A saltwater rod handles freshwater fine, but a freshwater rod fails in saltwater
Fresh water you can generally get away with just rinsing the reel
Ease of Maintenance Because chasing salmon via a variety of techniques will subject your reel to all sorts of baits, scents, sand, mud, saltwater and other grimy gunk, it is important you not only keep things cleaned and maintained from a scent/contamination standpoint, but also for smooth, dependable operation
And of course, because this is an electric bike with 20 mph top assisted speeds and the additional weight of that motor and battery, its important to have reliable braking power
The TMM post on Solo Backpacking with Kids has lots of great ideas on distributing gear weight