Shares in Banco Espírito Santo SA plummeted as much as 50% Thursday while its bonds also plunged, suggesting the most resilient shareholders are finally yanking their money out of the troubled lender in a long-drawn-out Portuguese banking drama.

Late on Wednesday, Portugal's No. 2 lender by assets, which brought in new management earlier this month, reported a record €3.49 billion ($4.68 billion) net loss for the second quarter, after it found more exposure to its troubled parent than it previously expected.

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