**2.3 Indo-Pacific Bottlenose dolphin**

This mammal scientific name is *Tursiops aduncus* and its local name is the Botolnak dolphin. The highest size recorded 250 cm; also have a snout, large flipper, dorsal fin, and flukes. The color outline is gray and marginally dark present. Although, about 402 Indo-Pacific bottlenose dolphins are sighted from 2004 to 2014 and also large population was recorded in the marine protected area in **Figure 3**. WCS [9] reported about 1700–2200 individual Indo-Pacific bottlenose dolphins that survived in the Bangladesh area. This species is also sighted in the face of the Swatchof-No-Ground which is a highly biological habitat in the Bay of Bengal. Although, IUCN considers the species as data deficient (DD) but due to their distribution and population remark as vulnerable in the environment of the Bay of Bengal. Fisherman occasionally caught this dolphin by gillnets and seines net during fishing. WCS considers about 282 km<sup>2</sup> as Marine Protected Area (MPA) for this dolphin whereas 90% of species are sighted.

*Perspective Chapter: Status of Dolphin in the Maritime Area of Bangladesh DOI: http://dx.doi.org/10.5772/intechopen.102022*

### **2.4 Spotted dolphin**

The spotted dolphin is the most dominant animal in the cetacean groups in tropical area. Generally, Pantropical spotted dolphins occurred in the marine protected areas of the Bay of Bengal. This dolphin's scientific name is *Stenella attenuate* and its local name is Chitra dolphin. Its body structure is slender and looks like streamlined. The dorsal fin is narrow and pointed at the tip. The spot is present in adult dolphins. The abdomen color is a brighter gray. Maximum sizes of spotted dolphins found about 260 cm long. WCS reported 29 sightings of spotted dolphins and an average group size of 84 in the marine protected area (MPA) [9]. The spotted dolphin population is reducing due to unplanned fishing in the Bangladesh region. IUCN is considered as least concern and very little study occurred in Bangladesh on this dolphin. In the Swatch-of-No-Ground, about 86% of spotted dolphins occurred due to well biological habitat and 263 km2 areas considered as MPA for this species.

#### **2.5 Spinner dolphin**

The Spinner dolphin's scientific name is *Stenella longirostris* and the local name is Ghurni dolphin. This dolphin's body shape is slender with a particularly long beak. Adult spinner dolphin's maximum size recorded is 240 cm. Generally male is larger than female. Triangular to curved shape present in the dorsal fin. Three types of color are present in Spinner dolphin. The dorsal cape is dark, body sides are light gray, and belly is white. This dolphin is show leaping and spinning activities. Usually, this dolphin survives in the tropical and subtropical waters at geographical areas 40°N and 40°S. Large group of populations are swim in the marine protected area. Some fisheries reported a yearly mortality rate of about 100–1000 dolphins in the marine water due to fishing interaction. Although, IUCN was considered as data deficient but WCS [9] reported 34 sightings and an average group size of 97 in the Swatch-of-No-Ground and 550 individuals was present. Sighting rate 91% in the marine protected area and 263 km<sup>2</sup> areas consider for conservation.

### **2.6 Ganges river dolphin**

This dolphin scientific name is *Platanista gangetica gangetica* (Roxburgh, 1801) and local people call "shusuk" as local name in Bangla. A total of 34 sightings of dolphin, mean density was 0.38 (SD ± 0.37) dolphins/km<sup>2</sup> and best-high-low estimated of 10–12–8 in November 2012 in the Buriganga River area [7]. Also, 62 sightings of dolphins and best-high-low estimated of 9–11–7 in august, monitored by October with 8–10–7 individuals in the Turag River [8]. Another one reported encounter rate of Gangs dolphin was 0.47 in Sundarbans area in **Table 1**. Dolphin group size estimated by the Lincoln-Petersen model and Huggins conditional likelihood model which abundance showed 196 individuals (CV = 12.7%) and 225 individuals (CV = 12.6%), respectively in mangrove channels of the Sundarbans area [12]. It is a freshwater dolphin species scattered throughout the Ganges, Brahmaputra, and Meghna river systems along with the coast area of Bangladesh, Nepal, India, and conceivably Bhutan and 266 dolphins encountered in the entire Brahmaputra river system [11, 26, 27]. In the Indian subcontinent, Ganges dolphin is a special aquatic mammal in the riverine ecosystem. The survey was conducted for Ganges dolphins especially in Turag River and Buriganga River that is a part of the Ganga basin. Department of Environment, Government of Bangladesh Turag and Buriganga River area consider


**Table 1.**

*Encounter rates of Ganges river dolphin.*

as "Ecologically Critical Area (ECA)" [28, 29]. This species is enlisted in the CITES and Bangladesh Wildlife (Conservation & Security) Act, 2012, and it is categorized as an endangered species due to the many anthropogenic activities and natural hazards included, such as, water pollution, traffic boat and ship, brickfield, industrial waste, water level reduce.
