Habitat and life cycle

M. rosenbergii lives in tropical freshwater environments with access to adjacent brackishwater areas, because its larval development must take place in low salinity water (John 1957; Ling & Merican 1961; Sandifer et al. 1975). Gravid females migrate downstream into estuaries, where the eggs hatch as free-swimming larvae. From egg hatching until metamorphosis into postlarvae (PL), the planktonic larvae pass through several zoeal stages (Ling 1969; Uno & Kwon 1969). The larvae actively swim tail first, with the ventral side uppermost, but at metamorphosis the PL resemble miniature adult prawns and tend to settle on surfaces and walk. When they do swim it is forwards, with the dorsal side uppermost (New & Singholka 1985). PL not only walk on the substratum but also attach to vegetation (Ling 1969). After metamorphosis PL become positively rheotactic and begin to migrate upstream towards freshwater (Fig. 3.1). This behaviour can be used to separate out PL from other larvae under culture conditions (Smith & Hopkins 1977). Migration upstream is not always immediate, with the PL staying in the brackishwater for up to two weeks (Ling 1969; George 1969). Ling (1969) reports that from one month old they can migrate quite rapidly and at two months can swim against strong currents and even cross rapids. They are also able to climb vertical surfaces (small waterfalls, weirs, etc.) and can utilise even very shallow water sources to move long distances; Ling (1969) reports up to 200 km. George (1969) pointed out that this upward migration of PL took place under different conditions in the Hooghly and Kerala river systems.

Adult prawns are active at night (Ling & Merican 1961; Nakamura 1975), and during the day prawns rearrange their positions to remain in shaded areas (John 1957; Karplus & Harpaz 1990). The juveniles exhibit nocturnal swimming activity, probably to take advantage of pelagic food resources, whereas during the day they settle on the bottom and crawl (Scudder et al. 1981).

The diet of larvae is principally zooplankton (mainly minute crustaceans), very small worms, and the larval stages of other crustaceans (New & Singholka 1985). Post-larval and adult M. rosenbergii are omnivorous, eating algae, aquatic plants, molluscs, aquatic insects, worms and other crustaceans (John 1957; Ling 1969). Cannibalistic behaviour may occur if food becomes insufficient, and/or in overpopulated ponds.

How To Have A Perfect Boating Experience

How To Have A Perfect Boating Experience

Lets start by identifying what exactly certain boats are. Sometimes the terminology can get lost on beginners, so well look at some of the most common boats and what theyre called. These boats are exactly what the name implies. They are meant to be used for fishing. Most fishing boats are powered by outboard motors, and many also have a trolling motor mounted on the bow. Bass boats can be made of aluminium or fibreglass.

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