I don't know that there's ever been an in-lore mention of Darkspear engaging in any kind of fishing specifically.

Sure, you'll see Darkspear fishing trainers, the Darkspear at Shadowprey Village are obviously fishing, and the Echo Isles show plenty of evidence to that effect, but I don't know that there's ever been a specific mention of the Darkspear saving the Orcs from starvation with fish.