Kill Everything around it. Your best bet is a Baryonyx. Ichthys will be as good as dead, Megalodons might get shred by Mantas as well. To get the aggro of Mantas, just attack one that is away from the Basilosaurus and the others will come to retaliate.
If you plan to use Raw Prime Meat or Raw Mutton, don't dare thinking that you can keep it all in your inventory before spoiling. Drop every piece of meat into your (well-feed) mount and pick one at a time, dismounting, feeding, mounting and repeating.
Bringing salts won't be harmful either, specialy when it comes to Raw Prime Meat. Raw Mutton will last more than enough without salts, but again, as long as it stays on a tamed creature.