See text The freshwater hatchetfish are a family, Gasteropelecidae, of ray-finned fish from South and Central America.

They tend to be an upper-level fish, often swimming directly below the surface of the water, biding their time patiently.

This is accompanied by large pectoral fins and "extraordinarily powerful" associated muscles which account for up to one-quarter of their total body weight.

"Quick beats of the pectoral fins" allow hatchetfish to "lift themselves half out of the water and glide along the surface ...

"[2] Because of this ability to fly and tendency to jump, aquaria used to keep hatchetfish should have a tightly sealed cover to prevent these fish from escaping.