КаспИнфо

Каспинфо
июнь 2002

Название: Экологические проблемы на англ. языках
Главные Пункты:
* Дискуссионный материал. Предложения по борьбе с мнемиопсисом на Каспии: - найти вид животных, питающийся икрой и личинками мнемиопсиса; - разработать меры, способствующие росту популяций этих видов; - создание биофабрик по размножению берое; - если будет найден эффективный истребитель гребневика, следует начать работу по его размножению.
(19.06.2002)

Полный Текст
Экологические проблемы на англ. языках
Экологические проблемы Каспия на англ. языке

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Discussion Document

WHAT SHOULD BE DONE WITH THE MNEMIOPSIS?

I will come straight to the point: I begrudge having to spend time
repeatedly answering the question "What is mnemiopsis?" Anyone
interested in rudimentary information about this invasive species of
jellyfish can read more about it here at Caspinfo or at
www.caspianenvironment.org.

Let me remind you that mnemiopsis has already destroyed the sardelle
and khamsa trade in the Black and Azov Seas, and has been destroying
the Caspian sprat since 1999. This destruction is taking place both
directly through the eating up of sprat roe and larvae, and indirectly
by disrupting its forage reserves of plankton. The latter led to a
mass die-off of sprats in the spring and summer of 2001. As a result
of the sprat species destruction, the Caspian littoral areas are not
only incurring financial losses, residents have lost approximately
200,000-250,000 tons of a cheap source of food - one that was rich in
protein and essential to their diet. Mniemiopsis drives out other
marine life that will suffer from being crowded out by this invasive
species.

KaspNIRKH (The Caspian Research Institute on the Fish Industry)
estimates that losses in sprat catches have amounted to 40 percent. In
my evaluation - I am sorry for the immodesty - losses should actually
be estimated at not less than 80 percent. My estimate differs due to
my strong conviction that overfishing of anchovy sprats has been
taking place in the Caspian Sea since approximately the mid-1970s.
Overfishing can be confirmed by the data on the age structure of the
fish that are now being caught, as well as through the persistent
failure of fishermen to fulfill the "scientifically-based" quotas set
up in the 1990s. I firmly maintain that it is precisely the decline of
sprat resources that led to the creation of an environmental niche
mnemiopsis has now rushed in to fill.

How can the situation be improved? Most specialists agree that out of
all the known natural remedies for fighting mnemiopsis incursions, the
best, safest option is to introduce another medusa jellyfish named
beroe into the Caspian Sea. Beroe has already gotten into the Black
Sea without any assistance (it's useful to remember that this species
didn't wait for human decisions about when to introduce it!). Today,
beroe in the Black Sea are contributing to remarkable decreases of the
number of mnemiopsis during summer. Beroe feed solely on
jellyfish-like organisms, so their introduction into the Caspian would
potentially affect only the indigenous medusa named Caspionema pallasi
in the South Caspian. Another problem with this scheme is the concern
that beroe would probably also carry "fellow travelers" - parasites
that could have unpredictable consequences. The question of whether to
introduce beroe may be moot: I tend to believe that beroe has already
gotten into the Caspian, given that the last three winters were warm
and experiments in Russia and Iran have already been held.

However, other complications exist. Beroe is very sensitive to
temperature and salinity. Mnemiopsis accommodates itself to such
complications much more successfully. Beroe does well in the Black Sea
because it enters from the warm Sea of Marmora, but it will be
destroyed by frost in the very first inclement winter in the Caspian
Sea.

An important question arises: who is studying mnemiopsis populations
in the cold North Atlantic Ocean? On this question I was unable to
find an answer. Scientists from the Black Sea littoral states have
conscientiously processed all the existent data on the mnemiopsis;
furthermore they have added a great deal of new and original
information. However, mnemiopsis is not an economically important
species near the American coast. Its photoluminescence and other
curious biological features have been noted, but according to the
highest standards of biology, the mnemiopsis has only been partially
studied. Frankly, no one is funding mnemiopsis research.

I propose to look at the problem from the other side. The species that
have been called mnemiopsis's "natural enemies" (butter fish, beroe,
and so on) only eat adult mnemiopsis. Yet of the 2,000-3,000 offspring
that an adult mnemiopsis can produce per day, only a few survive. In
the other words, the fundamental reduction of the mnemiopsis occurs at
the stage of spawn and larvae, so its "natural enemies" are those that
attack it at exactly this stage. The adult mnemiopsis itself is
unattractive as a food, but its spawn and larvae could turn out to be
more edible, or could be consumed along with other plankton organisms.
I have failed to find any literature on this issue.

Based on this conclusion, four directions for action are needed:

1. Future work on the mnemiopsis problem requires the publication in
North America of information about the digestive tracts of
plankton-eating animals. We are likely to succeed in identifying a
species that prefers the mnemiopsis spawn and larvae. In any case, we
could create a list of species that take part in controlling
mnemiopsis populations, and we could make projections regarding the
Caspian and Black Seas.
2. Field studies of the period of mass reproduction of mnemiopsis in
the Atlantic Ocean, Caspian Sea, and Black Sea will be essential. The
research goal would be the same: to identify indigenous species that
can control mnemiopsis numbers at the spawn and larvae stage. Next,
measures must be designed that will help increase the population of
this species. (By the way, it is very likely that the "services" of
beroe in reducing mnemiopsis quantities have been slightly
exaggerated).
In my opinion, we will turn again to the Caspian sprat problem. Sprats
comprised approximately half of all the Caspian fish, and they were
the primary consumers of animal plankton. Theoretically, the previous
high quantities of sprats should have been the foremost destroyer of
the mnemiopsis spawn and larvae. However, today it is impossible to
restore the sprats that have been depleted both by overfishing and
mnemiopsis itself. For the desalinated North Caspian Sea, the
essential biological control factor would probably be the common
sprat, and in the South section of the Sea it would seem that we would
still need beroe.
3. The next action follows from the second one: fish farms for
reproducing beroe will be required. Such beroe production facilities
will be responsible for keeping on hand enough beroe spawn or larvae
to apply in seasonal releases into the Caspian. At the same time, on
the east coast it will be appropriate to base production facilities
where warm wastewater is released by the Turkmenbashi thermoelectric
power station cooling system, which warms up part of the bay and would
provide conservation of beroe populations even during cold winters. I
think similar facilities could be found in the other areas of the
Caspian, allowing for substantially reduced project costs.
4. Finally, if one or more species that serve an effective destroyer
of the mnemiopsis spawn can be identified as a result of implementing
the first two steps above, then work on reproduction of these species
should also be started.

I surmise that funding for the research portion of this type of
project might be available from such sources as the IREX
Black-Caspian Sea Collaborative Program, CEP, and so on. I am ready to
start organizing such work in Turkmenistan. The weak point that
presents the primary obstacle is that we lack hard data about
mnemiopsis distributions in the Caspian Sea - a situation we could
rectify through our environmental NGO monitoring network.

It seems to me that the above plan could lead to substantial, concrete
results quite rapidly. At the same time, as I am not a biologist, I
may have omitted some factors, so I await your comments and
suggestions.

Timur Berkeliev
Tb79@cornell.edu