3 Fish biology and anatomy Биологија и анатомија на ... - UNDP
3 Fish biology and anatomy Биологија и анатомија на ... - UNDP
3 Fish biology and anatomy Биологија и анатомија на ... - UNDP
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60<br />
Biology<br />
Eels live in freshwater, <strong>and</strong> spawn in sea<br />
water for which it makes a long journey<br />
followed by significant anatomical,<br />
morphological <strong>and</strong> physiological changes.<br />
The spawning peaks are from the beginning<br />
of March until July in the Sargasso Sea,<br />
in the western sub-tropical Atlantic (about<br />
26 ο N 60 ο W) at a depth of 100-200 m<br />
<strong>and</strong> approximately 20 ο C. Adults die after<br />
spawning. Larvae emerging from the egg<br />
have a length of about 5 mm.<br />
As leptocephali (first eel larval stage), driven<br />
by the Gulf Stream <strong>and</strong> north Atlantic Drift<br />
they reach the continental slope at about<br />
65-70 mm<br />
Distribution<br />
It is found in all European rivers draining<br />
into the Mediterranean, the North <strong>and</strong><br />
Baltic Seas <strong>and</strong> in the southern Atlantic<br />
to the Canary Isl<strong>and</strong>s. It rarely enters the<br />
White <strong>and</strong> Barents Seas, recorded eastward<br />
to Pechora. Small numbers enter the Black<br />
Sea, migrating east to the Kuban drainage.<br />
Occasionally individuals reach the Volga<br />
basin through canals. It is stocked in most<br />
inl<strong>and</strong> waters. Large parts of the population<br />
remain at sea (north-western Atlantic <strong>and</strong><br />
Mediterranean). Before the construction of<br />
hydropower plants on the River Drim, their<br />
migration route to Lake Ohrid was open.<br />
After the construction, regular stocking<br />
was carried out in Lake Ohrid as well as the<br />
Glabochica <strong>and</strong> Shpilje reservoirs in order to<br />
preserve the population. However, officially,<br />
the Prespa Lakes were never stocked with<br />
European eel.<br />
<strong>Б<strong>и</strong>олог<strong>и</strong>ја</strong><br />
Јагул<strong>и</strong>те ж<strong>и</strong>веат во слатк<strong>и</strong>, а се мрестат<br />
во морск<strong>и</strong> вод<strong>и</strong>, порад<strong>и</strong> што патуваат <strong>на</strong><br />
огром<strong>на</strong> одалеченост пом<strong>и</strong>нувајќ<strong>и</strong> н<strong>и</strong>з<br />
з<strong>на</strong>чајн<strong>и</strong> а<strong>на</strong>томск<strong>и</strong>, морфолошк<strong>и</strong> <strong>и</strong><br />
ф<strong>и</strong>з<strong>и</strong>олошк<strong>и</strong> промен<strong>и</strong>. Мрестењето се<br />
одв<strong>и</strong>ва во пер<strong>и</strong>одот од почетокот <strong>на</strong> март,<br />
па сé до јул<strong>и</strong> во Саргасовото Море<br />
(западен суптропск<strong>и</strong> Атлант<strong>и</strong>к <strong>на</strong> околу<br />
26 ο N 60 ο W), <strong>на</strong> длабоч<strong>и</strong><strong>на</strong> од 100-200 m<br />
<strong>и</strong> температура од околу 20 ο C. Возрасн<strong>и</strong>те<br />
ед<strong>и</strong>нк<strong>и</strong> ум<strong>и</strong>раат по мрестењето. Ларв<strong>и</strong>те<br />
ко<strong>и</strong> <strong>и</strong>злегуваат од <strong>и</strong>кр<strong>и</strong>те <strong>и</strong>маат долж<strong>и</strong><strong>на</strong><br />
од околу 5 mm.<br />
Распространување<br />
Се среќава во с<strong>и</strong>те рек<strong>и</strong> во Европа ко<strong>и</strong><br />
се вл<strong>и</strong>ваат во Средоземното, Северното<br />
<strong>и</strong> Балт<strong>и</strong>чко Море, како <strong>и</strong> во Јужн<strong>и</strong>от<br />
Атлант<strong>и</strong>к, па сé до Ка<strong>на</strong>рск<strong>и</strong>те остров<strong>и</strong>.<br />
Ретко влегува во Белото <strong>и</strong> Баренцово<br />
Море. Мал број <strong>на</strong> ед<strong>и</strong>нк<strong>и</strong> влегуваат<br />
во Црно Море, м<strong>и</strong>гр<strong>и</strong>рајќ<strong>и</strong> <strong>и</strong>сточно кон<br />
сл<strong>и</strong>вот <strong>на</strong> реката Кубан. Повремено<br />
<strong>и</strong>нд<strong>и</strong>в<strong>и</strong>ду<strong>и</strong> пр<strong>и</strong>ст<strong>и</strong>гнуваат <strong>и</strong> до сл<strong>и</strong>вот<br />
<strong>на</strong> Волга преку ка<strong>на</strong>л<strong>и</strong>. Се лов<strong>и</strong> во многу<br />
копнен<strong>и</strong> вод<strong>и</strong>.<br />
Голем дел од популац<strong>и</strong><strong>и</strong>те останува во<br />
мор<strong>и</strong>њата (северозападен Атлант<strong>и</strong>к <strong>и</strong><br />
Средоземно Море). Пред <strong>и</strong>зградбата<br />
<strong>на</strong> х<strong>и</strong>дроцентрал<strong>и</strong>те <strong>на</strong> реката Др<strong>и</strong>м,<br />
јагулата <strong>и</strong>маше отворен<strong>и</strong> м<strong>и</strong>граторн<strong>и</strong><br />
пат<strong>и</strong>шта. По <strong>и</strong>зградбата <strong>на</strong> бран<strong>и</strong>те,<br />
Охр<strong>и</strong>дското Езеро <strong>и</strong> акумулац<strong>и</strong><strong>и</strong>те<br />
Глобоч<strong>и</strong>ца <strong>и</strong> Шп<strong>и</strong>лје, редовно се<br />
пор<strong>и</strong>буваат, со цел да се зашт<strong>и</strong>т<strong>и</strong><br />
нејз<strong>и</strong><strong>на</strong>та популац<strong>и</strong>ја. Преспанск<strong>и</strong>те<br />
Езера оф<strong>и</strong>ц<strong>и</strong>јално н<strong>и</strong>когаш не б<strong>и</strong>ле<br />
пор<strong>и</strong>бен<strong>и</strong> со јагула.<br />
Biologjia<br />
Ngjalat jetojnë në ujëra të ëmbël, hedhin<br />
vezët në ujë deti që për ato është një udhëtim<br />
i gjatë i përcjellur me ndryshime të<br />
konsiderueshme anatomike, morfologjike<br />
dhe psikologjike. Kulminacionin e hedhjes<br />
së vezëve e kanë në fillim të muajit<br />
mars dhe zgjat deri në korrik në Detin<br />
e Sargaseve, në Atlantikun subtropikal<br />
perëndimor (rreth 26 ο N 60 ο W) në thellësi<br />
prej 100-200 m dhe në temperaturë<br />
përafërsisht 20 ο C. Ngjalat e moshuara<br />
vdesin pas hedhjes së vezëve. Larvat që<br />
paraqiten nga veza kanë një gjatësi prej<br />
rreth 5 mm. Si leptocefale, të bartura nga<br />
Rryma e Golfit<br />
Përhapja<br />
Gjendet në të gjithë lumenjtë e Evropës që<br />
derdhen në Mesdhe, në Detin Verior dhe<br />
Balltik dhe në Atlantikun Jugor të Ishujve<br />
Kanarie. Rrallë herë hyjnë në Detin e Bardhë<br />
dhe Barenc, të regjistruar në drejtim të<br />
lindjes për Pekora. Një numër i vogël hyn në<br />
Detin e Zi duke migruar në lindje në kanalin<br />
Kubanez. Nganjëherë disa arrijnë përmes<br />
kanaleve në basenin e Vollgës. Grumbullohen<br />
në shumicën e ujërave në brendësi të<br />
kontinentit. Një pjesë e madhe e tyre ngel<br />
në det (Atlantiku Veri-Perëndimor dhe Mesdheu).<br />
Para ndërtimit të hidrocentraleve në<br />
lumin Drin, rruga e tyre për migrim deri në<br />
liqenin e Ohrit ishte e hapur. Pas ndërtimit,<br />
sasi të konsiderueshme të ngjalave rregullisht<br />
barteshin në liqenin e Ohrit si dhe<br />
në rezervuarët e Glloboçicës dhe Shpiljes<br />
me qëllim që të ruhej popullata me ngjala.<br />
Megjithatë, Liqenet e Prespës asnjëherë nuk<br />
janë populluar me ngjalë.<br />
Κατανομή<br />
Συναντάται σε όλα τα ποτάμια που εκβάλουν<br />
στην Μεσόγειο, στη Βόρεια και Βαλτική<br />
Θάλασσα και στον νότιο Ατλαντικό στα<br />
Κανάρια Νησιά. Σπάνια εισέρχεται στην<br />
Λευκή Θάλασσα και στη Θάλασσα Barents,<br />
ενώ έχει καταγραφεί ανατολικά στην Pechora.<br />
Μικροί αριθμοί εισέρχονται στην Μαύρη<br />
Θάλασσα μεταναστεύοντας ανατολικά στην<br />
λεκάνη απορροής του Kuban. Περιστασιακά,<br />
κάποια φτάνουν στην λεκάνη του Βόλγα<br />
διαμέσου καναλιών. Βρίσκεται κυρίως σε<br />
εσωτερικά ύδατα (στην ενδοχώρα). Μεγάλα<br />
τμήματα του πληθυσμού παραμένουν<br />
στην θάλασσα (βόρειο-δυτικός Ατλαντικό<br />
και Μεσόγειος). Πρίν την κατασκευή των<br />
υδροηλεκτρικών σταθμών στον ποταμό Drin<br />
(Δρήνος), η οδός μετανάστευσής τους στην<br />
Λίμνη της Οχρίδας ήταν ανοικτή. Μετά την<br />
κατασκευή, πραγματοποιούνταν τακτικοί<br />
εμπλουτισμοί του είδους στην Λίμνη Οχρίδα<br />
καθώς και στους ταμιευτήρες της Glabochica<br />
και της Shpilje έτσι ώστε να διασωθεί ο<br />
πληθυσμός. Αντίθετα, επισήμως, στις Λίμνες<br />
των Πρεσπών δεν έγιναν ποτέ εμπλουτισμοί<br />
χελιών.<br />
Βιολογία<br />
Τα χέλια ζούν σε φρέσκο νερό και<br />
αναπαράγονται σε θαλασσινό νερό<br />
για το οποίο κάνουν μεγάλο ταξίδι που<br />
ακολουθείται από σημαντικές ανατομικές,<br />
μορφολογικές και φυσιολογικές αλλαγές.<br />
Η κορύφωση της αναπαραγωγής γίνεται<br />
από τις αρχές Μαρτίου μέχρι τον Ιούλιο σε<br />
περιοχές της Θάλασσας των Σαργασσών,<br />
στον δυτικό υποτροπικό Ατλαντικό<br />
(περίπου 26 ο N 60 ο W) σε βάθος 100-200<br />
μέτρων και σε θερμοκρασίες περίπου<br />
20 ο C. Τα ενήλικα πεθαίνουν μετά την<br />
αναπαραγωγή. Τα ιχθύδια που εξέρχονται<br />
από το αυγό έχουν μήκος περίπου 5mm.
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