Eggplant Pest

I planted Japanese eggplant for the first time this year and was dismayed to discover that every single eggplant was riddled with holes.  Something bored into them but I did not find anything when I cut them open.  I tried googling eggplant pests but only came up with insects that ate the leaves.  Does anyone know what attacked my eggplants and what I can do to prevent this in the future?

Thank you!