Everything eats these. That is their role, and the school is the answer to it.
A silverside is a small, soft, defenseless fish with no spines, no venom, no armor and nowhere to hide, living in open surface water where it can be seen from every direction. What it has instead is company. Thousands of them move as one body, turning together on a delay of a few tens of milliseconds, which is faster than any of them can consciously react and comes from each fish watching only its immediate neighbors.
What that buys is confusion. A predator has to pick one target out of a shifting mass of identical flashing bodies and commit to it, and every time the school splits and reforms the choice has to be made again. Attack success rates on schooling prey are a fraction of what they are against the same fish alone.
It does not always work. When jacks, needlefish, terns and a couple of trevally arrive together the school is driven to the surface and worked from below and above at once, and that is the boiling water you sometimes see off a jetty at dawn.
This one is the common large silverside here, with a broad silver stripe along the side.
The genus. Atherinomorus Fowler 1903 - [h]omorus (having the same borders with). ETYFish
The species. Atherinomorus lacunosus (Forster 1801) - full of cavities. ETYFish
- broad silver stripe along the middle of the side, wider than in its relatives
- translucent greenish back, silver belly, large eye
- always in schools, always near the surface
- up to 14 cm
