Current practice on first-world vessels sometimes includes solar panels, but even better is an EPIRB [1]. Too expensive for third-world fishermen who anyway did not intend an ocean crossing. You don't need long-term power for it, because you only activate it once, it is more power efficient than talking on a radio, and it doesn't need to run for very long, because there is a high chance you will be rescued straight away.

[1] https://en.wikipedia.org/wiki/Distress_radiobeacon