This section deals with Pakistan’s marine ecosystems. It includes discussions of the present status of marine Biodiversity, major threats, and actions that have been taken or are required for marine Biodiversity conservation.
Pakistan has a 1050 km long coastline, 250 km falling in Sindh province and 800 km in Balochistan. It borders the productive NE Arabian Sea, famous for its upwelling phenomenon. Its Exclusive Economic Zone (EEZ) covers an area of 196,600 sq. km. In addition, the territorial waters cover an area of 24,000 km2. The continental shelf of the Sindh coast extends to a distance of 150 km whereas Balochistan only measures 15-40 km. The prevailing direction of the ocean current is clockwise during the southwest monsoon season and anti-clockwise during the northeast monsoon season. The salinity value is generally 36 ppt. Tides are neither very high nor very low, but intermediate; the mean average height is about 10-11 feet. Tides are higher on the eastern side and their velocity is generally between 1-2 knots but can increase to 4 knots in narrow creeks.
The coast is rugged and tectonic in origin as evidenced by the uplifted terraces, headlands and fluted beds. The mud volcanoes present along the shores further support this geographical condition. The coastline is mostly bare desert with unique landforms such as sandy beaches, mud flats, rocky cliffs, headlands, bays, deltas, etc. Brief descriptions of these are given in the following section.
7.1.1 Habitat Types along Pakistan’s Coastline
Sandy beaches are common along Balochistan's shores but rare in Sindh. Well-known beaches in Pakistan include Somniani, Hingol River, Ormara, Pasni, and Gawadar in Balochistan; and Clifton and Hawks Bay in Sindh.
22.214.171.124 Cliffs and Headlands
Rocky shores and cliffs are prevalent in Balochistan. They are generally composed of conglomerates of soft mudstone and sandstone, which are highly susceptible to erosion. Headlands are prominent in Jiwani, Pisukan, Gawadar Rasjaddi and Ormara, and are intervened by low-lying places comprised of alluvial deposits. Irregular cliffs present at Ras Malan are a result of tectonic activity. Several deep-seated faults are also evident. The Sindh coast on the other hand, is very poor in rocky shores. Buleji, Manora Rocky Ledge, Cape Monze, and a few other small sites are present in the extreme western part of the province. The steep cliffs at Cape Monze are a trajectory of Mor and Kirthar Ranges, and are composed of hard limestone.
126.96.36.199 Bays and Lagoons
Bays and lagoons are protected bodies of water surrounded by land having an opening into the sea. In bays, the opening is wide, whereas in lagoons it is very narrow. There are no bays or lagoons along the Sindh coast, but several along the Balochistan coast, such as Gawadar Bay, Ormara Bay and Somniani Bay. Sandy coasts in a curvilinear pattern fringe the first three mentioned bays, which are slowly being destroyed by erosion. There are only two lagoons in the country, both of which are also located in Balochistan. These are the lagoons of Kalmat Khor and Miani Hor. These harbour dense mangrove vegetation.
188.8.131.52 Mud Flats
Mud flats are gently sloping, unconsolidated inter-tidal parts of estuaries, and are always occupied by marsh vegetation. Tidal flats are the same except that they lack vegetation. The entire Indus Delta and most of the Sindh coast is comprised of mud flats with mangrove vegetation. Mud flats are non-existent in Balochistan except in Gawadar Bay, Kalmat Khor and Miani Hor lagoons.
184.108.40.206 Mud Volcanoes
Mud volcanoes are conical hills or mountains with a crater on top through which they gently emit liquid, mud and gas. They are commonly associated with petroleum deposits; hence, their presence indicates high petroleum potential along the Makran coast. Mud volcanoes generally emit muddy and saline water, but occasionally large masses of rock are violently blown hundreds of feet into the air. The gases that are discharged include methane, ethane and traces of unsaturated hydrocarbons. Mud volcanoes are a common occurrence in Balochistan but are not found in Sindh.
Estuaries are coastal embankments that receive substantial freshwater runoff from land, and experience open tidal circulation with the ocean. In other words, estuaries are the mouths of rivers opening into the sea. There are three major estuaries in Pakistan, the largest one being the Indus estuary on the Sindh coast. The other two are the Hingol and Dasht estuaries both located in Balochistan.
Deltas are an accumulation of sediments at the mouths of rivers where they empty into basins. Deltas consist of three major parts: the delta plain, delta front and prodelta. There are several small deltas at the mouths of seasonal rivers in Balochistan. However, one of the largest deltas in the world, the Indus Delta, is located at the mouth of the Indus River and covers almost the entire coast of Sindh. It forms a remarkably uniform landform with large extensive mud flats intervened by narrow creeks. These are remnants of old, Indus tributaries. The western part of the delta between Phitti Creek and Karachi Harbour is now abandoned, although at one time the Indus River used to flow close to Karachi.
7.2 Important Marine Species and their Status
Species diversity is generally a good measure of the Biodiversity index, but cannot be applied in places such as Pakistan, because the flora and fauna has not been adequately studied and documented. In addition, as Pakistan is not a bio-geographic entity and its borders are confluent with other countries, the rate of endemism is very low. While endemic species do exist in terrestrial flora and fauna, information about endemic marine forms does not exist. Some important groups and species of marine animals are described below.
There are approximately 788 marine fish species in Pakistan’s coastal waters (Ahmed, 1998). Large pelagics such as the tuna are common in the waters of Balochistan. The blind Indus dolphin (Platanista minor) is a resident of the Indus River and estuary. Palla fish (Tenalosailisha), which is considered a delicacy, is an anadromous10 fish that swims up the Indus River to breed. However, the palla fish can no longer migrate up the Indus River due to the construction of a number of dams. Now it is found up to the Ghulam Mohammad Barrage. This has seriously affected the reproductive potential and distribution pattern of the species.
The green turtle (Chelonia mydas) and the olive ridley turtle (Lepidochelys olivacea) are both found in Pakistan. Until recently, they were indiscriminately killed on the Makran coast.
Eight species of oysters occur in Pakistan. Squid are abundant, but surprisingly echinoderm populations are very small.
Eight mangrove species were reported to grow in Pakistan until recently, but now only four survive. These are Avicennia marina, Ceriops tagal, Aegiceras corniculatum, and Rhizophora mucronata (Saifullah, 1982,1997).