The Mexican lookdown is an oddly shaped, silvery fish with a steep forehead that gives rise to its common name. From the side, this fish has a tall, broad profile, but from a head-on perspective, it is extremely thin and is very difficult to see. Utilizing this difference in perspective, the Mexican lookdown can confuse both predators and prey, “changing size” by simply changing direction. This species is native to shallow, coastal waters from the Baja California Peninsula, Mexico to northern South America.
Mexican lookdowns are foraging predators that feed over sandy and muddy soft bottoms. They are known to eat a variety of small invertebrates – including shrimps, squids, and polychaete worms – as well as small fishes. They feed in small schools but do not have coordinated hunting/foraging behavior. Though Mexican lookdowns are eaten by large, coastal fishes and sharks, they have little nutritional value because they are so incredibly thin. They are excellent swimmers and can often outmaneuver potential predators.
This species reproduces through a behavior known as broadcast spawning, where females release eggs and males release sperm into the water column, above the seafloor, at the same time. This method increases the likelihood that eggs will become successfully fertilized and that fertilized eggs will not be eaten by egg predators near the bottom.
The Mexican lookdown is fished for local consumption throughout its range, but it has little commercial value. It is also accidentally captured in net fisheries targeting other species and targeted in catch-and-release sport fisheries, but none of these fishing activities is currently threatening this species. Though population trends are not well known, they are assumed to be stable, and the Mexican lookdown is a species of least conservation concern.