It's not a sexy rule. Limiting the number of tuna purse seine fishing vessels on the water may not grab many headlines in the consumer press, but in the world of tuna, it is a big moment, Mike Crispino, vice president of communications and outreach for the International Seafood Sustainability Foundation (ISSF), told IntraFish.

On Dec. 31, the ISSF will impose a cap on the number of tuna fishing vessels allowed on the water worldwide.

The rule is not backed by any government, but it does impact at least 75 percent of the world’s tuna processing capacity, which is about the amount of capacity ISSF’s members hold, Crispino said.