Marine biology


The submarine area of the Vis Archipelago has always been exceptionally heterogenous with rich biodiversity. One of the most characteristic sea mammal species which inhabit the arhipelago is the bottlenose dolphin. The bottlenose dolphin population size estimates are the minimum of 250 mature adults, and the Vis archipelago is the area where bottlenose dolphin raise their young. Around the waters of Biševo and on the southwestern coast of the island of Vis there are as many as 181 macroalgae families, 2 species of seagrass, 269 of invertebrates, 347 of phytoplankton and 100 zooplankton families and 4 whale species. Alongside 114 fish species recorded in the wider area of the Vis archipelago, there is also the total of 1017 registered families. Na strmim morskim dnima Viškog arhipelaga, na mjestima sa smanjenom vidljivošću i jačim Along the steep underwater seabeds of the Vis archipelago, in places with poor visibility and stronger currents, a heterogenous coralligenous biocenosis has developed, with gorgonias, stony corals, bryozoans, lobsters, starfish and other numerous organisms taking up the surface of approximately 1210 ha.

RED CORAL (Corallium rubrum)

Red coral is part of the Animallia Empire of the underwater fauna, a member of the Phylum: Cnidaria and the Genus: Corallium.

Red coral is an animal that grows in colonies. An exoskeleton made of calcium carbonate, fan-shaped spreading in the shapeof a tree.. It is usually found in the range of 10 - 30 cm in height. The red coral is distinctly red in color and wears 8 white polyps which he use for feeding and hunting. The red color from whom this cnidarian is named, comes from the carotenoid pigment while the polyps are distinctly white. Adult’s base diameter is about 3 cm. It is a sessile animal which depends on the sea water flow and on nutrient deposits. Thus the colonies must adapt to the intensity and direction of water flow. They can be planar in shape and directed in one plane in the direction of water flow, but in case of multidirectional water flow, the coral is bushy (three-dimensional) in shape.

Red coral grows slowly, 3-4 cm per year in height. It can live a very long time, even over 100 years. Although red coral colonies can be found in the range of 20–200 m, today, due to intensive hunting and exploitation in the Adriatic Sea, they are rarely found at depths less than 60 m.

It prefers shaded cliffs and marginal parts of caves. Coral is a stenothermic animal, sensitive to changes in the temperature of the marine environment which causes a coral disease called necrosis. Due to the negative impact of elevated temperature, the coral skeleton becomes white. Excep on climate change and rising of sea temperatures red coral is also sensitive onsea pollution

Red Coral is spreaded mainly in the western part of the Mediterranean, and in the Ionian and Adriatic Sea.

According to the Nature Protection Law (NN 70/05, NN 139/08), red coral is a protected animal and it is recognized under the European Union Habitats Directive The usage of red coral is regulated by regulations on marine fishery.


The common bottlenose dolphin is the best known of alldelphinidspecies. According tothe latest abundance estimate based on data collected by Blue World Institute, there is a community ofaround 300 resident bottlenose dolphins inhabiting the waters around Vis Island (including Hvar, Korčula, Sušac and Lastovo). Due to their presence, a part of Vis archipelago was included in the Natura 2000 European ecological network as one of six important areas forbottlenose dolphin conservation in Croatia.

The majority of bottlenose dolphins inhabiting this area are well known to researchers who are able to identify them using photographs of the animal, most often its dorsal fin. Throughout their lives, dolphins participate in various interactions with other individuals, resulting in injuries and scars on their body and particularly their dorsal fin that form a "fingerprint" of sorts and contribute to the distinctivenessof an individual. This makes itpossible to follow individual dolphins through years. Researchers usually give names to dolphins for easier data handling. Around Vis island it is therefore possible to observe Babalina, Matko, Grof, Dee Dee, Sir David or some other resident dolphin that has been regularly appearing in this area. Because there is no apparent visible difference between the genders, their names are often mismatched with respect to their sex. For instance,dolphins withmale names - Fratun and Eugen, arefemales and caring mothers which have hadseveral calves in the meantime.

Dolphins in the Adriaticusually mate in the spring, and given that pregnancy lasts for a year, the first calvesare also born at the end of spring and in early summer. At this time of year, the sea temperature has already increased enough to alleviate thedanger of excessive heat loss to new-born calveswith only a thin layer of subcutaneous fat. They are also left with a few warm months and enough time to accumulate fat tissueto protect them during the winter. Abottlenose dolphin female can give birth to five to eight calves in her lifetimewhich are highly dependent on their mother during the first few years. They suckle milk and are in close physical contact with their mother most of the time. They becomeindependentand separate three to five years after birth. Adult dolphins live in fission-fusion societies where groups of individuals are easily formed and broken up and can do this frequently, even many times during a single day. However, there are also long-term associations between some animals that can last for years.

Bottlenose dolphins are faced with numerous anthropogenic threats and are a strictly protected species. In the past, they were targeted by fishermen who considered them pests and today they are threatened by pollution and overfishing. Direct threats are by catch in fishing gear and mortality caused by plastic and other marine litter which they can swallow or get entangled in. Additionally, marine noise pollution has increased manifold over the last century and is impairing dolphin communication as well as the communication of other marine animals, affects their orientation and ability to hunt for prey and can have long-term effects on the overall fitness of an individual and the whole population. A sudden increase in the number of noisy vessels around the Island of Vis during the summer months, when most calves are born, certainly has a significant impact on the well-being of the community. Dolphins are also exposed to additional stress due to harassment by irresponsible individuals.

If you observe dolphins, approach them slowly and sideways. Maintain a distance of at least 50 meters to the group, unless they decide to approach you. Avoid sudden changes of speed and direction and do not follow them from behind. If you observe new-born calves or individualstail-slapping the surface as a clear sign of discontent, leave the group immediately. Dolphins are wild animals that need to feed and rest to survive, and your presence is almost always a disturbance. Hence, enjoy their presence, photograph them and share your impressions with others, but do not stay with them longer than 30 minutes.

You can support the research and conservation of bottlenose dolphins by adopting oneat!


The Adriatic Sea is one of the most important foraging and wintering areas for loggerhead sea turtles in the Mediterranean. Data collected by Blue World Institute indicate their abundance in the summer months is in excess of tens of thousands of individuals, with most animals inhabiting the northern Adriatic! In spite of this high abundance, they are rarely encountered alongside the Croatian coast and in the channels as they mostly inhabit open waters. Sea turtles are cold-blooded animals and have to warm up in order to move so they are most often observed while sunbathing on the sea surface.

Sea turtles can be regularly observed in the vicinity of Vis Island, situated in the midst of a migration route used by loggerheads travelling from the eastern Mediterranean, where they hatch, towards the northern Adriatic where they grow and spend the winter. During reproductive season, adult sea turtles from the Adriatic (and other parts of the Mediterranean) migrate back towards Greece, Turkey and Cyprus where most sandy beaches used for laying eggs are situated. Sexually mature individuals mate in the sea in front of the nesting sites, after which females lay eggs in holes they dig during the night. Adult females do not reproduce every year but will nest several times during a single reproductive season. Interestingly, the sex of the hatchlings is determined by the temperature within the nest that is prevailing during the incubation period lasting roughly 60 days. A nest temperature of 30°C or higher will result in a higher ratio of female hatchlings and vice versa.

Animals that have not migrated for reproduction stay in the Adriatic all year long. Their abundance in parts of the basin changes depending on water temperature which is responsible for a seasonal migration during the colder periods. Animals move from the shallowest northern Adriatic in areas around Venice and the coast of Istria to the deeper waters alongside Susak and Dugi islands and further towards the central and southern Adriatic.

Loggerhead sea turtles are threatened by many human activities. A significant drop in abundance is attributed to hunting of adult individuals and egg harvesting. Today, the largest threats to loggerheads in the Mediterranean arebycatch in fishing tools (responsible for thousands of deaths per year) and pollution, especially with respect to plastic debris, causing further mortality. Thanks to intensive nesting site protection activities, the population of loggerheads in the Mediterranean is recovering. However, loggerheads regularly use a very large marine area spanning well outside the scope of the territory of any individual country. This is why nesting site protection is not the only solution. You can contribute to their conservation and protection by avoiding the use of plastic items such as disposable bags, straws, plates and similar as well as by slowing down at sea, thereby avoiding collisions with sea turtles sunbathing on the surface.

You can also contribute by reporting your own sightings using the dedicated eTurtle app, available for smart devices which will help scientists in monitoring their status!

SEA CUCUMBERS (Holothuroidea)

There are 37 species of sea cucumbers in the Adriatic sea. Some species are edible, but in the Adriatic, commercial fishing of sea cucumbers is prohibited by law.

Sea cucumbers are echinoderms from the class Holothuroidea. While their spines are not visible, underneath their skin are well-developed limestone plates. The endoskeleton consists of microscopic, calcareous spicules scattered throughout the warty skin. Flexibility is achieved by a well-developed muscular system. Many sea cucumbers are deposit feeders. The tube feet around the mouth are modified into branched tentactles that are used to pick up organic matter from the bottom or scoop sediment into the mouth. Some sea cucumbers burrow or hide, and extend only their tentacles to obtain food directly from the water.

Sea cucumbers are extremely important for the functioning of the marine ecosystem. These organisms are "decomposers" who, through their digestive tract "suck in" the sand, or the sea sediments, and then remove the organic substances which they feed by. A lack of sea cucumbers causes the accumulation of organic substances, which leads to an increase the number of bacteria. Due to bacterial growth, oxygen disappears, a condition that is called anoxia. All moving organisms will leave the anoxic habitat while immobile animals will die, which will further aggravate the situation.

To defend themselves from the predators, they throw out their wombs through the mouth, to scare the enemy. This process is called evisceration. Messy but effective!

CORMORANTS (Phalacrocorax)

There are two submarine subtypes in Europe:
- Northern subspecies (Phalacrocorax aristotelis aristotelis) which resides in Northern Europe
- Mediterranean subspecies (Phalacrocorax aristotelis desmarestii) which is endemic to the Mediterranean and Black Sea.

Croatia has one of the largest populations in the Mediterranean (approximately 2000 pairs). Cormorants are black, long-necked seabirds that dive and pursue their prey. They can be easily identified by their low flights over water and the fact that they float low in water, with only their neck above the surface.

The shag is a sea bird that exclusively eats fish and hunts by diving. Their dives can last a few minutes, and extend to a depth about a 60 meters. The shag most often nests in colonies that are found on small islands and rocks without terrestrial predators. Across the Adriatic, the largest number of nests is in the north, specifically in Istrian waters and in the Zadar archipelago.

In the nest it lays 1-6 eggs (usually 3-4), on which both of parents sit. Incubation lasts about a month, and after hatching parents feed them for next 50 days.

The main threats to the shag are a lack of food and pollution from fishing equipment.

The most dangerous fishing item is drift net, in wich the shag can entagle itself and choke. These nets are ingested accidentally when the shag hunts fish, since fish become entangled int he nets.

A lack of food is caused by overfishing of marine organisms, especially fish. Other threats include the disturbance of birds during nesting and increased boat traffic.

SEAHORSES (Hippocampus)

These marine inhabitants have an unusual shape, and look like chess pieces. These are the fish from the superclass of bonyfish (Osteichthyes), family Syngnathidae. They swim upright and can escape their predators by imitating the color of underwater plants. This process is called mimicry - the ability of some species of animals and plants to adapt to the environment to protect them from natural enemies. Seahorses are lovely inhabitants of warm seas. There are 54 species of seahorses. Two of these seahorse species are present in Adriatic sea. First, the long - snouted seahorse, which has on their body well-developed skin extensions (Hippocampus ramulosus). Second, the short-snouted seahorse, without skin extensions on the body (Hippocampus hippocampus) both are strictly protected species.

The seahorses usually stay on the seabed covered with seagrasses (Posidonia oceanica, Cymodocea nodosa, Zoostera marina), in warm, shallow waters, near the sea currents, where they are provided a sufficient quantity of their main food sources plankton. They are protected from sea currents due to their long trail, which wraps around the nearest plant and acts as an anchor.

Their mating season coincides with the full moon.

After a long and noisy courtship, the female deposits the female eggs into the male abdominal pouch. Then, the male is responsible for maintaining the young. The male seahorse is the only male in the animal kingdom to give birth to its young.

Incubation of eggs: usually 14-28 days, depending on water temperature.

GIANT TUN (Tonna galea)

The giant tun (Tonna galea) lives individually and in rare cases, in a group. The preferred habitat for this species is a seabeds that are muddy or sandy and has beds of seagrass. In the Mediterranean, these snails are typically found at depths that range from just beneath the surface to 120 metres. The shell is thin and bulbous, but still relatively solid and durable. This thin shell is much lighter than the shell of most other big sea snails. It can grow up to 30 cm, making it one of the largest snails in the Adriatic sea. The body of the sea snail is white with black spots. The outer lip is broad, undulated, and ha san edge marcanble tinged with black or a deep brown. It is carnivorous and utilizes its two proboscises - located on top of its head - to envelop its prey, which primarily consists of sea cucumbers. To a lesser extent it also feeds on sea urchins, starfish, bivalves and crustaceans.  As a defense mechanism, the snail will squirt its highly-acidic saliva when disturbed. This contains approximately 2–5%  of sulfuric acid, which is used to kill its prey. Furthermore, the giant tun is also a luminescent species; this is an extremely rare characteristic among the prosobranch gastropods. The animal gives off light that is green-white in colour when it traverses through the water with its foot "well-extended". Its habitat includes the Indo-Pacific, the eastern Atlantic and the entire Mediterranean and Adriatic Sea.

In the Adriatic these snails are typically found in coastal areas up to 5 nautical miles away from the land. In the northern part of the Adriatic they are very rare. The largest number of giant tun settlements of this type were recorded in middle Dalmatian channels and bays. Due to its attractive appearance and its size, it is often lured and sold as a souvenir. Therefore, its populations have become more and more rare in recent years. Since 1994hunting the giant tun is strictly protected by law.


Caulerpa belongs to a genus of green algae from the Caulerpaceae family, which are common in tropical and moderately warm seas. This species was first described by the French botanist Jean Vincent Félix Lamouroux at the beginning of the 19th century, and the name of the genus derives from the Greek word "caulos“ – to grovel.

What makes Caulerpa so special is that they are the largest single - body organisms in the world. Though the whole algae is built from only one cell, its branched stems can grow up to a few feet and have thousands of roots with hundreds of small leaves.

There are different shapes, depending on the type of algae. Small spotted leaves define Caulerpa taxifolia. Caulerpa racemosa is defined by grape shape, and Caulerpa prolifera is defined by completly rounded leaves.

Seedlings can grow vegetatively and sexually. Vegetative reproduction is accomplished by cleavage of fragments that then develop in to a new plant. In cytoplasmic sexual replication that plant develops millions of gametes. At dawn, male and female gametes leave the parent algae and connect to the zygote that sits on the sea floor. For ten days, a new algae develops and parental cell die.

The genus Caulerpa is one of the most extreme systematic groups with over 70 different species, subspecies, taxa, varieties and shapes. Eight species have been found in the Mediterranean Sea, seven of which are not native to that area, but originate from the Red Sea. These organisms was dredged, settled in the Mediterranean after the Suez Canal was construited, and these organisms are called leseps organisms as Ferdinand de Leseps, the Suez Canal constructor. The genus Caulerpa is most likely a relic from Tethys Sea, and today it settles in the tropical sea while living in the Mediterranean on a shallow, sandy bottom, often with sea flora. In the Adriatic Sea, the sites where it grows, range from Albania, Montenegro and Croatia in the eastern Adriatic coast to the southern and middle Dalmatian islands and Istria. Scientists believe it is expanding with sea currents.

Caulerpa racemosa

This invasive algae in the Adriatic was discovered by Dr. Ante Žuljević from the Institute of Oceanography and Fisheries in Split. It was first discovered in the fall oft he year 2000 in the underwater world of the Pakleni islands.

Morphological - genetic research has shown that at least three different varieties of Caulerpa racemosa are found in the Mediterranean. Genetic research shows that C. racemosa var. cylindracea is an invasive variant associated with racemoses from southwestern Australia. If indeed the algae came from Australia, it is not clear how this accured since ballast water and dredging ships are not good for distribution of Caulerpa.

In general, C. racemosa reproduces sexually and vegetatively, but for now there is no evidence of its successful sexual reproduction in the Mediterranean. Although algae with male and female gametes have been found in Greece, their zygotes have not joined, and therefore these zygotes die after one day. The release of the gamets usually comes 15 minutes before sunrise. In the Mediterranean, Caulerpa racemosa typically settles on all types of seafloor, and its densely populated settlements can be found up to a depth 40 meters. In the Adriatic, the deepest specimen was recorded between at a depth 55 and 60 meters. It is also able to tolerate low winter temperatures, which allows it to inhabit the Vrsar area of ​​Istria where the temperature can drop lower than 7 ° C. The largest settlement was found near the island of Mljet near Sobra, and at the end of 2005 it extended along more than 14 km of coastline.

Caulerpa racemosa grows 1cm per year and is an invasive species in the Adriatic. The most dense settlements so far have been recorded on the rocky bottom, which used to be covered with autochthonous algae until the appearance of this invasive algae. Within this thick patch of staple C. racemosa, there is significant accumulation of organic matter and inorganic sediment particles. During the biodegradation of these particles, oxygen consumption is increased, sometimes leading to anoxia. The newly established hypoxic or anoxic environment is deadly to most organisms. Sea sponges are very useful in aiding the development of this algae, because they grow spores that algae uses as nutrients. When it grows on the sponge, it blocks the openings through which the sea water enters, and the sponge slowly begins to flinch. This flinching favors further algae growth as the biological degradation of the sponge releases nutrient salts. It has been observed that Caulerpa racemosa develops poorly in healthy and dense meadows of sea grass, but if the Posidonia oceanica is damaged then the alga is easily overwhelmed.

Caulerpa in the Adriatic does not have predators, and because of this spreads quickly and uncontrollably, and occupies large areas of rocky sea bottom. All Caulerpa algae produce toxic metabolites that protecte from herbivores. Adriatic herbivores include urchins and the salpa fish, but do not feed on Caulerpa because they have not developed a metabolism that is resistant to toxins from the Caulerpa. One group of snails has adapted to the consuption of the Caulerpa because it developed an evolutionary resistance to its metabolites. Only two species of snails live in the Mediterranean sea and are endemic Mediterranean snails known as Oxynoe olivacea and Lobiger serradifalci.


Sea temperatures are measured according to surface temperature, usually one to three times a day on coastal and island stations (picture). For the entire Adriatic between 1911 and 1964, a minimum temperature of 4.1 ° C and a maximum temperature of 28.8 ° C were recorded as the surface temperature of the sea.

The minimum sea temperatures occur at all stations either in February or March. All stations have maximum sea temperatures in August. During the winter the sea temperature in the northern Adriatic is about 3 ° C lower than the ones in the south. The southern part of the Adriatic has hot water flowing from the Mediterranean. According to the open sea (see Split and Hvar) the sea temperature values ​​increase. In the summer, sea temperature differences between the north and the south are almost unavailable. There is only a slight increase in value to the north. The cause lies in the inlet of the waters of the northern rivers, especially the Po river. An exception in the temperature field is the station in Senj, which represents the summer singular point. In Senj the temperature must be lower than the temperature at other stations and up to 3.5 ° C (Penzar et al., 2001). The results can be seen in the picture, source:

The increasing frequency of hot summer temperatures in Croatia over then past 10 years or more, has not only adversely affected humans but also marine organisms due to an unnatural warming of the sea. The sea temperature sometimes reaches an incredible 30 °C, which has almost never occurred int he past. A warming of the surface of the sea is not what scientists are most concerned about, however they fear an icreasein temperature occuring in deeper layers. As a result of these temperature changes, vulnerable marine organisms, such as coral and sponges, are threatened.

Petar Kružić, from PMF Zagreb, suggests the collapse of the corals and the gradual disappearance of the coral is an example of the effects o fan elevation of temperature. On a coral reef in a large lake on Mljet, about 30% of the coral polyps had necrosis and entire colonies died.

Jakov Dulčić, leader of the Ichthyology and Coastal laboratory of the Institute of Oceanography and Fisheries in Split, states that such changes in the environment favor the attraction of other invasive foreign species in the Adriatic. For example, invasive species Sparisoma cretense, which eat corals. Today it is widespread throughout the Adriatic.

Because of higher temperatures in the Mediterranean and in the Adriatic, a tropical species of fish known as „fuga“ Lagocephalus sceleratus, and which is characteristic of Japan is founded here. It is extremely poisonous (deadly) and requires a large amount of patience when preparing for a meal.

Fish like palamids and mackerel they no longer stay close to the surface, but are more often foundin deeper parts oft he sea.

The human factor is still the biggest danger to biodiversity, especially because of pollution. The combination of pollution, excess organic matter and rising sea temperatures result in an ever greater flowering of the sea across the Adriatic. The flourencyof the sea is another reason that causes sedative organisms, such as corals and sponges, to die, and thus indirectly affects their habitats. Namely, the flowering of algae on the surface of the sea, which we see as a gelatinous green patch on the surface, after fals down to the bottom and covers sedimentary organisms. This creates anoxic conditions that further complicate the survival of sedimentary organisms.


Plankton (plankton - traveler, wanderer) include single-celled autotrophic or heterotrophic organisms that inhabit the water column, float in water or have limited motion capabilities, and depend on the motion of water mass (Hensen, 1887), sea currents and wastewaters from ships.

Phytoplankton belong to plant plankton, and are single cell autotrophic organisms.They are primarily green algae and experience photosynthesis. Through this photosynthesis of carbon dioxide and nutrients, they build their body substance (biomass). Thus, phytoplankton are the base of the food pyramid in the sea, in landlocked waters and in large rivers. There organic substances in the sea are important for the growth and subsistence of other marine organisms.

Direct feeding circule: Phytoplankton - Zooplankton - Krill - Whale

We divide them by diatomaceous cells, dinoflagelates, chocolitoforids, silicoflagels, microflagels, cyanobacteria. Most remain in the illuminated areas of the sea during the day, and at night sink down to a greater depth. They are of the utmost importance for the entire ecosystem.

When quiet, windless periods with lots of sunshine are coupled with high sea temperatures, the concentration of nutrients int he aquatic ecosystem increases. This can hepen through either natural or anthropogenic means, and results in significant increase in algal biomass, a process which is called euitrophication. A sign of eutrophication is visible on the surface oft he sea as a gelatinous accumulation of a green or orange/red layer known as "red tide" or "flowering of the sea".

As a consequence, there is increased oxygen exhaustion. Bacteria break down all the organic matter produced by phytoplankton, use the oxygen, and create anoxic conditions, causes the death of fish or other marine organisms.

If the bacteria fail to break down the aggregates of organic matter, they fall to the bottom and cover other sedimentary marine organisms, which additionally cause oxygen deficiency to decrease.

An increased intake of nutrients into the aquatic environment caused by human activities, such as the influx of agricultural chemicals that flow into the sea from the soil, urbanization, tourism, industry, mariculture and pollution, also exacerbaters eutrophic phenomena.

Here, we will outline only one example of anthropogenic cause of increased nutrients in aquatic environments. This is increased usage of synthetic detergents which pollute drinking water (increased levels of phenol and phosphorus), and disturbing the balance of aquatic ecosystems.


Mediterranean monk seal (Monachus monachus, Hermann 1779) belongs to the order of the (Pinnipedia), the family of seals (Phocidae), the genus of the Monk seal (Monachus).

Local Croatian names for the Mediterranean monk seal is seaman, , marine friar, sea bear.

Today, they live in smaller groups on the Adriatic, Mediterranean and Atlantic coasts, on the coast of Mauritania - Morocco. The total population is about 350 units, living in smaller isolated groups of 5 to 7 individuals, whose biology still does not known enough. For the first time it was scientifically described in 1779 on the basis of carcasses, found in Osor - the Island of Cres.

The Mediterranean monk seal is adapted to life in the sea area. Earless seals, the back limbs can not turn forward, they are always outstretched, awkwardly moving on the land, but due to hydrodynamic shape they are very skillful and fast moving in the sea. The Mediterranean mok seal has large round eyes and 32 sharp teeth. On the front limbs there are well-developed and long-range (nails), while the backs are considerably less. It has a thick, short, soft coat of brown / gray color. Around the nostrils and above the eye grow large tanned hair.

They grow up to three meters and can weigh up to 400 kg. Sexual maturity reaches between age five and seven, they steam and food themselves in the sea. Female pregnancy lasts 10 to 11 months, and every two years she borns of one young cub, which is breast-feeding for 10-18 weeks. It is retained in the area of birth and the use of the cave of this area whose interior is pebbled or stone slabs. They also use them to raise cubs and rest, where people do not disturb them.

The Mediterranean monk seal lives up to 40 years old, feeds on cephalopods, crabs and molluscs ecc., 10 to 12 kg of food in multiple meals.

Because of its critical status, it is among the ten most endangered mammals of the world.

The Mediterranean monk seal has been protected since 1935. in Adriatic sea, Croatia.