Overview of the Romanian Sturgeon Supportive Stocking Programme in the Lower Danube River System

Abstract

Due to the worldwide decline of the sturgeon population, stocking programmes were developed for many of these species. The critically endangered anadromous sturgeon populations inhabiting the NW Black Sea and spawning in the Lower Danube River are not an exception. Despite no knowledge of the genetic diversity of the remnant populations, the Romanian supportive stocking programme started in 2005, along with the fishing ban in 2006. These actions were aimed to restore the wild sturgeon populations, spawning in the Lower Danube River. This paper presents and discusses the sturgeon supportive stocking programme implemented in Romania and its achievements. Our screening revealed that the minimum effective number of breeders (Ne) could not be achieved for beluga sturgeon (Huso huso) in 2006 and for Russian sturgeon (Acipenser gueldenstaedtii) throughout the entire programme due to the lack of spawners in the wild. Evaluation of the supportive stocking programme success revealed a good survival rate and adaptation of fish stocked to the wild conditions in the river and sea. It showed that two of the species, beluga and stellate sturgeon (A. stellatus) still spawn naturally in the wild, and their populations are in a good genetic shape, so far, having in mind the habitat decline due to the dams constructions on the river and the post genetic bottleneck recovery. Russian sturgeon population do not exhibits any improvement sign so far. The lack of its spawning events in the wild is still noticed, as the majority of fish captured during the evaluation are of hatchery origin, first generation from wild spawners. Therefore, for beluga and stellate sturgeon, the conservation measures should be revised based on the genetic structure of the spawners and a well-defined breeding schemes. For Russian sturgeon the supportive stocking programme should continue, being highly demanded in order to produce a continuum age structured population. The crucial moment for sturgeon conservation will be when hatchery reared specimens return in the river as adults and participate in the spawning events, an event which should be expected within the next years. Overall, the return of the reared individuals in the river as adults and their participation in the spawning events is expected to produce a real change in the Danube sturgeon species fate with a long-term ripple effect.

Keywords

• wild sturgeons
• hatchery origin sturgeons
• Lower Danube River
• NW Black Sea