Mangrove Management

FAO Report, Assessed on 26 June 2016 Saturday

Fauna

A compilation of wildlife species (mammals, reptiles and amphibians) and birds found in the Sundarbans, the world's greatest contiguous mangrove area, is presented in Das and Sidddiqi (1985). McNae (1968) gives a general account of the fauna of mangroves in the indo West Pacific Region and Saenger et al. (1983) look at the global status of mangrove ecosystems including their fauna.

Reptiles and amphibians

Crocodiles and alligators are some of the most significant reptiles that naturally inhabit marine and estuarine environments.

Two species, Crocodilus acutus (lagarto) and Caiman crocodilus (largarto cuajipal), are found in Costa Rica where they are listed as endangered species, largely due to international trade in their hides. C. acutus has a very wide geographic range and is found in Cuba, Pacific Coasts of Central America, Florida and Venezuela. The Cuban species, Crocodilus rhombifer is found in Cienaga de Lanier and is endemic. The American alligator Alligator mississippiensis is listed as endangered in Florida (Hamilton and Snedaker, 1984). In West Africa the Long Snouted Crocodile (Crocodilus cataphractus) is found in mangrove areas and in Asia the saltwater crocodile Crocodilus porosus is endangered over a large part of its range. Efforts are, however, being made to conserve it in India, Bangladesh, Papua New Guinea and Australia (FAO, 1982).

The large lizards, iguana iguana (iguana) and Cetenosaura similis (garrobo) are commonly found in the mangroves in Latin America, where they are eaten by the local people, as are their cousins in West Africa (Varanus exanthematicus) and Asia (Varanus salvator).

Riverine tortoises are common and marine turtles are known to lay their eggs on the sandy beaches in many mangrove areas throughout the world. Along the Pacific coast of Costa Rica, the two most important egg-laying sites visited by the Pacific Ridley Turtle (Lepidochelys olivacea) is in the Playa Nacite in the Santa Rosa National Park and in the Playa Oe ostional near the Rio Nosara. This turtle is relished for its meat and weighs an average of 40 kg. Its numbers are diminishing because of predation and over-exploitation in some countries, notably Mexico and Equador.

A number of snakes can also be found in mangrove areas especially in the landward fringe.

Aquatic resources

The importance of the mangrove areas as feeding, breeding and nursery grounds for numerous commercial fish and shellfish is well established (Heald and Odum, 1970; MacNae, 1974; Martosubroto and Naamin, 1977). Similarly, Chong (1987) reported that the location of fishing grounds in Sierra Leone is geographically correlated to the distribution of coastal mangroves.

The development of soft clayish mud, where the crabs can make their burrows, and the growth of seagrass or turtle grass have been observed to attract the crustacean fauna along the mangrove areas.

Matthes and Kapetsky (1988) have prepared a worldwide compendium of mangrove-associated aquatic species of economic importance including such information as geographical extension of each species; the parts of the mangroves in which it is found; the organism's dependency upon the mangroves and its quality and use in fisheries.

Fish

There are reported to be over 120 species of fish caught by fishermen in the Sundarbans (Seidensticker and Hai, 1983), almost all of which are brackish water and esuarine species. Ulloa (1978) reported 92 species of fish belonging to 13 families caught in Jiquilisco Bay in El Salvador.

Species of commercial interest include mullets (Mugilidae) snappers (Lutjanidae), milk fish (Chanos chanos), sea bass (Lates calcarifer) and tilapia (Cichlidae). The most conspicuous fish is perhaps the mudskipper (Periophthalmus sp.), which is endemic to the mangroves.

Shellfish

Despite the presence of the more spectacular mammals and reptiles, indications are that the animals which contribute the greatest biomass in the mangroves are the shellfish [a collective term for crustaceans (crabs and prawns) and molluscs (bivalves and gastropods)].

The fiddler crab Uca sp. and the various species of Sesarma are common inhabitants in the intertidal mangrove zones throughout the Indo-Pacific region. Crabs of the Pox-tunidae family have been observed in the Arabian Gulf area and the United Emirates. The edible crabs (Scylla serrata in Asia and East Africa and Callinectes latimanus in West Africa) are a highly valued mangrove product.

The most common prawns include the giant freshwater prawn (Macrobrachium rosenbergii) and the marine penaeid prawns (Penaeus indicus, P. merguiensis, P. monodon and Metapenaeus brevicornis). All of these species probably have a similar basic life history with spawning occurring offshore, an inshore migration of larvae, an estuarine juvenile stage followed by an offshore breeding migration to complete their biological life cycle. However, the species differ in the extent to which they move offshore during this migration. Surveys in Malaysia showed that the genus Penaeus was abundant across all depths up to 50 m, while Metapenaeus were most abundant in the 11-30 m range and Parapenaeopsis were more restricted to the 5-20 m zone.

Reportedly, penaeid shrimps off the coast breed throughout most of the year but with observed peak periods during May-July and October-December, which coincide with the coming of the monsoons. In Western Malaysia peak ingress of P. merciuiensis postlarvae was reported during November and December.

After three to four months in mangrove estuaries, juvenile shrimps migrate into the shallow coastal waters from March to June where sexual maturity takes place. When larger, they move further offshore to spawning grounds in depths exceeding 10 fathoms. Major spawning migrations begin in June and continue to late January.

Regarding molluscs, in Central America, the larger bivalve Anadara grandis (chucheca), is now rare due to overexploitation. The smaller ark clams 'pianquas' comprising principally two species Anadara inulticostata and A. tuberculosa are now exploited in place of chucheca. Anadara tuberculosais the molluscan bivalve commonly found in mangrove ecosystem from Lower California to Peru (Keen, 1971).

The most important bivalve in the Indo-Malayan mangroves is the blood cockle (Anadara granosa) and gastropods commonly collected include Cerithidia obtusa, Telescoplum mauritsil and T. telescopic.

Oysters are also important sources of aquatic production, which like shellfish can be cultured provided suitable substratum is provided to attract the spats and the estuarine conditions are right.

The importance of shellfish as a source of readily accessible protein and an economic renewable resource for coastal dwellers makes it the single most important exploited species in the mangroves.

Benthos

Benthic fauna includes juvenile fish, crustaceans, crabs and bivalves.

Until recently, studies on the benthic fauna of intertidal mudflats in tropical regions have been exceptionally rare in spite of the fact that such studies would provide indications of the value of mudflats as potential feeding habitats for water birds and marine and estuarine fish (Erftemeijer, Balen and Djuharsa, 1988; Silvius, Chan and Shamsudin, 1987). Recent studies have however been carried out for instance in Hong Kong, China and Taiwan - often in connection with feasibility studies on the use of mangroves for waste water treatment (refer to HKUST, 1993).

Mammals

Many mammals frequent mangrove habitats but only a few live there permanently and fewer are restricted to them (FAO, 1982). In many countries however, the mangroves represent the last refuge for a number of rare and endangered mammals.

During low tide monkeys (Macacus irus) in Malaysia are commonly seen foraging for shellfish and crabs, and the white-faced monkey (Cebus capucinus) feed on pianguas (cockles) in Costa Rican mangroves. Reportedly, where such monkeys are numerous, the area is poor in pianguas. They also do a certain amount of damage to newly established seedlings by uprooting them. The Malaysian proboscis monkey (Nasalis larvatus) is endemic to the mangroves on Borneo, where it feeds on the foliage of Sonneratia caseolaris and Nipa fruticans (FAO, 1982) as well as on Rhizophora propagules. The monkeys, in return, are preyed on by the crocodiles and hunted by poachers.

Other mammals include the Royal Bengal Tiger (Panthera tigris), the leopard (Panthera pardus) and the spotted deer (Axis axis) in the Sundarbans; wild pigs (Sus scrofa) and mousedeer (Tragulus sp.) in Nipa swamps throughout South and Southeast Asia; and small carnivores such as fishing cats (Felix viverrima), civets (Viverra sp. and Vivererricula sp.) and mongooses (Herpestes sp.). Otters (Aonyx cinera and Lutra sp.) are common, but rarely seen.

Dolphins, such as the Gangetic dolphin (Platanista gangetica) and the common dolphin (Delphinus delphis) are also found in the rivers of mangroves, as are Manatees (Trichechus senegalensis and Trichechus manatus latirostris) and Dugongs (Dugong dugon) although these species are becoming increasingly rare and in many places are threatened with extinction.

Avifauna

The tidal swamp is an ideal sanctuary for avifauna, some of which are migratory. According to Saenger et al. (1983), the total list of mangrove bird species in each of the main biogeographical regions include from 150 to 250 species. Worldwide, 65 of these are listed as endangered or vulnerable. Several surveys of avifauna in mangrove areas in South East Asia have been carried out.

In Cuba, there are several endemic species which occupy highly specialized ecological niches such as the canario del manglar (Dendroica petechis gundlachi) and the smaller oca del manglar (Rallus longirostris caribaeus).

The most numerous birds are the waders, herons, egrets and storks.

Birds of prey include the sea eagles (Haliaetus leucogaster), brahminy kites (Haliastur indus), ospreys (Pandion haliaetus) and fish eagles (Ichthyphagus ichthyaetus).

Kingfishers and bee-eaters are among the most colourful birds commonly observed in mangroves.

References 

Chong, P.W. 1987. Proposed Management and integrated utilization of mangrove resource in Sierra Leone. Project UNDP/FAO: SIL/84/003, Field Document No. 6.
Das, S. & Siddiqi, N. A. 1985. The mangroves and mangrove forests of Bangladesh. Magrove Silviculture Division Bulletin No. 2, Bangladesh Forest Research Institute and UNDP/FAO Project BGD/79/017. Chittagong, Bangladesh.
FAO. 1982. Management and utilization of mangroves in Asia and the Pacific. FAO Environmental Paper 3. Rome.
Erftemeijer, P., Balen, B. & Djuharsa, E. 1988. The importance of Segara Anakan for nature conservation, with special reference to its avifauna. Asian Wetland Bureau/INTERWADER ?PHPA. Bogor.
Hamilton, L.S. & Snedaker, S.C. 1984. Eds. Handbook of mangrove area management. IUCN/UNESCO/UNEP. East-West Center, Honolulu, Hawaii.
Heald, E.J. & Odum, W.E. 1970. The contribution of mangrove swamps to Florida fisheries. Proc. of the Gulf and Caribb. Fish. Inst., 22: 130-135.
HKUST. 1993. Programme and abstracts. Asia-Pacific symposium on mangrove ecosystems. Hong Kong 1-3 September 1993. Hong Kong University of Technology, Hong Kong.
Keen, A. 1971. Sea shells of tropical West America. Stanford University Press.
Martosubroto, P. & Naamin, N. 1977. Relationship between tidal forests (mangroves) and commercial shrimp production in Indonesia. Mar. Res. in Indon., 18: 81-86.
Mattes, H. & Kapetsky, J.M. 1988. World wide compendium of mangrove-associated aquatic species of economic importance. FAO Fisheries Cic. No. 814. Rome.
McNae, W. 1968. A general account of the fauna and flora of swamps and forests in the Indo-West-Pacific Region. Adv. Mar. Biol., 6: 27-270.
Saenger, P., Hegerl, E.J. & Davie, J.D.S. 1983. Global status of mangrove ecosystems. Commission on ecology papers No. 3. Gland, Switzerland, IUCN.
Seidensticker, J. & Hai, Md. Abdul. 1983. The Sundarbans wildlife management plan: conservation in the Bangladesh coastal zone. Gland, Switzerland, WWF/IUCN.
Silvius, M.J., Chan, H.T. & Shamsudin, I. 1987. Evaluation of wetlands of the west coast of Peninsular Malaysia and their importance for natural resource conservation. WWF/FRI/University of Malaya/INTERWADER Joint Project. Kuala Lumpur, WWF Malaysia.
Ulloa. 1978. 

Extracted from
FAO. 1994. Mangrove forest management guidelines. FAO Forestry Paper No. 117. Rome.

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