Due to
its distinctive nature, Lake Jezero attracted the attention of researchers from
an early period. The first scientific study was carried out as far back as 1874
(Cubich). It can be concluded that this is the most intensely and best studied
ecosystem in the area of the Municipality of Omišalj. In the past, it had great
importance for the economy of Omišalj in terms of fishing and hunting.
The
lake is located close to Njivice just a hundred metres from the
Omišalj-Malinska road. Its waters cover an area of approximately 35 hectares, and
the reed and peat along the shore cover approximately 60 hectares. Depending on
the water level, the lake is between 7.9 and 9.9 m deep. At its lowest water
level, the bottom is 7 metres below sea level (a cryptodepression). Hunting,
fishing and access to the lake are prohibited in the first water protection
zone, which has been fenced off. This contributes to the preservation of its
flora and fauna.
As the
largest natural freshwater habitat on the island of Krk, Lake Jezero is
extraordinarily important for the preservation of the biodiversity of the
island of Krk and the wider Kvarner region. In the lake and its surroundings,
there are numerous types of wetland and freshwater vegetation, which are
otherwise rather rare in karst areas. Wetland species that grow in the lake
include the common reed (Phragmites australis), bulrush (Typha angustifolia and
T. latifolia), simplestem bur-reed (Sparganium erectum), common club-rush
(Schoenoplectus lacustris), yellow flatsedge (Cyperus glomeratus), common
water-plantain (Alisma plantago-aquatica), water mint (Mentha aquatica),
bugleweed (Lycopus europaeus), and others. The flowering rush (Butomus
umbellatus) has also been found, which is a nearly threatened taxon. Aquatic
plants (macrophytes) include the water lily (Nuphar luteum), water milfoil
(Myriophyllum spicatum), floating pondweed (Potamogeton natans), and others.
Saw sedge (Cladium mariscus) is particularly important because of its
distinctive features and rareness.
The
lake is home to indigenous fish species such as the eel, but also to several
non-indigenous species that have been introduced, such as carp (Cyprinus
caprio), pike (Esox lucius), tench (Tinca tinca), and mosquitofish (Gambusia
affinis). In the 1970s, people introduced the grass carp (Ctenopharyngodon
idella) and silver carp (Hypophthalmichthys molitrix) into the lake, which
caused a significant decline in submerged aquatic plants (macrophytes) and
multicellular green algae (Chara sp., Nitella sp.)
The zooplankton
includes numerous water fleas, copepods and rotifers. Three species of
amphibians and pond turtle (Emys orbiculatus) have also been observed.
Lake
Jezero is also important for the migration and wintering of birds. The wetland
vegetation provides an ideal habitat for numerous nesting birds, such as the
great crested grebe (Podiceps cristatus), wild duck (Anas platyrhynchos), reed
warbler (Acrocephalus scirpaceus), Cetti's warbler (Cettia cetti), and others.
In spring and autumn, an intense migration of songbirds takes place over Lake
Jezero (swallows, house martins, sand martins, yellow wagtails, kinglets, and
others). Other frequent bird species include herons (grey herons, great white
herons, little egrets), short-toed snake eagles, and others.