Fouling is the growth of barnacles, weed, and other water life on the submersed hull of the boat. The colonization of fouling organisms on the boat hull adversely affect the sailing boat or ship in several ways including reducing its speed and durability especially when marine borers colonize wooden boats and dhows. Moreover, fouled ships act as biological belts that carry marine organisms from one location to another. Fouling accumulates on the exterior underwater surfaces of the vessel throughout the period the ship remains in water.
In order to reduce the fouling problems, ship owners often carry out some practices known collectively anti-fouling practices which could range from the periodic dry-docking the ship to remove the marine growth from the hull before applying the new coats of antifoul paint.
The antifouling paints vary in regard their effectiveness and environmental concerns. In general, copper-based tin-based paints have been used for anti-fouling. In fact, paints containing tin such as tributyltin (TBT) were highly effective and have been widely used before its banning due to its toxic effects on marine life. For example, large Tiger Shark is targeted because of their enormous livers.
In several fishing communities, fishermen discovered long time ago the effectiveness of shark liver oil in limiting the growth of marine fouling organisms as well as in discouraging marine wood borers. The adoption of the use of shark oil goes mainly to its availability to shark fishermen as well as to its low cost. The liver size and so the oil contents vary among shark species. Sun-warming and/or cooking (boiling) are means which are adopted to extract oil from shark livers before straining it before use.
The barrels shown in the photo are filled with prepared shark liver oil produced in a shark processing plant in the Sultanate of Oman whereas the owners of wooden fishing boats are the main clients of this oil.