Aggressive Shark Behavior?

[QQQ99999]

Several times I recall reading that a couple of signs that a shark is becoming aggressive is arching its back and lowering its pectoral fins.

My question is (and I am sorry if it is stupid) is what exacting is meant by a shark arching its back? Does it mean arching it like a U or an upside down U?

Any other behaviors to keep an eye on?

[Walter]

Upside down U, like an arch.

Erratic motions; circling, especially if the circles get smaller and jutting jaw movements come immediately to mind.

[tiburon72157]

As stated before, arching of back (within relative flexibility range - they can't physically arch into full inverted U), erractic swimming motion i.e. zig-zagging back and forth, mouth agape (partially open), lowering of pectoral fins, overall increased ridgidity of the body. Generally speaking, they are cautious by nature and circling is their method of checking things out and getting a closer look. The circles get smaller as the fish becomes bolder and more aggressive. Some species such as the Great White, Tiger, Bull, Reef and a few others can attack without any kind of warning, or exhibiting prior observable "signs" of imminent aggressive behavior.

[QQQ99999]

Thanks for clearing that up. Much appreciated.

[mnj1233]

Hunching the back is a better description.