The Laguna’s dolphins population is small and isolated. In the last 15 years we are following, from photographs of the dorsal fin, the number of dolphins that use the waters of the Santo Antônio Lagoon. This number ranges from 50 to 60 individuals, and apparently has not changed significantly in recent years, despite the many human activities that have contributed to the death of some individuals. This constant number of individuals is good news, but not enough for big celebrations and dismay. For a species that can live more than 50 years, which begins to reproduce only after 10 years, a population of 50 individuals is a very small population and will always be at risk of extinction.
Ecologists who study populations say that small populations are subject to events of luck or chance. That’s right, they may be lucky enough to persist in time, or the misfortune of disappearing, and it depends on the so-called ‘stocasticity’. Stocasticity is nothing more than unpredictable variations. For example, a fundamental resource for a population can vary in time, occurring years with a lot of resource availability, and others with little. Similarly, in a very small population, individuals need to be lucky to meet and mate, otherwise the population does not reproduce. Being more extreme, by a bit of bad luck, a catastrophic event can occur, such as an oil leak, suddenly increasing the mortality of individuals.
Thus, being Laguna’s dolphins population too small, it can’t play with luck. That’s why we monitor its tirelessly. In addition to photo identifying individuals by dorsal fin, we use specific methods that allow us to accurately estimate the number of individuals from year to year, to find out the probability of these individuals to survive and the chances of leaving the area. All this information allows us to predict what may happen to Laguna’s dolphins population over the next 100 years. An important result that we found is that without drastically reducing the cases of gilling in fishing nets, the population of dolphins of Laguna will have little chance of persisting in the coming years.
Although, we want to go further. Within our PELD, the plan is to continue monitoring the dolphins population as we have been doing for the past 15 years. But now, in more detail, evaluating the effects of the availability of important resources, such as the mullets, and various impacts such as acoustic, chemical and biological pollution. Similarly, we intend to evaluate how interaction with fishermen can help Laguna’s dolphins population survive.
This is a key piece of our PELD, as is the porpoise population for this system. We’re already doing it, and we’re going to keep going…