Sunday, October 10, 2010

Crabs and Lobster of Croatia. 2007


In continued the isssuance of the fauna theme on stamps series, the stamps series of Lobster have issued by Croatian Post Office on year 2007. The species have depicted are Lobster ( Palinurus elephas ), Norway Lobster (Neophrops norvegicus) and River Crayfish (Astacus astacus).

Lobster (Palinurus elephas).

Lobsters are species of the genus Palinurus – long-tailed or spiny lobsters which are distributed from Norway on the north, along the western coast of Ireland, the western and southern coast of the British Isles (to the north up to the Orkney Islands and Shetland Islands), to the south to the Azores, in the western Mediterranean and the Adriatic Sea and the Aegean Sea. Lobsters can be found in the open deep-sea rocky bottom in the circa-littoral and infra-littoral zone (below the sub-littoral zone of the tide) at the depths of 5 to 70 metres,

They actively migrate in the course of the year into greater depths of the Atlantic to return to the shallower parts of the -coastal area.The body of adult lobsters is covered with a thick shell, an exoskeleton. The adult samples have the total length of between 40 to 50 cm, (maximal length up to 60 cm), and weigh between 6 to 8 kilos. The males are usually larger than the females. They do not grow continuously but through molting, which means when they lose their rigid shell and while their body is soft they grow in length and then their shell gets rigid again. They are omnivorous though their diet is mainly based on brown bullhead, mollusks (snails and shells), shrimp larvae, invertebrate, Pentapora fascialis and seaweed. They are social animals, gathering in groups.The population has been significantly decreasing due to the fishing results and the average smaller length of the caught lobsters.

Norway lobster (Nephrops norvegicus L.)

Norway lobster (Nephrops norvegicus L.) often called scampi belongs to the family Nephropidae – crawfish .The animal lives in the soft sediment of the Atlantic Ocean (from Iceland on the north to Portugal and Morocco on the south), the Mediterranean and Adriatic Sea. The densest populations in the Adriatic Sea have been recorded near the island Jabuka/Poma, in the Velebit channel, in the sea of the Kvarner Bay and in Kvarnerić. They live at the depth of between 200 to 800 metres but they can also be found in shallower parts.

Norway lobster dig burrows in the muddy bottom for their place of life. The burrows are 10 cm in diameter, about one meter long and enter the muddy bottom some 20 to 30 centimetres. Norway lobster stay in their burrows during the day, and at sunset they come out to find some prey.Norway lobster are solitary predators feeding mostly on molluscs and other crabs, but they also eat dead animals. Norway lobster live on their own burrow , sometimes share the with other crabs (scampi).

The body of the Norway lobster is slim, orange-pink in colour, elongated and flat laterally. The head and thorax are fused into a non-segmented cephalothorax, while the abdomen consists of clearly segmented carapace ending with a fan-shaped tail that helps the lobster to swim. The first three pairs of legs bear claws. The first pair of claws is very narrow and elongated and has laterally placed longitudinal spiny ridges. Their eyes are large, black and placed on mobile stalks.Females grow to 17 cm in length and males up to 25 cm.It is known that they can live up to the age of 15 years. They spawn once a year, usually in summer.

River crayfish or noble crayfish (Astacus astacus L.)

The river crayfish or Astacus one of the four autochthonous species of freshwater decapodous crabs from the family Astacidae that lives in Croatian rivers and lakes. They live in rivers and lakes with clayey and pebbly bottoms and along the coast among the water vegetation. In Croatia they are spread in the waters of the Sava and Drava river-basin, and they have also been brought into some rivers of the Adriatic river-system territory

The river crayfish rarely grow bigger than 15 cm in total length. On the back side the animal is usually dark brown (olive green to black, sometimes bluish or reddish), while the lower side is green-brown coloured. The surface of the body is covered by a strong “shell”, a carapace (exoskeleton), so that crayfish cannot grow continuously. In the warmer seasons of the year they molt – lose their old shell. While they are soft they grow in length and grow a new, strong exoskeleton, usually using minerals from the old shell by eating it.

The river crayfish are nocturnal and sedentary animals, living on the bottom, they are not territorial but show aggressive forms of behaviour in cases when the space becomes a limiting factor. It is well-known that this type of a small radius of movement is characteristic of animals adapted to a habitat.

The river crayfish is endangered by the great quantities of waste matter in water ecosystems, the regulation of water courses and the excessive uncontrolled fishing out. Therefore the river crayfish in Croatia is to the full protected by law . It is also protected on the European level as a rare and endangered species and listed in the IUCN ((International Union for the Conservation of Nature and Natural Resources) Red List of Threatened Species.

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