VANCOUVER, CANADA—What’s killing the giant totoaba of the Gulf of California? The long-lived fish has been hunted nearly to extinction by fishermen and poachers in Baja California—or so you may have heard. Now, new data presented today at the Society for American Archaeology meeting here confirm that changes to the fish’s environment may have been even more devastating. Archaeologists studying totoaba bones from Rancho Punta Estrella—a site in Baja California occupied by humans 10,000 years ago and then again 5000 years ago—used a special bone from the fish’s inner ear, called an otolith, to help them reconstruct the totoaba’s early environment. Otoliths grow a new layer for each year of the fish’s life, like tree rings. Each layer preserves the chemical composition of the water in which the fish lived during that year, in the form of oxygen isotopes. The newly analyzed ancient totoaba otoliths show the species once spent its early years in brackish water, the lightly salty mix found where a river empties into the sea. Before it was dammed over the course of the 20th century, the Colorado River emptied into the Gulf of California and formed a large estuary; now, the freshwater has been reduced to just a trickle. Earlier analyses of ancient totoaba ear bones show that juveniles once stayed in the estuary for the first several years of their lives. They also matured up to 5 years earlier than their modern counterparts and grew to twice their current size of 100 kilograms. Those results suggest that even if the Mexican government put a halt to today’s profitable totoaba poaching (a swim bladder can go for $14,000 on the black market), the species would still struggle to survive in the gulf’s radically altered environment.
*Correction, 4 April, 3:50 p.m.: This item has been updated to more clearly acknowledge a previous, independent analysis of ancient totoaba ear bones.