Following the implementation of the Framework Convention for the Protection of the Marine Environment of the Caspian Sea, August 12 was named the Day of the Caspian Sea by the Caspian littoral states. The Joint Treaty of the Caspian littoral states, known as the "Tehran Convention", was signed in 2003 and entered into force on August 12, 2006. The purpose of this Convention is to protect the environment of the Caspian Sea from all polluting sources and to conserve, maintain, rebuild and use rationally and sustainably its living resources. Aware of the devastating effects of pollution from various sources of human activity, the five Caspian littoral states decided to protect the living resources of the Caspian Sea in order to preserve this valuable treasure for present and future generations and future inhabitants. The purpose of holding the National Day of the Caspian Sea as a cultural and social event is to introduce the capacities of the Caspian Sea and the dangers threatening this sea to the public. Currently, the most important threats to the Caspian Sea are declining fish stocks, coastal degradation, the risk of biodiversity loss, declining environmental quality and invasive alien species. The Caspian Sea, as the largest lake in the world, is one of the most valuable natural resources and treasures in the north of the country. This sea was once part of the Tethys Sea, which connected the Pacific Ocean to the Atlantic Ocean. The Caspian Sea route gradually closed to the Pacific Ocean and then to the Atlantic Ocean from about 50 to 60 million years ago. In the past, the Caspian Sea was called by names such as the Hyrcanian Sea, Gorgan Sea, Mazandaran Sea, Abaskun Sea and Caspian Sea. Caspian is the name of a lake with a surface area of approximately 360 thousand square kilometers and a volume of 740 thousand cubic kilometers, the length of which reaches 7000 kilometers. The countries of Iran, Russia, the Republic of Azerbaijan, the Republic of Turkmenistan and the Republic Kazakhstan surround the lake and all enjoy its benefits. More than 130 rivers enter the Caspian Sea. The Volga River, Kura River, Ural River and Terek River are the source of 80.7, 6.1, 9.2, and 2.8 % of the Caspian’s inflow, respectively. Iranian rivers make up about 5 % of the share of other rivers (13.3 %). What gives this water body a lot of value is the presence of more than 400 aquatic species in it. The Caspian Sea has valuable species of biological resources, the most prominent of which are the sturgeons and the Caspian seal (symbol of the Caspian Sea). Therefore, the health of this sea is equal to the health of aquatic organisms, and the health of human beings who benefit from its blessings. Currently, according to research by the International Union for Conservation of Nature (IUCN), six percent of the Caspian Sea fish are in the critically endangered class and the rest are in the following categories: vulnerable (2 %), endangered (6%), neat threatened (8 %), conservation dependant (21 %), least concern (36 %) and data deficient (21 %). Therefore, the conservation of genetic resources and biodiversity (plant and animal) of this sea is very important and necessary for environmental sustainability and bioavailability. In the last two decades, due to effective human factors such as overfishing activities and changes in climatic and environmental conditions, as well as the entry of non-native species such as the warty comb jelly into the Caspian Sea have had adverse effects on the structure of bony fish and kilka fish. So that two species of Caspian white fish and golden grey mullet make up about 70 – 90 % of Iran's bony fish catch in the Caspian Sea. Previously, out of 126 species of fish living in the Caspian Sea, about 16 species were commercially valuable and provided employment and livelihoods for more than 10,000 fishermen. Also, in recent years, with the sharp decline in the population of two species of Southern Caspian sprat and Anchovy, the catch of kilka has decreased from 95,000 tons in 1999 to about 20,000 tons of Clupeonella cultriventris. Fortunately, with the research conducted by the experts of the Iranian Fisheries Science and Research Institute and determining the optimal level of harvest from resources, the amount of Black Sea sprat fishing off the coast of Iran in the last ten years has reached an average of 23,000 tons. Numerous challenges including illegal fishing, overfishing, harvesting of broodstocks and young herds, destruction of spawning sites (natural habitats), climate change and environmental pollution (physical, chemical and biological) threaten fish stocks in the Caspian Sea. Strategies to conserve the commercially valuable species of the Caspian Sea are: Short - term plan: (prevent illegal fishing, observe the standards of fishing equipment, observe the start and end time of fishing, etc.) and long - term plan: Since 79 % of the Caspian Sea fish are anadromous fish, river rehabilitation is needed for the natural reproduction of anadromous fish in order to achieve sustainable fisheries development in the Caspian Sea. In the last decade, according to the Sixth Development Plan and the Resistance Economy Plan, the exploitation of the country's marine water resources has been considered by the relevant government agencies due to the limited possibility of using fresh water resources. This approach aims to develop mariculture in order to reduce the pressure on catching and conserve economically valuable species, increase per capita consumption of aquatic products in the country, the development of marine ecotourism and job creation, which has doubled the importance of the Caspian Sea in the north of the country. Also, according to research, good and reliable capacities such as sturgeon farming in the coastal areas of the Caspian Sea and shrimp farming in coastal areas are other suitable areas for the development of aquaculture in coastal areas. According to research by the Iranian Fisheries Science and Research Institute, more than 400 species of microalgae have been identified in the Caspian Sea, some of which (Spirulina, Chlorella, etc.) can be turned into wealth. With recent advances and due to the antioxidant, antimicrobial and anti - cancer properties of microalgae, the use of microalgae and their pigments in the world has been provided. So given this capacity of the Caspian Sea, with the cooperation of knowledge - based companies and start - ups, effective steps can be taken in order to create jobs and also produce beverages based on microalgae pigment.