These are passive tames. In my experience trying to tame a 145. You will find having a Basilosaurus will provide you with a mount immune to the shock.
Wear a combination of Riot and Scuba gear. Bring multiple sets. They will destroy your tanks and flippers if you get hit enough times. Lone eels do not deal enough torpor to be a substantial threat with the riot gear.
The hard part is feeding them. They will glow bright blue (without goggles on) when they have built up a charge, and charge you. Discharge a 7 second stun, bite and then flee.
Lure them into an enclosed area. Such as a trap for water tames or a river. This will reduce their mobility and make them an easier tame than in the open ocean. Because they will flee the majority of the tame if they have the room to do so.
-Results of 3/20/17 taming test on Xbox official servers.
The best way I've found to tame them is to use a basilosaurus,then lure a single electro away from the group and have it shock you (on the mount). Wait about a second for the shock to end and quickly jump off and spam E (keep biotoxin in the 0 slot). *A large school of these can quickly stun and immbobilze larger mounts and knockout players fairly quickly, so use caution!*