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:: MAIN
GEOGRAPHIC - HYDROGRAPHIC FEATURES ::...
 Lake
Ohrid, that came into being between four to ten million years ago, is Europe's
oldest lake, and is amongst the oldest in the world. It is a typical
oligotrophic lake, meaning that it contains low levels of nutrients. By its
origin the lake is a tectonic one and belongs to the so-called group of
"Desaretian lakes" (named by an ancient region called Desaretia). The
Lake came about in the tertiary period, prior to the glaciations.
Otherwise, most of
the lakes of the world came into being immediately after the end of the latest
glaciations period. Only a few lakes in the world are older than this one.
Famous examples are Lake Baikal, Caspian Lake, and Lake Tanganyka and just a few
lakes situated on Celebes, Philippines and China.
Research on the
living world of the Lake Ohrid has shown the existence of an exquisit flora and
fauna, prolific in endemic, as well as relic fauna forms. Thus, the Lake is
thought to be unique in Europe. Similarities can be found only with Lake Baikal
and with the Caspian Lake.
 Lake
Ohrid lies in the valley between
Ohrid
and
Struga, in the border
region between Macedonia and Albania. It is situated on 41 degree northern
latitude and 20 - 21 degrees eastern longitude, and its altitude is 695 meters
above sea level. It covers an area of 358.2 square kilometers, two thirds of
which belong to the Republic of Macedonia, and the rest to the Republic of
Albania. The shoreline is 87.5 kilometers long - the maximum length being 30.8
kilometers, and its maximum of 14.8 kilometers. The average depth is 164 meters,
and the maximum depth 289 meters. The Lake is surrounded by mountain ranges of
Mount Mokra (Mokra Planina - 1589 m.) and Jablanica (1945 m) on the Albanian
side and by the limestone ridge of Mount
Galičica
(2255m) on the eastern side. The surrounding mountains are extremely
carstic.
"Ohrid & Prespa Lakes
from satellite view"
Lake Ohrid is the
seventh deepest lake in Europe.
Most of the Lake's
water bulk comes from numerous surface and underground springs. That is the
reason certain researchers consider it unique in the world. Most of the surface
springs lie along the southern shore, near the monastery of St. Naum on the
Macedonian side, and near the villages of Tusemiste and Starovo and the town of
Pogradec in Albania. There are about 40 rivers and springs that flow into the
Lake (23 on Albanian, and 17 on Macedonian territory). During summer, most of
them dry out, whereas the rivers Sateska, Koselska, and Serava are the only
waters with significant water flow that feed up the Lake.
In the beginning of
this century Jovan Cviik stated his assumption that the water of the adjacent
Lake Prespa, with a water level 158 meters higher, will sink through the carst
areas of the mountains
Galičica
and Suva Gora. By using natural isotopes, in 1980 it was proved that the lakes
of Prespa and Ohrid were connected hydrographically. Evidence have confirmed
that more than 50% of the water from the springs near St. Naum come from the
Lake of Prespa.
The climate of the
Lake Ohrid is classified as a local-continental type. Medium annual temperatures
average to 11.4 degrees Centigrade. Medium monthly temperatures average to about
21.2 degrees in July and August, and 34.4 being the absolute maximum in August.
The lowest medium monthly temperature amounts to 1.5 degrees in January, whereas
- 17.2 degrees is the absolute minimum. The average annual rainfall in the Lake
basin amount to approximately 759 mm.
The most common
wind is the one blowing from north, particularly in autumn and winter. The winds
blowing from southern and south-east directions dominate during spring and
summer periods. Southeast and east winds are insignificant. Windy and calm
periods change during the day, particularly in summer. Mornings are
characterized by the shifts between blowing northern winds and calm periods.
Weather conditions become quite different in the afternoons when the southern
and south-east winds overtake the silence. Average speed of the wind in the
Ohrid region is relatively low, 3.4 m/sec.
The water
temperature in the deepest layers of Lake Ohrid is approximately 6 degrees
Centigrade, whereas the surface layers may warm up to 24 degrees, and even to 26
degrees closer to the shore.
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:: ANIMAL AND PLANT
WORLD ::...
  Lake
Ohrid is a distinctive shelter of large number of freshwater organisms
originating from the tertiary period, whose close relatives can be found in
fossil forms only. For precisely this reason it bears the name "Museum of
living fossils". Its remarkable age, continuing existence, geografic
isolation, and the permanency of its living conditions - all of these together
enabled most of its inhabitants to continue the process of their further
evolution up to this day. This also made it possible for the already existing
tertiary living forms in the Lake to further evolve into new taxonomic classes
including, subspecies, species, even entire families of newly evolved organisms.
Thus, the endemism (presence of distinctive, unique organisms), although less
underlined than in Lake Baikal, is the feature of the living world of Lake
Ohrid, comprising 88% of endoparasitic Infusoria (tiny parasitic organisms), 44%
of rabdocelite, and 71% of trikladite (flat worms), 90% of snails, 66% of small
crabs, and 60% of fish.
"Letnica - Macmus Salmo"
The so-called
intralacustric speciation process, particular for old, deep and large lakes in
the world, is on-going in Lake Ohrid and it has encompassed even the fish fauna.
"Valvata Bicarinata - Lea"
The size of the
Lake and the quality of its fish fauna underpin its significance in fishing
terms. The quality and economic importance of the fish population of the Lake
are of a far more higher level than that of the rest of Balkan's lakes, even
higher than the shallow and highly productive lakes of the Aegean region.
"Valvata stenotrema - Polinski"
The fish population
of Lake Ohrid comprises 17 native species belonging to four families: Salmonidae
(2 species), Cyprinidae (12 species), Cobitidae ( 2 species) and Anguillidae (1
species). Ten species are commercially important for the fishing industry,
priority being given to the two endemic and relic trout species - Ohrid Trout
and Belvica, with European Eel and Plasica following the first two. Several
analysis have been carried out since 1929. They have shown that the trout and
eel account for 45.6% of the catches. That is why the Lake is also called
"Trout Lake". The same analysis has shown that the catchments in the
Lake Ohrid, in terms of area units, is 9 kg/ha for the Macedonian part of the
Lake. This is caused by the low levels of nutrients and is another indicator of
its oligotrophic character.
 Ohrid
Trout is well-known worldwide and can weight more than 10 kg. However, in the
present conditions in the Lake it reaches the weight of 1 kg in the seventh year
of its life. The latter type of trout, Belvica, is smaller than the former. It
can reach 30 cm in length and weigh up to one kilogram, but rarely does, since
this weight can be reached only in the twelfth year of its life. The fish
Plasica is caught during winter period and can reach 5 to 15 cm in length. The
famous Ohrid Pearl is produced by using special technology for processing its
scales.
Alongside these
fish species, there are also chub, carp, skobal, grunec, etc.
Due to the main
focus on Ohrid Trout in fishing, the Hydro biological Institute was founded in
the far back past, in the year 1934. Its establishment, along with the
installation of its reproducing units, marked the beginning of Ohrid Trout
artificial spawning process aimed at stocking Lake Ohrid with Ohrid Trout
progeny. Ever since this process has been continuously advanced. Up til now, the
Lake has been stocked by over 520 million pieces of Ohrid Trout offspring
cultivated to various ages and sizes - starting from larvae and up to the age of
18 months. Sexually matured fish caught in the Lake are used in the process of
"artificial spawning". First roe and milt are pressed out from the
fish. Then, they are mixed in the water environment resulting with in situ
insemination of the roe. The inseminated roe is then transported into the
reproducing units and further nurtured before being stocked into the Lake. The
Lake is also stocked with the spawn of the European eel, a species whose natural
production circle has been discontinued.
 The
fauna in the Lake also includes freshwater shells, crabs, sponges, etc. There
are four types of sponges in the Lake, amongst which is the most famous endemic
round Ohrid sponge that lives in 40-50 m depth.
The Lake's fauna is dominated by various types of algae and superior water
plants. Typical for Lake Ohrid is the underwater plant called "hara",
that forms a continual ring on the lake's bottom, at the depth of 6 - 15 m.
There are also
endemic species in the plankton population (tiny microscopic organisms floating
or drifting in the water) - both in zooplankton (animal component) and in
phytoplankton (plant component). |
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