Short communicationInferring functional extinction based on sighting records

- The term functional extinction denotes permanent reproduction or recruitment failure.
- It can be very difficult to detect in poorly studied populations.
- We describe a novel statistical method for detecting functional extinction.
- The method is applied to the ship sturgeon population in the Danube River.
- Results indicate its functional extinction, most likely no later than 2002.

The term functional extinction is used to describe a permanent failure of reproduction or recruitment in a population. Functional extinction results in a truncation of the age distribution, but this can be very difficult to detect in poorly studied populations. Here, we describe a novel statistical method for detecting functional extinction based on a sighting record of individuals of known or estimated ages. The method is based on a simple population dynamic model and simulation results show that it works well even with limited data. The method is illustrated using a sighting record of the ship sturgeon (Acipenser nudiventris) in the Danube River. The results indicate that this population is functionally extinct, most likely by 2002. Management implications of this finding are discussed.

57