Why there are marine preserves

I started diving in the Florida Keys in the early eighties. There were a lot of fish there at the time, but not all that many large ones. The old-timers would tell me “you should have been here twenty years ago.” Fishing pressure had reduced numbers and average size. In the nineties I had the chance to dive in Curaçao. I was excited—my first dive in the Caribbean—there had to be lots of great fish, including lots of big ones. Well, not quite what I’d expected. Once again, I was told I should have been there decades ago. Since then we’ve done a lot of diving and snorkeling in Hawaii, Samoa, and Bali. We were always told the same story—it was way better years ago.

The other week Marla and I dove in Cabo Pulmo, about sixty miles northeast of Cabo San Lucas on the Sea of Cortez*. This time it was a different story. It was made clear to us that there were far fewer fish there in the past. The reason: Cabo Pulmo was designated a Mexican National Marine Park in 1995. The region had been seriously overfished in the past, but fishing of any sort has been prohibited since the National Park designation. Fish have responded accordingly, both with respect to abundance and average size. Cabo Pulmo provided some of the best diving we’ve ever had.

Large schools of fish everywhere you looked. Those are Mexican Goatfish on the upper left and Graybar Grunts on the lower right. There are only a few species of goatfish in the eastern Pacific, in contrast to Hawaii and the other side of the Pacific. Grunts are well-represented in the eastern Pacific as well as the Caribbean and tropical Atlantic, but are replaced by their close relatives, the sweetlips, in the western Pacific.

Lots of big fish, too. This largish Leopard Grouper—I estimate it was just short of two feet—swam up and gave me the eye. We saw many other large groupers, some up to four feet in length. I got a few photos but managed to accidentally delete them, along with a pile of other photos.

It’s been well established that allowing fish to grow large benefits fisheries outside the protected area. Large fish produce many more offspring than smaller fish, with the excess moving to adjacent areas where they’re fair game.

A better look at some Graybar Grunts. To me these guys look a lot like emperors or snappers, to which the grunts are related.

Panamic Pigfish, another species of grunt. Superabundant on Cabo Pulmo reefs.

This is a young King Angelfish. There are only four species of angelfish in the eastern Pacific, but they’re all big and showy. More on angels and general fish geekery in the next post.

* Mexico has just moved to change the name from Sea of Cortez to Gulf of California because Cortez was not a nice man.