|
|
|
 |
||
Brief Report Background At the first meeting of the CEP regional invasive species advisory group, the experts present adopted an action plan to counter the invasion of the Caspian Sea by the carnivorous comb jelly Mnemiopsis leidyi which, by late 2001, had caused serious symptoms of degradation in the pelagic food web of the Sea. At its meeting in December 2001, the experts had reviewed the situation in detail, and had concluded that the expansion of Mnemiopsis in the Caspian was (1) much more rapid than anticipated and much more rapid than in the Black Sea; (2) had reached levels comparable to the highest levels in the Black Sea in 1988, and (3) had exhausted the zooplankton stocks, especially these of the endemic onychopod crustaceans. Early signs of a forthcoming collapse of kilka fish, and of Caspian Seal had been reported as well. The experts had identified a single workable remedy: a counter-introduction of another, even larger ctenophore, Beroe ovalis. This species, already present in the Black Sea, had greatly contributed to the restoration of the latter, and had been judged sufficiently stenophagous and free of parasites and diseases to be safely introduced to the Caspian, even if more work on these safety aspects were deemed desirable. The second meeting of the CEP Regional Invasive species Advisory Group, held in Baku, Azerbaijan at the CEP PCU on 27 June 2002, therefore had the following objectives:
I. Opening of the meeting Tim Turner, coordinator of the Caspian Environment Programme, opened the meeting and welcomed the participants. He stressed the urgency in addressing the Mnemiopsis invader, which now clearly had reached an alarming abundance in most of the Sea. He also announced that, sadly, this was V. Vladymogrov’s last working day. All participants expressed their thanks and administration for all the work Vladymir had done for the programme, and hoped to see him return to the job in the next phase of the programme. Henri Dumont was proposed as the chairman of the meeting. The agenda and chairman were adopted unanimously. II. Overview of the current Caspian situation regarding Mnemiopsis At the very start, it was pointed out that Mnemiopsis is a summer species, and that, therefore, the 2002 bloom in most places yet had to start. However, in the warm south basin, where Mnemiopsis is now perennnial, the outbreak was clearly in evidence. Dr. H. Negarestan confirmed these alarming facts for the Iranian sector, adding that many Iranian fishermen were in great financial trouble, and unable to repay their loans because of low kilka catches. Dr. T. Shiganova commented on the Russian cruises, which covered most of the Caspian, and confirmed the alarmingly high biomasses of Mnemiopsis now present in most of the Central and South basin of the Caspian, moving up north towards the Volga delta in the Volga navigation channel in spite of the local salinities being as low as 5g per litre. Like the preceding speakers, she noted that Mnemiopsis in the Caspian in generally small-sized; however, their abundances are so high that this compensates largely for this smaller size, such that locally biomasses overshoot 3 kg m-2. In the fresher-water north-western part, Mnemiopsis are fewer in number, but larger in size. The suggestion here is that in the south, food resources are scarcer or already used up, such that specimens move up to a suboptimal environment (the north) to feed. Dr. F. Shakirova had just returned from a prospection of the Turkmen sector a week earlier. She had now used the standardized sampling techniques agreed by the five littoral countries earlier. She reported on a patchy distribution of Mnemiopsis along the Turkmen coast, with locally high to very high surface concentrations of Mnemiopsis. Dr. Y. Kim, finally, reported that in the Kazakh NE sector, strongly influenced by inflow of freshwater from the River Ural, Mnemiopsis was nearly absent; a situation identical to that recorded here the year before. Occasionally, jelly masses were found to be present in the samples, but there were unstructured. T. Shiganova confirmed that during Russian surveys such jelly masses had been found as well in the NE sector of the Caspian; microscopic examination had revealed comb rows, and thus the jelly was indeed composed of disintegrated Mnemiopsis. That so relatively little Mnemiopsis biomass occurs in the North-East, as appeared to the North-West might reflect the prevailing surface currents in summer, which are southwardly directed along the East coast of the Caspian, thereby causing the well-known eastern shore upwellings. III. A summary of the findings of the NATO ARW Workshop. H. Dumont reported on the main conclusions which had emanated from the deliberations of the Nato ARW Workshop on Mnemiopsis and other invasive species. An extended summary is given in Annex. It is now clear that, because of increased maritime traffic and the fact that – at least in Europe and Asia – all major rivers are now linked by a network of canals, there is about one major outbreak of an invasive aquatic species per month. Many of these have detrimental effects, and the Baltic Sea, for example, is now almost exclusively populated by alien species, quite a few of which are of Caspian origin. The Caspian itself tends to suffer so strongly from its jelly invader because it is a closed system. The zooplankton has now been reduced to a single species of Acartia, a copepod; all cladocerans have become unobservable. Last year, the kilka fisheries and seals had already shown signs of degradation; now, also the Beluga seems affected, due to the share of kilka in its diet. The Beluga diet in 2002 shows a significant shift towards gobies, for lack of kilka! IV. Review of the action plan, and discussion of forthcoming actions V. Vladymyrov briefly reminded the audience of the salient points of the action plan. The main point to be discussed was clearly the practical implementation of the introduction of Beroe, and the elimination of the last reservations that might still exist against this intervention by man. To the question by Hosseini Emami, whether safety of the introduction of Beroe could be guaranteed, it was argued that this is never the case; there may always be unanticipated effects, but, as V. Panov pointed out, these were much more likely in the case of vertebrates, which are noted for their flexible ethology. In the case of a lower invertebrates, which, as G. Finenko remarked, even lacked the enzymes to degrade any food other than other ctenophores, that risk is probably nonexistent. Would Beroe not introduce new pathogens or parasites to the Caspian ? Parasites could present a risk if Beroe was the intermediate host to a parasite species that would find its final host in one or more Caspian species. A. Kideys then presented the results of studies on parasites of Beroe. The list of these is rather long, and includes ectoparasites and commensal species, but none of those are known to have complex life cycles and/or pathogenic effects. That Beroe carries parasites should not come as a surprise: all animals, including man, have parasites; actually it would have been a surprise if none could be found. The conclusion, reached at an earlier meeting, that the risk (and the responsibility) of not-introducing Beroe by far outweighed that of introducing, was thus confirmed once again. The question whether we now had sufficient knowledge of Beroe ovata to commission a full EIA and decide on a date and place of introduction elicited a long discussion. A. Kideys argued that, while none of the experiments conducted so far (mainly in Iran) had revealed any problems, the still would like to see some aquarium experimentation take place at the mesoscale level, involving Beroe exposed to a variety of Caspian biota. Against this it was argued that the “natural experiment” of its appearance in the Black Sea had now lasted for more then five years, and no effects other than a restoration of the “old” ecosystem had been recorded, which seemed to argue against the need for such an effort. However, in previous experiments attempting to rear Beroe through its complete life cycle in Caspian water, larval mortalities had been noted, for which the reasons were as yet unknown, azlthough they might be due to shortage of food of a suitable size. For this reason, and because the technique of introduction should aim at a full knowledge of the genetic material introduced, it was agreed that much mesoscale experiments, if not absolutely necessary, could certainly be helpful. H. Dumont argued that controlling the source of the Beroe specimen(s) that were destined to be introduced (if possible, the offspring of a single female) was desirable, because it would enable later researchers to see whether no “extra” invasions of Beroe had taken place separately, or at a later date. Further, if Beroe would – against all expectations – cause some ill effects at a later date, it was better to introduce a single genotype. Inbreeding depression after some time (five to ten years) might than perhaps lead to a natural extinction of the introduced propagule. Only if still needed, new propagules could then be released. To the question of funding the controlled introduction, Tim Turner said that he had about 40,000 $ available to carry out the operation of collecting Beroe in the Black Sea, and flying it to the shores of the Caspian in Iran. If, in parallel, additional experiments were deemed necessary, these would need to be financed by other means. It was agreed that September 2002 would be the earliest possible date for such an introduction. Prior to that, A Kideys and H. Negarestan would write a Biological Feasability study, to be submitted to the Iranian Authorities and T. Shiganova would write a draft EIA, to be edited by H. Dumont. In the meantime, the Mnemiopsis monitoring program would need to be continued, and certain intriguing questions (e.g. why did one species of copepod, Acartia, manage to survive under Mnemiopsis predation pressure, while others did not?) addressed. V. Data management. V. Vladymyrov gave an overview of the state-of-the-art of the Caspian biodiversity data base managed by the CEP. There would be a brief interruption in the functioning of the CEP server during the transition to phase II of the project, but all precautions had been take to make sure that the database remained intact. V. Panov then offered a presentation of the database on invasive species maintained by the RBIC (Regional Biological Invasions Center), housed by the Russian Academy of Sciences in St Petersburg, and freely available through the internet. The meeting was closed around 5 p.m. The chairman thanked all those present for their cooperation, noted that substantial progress had been achieved, and expressed hopes that 2002 would be remembered as the year in which the counter-offensive against Mnemiopsis in the Caspian was finally launched. |
Brief Report
|
|
|
||
