By Ellen K. Pikitch, Ph. D.
The Report on Results of Complex Interstate All-Caspian Sea Expedition on the Assessment of Sturgeon Species Stocks, 2002 covers many aspects of the results of a survey conducted in the Caspian Sea during 2002 (hereinafter referred to as 2002 report). I will focus my comments primarily on the estimates of beluga sturgeon abundance and on the inferences I draw based on a comparison of the results of this survey with the Caspian Environment Program Survey conducted in 2001 (2001 report).
The 2002 report indicates that a total of 56 beluga sturgeon were caught in the survey. Of these, 38 were obtained in 333 trawl catches, with the remaining 18 beluga caught in some unspecified number and type of net catches. From these extremely small numbers of beluga sturgeon actually caught, the summary of the 2002 report states that the abundance of beluga sturgeon in the Northern Caspian is 11,105,900 (or about 11.1 million) individuals. I have studied this report many times, and I cannot find a rationale for this extrapolated estimate.
However, it appears likely that at least one of the factors used in the extrapolation is a catchability coefficient of 0.04 for the 9 m trawl, as this number is given in the text of the report. In previous comments I submitted to the U.S. Fish and Wildlife Service I provided extensive scientific evidence that the 0.04 factor used is much smaller than is scientifically justifiable, and that use of this factor would result in overestimation of population abundance by a factor of 25 times. The other factors used to estimate abundance in the 2002 report are neither presented nor justified, and clearly, any inaccuracies and biases in these factors would be magnified in an extrapolation from the small number of beluga sturgeon sampled to the large population estimate given.
As I indicated in my previous comments I believe the most rational use of the survey data is as a tool for assessing relative trends in abundance across years, especially given the lack of documentation or justification for most of the factors used to estimate total abundance, and the fact that a key factor being used in the analysis is one which, on its own, overestimates abundance by 25 times. When results of the 2002 trawl survey are compared to those in the 2001 trawl survey they indicate a marked decline in beluga sturgeon abundance in the Caspian Sea in just one year. In 2001 a total of 28 beluga sturgeon were caught in the 159 trawl catches conducted, for a ratio of 0.18 beluga per trawl tow; whereas in 2002 a total of 38 beluga sturgeon were caught in 333 trawl tows conducted for a ratio of 0.11 beluga sturgeon per trawl tow. This indicates a 39% decline in beluga sturgeon abundance between 2001 and 2002. In fact, this procedure is a minimum estimate of the decline because in 2002 a greater percentage of the trawl tows were conducted using a large trawl (24.7 m) as compared to 2001. Large trawls are more efficient than the smaller trawls (9m), but because a breakdown of beluga catch by trawl type is not given in the 2002 report, it is not possible to refine the estimate of the decline to reflect that difference.
I am also quite concerned by the indications of extremely poor food supply for beluga sturgeon as indicated by the high percentage of empty stomachs reported from the 2002 analysis, and especially by the observations that “beluga stomach [contents] consisted of algae, paper and cellophane packages because of the lack of food.” and that “Average population total rate of beluga stomach fullness at the Northern Caspian feeding grounds didn’t exceed 4%.”
Finally, I would note that in the summary of the section on beluga abundance the lack of mature fish is emphasized and it is concluded that: “In order to increase the beluga abundance in the Caspian sea it is necessary to raise the amount of the industrial reproduction of its juveniles by the littoral states.” My comments here are two-fold. First, increasing hatchery reproduction would require reducing or eliminating caviar production as there are simply not enough mature females being captured to increase hatchery output and sustain caviar production simultaneously. Second, as beluga does not mature until 15 years of age, hatchery reared fish will not contribute to the mature, harvested stock until 15 years after their release. More importantly, the most effective means to stabilize, and ultimately increase, the number of mature beluga sturgeon is to minimize or eliminate the killing of mature beluga currently inhabiting the Caspian Region.
As I’ve discussed with you previously, I have made four trips to the Caspian region since May 2001 (Russia, Azerbaijan, and Kazakhstan), and have seen that there is widespread concern about the dire state of beluga sturgeon throughout the region. Fishermen, government officials, scientists, hatchery managers, and others repeatedly described the precipitous decline in adult beluga sturgeon that they have observed both in the past and in recent years. Nearly all expressed extreme concern about the real possibility of extinction of this fish if drastic action is not taken soon. Hatchery managers in both Russia and Kazakhstan relayed to me the difficulties they have had in obtaining mature beluga sturgeon to supply their hatcheries because of a lack of adults coming in to the rivers. Several managers shared proposals and project ideas with me for enhancing the availability of adults to the hatcheries that entailed using non-fatal means of extracting eggs and sperm for hatchery production, and for holding adults in “safe” quarters on the hatchery grounds for reproduction in future years. In fact, this July we successfully completed a pilot project with the broad cooperation of officials, scientists, and hatchery managers in Kazakhstan, during which 4 mature beluga sturgeon were returned alive to the sea following their use for hatchery reproduction. This pilot project, which included a study on tagging juvenile and adult beluga, was a first in the region, and opened up the possibility of creating combined hatchery and scientific research programs that would provide essential scientific information vital for accurate management of the species. Such research, however, can only continue if enough beluga can be captured for such studies and if an incentive is provided for responsible management.
In summary, I believe the beluga sturgeon in the Caspian region is critically endangered and its abundance, particularly of mature fish, is at an historic low point. Comparison of the 2002 trawl survey results with the 2001 results indicates an extremely alarming decline in abundance of 39% in just a single year. I would urge you to reach a final determination of endangered status as swiftly as possible to prevent the extinction of the beluga sturgeon.
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