32 DECEMBER 2016 • WORLD AQUACULTURE • WWW.WAS.ORG totoaba meat began to develop across the US border in California and Arizona. During those years the totoaba fishery attracted people to areas that previously had been practically unpopulated, with important sociological and ethnographic consequences. For example, permanent settlement of the Seri indigenous group in Bahia Kino ended their traditional seminomadic ways as huntergatherers and was the main cause of their assimilation into Mexican culture (Bahre et al. 2000). The evolution of totoaba capture between 1930 and 1975 (Fig. 4) constitutes a typical example of overfishing and habitat degradation contributing to the collapse of a fishery. The emerging industry responded to the growing US market by developing transportation and refrigeration infrastructure and by improving fishing gear efficiency and boat facilities (Flanagan and Hendrickson 1976). Fishing effort and captures grew steadily. At its peak in 1942, roughly 2,400 t of totoaba were landed and nearly 1,300 t of totoaba fillets were exported to the United States (NOAA 2016). More effective gear and the sheer intensity of fishing pressure were decimating the population and making capture increasingly difficult. Other than indiscriminate fishing, other causes contributed to the decline of totoaba. In the United States, completion of Hoover Dam in 1935 and Glen Canyon Dam in 1966 greatly reduced the volume of freshwater flow from the Colorado River to the Sea of Cortez (Fig. 4). With the addition of more dams along the river, little fresh water has flowed into the Sea since the late 1960s (NOAA 2016). Given the state of the Colorado River delta today, it is difficult to imagine that only 80 years ago the river delivered an average of 18 billion m3 of fresh water per year, creating tidal estuarine conditions that extended 40 km into the upper Sea of Cortez. The delta ecosystem covered an area of 8,600 km2 of river channels, marshes, lagoons, and riverside forest vegetation, supporting an abundance of wildlife such as jaguar, deer, beaver, migrating birds, shrimp, and fish, including totoaba (Alles 2012). Today practically all Colorado River water is diverted on both sides of the US-Mexico border to irrigate crops and for residential use. Along with the reduced flow, water temperature and salinity have increased in this area critical for totoaba spawning and early life. Incidental bycatch of juvenile totoaba by shrimp trawlers and the resulting degradation of nursery grounds have also been identified as factors contributing to decline of the fishery (Flanagan and Hendrickson 1976). During the 1950s, with captures scarce, fishermen resorted to more aggressive methods. Gill nets replaced angling with hook and line in such quantities that they practically blocked the totoaba’s migratory pathway. Totoaba are very susceptible to such methods because their population occupies limited, well-defined areas, and undergoes reproductive migrations along predictable routes. Also, because totoaba typically do not feed much during their pre-spawning migration to the north, they had up to this time been relatively protected from capture with hand lines, but gill nets decimated the fish before they could reach their spawning grounds. In further desperation, some fishermen resorted to fishing with dynamite. With such fishing pressure the reproductive population declined precipitously, and the catch decreased to about 300 t by 1958. It then increased temporarily during the first half of the 1960s, probably due to the introduction of highly efficient nylon monofilament nets, only to fall dramatically to 58 t by 1975. At that time, the fishery was completely closed by the authorities and a sanctuary zone was designated at the mouth of the Colorado River. No assessment of the totoaba population has been conducted since the fishery closed in 1975, but the fish appears to have had made a modest comeback. However, in the last few years the rebound was set back by reemergence of an illegal fishery that serves the Chinese black market for swim bladders and a regional market for meat, which is disguised by mislabeling the product as the closely-related Official protections Totoaba are, on paper, one of the best protected fish on earth, but because of ineffective enforcement, these protections have failed to prevent the decline of the population: 1940: Mexico institutes a closed season for the totoaba fishery during the peak reproductive season. 1975: The Mexican government institutes a permanent ban on totoaba fishing. 1976: Totoaba is listed in Appendix I of the Convention on International Trade in Endangered Species (CITES), which restricts trade of listed species in all but exceptional circumstances. However, if a breeding facility of an endangered species in Appendix I is registered with CITES, products are treated as if they were in Appendix II, which can be traded legally. 1979: Totoaba is listed under the U.S. Endangered Species Act. This protection criminalizes the introduction of totoaba products, including swim bladders, into the United States. 1986: Totoaba is listed as endangered under the Red List of the International Union for Conservation of Nature and Natural Resources (IUCN). 1993: The Mexican Government decrees the Upper Gulf of California and Colorado River Delta Biosphere Reserve for the protection of multiple species of interest, including totoaba. 1994: The Mexican government prohibits all fishing in the nucleus of the Upper Gulf of California and Colorado River Delta Biosphere Reserve, a UNESCO’s world heritage site, as well as the use of totoaba-specific gill-nets throughout the major distribution of the species. 1996: Totoaba is listed as critically endangered under the Red List of the International Union for Conservation of Nature and Natural Resources (IUCN). 2015: The Mexican government temporarily suspends gill-net and long-line fisheries in the northern Gulf of California in an effort to stop illegal fishing for totoaba and accidental bycatch of vaquita Phocoena sinus, the smallest and most endangered cetacean in the world. This measure includes compensation to fishermen for loss of income. 2016: Mexico makes permanent the ban on the use of gill-nets throughout the upper Gulf of California. Mexico and the US agree to increase cooperation and enforcement efforts to halt illegal fishing and trade of totoaba swim bladders.
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