Critically Endangered totoaba Totoaba macdonaldi: signs of recovery and potential threats after a population collapse

Abstract

The lack of long-term monitoring programs makes it difficult to assess signs of population recovery in collapsed marine populations. Fishery-induced changes in the life history of exploited marine fishes, such as truncated size and age structure, local extirpations, reductions in age at maturity, and changes in mortality patterns, have occurred. In the present study, we explored life history aspects of totoaba Totoaba macdonaldi, almost 40 yr after a population collapse, to examine whether totoaba maintained their life history pattern and to identify the potential threats of using fishing gear (hooks, gillnets). The results of the present study indicate that the totoaba size structure was not truncated as expected in overexploited populations; indeed, it was similar to that observed in the past. Totoaba have maintained their known historical distribution range. The spatial size structure and temporal distribution followed the known migration patterns of totoaba. Total and natural mortality were similar. Contrary to recommendations for sustainable fisheries, caught fish contained a large number of juveniles, irrespective of method used. We conclude that the general life history (size structure, distribution, migration, and mortality) has not changed since the fishery collapse. However, the choice of fishing gear could compromise a positive recovery trend of the population. Moreover, poaching is a major ongoing threat to the recovery of totoaba.

Extinction is Imminent for Mexico's Endemic Porpoise Unless Fishery Bycatch is Eliminated

“…Much of this decline resulted from the resurgence of illegal gillnetting to supply swim bladders of totoaba ( Totoaba macdonaldi ) to lucrative Chinese markets (Valenzuela‐Quiñonez et al . ; Anonymous , ). Totoabas are large endangered endemic fish about the same size as vaquitas.…”

“…Between 2011 and 2015, a passive acoustic monitoring program determined that vaquita abundance was declining by 34%/year (95% CRI, −48% to −21%; Jaramillo- Legorreta et al 2016). Much of this decline resulted from the resurgence of illegal gillnetting to supply swim bladders of totoaba (Totoaba macdonaldi) to lucrative Chinese markets (Valenzuela-Quiñonez et al 2015;Anonymous 2016aAnonymous , 2016b. Totoabas are large endangered endemic fish about the same size as vaquitas.…”

Passive acoustic monitoring of the decline of Mexico's critically endangered vaquita

“…Fishers have reported receiving up to US$5,000 on the black market in recent years for the swim bladder of a large totoaba (Valenzuela‐Quiñonez et al. ). Of the documented 128 vaquitas caught in gillnets from 1985 to 1992, 65% were caught in totoaba nets, which have a mesh size from 20.0 to 30.5 cm (Vidal ).…”

“…A long-standing illegal fishery for an endangered fish species, the totoaba (Totoaba macdonaldi) (Fig. 2), has boomed in this area within the past 3 years, fueled by a new and lucrative illegal trade with China for totoaba swim bladders (Valenzuela-Quiñonez et al 2015;EIA 2016). Fishers have reported receiving up to US$5,000 on the black market in recent years for the swim bladder of a large totoaba (Valenzuela-Quiñonez et al 2015).…”

“…2), has boomed in this area within the past 3 years, fueled by a new and lucrative illegal trade with China for totoaba swim bladders (Valenzuela-Quiñonez et al 2015;EIA 2016). Fishers have reported receiving up to US$5,000 on the black market in recent years for the swim bladder of a large totoaba (Valenzuela-Quiñonez et al 2015). Of the documented 128 vaquitas caught in gillnets from 1985 to 1992, 65% were caught in totoaba nets, which have a mesh size from 20.0 to 30.5 cm (Vidal 1995).…”