Bhismadeva was the foremost of all warriors. When he defeated Lord Parasurama in a fight, Lord Parasurama was very satisfied with him. By the semen of Santanu in the womb of Satyavati, the daughter of a fisherman, Citrangada took birth
SB Canto 9
Bhīṣmadeva was the foremost of all warriors. When he defeated Lord Paraśurāma in a fight, Lord Paraśurāma was very satisfied with him. By the semen of Śāntanu in the womb of Satyavatī, the daughter of a fisherman, Citrāṅgada took birth.
Satyavatī was actually the daughter of Uparicara Vasu by the womb of a fisherwoman known as Matsyagarbhā. Later, Satyavatī was raised by a fisherman.
The fight between Paraśurāma and Bhīṣmadeva concerns three daughters of Kāśīrāja—Ambikā, Ambālikā and Ambā—who were forcibly abducted by Bhīṣmadeva, acting on behalf of his brother Vicitravīrya. Ambā thought that Bhīṣmadeva would marry her and became attached to him, but Bhīṣmadeva refused to marry her, for he had taken the vow of brahmacarya. Ambā therefore approached Bhīṣmadeva's military spiritual master, Paraśurāma, who instructed Bhīṣma to marry her. Bhīṣmadeva refused, and therefore Paraśurāma fought with him to force him to accept the marriage. But Paraśurāma was defeated, and he was pleased with Bhīṣma.