I would recommend taming a Basilosaurus first because they are not affected by shocks from eels and easy way to get bio toxin then you can scout one out. Best bet use harpoon gun with tranq spears to not kill. Spend a little time on icebergs gathering kairuku eggs and your all set.
Be really care when knocking these things out from a distance! Unfortunately they don't look knocked out when they are so continuing to shoot darts at them can be an easy an unfortunate mistake to make.