There is an increasing demand for fisheries resources worldwide. The brown sea cucumber *Isostichopus fuscus* is the most valuable species from the Eastern Pacific and it has been almost depleted due to overfishing. Here, we show that it is important to consider the spatial structure of *Isostichopus fuscus* populations when granting quotas. Given the high levels of illegal fishing within the Gulf of California, it is imperative that quotas are based on the lower bounds of spatially explicit density estimates – along with increased surveillance and enforcement – if the long-term commercial sustainability of the fishery is to be maintained.