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A Proposal for a Low-Cost Mnemiopsis Monitoring System for the Caspian Sea

Richard Harbison, Woods Hole Oceanographic Institution, Woods Hole, MA 02543 U.S.A.

As person who has lived and collected ctenophores in a region where Mnemiopsis leidyi is only seasonally abundant, I (as have many other persons) have become well aware of the transitory nature of its abundance. One day the water may be filled with ctenophores, and on the next day there may be none at all. This is the major reason that I think that frequent collections of ctenophores provide better information than a few oceanographic cruises that only sample them over short time periods a several times a year. Further, oceanographic cruises are expensive, and fiscal demands may be more important in determining their duration and time than scientific priorities.

Therefore, should the nations surrounding the Caspian Sea decide that the monitoring of Mnemiopsis populations is an important task, I would respectfully suggest that they consider a low-cost monitoring programme such as the one I outline below. As we have learned in this meeting, and at other meetings, different methods of collection and analysis produce different results. This is an important point, since it means that we cannot, for all practical purposes, determine the “real” concentration of Mnemiopsis in the Caspian or any other sea. Given this problem, I think that a standardised method that is extremely simple and gives a broad geographical coverage is preferable to a more sophisticated method that covers only a small part of the Caspian Sea. Information on how Mnemiopsis population levels change over the entire basin on a synoptic basis would be extremely valuable, and would also create a unique data set. An analogy to this method is oceanography from space. Although the color measurements made by satellites are extremely crude approximations of primary production, compared with in situ incubation techniques, these crude approximations are extremely valuable, since they provide synoptic information that is unavailable with more sophisticated methods.

How can we obtain this kind of this synoptic information for the entire Caspian Sea? I think that it can be done with the cooperation of all of the Caspian basin countries, using the human resources that they have available in the form of secondary school classes, fishermen, NGO’s oil companies and other volunteers. For the method to work, it should be extremely simple, so that data can be collected on as near a daily basis as possible. I suggest that the method be something like this:

  1. A small standardized net, made from extremely simple materials, with a mesh size that will adequately sample Mnemiopsis should be provided to all participants in the programme. This net should be small enough that it can easily be deployed by hand, and it should be let out to a specified length and drawn in for a short, specified time.

  2. The participants, located in all regions of the Caspian Sea, will identify the gelatinous organisms. Dr. Aladin has informed me that there are only five species of gelatinous organisms in the Caspian Sea: the ctenophore, Mnemiopsis leidyi, and the medusae, Aurelia aurita, Blackfordia virginica, Bougainvillia megas and Moersia maeotica. I think that it would be easy to train volunteers to identify these five species, but, if this is too difficult, the categories could be reduced to two: Mnemiopsis and medusae.

  3. Once the categories have been identified and separated, their volumes would be measured with a simple method, such as placing them in a graduated cylinder.

  4. The information obtained would be sent to a central analytical center, perhaps the Caspian Environmental Programme. In order to stimulate public interest, the synoptic analysis of these data should be published on a weekly basis, perhaps in newspapers, showing the changes in population density across the entire Caspian Sea. This report on the status of the Mnemiopsis populations would thus be like a weather map, giving people advice on the current threat of the ctenophore to fisheries. The publication of results on a weekly basis would keep the issue of Mnemiopsis in the public awareness.

It seems to me that the obtaining of this information would be an ideal project for secondary school science classes and for NGO volunteers. It is also important that fishermen be involved in this project, so that data can be obtained at locations away from the coast. It should be relatively easy to interest fishermen in this project, if the threat of Mnemiopsis to their livelihoods is made clear, perhaps by telling them the story of the collapse of fisheries in the Black Sea. Perhaps samples could also be collected from offshore oil platforms, since I have been told that oil companies are interested in the Mnemiopsis problem. Above all, it should be kept in mind that the simplest methods possible should be used, so that no one regards the collection of this information as an unpleasant task that takes too much time from their work.

Synoptic data such as this would be unique in the study of patchy organisms such as Mnemiopsis. With these data, scientists could make good estimates of basin wide distributions and abundance. The development of blooms of ctenophores spreading from the south to the north could be followed, and correlated with meteorological data. One could follow the blooms as they spread, and perhaps use this information to understand the effects of Mnemiopsis on fish, plankton and benthic organisms.

I recognize that a project such as this would require considerable organisation, and needs to be closely coordinated by a central agency such as the CEP. I put this suggestion forward because I think that the prospects are good that a programme like this will succeed in the Caspian Sea. I think that it will work here because this is a closed sea of manageable size for such a study. Since I know very little about the Caspian Sea, I do not know if a project such as this one is feasible for political or economic reasons. Please regard this proposal as only a first draft that could be completely modified by scientists from the Caspian Sea countries as they consider it. At any rate, I think that there is a unique opportunity in the Caspian Sea to generate information on a spatial scale that has never been previously achieved for gelatinous organisms.

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