Pete,

There are spinning reels that can be used to take saltwater species large and small (not sure about bill fish and sharks) but certainly up to 200 kilos no problem. It just comes down to $ and good spinning reels that have heavy drags and can handle big fish are going to cost.

As to rod length, while longer rods do provide more leverage to the fish, there are a couple of things to remember especially as most fishermen have moved to braided lines which are wonderful due to their low drag in the water and sensitivity. That nearly no stretch wonderful braided line that replaced quite stretchy mono has put the strain that was previously born by the mono onto the reels drag and the rod itself. So the advantage of the longer rod is it can better absorb the stress of the fish as it runs. Also the longer rods will load up to keep tension on the line and keep the hook in the mouth vs. a short rod that just doesn't have the length to load up.

Of course as technology has marched on, rod manufacturers have followed suite with "parabolic" rods i.e. those that bend over their entire length essentially offering the advantage of a longer rod in a shorter rod package.

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The parabolics do have a different feel when jigging and fighting a fish.

I can't comment on the heavier spinning reels as I haven't taken the plunge yet but do pan on setting up a pair in the next season or two.