The Beluga sturgeon is in trouble, serious trouble.... and requires immediate conservation focus to save the species.
A study of a Caspian Sea fishery and the Beluga sturgeon, demonstrates current harvest rates are four to five times higher than those that would sustain population abundance.
The study’s results suggest that conservation strategies for sturgeon should focus on reducing the overfishing of adults rather than heavily relying upon hatchery supplementation.
The analysis was conducted through a collaboration of scientists from the United States and Kazakhstan. Data used were collected in the Ural River, the only remaining Caspian Sea river where this species of sturgeon reproduce unhindered by dams.
“This is the first time that anyone has calculated sustainable harvest limits for Caspian Sea Beluga sturgeon and compared them to present fishing pressure,” said Dr. Phaedra Doukakis, Senior Research Scientist with the Institute for Ocean Conservation Science at Stony Brook University and lead author of the study. “We can finally attach numbers to what people have suspected – that current management of Caspian Sea sturgeon fisheries will not prevent further population decline. We hope that this study provides the evidence needed to shift mindsets and management practices,” added Dr. Doukakis.
These sturgeon have declined by nearly 90 percent in the past several decades due to the demand for black caviar, inadequate management, and habitat degradation. Black caviar, the unfertilized roe (eggs) of the Beluga sturgeon, is the most valuable of all caviar, sold for as much as $8,000 for one kilogram (2.2 pounds). The species has gone extinct in the Adriatic Sea and is on the brink of extinction in the Azov Sea.
This sturgeon can live more than 100 years, and do not reach maturity until 9 to 20 years of age.
The researchers found that the optimal age of first harvest is 31 years because older and larger fish produce more eggs.
Conservation efforts would be much more effective than current practices if minimum size limits for fishing targeted this optimum age for first capture and if the illegal harvest of subadult fish were reduced.
These fishing limits would allow the survival of subadult and adult females and would increase population by ten times that achieved by hatchery supplementation, which is the current conservation focus by fisheries .
Survival of hatchery-reared fish in the wild is thought to be very low and genetic diversity may be compromised by hatchery practices, which can jeopardize the long-term survival of all sturgeon.
“This study clearly shows that reducing the mortality of wild sturgeon adults is a much more effective conservation strategy than hatchery supplementation,” said Dr. Ellen Pikitch, Executive Director of the Institute for Ocean Conservation Science and a co-author of the study.
“Ten hatchery fish would need to be produced to achieve the same conservation benefit as preventing the kill of a single wild sturgeon.”
The Convention on International Trade in Endangered Species (CITES) listed beluga and most other species of sturgeon as threatened in 1998 with an Appendix II listing. Since then, Beluga numbers have declined by approximately sixty percent showing current methods of conservation are not working.
Drs. Pikitch and Doukakis presented the findings of this study and related research on the status of beluga sturgeon at a meeting March 18, 2010 at the 15th Conference of Parties to CITES in Doha, Qatar.
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