How does the Sand Goby build its nest?