From WoWWiki

The Big Iron Fishing Pole is a specially-made pole that requires skill to use, but enables the angler to have a better chance of catching fish.

Source

The pole will occasionally drop from Shellfish Traps in Desolace.

Notes

This item does not drop from the monsters that spawn in the area or from the monsters that may spawn from the traps, but will be lootable off the trap itself. The traps will give you either a few shellfish which are only used for the quest Fish in a Bucket, the pole, random vendor trash items, occasionally some random green items, or a hostile level 35 or 36 makura. This last makes it slightly hazardous for level 35s to grind for the pole.

The +20 bonus to fishing skill on this pole is only midway in the fishing poles, but it is better than it may seem. It is much better than the [Strong Fishing Pole], the next lesser fishing pole. It is as good for fishing as [Seth's Graphite Fishing Pole], the next better fishing pole, and is available earlier. It is nearly as good for fishing as the [Nat Pagle's Extreme Angler FC-5000], the next better fishing pole beyond that, is available earlier, and is available to both factions.

Getting the [Arcanite Fishing Pole], the one much better fishing pole, is extremely competitive, there are only 52 opportunities per year to even attempt to obtain one (per server, but the event is happening concurrently on all servers, so you still only get 52 attempts (... sort of; if you are on server A, the contest might end before server B ends, and you could switch servers and compete on server B, but you are not going to win; too many other competitors are already way ahead of you.))

Also, since this item is a white-ranked non-BoP item, you can auction it, buy it, trade it between characters, or let a friend or one of your alts "borrow" it. You can make a decent income farming these at moderately high levels.

At fishing skill level 375, the Big Iron Fishing Pole and a +100 fishing lure will give you 495 fishing skill. This is enough to fish in all areas and to not have fish get away in all but the hardest (Tier 10) areas. On the other hand, no fishing skill bonus beyond lures is necessary until the hardest areas, if you keep your fishing skill up.

External links

Fishing Poles
Fishing Pole • Blump Family Fishing Pole • Strong Fishing Pole • Big Iron Fishing Pole Seth's Graphite Fishing Pole • Nat Pagle's Extreme Angler FC-5000 • Arcanite Fishing Pole