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Rufiji-Mafia Channel - Key Species

Penaeid Prawns

Mullidae

Leiognathidae

Gerreidae

Teraponidae

Trichiurus lepturus

Sphyraeridae

Sciaenidae

Penaeid Prawns

There are four dominant penaeid prawn species; Penaeus indicus (H.Milne Edwards 1837), Metepenaeus monoceros (Fabricius, 1798), Penaeus monodon (Fabricius, 1798), Penaeus semisulcatus (De Haan, 1844) in the Rufiji-Mafia Channel ecosystem, all with significant economic value. These penaeids spend part of their life cycles in brackish water estuaries. The life cycle goes through several stages of development, from fertilized egg nauplius zoea mysis larva juveniles and finally adult. Sexually mature prawns spawn in the deeper marine (open sea). Through the larval stages, the nauplius reaches juvenile stage while migrating to the shallower coastal waters where vegetation provides nursing grounds for their development. Reaching sub-adult, they return back to the sea where they are recruited to the fishery. The prawn stocks have been assessed by the Tanzania Fisheries Research Institute (TAFIRI) as a depleted stock.

Mullidae

Species belonging to family Mullidae (Upeneus sulphureus, Upeneus taeniopterus, Upeneus bensasi, Upeneus tragula and Upeneus moluccensis) inhabiting shallow coastal waters on sandy or silty bottoms, near coral reefs to 40 m depth, sometimes found in turbid waters and over muddy bottoms to 100m depth. They feed on small worms and crustaceans forming large schools during the day but are solitary or in small groups at night when feeding. Juveniles are usually found offshore (TAFIRI, 2008). These species are caught either as by-catch in the prawn fishery or by artisanal fishers.

Leiognathidae

These small, bony fish inhabit shallow coastal waters and move in schools mostly near the bottom. Often they enter the estuaries and their seawards distribution is not beyond depths of 40 m. They are effectively caught in trawl nets, beach seines.

Gerreidae

The Gerridae inhabit shallow coastal waters up to depths of 50 m, often entering the estuaries, lagoons and sometimes lower fresh water reaches of River Rufiji, hunting macro fauna. Juveniles are found in brackish mangrove estuaries and on sand or muddy-sand bottoms (TAFIRI 2008).

Teraponidae

Species belonging to this family (Pelates quadrilineatus, Pomadasys stridens, Terapon jarbua, and T. theraps) are also effectively caught as by catch in the prawn fishery in Rufiji Delta. They are found in schools in brackish waters, commonly in estuaries of the River Rufiji. Juveniles commonly occur in sandy intertidal areas. P. stridens feeds on small fishes and invertebrates, while T. jarbua feeds on small fishes, insects, algae and sand dwelling invertebrates. T. jarbua spawns in the sea and juveniles migrate into fresh water

Trichiurus lepturus (Trichiurus lepturus)

T. lepturus is commonly caught as by-catch by shallow-water prawn trawlers along the Rufiji Delta coastal waters. It is a predator feeding on fish and occasionally squids and crustaceans. Adults and juveniles have opposing complementary vertical diurnal feeding migration patterns: large adults usually feed near the surface during the day then migrate to the bottom at night; juveniles and small adults form schools about 100 m above the bottom during the day and form loose feeding aggregations at night near the surface where they prey on planktonic organisms such as euphausiids, small pelagic planktonic crustaceans and small fish (anchovies, bregmacerotids, etc.).

Sphyraeridae (Sphyraena obtusata)

S. obtusata inhabits bays and estuaries, found in large schools in sea grass beds and rocky reefs of the Rufiji Delta. Feeds mainly on fishes, but also penaeid shrimps and squids during the day as well as at night (diurnal and nocturnal). Juveniles prefer brackish water areas, bays and stream of River Rufiji

Sciaenidae

The members of this family (Johnieps sina and Johnius dussumieri) are found in coastal waters of the Rufiji Delta down to 40 m depth, they enter the estuaries feeding on invertebrates and small fishes. Otolithes ruber, belonging to the same family has a wide range of occurrence with in this ecosystem, feeding on fishes, prawns and other invertebrates.