The Bodhisatta was once a king’s chaplain. One day some fishermen caught a large fish and decided to eat it right there on the beach. As they sharpened a spit to cook it on, the fish began to cry. He was not upset over his impending death; rather he did not want his beloved wife to think he had run off with another fish. The Bodhisatta came down to the river and heard this fish lamenting its fate. Feeling pity for him, the Bodhisatta told the fishermen to release him back in the river.
In the Lifetime of the Buddha
The two fish were earlier births of one of the Buddha’s disciples and his wife from before he joined the sangha. When the disciple began to long for her, the Buddha told him this story to let him know she was ultimately harmful to him (he was caught in the fisherman’s net because he was paying attention to her and not to his own safety) and that he had saved him from death in a previous life.