information:classification, structural:expansion
Aquatic mammals

Along the mediterranean regions of the Arabian Sea, including the Persian Gulf, the Red Sea, the Gulf of Kutch, the Gulf of Suez, the Gulf of Aqaba, the Gulf of Aden, and the Gulf of Oman, dolphins and finless porpoises are the most common marine mammals in the waters, while larger whales and orcas are rarer today. Historically, whales had been abundant in the Persian Gulf before commercial hunts wiped them out. Whales were reduced even further by illegal mass hunts by the Soviet Union and Japan in the 1960s and 1970s. Along with Bryde's whales, these once common residents can still can be seen in deeper marginal seas such as Gulf of Aden, Israel coasts, and in the Strait of Hormuz. Other species such as the critically endangered Arabian humpback whale, (also historically common in Gulf of Aden and increasingly sighted in the Red Sea since 2006, including in the Gulf of Aqaba), omura's whale, minke whale, and orca also swim into the Persian Gulf, while many other large species such as blue whale, sei, and sperm whales were once migrants into the Gulf of Oman and off the coasts in deeper waters, and still migrate into the Red Sea, but mainly in deeper waters of outer seas. In 2017, waters of the Persian Gulf along Abu Dhabi were revealed to hold the world's largest population of Indo-Pacific humpbacked dolphins.

One of the more unusual marine mammals living in the Persian Gulf is the dugong (Dugong dugon). Also called "sea cows", for their grazing habits and mild manner resembling livestock, dugongs have a life expectancy similar to that of humans and they can grow up to 3 metres (9.8 feet) in length. These gentle mammals feed on sea grass and are closer relatives of certain land mammals than are dolphins and whales. Their simple grass diet is negatively affected by new developments along the Persian Gulf coastline, particularly the construction of artificial islands by Arab states and pollution from oil spills caused during the "Persian Gulf war" and various other natural and artificial causes. Uncontrolled hunting has also had a negative impact on the survival of dugongs. After Australian waters, which are estimated to contain some 80,000 dugong inhabitants, the waters off Qatar, Bahrain, UAE, and Saudi Arabia make the Persian Gulf the second most important habitat for the species, hosting some 7,500 remaining dugongs. However, the current number of dugongs is dwindling, and it is not clear how many are currently alive or what their reproductive trend is. Ambitious and uncalculated construction schemes, political unrest, ever-present international conflict, the most lucrative world supply of oil, and the lack of cooperation between Arab states and Iran, have had a negative impact on the survival of many marine species, including dugongs.