Skimming through the various google search articles on this event, it appears that this was mostly a con job by a California businessman to get some money ($2.5M) from a Haida Gwaii community under the guise of increasing plankton which would feed salmon and also create carbon credits. The salmon part was the carrot for the money from the Haida Gwaii village, the carbon credit part was probably what the CA business guy thought he could make the real financial killing on. The project was described as dumping 100 metric tonnes of "iron fertilizer" in a 1 Km area in a known current eddy about 200 KM off of Haida Gwaii. Description of post application assessment was not included in the project by the sponsors. But they said "it worked". Even though that's a lotta fertilizer, it's a nightly big ocean and it's hard to think that the effect would be anything other than short term and localized and only by chance would some salmon benefit.