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.
depending on how big they are yes
piranha
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.
No. Spoonbills eat small fish, amphibians and invertebrates.
Angler fish eat practicly anything in it's path and can strike it's prey in 0.09 seconds so less then a second
fish food is a great food for cray fish
depending on who hungry they are they eat small fish or human
sharks
Yes called caviar.
No, because it can be poisonous to the fish and they will eventually die. So, I recommend feeding them fish food.