10 years ago, there was an article on CNN that predicted fish would move out of the tropics towards colder northern waters at a rate of 40-45 KM per decade. 10 years later, another study found that the number of tropical species have halved in the last 40 years.
As predicted, they're moving northward and southward (as are land animals, insects, and plants) and also predictably, causing temperate climate fishes to flounder and loss of kelp as these new species eat them.
Other thing to consider, "Some fishes might be found across more of our coastline while others will become less abundant. So while we see more fish here overall, our study shows that the loss of kelp only has negative effects on temperate and not tropical species" says Dr. Shannen Smith, candidate with UNSW's School of Biological, Earth and Environmental Sciences.