Natural seawater

Natural seawater supplies may originate either from the open sea or sometimes from shallow beach wells, where natural filtration helps to exclude harmful protozoa and bacteria. Usually, locations are chosen where the salinity is 30 to 35 p.p.t. Although estuarine water can be used, when its salinity is above 12 p.p.t., this source is normally avoided because the high level of micro-organisms, which require enhanced treatment before the water is used. Natural sea-water from shallowbeach wells wouldbe preferable (New& Singholka 1985); however, water analyses should be done to profile the chemical composition and detect any abnormalities or potential toxins (e.g. heavy metals, ammonia). The site requires careful choice to avoid pollution or low salinity during rainy seasons. Hsieh et al. (1989) reported lower M. rosenbergii postlarval production in Taiwan when polluted seawater was used in hatcheries.

Some inland hatcheries in Thailand, the Philippines and Bangladesh dilute brine or rock salt with freshwater to obtain brackishwater (New 1990; Chowdhury et al. 1993; Kongkeo et al. 2008). This reduces the cost of transporting seawater to inland hatcheries. However, ionic composition is not always maintained after the dilution. The use of natural seawater in M. rosenbergii hatcheries is preferred because it increases productivity (Daniels et al. 1992; Mallasen & Valenti 1998a). The cost is very low for coastal hatcheries. On the other hand, truck transportation for 100 km or more is frequent in Brazil (Valenti 2007) and costs (in 2008) about US$,TS>50 to 80/m3 for every 500km; such costs have stimulated research into the use of artificial seawater.

The volume of seawater required can be calculated by the following formula:

Vmt Sbw

Vsw = saltwater volume;

Vmt = mixing tank volume;

Sbw = brackishwater salinity desired;

Ssw = saltwater salinity.

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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