Keywords

1 Introduction

Mangrove is a plant community of salt tolerant species such as trees, shrubs, palms, and ferns which grow within transitional or inter-tidal zones of coastal, estuary and riverine areas of tropical and subtropical regions where rivers drain into the sea (Macintosh and Ashton 2002; FAO 2007; Rajkumar et al. 2009; Naidoo 2009; Wan Juliana et al. 2010; Zhou et al. 2010) . Worldwide, mangrove vegetation covers an area of 137,760 km2 (Giri et al. 2011) and the higher percent of mangrove vegetation occurs between 5 N and 5 S, 32 N and 38 S (Morrisey et al. 2010; Friess et al. 2012) . Out of the total mangrove areas, around 42.0 % occur in Asia, 21.0 % in Africa, 15.0 % in North/Central America, 12.0 % in Oceania, and 11.0 % in South America (Giri et al. 2010) . Mangrove areas are considered as a wetland that include waterways such as estuaries, creeks, canals, lagoons, backwaters, mudflats , salt pans and islands (Kjerfve 1990; Wan Juliana et al. 2010) . However, vegetation composition and structure of mangrove areas may vary from area to area or region to region depending on soil condition, rainfall pattern, and inflow of river water into the sea. Mangrove areas are rich in tree diversity that comprise about 69 true tree species that represent 27 genera and 20 families (Selvam et al. 2004) . Mangrove trees are divided into three categories such as (i) true mangroves or mangrove exclusive, (ii) mangrove non-exclusive and (iii) mangrove associated (Wan Juliana et al. 2010) .

1.1 Mangrove Exclusive or Major Mangroves

Tree species that are mainly restricted to the intertidal zone within deep water and high salinity include Avicennia lanata , A. marina , A. officinalis , Bruguiera cylindrical , B. gymnorrhiza , B. parviflora , B. sexangula , Ceriops decandra , C. tagal , Kandelia candel , Lumnitzera littorea , Nypa fruticans, Rhizophara apiculata , R. stylosa , Sonneratia alba , and S. caseolaris, etc. (Saenger et al. 1983; Tomlinson 1986; Rotaquio et al. 2007) .

1.2 Mangrove Non-exclusive or Minor Mangroves

Tree species that tolerate low salinity and are restricted to shallow water where salinity fluctuates from time to time include Acrostichum aureum, A. speciosum, Aegiceras corniculatum , A. floridum, Excoecaria agallocha , Heritiera littoralis, Osbornia octodonta, Pemphis acidula, Planchonella obovata, Scyphiphora hydrophyllacea, and Xylocarpus granatum, etc. (Saenger et al. 1983; Tomlinson 1986; NTG 2002; Rotaquio et al. 2007) .

1.3 Mangrove Associated

Plant species that grow with mangrove tree species include grasses, epiphytes, pteridophytes, bryophytes, and parasitic plants, e.g. Acanthus ilicifolius , A. volubilis , Barringtonia asiatica , B. racemosa , Brownlowia tersa , Cerbera odallam , C. manghas, Clerodendrum inerme , Crinum asiaticum , Dolichandrone spathacea , Inocarpus edulis , Hibiscus titiaceus , Morinda citrifolia, etc. (Tomlinson 1986; Rotaquio et al. 2007) .

2 Threats to Mangrove Fauna

Being an important habitat for wildlife species, about one-third of the mangrove area has been lost over the past two decades due to land reclamation, conversion into agricultural fields, deforestation, aquaculture , and urbanization, i.e. coastal development (Macintosh and Ashton 2002; Penha-Lopes et al. 2011) . The habitat loss and degradation have caused serious threats to wildlife species, particularly bird species, i.e. 40.0 % of the bird population has been decreased in mangrove areas (Sandilyan et al. 2010) . In addition, 100 % turtles species, 43 % crocodiles species, 20 % fish species, 37 % mammal species, 21 % bird species and 43 % amphibians that directly or indirectly depend on mangroves, mudflats and estuarine habitats are globally critically endangered (Millennium Ecosystem Assessment 2005).

The major driven factors that cause population decrease of mangrove fauna are habitat loss (Tidwell and Allan 2001) , over exploitation (FAO 2009), coastal degradation and climate change (Gracia and Rosenberg 2010) , organic pollution and toxic contamination (Naylor et al. 2000; Gracia and Rosenberg 2010) . These factors cause habitat degradation, reduced food resources, and destroy nursery grounds that ultimately affect the fauna population of mangrove habitats .

3 Economic Importance of Mangrove

The diverse vegetation structure and composition of mangroves with denser foliage (Stafford-Deitsch 1996) has created different layers of vegetation that offer heterogeneous habitats which support a variety of marine, freshwater and terrestrial wildlife species. The mangrove vegetation interacts with aquatic, inshore, upstream and terrestrial ecosystems that also form intertidal habitats for birds , fishes, reptiles, amphibians, mammals and a variety of aquatic invertebrates such as insects, mollusk, i.e. gastropods (snails) and bivalves (mussels), crabs, shrimps, oysters, sponges, barnacles, and polychaetes (worms).

Some of the animals depend on mangrove areas their whole lives while others utilize them only during specific periods such foraging, shelter and breeding (Hutchings and Recher 1982; Hutchings and Saenger 1987; Yaez-Arancibia et al. 1988; Macintosh and Ashton 2002; Northern Territory Government 2002; Thu and Populus 2007; Han 2011; Talaat et al. 2011; Nyanti et al. 2012;) .

Mangrove fauna can be divided into three inhabitants such as (i) aquatic animals, i.e., fishes, amphibians , (ii) semi-aquatic animals (i.e., reptiles, amphibians and birds) and (iii) terrestrial animals based on their living behaviour (i.e., mammals and birds) . These animal communities utilize mangrove areas for their daily activities such as foraging, breeding, and loafing. These animals play a significant role in the management of mangrove forests and in balancing nature in and around the mangrove areas (Spalding et al. 2010; Nyanti et al. 2012) .

3.1 Mangroves as a Habitat for Avifauna

Mangrove areas are a favorable habitat for a variety of waterbirds (i.e., the bird species that entirely depend on water for a variety of activities such as foraging, nesting, loafing and moulting) as well as terrestrial birds (i.e., bird species that do not entirely depend on water but may visit some time in search of food, shelter and perch) (Table 1). This is due to the diversity of habitats such as mangroves, mudflats , estuaries and richness of food resources which includes fishes (Blaber 2000; White and Potter 2004; Martin 2005) , turtles (Blanco et al. 1991) , snake (Guinea et al. 2004) , amphibians (Kathiresan and Bingham 2001; Nagelkerken et al. 2008) , mammals (Nijman 2000; Angelici et al. 2005; Bordignon 2006) , and invertebrates such as gastropods (Plaziat 1984; Jiang and Li 1995) , bivalves (Lebata and Primavera 2001) , prawn (Kenyon et al. 2004) , nekton (Minello et al. 2003), crabs (Ashton 2002; Skov and Hartnoll 2002) and insects (Nagelkerken et al. 2008).

Table 1 List of bird species recorded in different areas of mangrove and adjacent habitat
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Noske (1996) reported that mangroves support more than 200 bird species that utilize mangrove forest, mudflats, estuaries and adjacent areas. Avifauna of mangrove can be divided into four categories including (i) aerial feeders, (ii) waders, (iii) surface/diving foragers and (iv) foliage gleaners .

3.1.1 Aerial Feeders or Sallying Birds

The bird species that catch their prey on wing i.e. Fish Eagles (Fig. 1) and Kites (Fig. 2) (Accipitridae), Wood Swallow (Artamidae) (Fig. 3), Swallows (Hirundinidae), Bee-eaters (Meropidae) (Fig. 4), Kingfisher (Alcidinidae) (Fig. 5), and Swiftlet (Apodidae) always hovers on mudflats and mangrove areas in search of food such as fishes, birds, monkeys, snakes, and insects. Raptor birds such eagles, hawks, kites and osprey extensively prey on fishes, small birds, small mammals, reptiles, amphibians and large invertebrates (Ridgely and Greenfield 2001; Solano-Ugalde et al. 2009; Alava et al. 2011) while swallows, bee-eaters and swiftlets catch flying insects on the wing over mangrove areas and roost within mangrove areas.

Fig. 1
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White-bellied Fish Eagle—Haliaeetus leucogaster hovers over mangrove area in search of food

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Fig. 2
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Brhaminy Kite—Haliaster indus hovers over mangrove area in search of food

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Fig. 3
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White-breasted Woodswallow—Artamus leucorynchus perching on the dead branches of Rhizophora sp

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Fig. 4
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Blue-throated Bee-eater—Merops viridis sitting in wire near mangrove area

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Fig. 5
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Different Kingfisher species loafing in mangrove area

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3.1.2 Wader Birds

These are a group of waterbird species that wade in shallow water (Fig. 6) to catch different food resources such as fishes, prawns, mollusks, crustaceans, polychaetes and other invertebrates during low tides or in soft mud such as Egrets, Herons, Bitterns (Ardeidae), Finfoots (Heliornithidae), Plovers (Charadriidae), Oystercatchers (Haematopodidae), Sandpipers, Curlews, Shanks (Fig. 7), Tattlers (Fig. 8), Stints, Ruffs, Godwits, Knots, Dowitchers, Turnstones, Whimbrel, Snipes, Oystercatchers (Scolopacidae), Stilts and Avicets (Recurvirostridae), Phalaropes (Phalaropidae), Gulls, Terns and Noddys (Laridae), Spoonbills, Ibis, and Storks (Ciconiidae), Frigate birds (Fregatidae) and Famingos (Phoenicopteridae) (Fig. 9). These bird species utilize mangrove areas for foraging, roosting, nesting and shelter from harsh weather and hide cover from predators. Habitat selection among bird species may vary depending upon the nature of food selection, shape of the bill and location of food resources. It has been reported that mangrove forests may harbour a variety of water as well as terrestrial bird through offering safe habitats, foraging and loafing sites (Jayson 2001; Laakkonnen 2003; Berg and Angel 2006; Carvajal and Alava 2007; Saari and Ibrahim 2011) .

Fig. 6
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a Different wading birds searching for food in mudflat area. b Whimbrel—Numenius phaeopus foraging in shallow water during low tides. c Whimbrel—Numenius phaeopus loafing on mangrove tree

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Fig. 7
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Shank species—Tringa spp. perch on soft mud under Rhizophora sp. during low tides

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Fig. 8
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Grey–tailed Tattler—Tringa brevipes loaf on the roots of Rhizophora sp. during low tides

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Fig. 9
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Greater Flamingo—Phoenicopterus roseus foraging in shallow water of estuary

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3.1.3 Surface/Diving Foragers

Some bird species forage on the surface of water and sometimes dive into deep water to catch their prey especially fishes, amphibians, aquatic invertebrates, and vegetable matter. For example, Pelicans (Pelecanidae) (Fig. 10), Ducks and Goose (Anatidae) mostly swim on the surface of water to forage small fishes, amphibians, aquatic invertebrates, and vegetable matter while Cormorants (Phalacrocoracidae), Darters (Anhingidae) (Fig. 11), Loons (Gaviidae), and Grebes (Podicipedidae) dive into deep water, particularly river beds, in search of food, mainly fishes and aquatic invertebrates such as mollusks.

Fig. 10
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Juvenile of Great White Pelican—Pelecanus onocrotalus loafing on dead wood fallen into water

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Fig. 11
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Oriental Darter—Anhinga melanogaster perching on the dead branches of Rhizophora sp

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3.1.4 Foliage and Bark Gleaners

These are mostly terrestrial bird species which prefer to use mangrove vegetation, i.e. trees, shrubs, palms, and ferns for foraging, perching, nesting and roosting (Fig. 12) such as woodpeckers (Picidae), Tailorbirds, Warblers, Flyeaters (Sylviidae), Flycatchers (Muscipcapidae), Trush, Shama and Robins, (Turdidae), Nuthatch (Sittidae), Sunbirds and Spiderhunters (Nectariniidae), Pigeons (Columbidae) Owls (Strigidae), Cuckoos and Malkohas (Cuculidae), Parrots (Psittacidae), Tits (Paridae), Orioles (Oriolidae), Drongos (Dicruridae), Ioras (Chloropseidae), Flycatcher Shrikes (Campephagidae), and Pittas (Pittidae). Some of them are frugivorous birds that feed on fruits such as pigeons and parrots, insectivorous birds that feed on insects such as woodpeckers, robins, warblers, tits, and nectarivorous birds that nip on the nectar such as sunbirds and spider-hunters, and carnivorous birds that forage on other animals such as owls.

Fig. 12
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Different foliage and bark gleaning birds resting in mangrove area

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Bird species are a bioindicator of a mangrove ecosystem and play a significant role in the management of vegetation. They control the population of insect pest that cause the defoliation among trees and reduce their growth and also cause damage to the seeds. For example, insect eating birds such as tailorbirds, shrikes, flycatchers, iroas, and robins prey on different insect species such as caterpillars, beetles, bugs, and aphids that may cause the defoliation, bark damage that vigorously decreased the productivity and health of trees. Sunbirds and spider-hunters play a vector role in pollination, i.e., they transfer pollen from one flowering tree to another thus increasing the process of pollination that ultimately increases the seed production. Raptors such as eagles, falcons, and hawks prey on mammals such as monkeys and squirrels that foraged on fruits and tender leaves in the mangrove. Waterbirds are predators of fishes, amphibians, reptiles and a variety of aquatic invertebrates. They control their population and balance the mangrove and mudflat ecosystem. In addition, they are also an important source of food for other animals such as snakes, lizards, fishes, and crocodiles.

3.2 Mangrove as a Habitat for Reptiles

Mangroves are an ideal habitat and are rich in reptile fauna, which include snakes, turtles, crocodiles and alligators . The turtle species found in the mangrove area include Loggerhead Turtle—Caretta caretta, Green Sea Turtle—Chelonia mydas, Ornate Diamondback Terrapin—Malaclemys terrapin macrospilota (Laakkonnen 2003; Boykin 2004; SPGMEC 2013) , Mangrove Diamondback Terrapin—Malaclemys terrapin rhizophorarum (Burke 2000; Laakkonen 2003; Boykin 2004) , Hawksbill Sea Turtle—Eretmochelys imbricate, Atlantic Ridley Sea Turtle—Lepidochelys kempii (Laakkonnen 2003), Olive Ridley—Lepidochelys olivacea, and Leatherback turtle—Dermochelys coriacea (SPGMEC 2013). These turtle species utilize mangrove areas, estuaries and creeks for foraging and breeding purposes due to the richness and diversity of plankton and benthic food resources .They use sandy beaches for breeding purpose.

Mangrove areas are also rich and diverse in snake fauna which include, e.g., Dog-faced Water Snake—Cerebus rynchops (Lim et al. 2001; Han 2011) , File Snake—Acrochordus granulates (Lim et al. 2001) , Mangrove Snake—Boiga dendrophila (Norhayati et al. 2009) , Mangrove Pit-Viper—Trimeresurus purpureomaculatus (Lim et al. 2001) , Mangrove Skin—Emoia atrocostata (Lim et al. 2001; Norhayati et al. 2009; Han 2011) and Green Pit Viper—Vipera trimeresurus (Macintosh and Ashton 2002) . These snake species prey on a variety of animals such as birds, amphibians, small mammals and are also eaten by fishes, crocodiles and eagles.

Only a few crocodile species exist in mangroves, estuarine, and adjacent rivers, e.g., Saltwater/Estuary Crocodile—Crocodylus porosus (Fig. 13) (Macintosh and Ashton 2002; Foote 2013) , Common Caiman—Caiman crocodylus (Macintosh and Ashton 2002) and Marsh Crocodile—Crocodylus palustris (Fig. 14) (SPGMEC 2013). These crocodile species prey on a wide array of animals such as birds, fishes, snakes and mammals.

Fig. 13
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Saltwater/Estuary Crocodile—Crocodylus porosus resting in mangrove roosts in shallow water

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Fig. 14
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Marsh Crocodile—Crocodylus palustris taking a sunbath on soft mud

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Mangrove areas are also home to a few lizard species such as Mangrove Monitor Lizard—Varanus indicus (Fig. 15) and Malaysian Water Monitor Lizard—Varanus salvator (Fig. 16) (Lim et al. 2001; Macintosh and Ashton 2002; NTG 2002; Norhayati et al. 2009) . These are predators of different animals such as birds, amphibians and small reptiles .

Fig. 15
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Mangrove Monitor Lizard—Varanus indicus search for food near mangrove roots in shallow water

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Fig. 16
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Malaysian Water Monitor Lizard—Varanus salvator resting in grasses near a mangrove area

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3.3 Mangrove as a Habitat for Amphibians

Only a few species of frogs occur in mangrove forests including Giant Toad—Bufo marinus (Fig. 17) , Tree Frog—Osteopilus septentrionalis and Mangrove Frog—Fejervarya cancrivora (Fig. 18) (Dicroglossidae) (Macintosh and Ashton 2002; Wright et al. 2004; Satheeshkumar 2011) . The occurrence of such a few number of amphibians could be due to high salt contents of the water. Mangrove frogs are predators that may eat almost every small living thing such as insects (e.g., beetles, bees, ants, termites, crickets and bugs), snails, smaller toads, prawns, and fishes.

Fig. 17
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Giant Toad—Bufo marinus resting on soft soil

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Fig. 18
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Mangrove Frog—Fejervarya cancrivora resting on mangrove root

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3.4 Mangrove as a Habitat for Mammals

Mangrove forests are rich in mammal species such as White-tailed Deer—Odocoileus virginianus , Key Deer—Odocoileus virginianus clavium, Bengal Tiger—Panthera tigris, Leopard—Panthera pardus, Spotted Deer—Axis axis, Long-tailed Macaque—Macaca fascicularis (Fig. 19), Crab-eating Macaque—Macaca fascicularis (Fig. 20), White-faced monkey—Cebus capucinus, Malaysian Proboscis Monkey—Nasalis larvatus (Fig. 21), Wild Pigs—Sus scrofa and Mousedeer—Tragulus sp., Long-tongued Nectar Bat—Macroglossus minimus, Lesser Dog-faced Fruit Bat—Cynopterus brachyotis, Marsh Rabbit—Sylvilagus palustrias, Cotton Rat—Sigmodon hispidus, and Marsh Rat—Oryzomys palustris (Table 2). In addition, Bottle-nosed Dolphin—Tursiops truncates, Gangetic Dolphin—Platanista gangetica, Common Dolphin—Delphinus delphis, Manatees—Trichechus spp., Smooth Otter—Lutrogale perspicillata, Small-clawed Oriental Otter—Amblonyx cinereus and Manatees—Trichechus manatus are often observed swimming in canals, coastal rivers, and other waters close in proximity to mangroves (FAO 1984, 1994; Hogarth 1999; Ng and Sivasothi 2001; Laakkonnen 2003; Warne 2013) .

Fig. 19
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Long-tailed Macaque—Macaca fascicularis sitting on mangrove tree

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Fig. 20
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Crab-eating Macaque—Macaca fascicularis swimming in mangrove area

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Fig. 21
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Malaysian Proboscis Monkey—Nasalis larvatus sitting on trees

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Table 2 List of mammal species recorded in different areas of mangrove and adjacent habitat
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Mammals are a major source of food for a variety of animals such as raptor birds, snakes, crocodiles, and a significant component of mangrove ecosystems. Frugivore mammals such as monkeys, squirrels, and bats are also important as seed dispersal agents. Herbivorous mammals browse on young shoots of trees, shrubs and other vegetation; hence, they control the growth of shrubs and bushes that may compete for nutrition with trees.

3.5 Mangrove as a Habitat for Fish

Mangrove areas are rich in fish fauna (Table 3). For example, a total of 128 fish species were sampled in mangroves of Paglibao , Philippines (Pinto 1988) , 119 fish species have been recorded in the mangrove of Selangor , Malaysia (Chong et al. 1990) , 135 fish species in the mangrove estuary of Sikao Creek, Trang Province, Thailand (Prasert et al. 2002) , 33 fish species in the mangrove river of Sarawak, Malaysia (Nyanti et al. 2012) , and 105 fish species in the mangrove of India (Naik et al. 2013). In addition, mud skippers are one of the fish which live on the mud flats associated with mangrove shores. This indicates that a variety of fish species use mangrove areas for foraging, i.e. feed on amphipods, isopods, crabs, snails, insects, spiders, copepods, shrimp, and organic matter (Sasekumar et al. 1992; Ewel et al. 1998; Clayton 1993; Macintosh and Ashton 2002; Nagelkerken et al. 2008) . Many scientists have reported that an array of fish species extensively use mangrove areas as breeding and nursery sites especially during early juvenile stages (Robertson and Duke 1987; Morton 1990; Chong et al. 1990; Laegdsgaard and Johnson 1995; Dorenbosch et al. 2007; Jaxion-Harm et al. 2012) . This could be due to the abundance and richness of food resources (Nyanti et al. 2012) such as invertebrates that inhabit the vegetated area (Lubbers et al. 1990; Schneider and Mann 1991) , and richness of benthic fauna (Laegdsgaard and Johnson 2001; Marlena 2005) .

Table 3 List of fish species recorded in different areas of mangrove and adjacent habitat
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Fishes utilize a variety of aquatic habitats (Gratwicke et al. 2006) such as fresh water, brackish water and salt water. The fish fauna of mangrove areas include mud skippers, carangids, clupeids, serranids, mullets, hilsa, seabass, and milkfish (Naik et al. 2013). Some of the common fishes that may occur in mangrove area of southeast asia such as Malaysia include Mullet—Liza sp. (Fig. 22), Black Snapper—Apsilus dentatus (Fig. 23), Spottail Needle Fish—Strongylura strongylura (Fig. 24), One Spot Snapper—Lutjanus monostigma (Fig. 25), Orange Spotted Grouper—Epinephelus coioides (Fig. 26), Snapper Fish—Lutjanus sp. (Fig. 27), Cloudy Grouper Fish—Epinephelus erythrurus (Fig. 28), Mangrove Red Snapper—Lutjanus sp. (Fig. 29), Garfish—Hemiramphus sp. (Fig. 30) and Whipfin Silver-biddy—Whipfin mojarra (Fig. 31).

Fig. 22
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Mullet—Liza sp. caught in mangrove area

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Fig. 23
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Black Snapper—Apsilus dentatus caught in mangrove area

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Fig. 24
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Spottail Needle Fish—Strongylura strongylura caught in mangrove area

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Fig. 25
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One Spot Snapper—Lutjanus monostigma caught in mangrove area

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Fig. 26
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Orange Spotted Grouper—Epinephelus coioides caught in mangrove area

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Fig. 27
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Snapper Fish—Lutjanus sp. caught in mangrove area

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Fig. 28
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Cloudy Grouperfish—Epinephelus erythrurus caught in mangrove area

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Fig. 29
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Mangrove Red Snapper—Lutjanus sp. caught in mangrove area

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Fig. 30
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Garfish—Hemiramphus sp. caught in mangrove area

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Fig. 31
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Whipfin Silver-biddy—Whipfin mojarra caught in mangrove area

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However, the fish species composition and distribution may vary from area to area depending on the water quality, aquatic vegetation structure and composition (Pittman et al. 2004) , richness of food resources, i.e. invertebrates, vertebrates and vegetable matter (Verweij et al. 2006), detritus (Naik et al. 2013), suitability of breeding sites (Almany 2004) , habitat connectivity (Paris et al. 2007; Nakamura et al. 2008) and rate of predation (Chittaro et al. 2005) .

The occurrence of a higher diversity of fish species in the mangrove area might be due to the richness and diversity of food resources (Nagelkerken et al. 2002; Aguilar-Perera and Appledoom 2007) . The other reason could be due to the complex and extensive root system that reduces the risk of predation and provides safe breeding and nursery grounds, i.e. fishes lay their eggs in extensive roots of mangrove trees (Robertson and Duke 1987; Thayer et al. 1987; Laegdsgaard and Johnson 2001; Huxham et al. 2004; Naik et al. 2012) , and after hatching they feed on detritus and other food resources which are easily available in mangrove areas. The water in mangrove areas is turbid and rich in detritus which provide instant food material for juvenile fishes and also reduced predator’s vision (Abrahams and Kattenfeld 1997) .

Fish is highly nutritious and a major source of human diet, i.e. proteins, vitamins and micronutrients, particularly for low income rural communities (Gracia and Rosenberg 2010) . Mangrove supports 75–90 % of the commercial and subsistence fish industries (Lee 1999; Hoyle and Gibbons 2000; NTG 2002) . It has been reported that almost 400 million low income people depend on fish as their food (Hortle 2007; Laurenti 2007) . Globally, fishes provide around 16 % of animal protein for human beings (Tidwell and Allan 2001) . They are economically important for humans, i.e. more than 200 million people directly or indirectly obtain income from the fish industry (Gracia and Newton 1997; FAO 2009) .

In addition, fishes are sources of food for a variety of wildlife species such as birds, reptiles and amphibians, mammals, carnivore fishes and invertebrates (Battley et al. 2003; Yu-Seong et al. 2008; Liordos 2010) .

3.6 Mangrove as a Habitat for Invertebrate Fauna

Mangrove vegetation has attracted diverse insect species (Macintosh and Ashton 2002 ) (Table 4) such as Tide-watching Moth—Aucha velans, Avicennia Seed Moth—Autoba alabstrata, Pneumatophore Moth—Hymenoptychis sordid, Common Aquatic Moth—Erisena mangalis, Mangrove Moth—Odites spp., Avicennia leaf Beetle—Monolepta spp., Rhizophora Root Borer—Coccotrypes rhizophorae, Sonneratia Weevil—Rhynchites sp., Ants—Crematogaster sp., and Mangrove Cricket—Apterombius asahinai (Lim et al. 2001) . These insects play a significant role in the mangrove ecosystem such as pollinator and detritivore, and are a major source of food for birds, fishes and amphibians. It has been reported that Rhizophora mucronata and Avicennia marina support a higher abundance of crabs (Macintosh et al. 2002; Bosire et al. 2004; Walton et al. 2007) .

Table 4 List of invertebrate species recorded in different areas of mangrove and adjacent habitat
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Mangroves are also ideal habitats for a variety of crustaceans, e.g., prawn species such as Mangrove Snapping Prawn—Alpheus spp., Fiddler Shrimp—Macrobrachium sp., Glass Shrimp—Palaemon stylifera, Red-tailed Prawn—Penaeus penicillatus, Edible Prawn—Metapenaeopsis affinis, Small White Prawn—Metapenaeus lysianassa, Giant Tiger Prawn—Penaeus monodon and Mangrove Mud Shrimp—Wolffogebia sp. (Chong et al. 1990; Lim et al. 2001; Penha-Lopes et al. 2011; Nyanti et al. 2012) and crab species such as Mud Crab—Scylla tranquebarica, Mangrove Mud-hopper—Microrchestia sp., Sentinel Crabs—Macrophthalmus spp., Shen Crab—Shenius anomalum, Fiddler crab—Uca sp. (Fig. 32), Orange Mud Crab—Scylla spp., Tree Climbing Crab—Episesarma spp. and Mangrove Tree-dwelling (Lim et al. 2001; Skov et al. 2002; Penha-Lopes et al. 2009; Han 2011; Nyanti et al. 2012) (Fig. 33).

Fig. 32
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Fiddler crab—Uca burgersi feeding in mudflat area

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Aquatic invertebrates play an important role in the ecology of mangrove because they break down leaf litter that act as fertilizer (Robertson 1986; Smith 1987; Slim et al. 1997) , increase surface area of mud through burrowing (Botto and Iribarne 2000; Macintosh and Ashton 2002; Kristensen 2008; Penha-Lopes et al. 2009) and increasing the diffusion rate of gases (Lee 1998; Gribsholt et al. 2003) that ultimately affect the growth and productivity of the mangrove vegetation (Smith et al. 1991; Nielsen et al. 2003; Kristensen and Alongi 2006) . In addition, aquatic invertebrates are a major source of food for different animals such as monkeys, birds, snakes, fishes, and even for humans such as oysters and mussels (Macintosh and Ashton 2002) .

Fig. 33
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Bivalve mollusc in muddy soil of mangrove area

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4 Management of Mangrove Fauna

Mangrove is considered as the most productive natural wetland ecosystem on the earth (Ahmed 2008; Jusoff 2008) due to the richness of nutrients, as well as diversity of flora and fauna . They are rich and diverse in fauna species such as birds, mammals, reptiles, amphibians, fishes and aquatic invertebrates (gastropods, bivalves, echinoderms, arthropods, crustaceans, flatworms, etc.). The majority of fauna species depend exclusively on mangrove for their whole life while others utilize this area in search of food, shelter and breeding purposes.

Nowadays, mangrove areas are decreasing at an alarming rate due to anthropogenic activities such as over-exploitation for fuel wood and fodder, conversion into urbanization, agricultural fields, aquaculture and fish farming, diversion of rivers due to construction of the water reservoirs which decrease inflow of fresh water into mangrove areas, pollution (oil spills, domestic and industrial sewage) and reclamation of inter-tidal areas (Barter 2002; Barbier and Cox 2004; Mineau et al. 2005) . These activities have negatively affected the fauna population of the mangrove. In addition, natural causes can also affect the population of wildlife species such as global warming (Robinson et al. 2009) and diseases outbreak (Rocke et al. 2005; Boyce et al. 2009) . Pullin et al. (2013) argued that species extinction and vulnerability is associated with habitat loss and over-exploitation that may cause the loss of ecosystem functions. Mangrove fauna are under severe pressure, and therefore they need protection and proper management to sustain their population in the future .

4.1 Management Through Habitat Restoration

The regeneration of mangrove vegetation in previously exited areas which have been degraded or destroyed can be done through artificial plantations by the relevant agencies (e.g. Forestry Department and NGOs). This will successfully restore the disturbed mangrove ecosystem into its preexisting condition and also strengthen its capacity to adapt change over time. In addition, the areas devoid of vegetation should be planted with economic and ecologically important mangrove tree species on a large scale to compensate the loss of vegetated areas. This will trap sediments, improve water quality and provide a crucial habitat for a variety of fauna .

4.2 Management Through the Involvement of Local Communities

Involvement of local communities residing near the vicinity of mangrove areas and directly dependent on mangrove goods and service for their livelihood is an essential element in sustainable management and conservation of mangrove fauna . A mass awareness programme should be launched in local communities to create awareness among the people about the benefits, economic and social importance of mangrove fauna . Local communities should be involved in the decision of restoration and management activities. Their involvement and collaboration with stakeholder and government agencies will be fruitful and effective for conservation and management of mangrove fauna in the future .

5 Conclusion and Future Perspectives

The current review indicated that mangrove areas are ideal habitat for a variety of fauna such as birds, fishes, reptiles, amphibians, mammals and aquatic as well as terrestrial invertebrates. These fauna are an important component of the food web and play a significant role in the mangrove ecosystem . In this review we focused on the various fauna of mangrove and adjacent area, threats and their important roles in the ecosystem. We have found that these fauna species are facing overwhelming pressure due to habitat loss and degradation. Furthermore, the current information on the various fauna such as reptiles, mammals, invertebrates, and fishes is not sufficient; thus, there is a need to conduct a more detailed research on various aspects of fauna such as species richness, diversity, distribution and the association of fauna with water quality, food resources and habitats. We hope the findings will provide the ways and means to conserve the fauna in and around mangrove areas.