Shark,
Piranha(although they attack only in packs),
Some very big Catfish (http://www.snopes.com/photos/animals/giantcatfish.asp) ,
Some huge Squids (http://www.msnbc.msn.com/id/17275072/ns/world_news-world_environment/t/huge-squid-caught-could-be-biggest-ever/#.UPuyFazCa04)
We really don't know that much about ocean,some scientist say that we know more about the Universe than we know about the depths of our seas.
You could watch Jeremy Wade's tv series :"River monsters" to find more man-eating fish.
sharks
It mainly steals the food from other animalsThey eat fish.
piranha
depending on how big they are yes
No. Spoonbills eat small fish, amphibians and invertebrates.
They can eat lures, bait, worms, corn, bread, popcorn, and a lot of other human food. They also eat each others fish eggs. Some fish, like a carp, will just eat about any human food, bait, lure you give them.
fish food is a great food for cray fish
Angler fish eat practicly anything in it's path and can strike it's prey in 0.09 seconds so less then a second
depending on who hungry they are they eat small fish or human
Yes called caviar.
sharks
No, because it can be poisonous to the fish and they will eventually die. So, I recommend feeding them fish food.