Parents in Asia like to provide fish for their children's meal.

     Fish, especially salt water fish, is high in omega-3 fatty acids, which is heart-friendly.
Fish is also rich in DHA which boost children's brain, and less in fats and cholestrol.
Most believe that Japanese and Nordic have high life expectancy are due to their consumption of fish and fresh seafood.

     Due to industralization and urbanization, some of our seas have been polluted. Thus, fish living in the polluted sea will carry and accumulate the toxins/metals. One of most common metal found in fish is Mercury. The presence of Mercury is harmful for pregnant ladies, nursing mother and children. Mercury will accumulate in our body if constantly taking fish contaminated with mercury.
If reach a high level, mercury will acts as a neurotoxin, interfering with the brain and nervous system. It might also affect the development of feotus in pregnant lady.

     So, what are the fishes that have highest mercury level?
The NRDC compiled a list of fish and their level of mercury

LOWER MERCURY
Akagai (ark shell)
Anago (conger eel)
Aoyagi (round clam)
Awabi (abalone)
Ayu (sweetfish)
Ebi (shrimp)
Hamaguri (clam)
Hamo (pike conger; sea eel)
Hatahata (sandfish)
Himo (ark shell)
Hokkigai (surf clam)
Hotategai (scallop)
Ika (squid)
Ikura (salmon roe)
Kaibashira (shellfish)
Kani (crab)
Karei (flatfish)
Kohada (gizzard shad)
Masago (smelt egg)
Masu (trout)
Mirugai (surf clam)
Sake (salmon)
Sayori (halfbeak)
Shako (mantis shrimp)
Tai (sea bream)
Tairagai (razor-shell clam)
Tako (octopus)
Tobikko (flying fish egg)
Torigai (cockle)
Tsubugai (shellfish)
Unagi (freshwater eel)
Uni (sea urchin roe)

HIGH MERCURY

Ahi (yellowfin tuna)
Aji (horse mackerel)
Buri (adult yellowtail)
Hamachi (young yellowtail)
Inada (very young yellowtail)
Kanpachi (very young yellowtail)
Katsuo (bonito)
Kajiki (swordfish)
Maguro (bigeye, bluefin or yellowfin tuna)
Makjiki (blue marlin)
Meji (young bigeye, bluefin or yellowfin tuna)
Saba (mackerel)
Sawara (Spanish mackerel)
Seigo (young sea bass)
Shiro (albacore tuna)
Suzuki (sea bass)
Toro (bigeye, bluefin or yellowfin tuna)

 source: NRDC - http://www.nrdc.org/health/effects/mercury/sushi.asp

Please choose your fish carefully.