There is a raging argument still going on after all these years, rod weight for specific fish? This is a personal choice different govening bodies views apart. Through 80% of my saltwater fly fishing, I opt for a 9wt rod. Why? due to coastal condtions, wind rain and temperature, all combines add to weight of flies used and power needed to deliver them correctly to point of impact. Though i have also used rod in the 6,7,8,9,10,12 wt ranges on occassions.

The following is my personal view and not endorsing the use of or otherwise implying this is correct.

7wt rods are ideal for mullet and mackeral if feeding close in or from a kayak.
8wt ideal general purpose bass and pollock rods
9wt for when the weather is bad or you have to target bigger species like, pike, zander, big bass. Or are fishing abroad for larger species tarpon big bone fish ect.
10wt for deep fishing if fishing from a boat, or kayak in deep water where you could encounted big cod, pollock, ling, bass ect

12wt now we are getting into bigger guns here, recently the guys from www.sportfish.co.uk managed to bag a blue shark on a sage Xi3 rod that is a cracking achievment in itself and i am indeed loong to do this in 2012 when time allows a little more. 

14 and 16wt rods are available for big game shark, bill fish, sailfish, ect the list goes on though these are tropical water fish. If i could only fish a single rod for seffing it would be a 9wt due to power ti handle conditions that often fcae us and also the lightness of the tippets that can be used for mullet fishing if chose. I have hked mullet that couln't be handled by the 7wt rods, thus resulting in lost fish. This said i still feel that if i was using the sage Xi3 or orvis helios a professional salt rod then i may have stood a chance. The reason i say this is that the rods are designed with a different task in mind. Remember that all trout rods are designed to give and bend a lot more salty rds on the other hand are desiged with a much steeper power curve right through to the butt section. 

The following are situations that are real world. By this, i mean i have used or indeed witness them being used. 

7wt greys g-tec, mullet fishing on the plym enough power to present the fly at medium distance, but trong enught to handle fish into the 7lb marker.
8wt bass fishing off a secret mark in the dead of night with only a headlight, and hooking into a 9lb bass and fighting it hard landing on the reef in waders up to my waits in water.
9wt blowing a gale and fishing at wembury off the rocks no matter the wind i could side cast under the worst of it and still reach fish.
10wt carp fishing on the fly surfcae fishing for them hooked and landed a 27lb mirrir carp faster than i could on carp tackle.
12wt pike fishing in exeter canal a few years ago i was using a fly that was 9 inches long though the rod still managed to cast this with relative ease.

Now in the end rod weights and choice are all personal preference, if fishing in the salt then rods designed for this tast are lways preferable. though n need to spen a fortune. Though this said if you do then you get what you pay for. Sage, Orvis, Scott, Thomas and Thomas the list goes on they are all proiving at least 25 year garantees, i have broken many rods though when this happens i drop it back to them and get a replacment in a couple of days. 

if you should have any queries or questions then feel free to contact me through the site. After all, it is free to join and just there to assist other anglers in the pusuit of happiness (well fish, anyway...)

tight lines all...