ATTACHMENT
13.
Presence of the Ctenophore
Mnemiopsis leidyi in south Caspian Sea
H. Negarestan, S. Hoseini,
A. Rouhi, S. Bagheri, Z. Pajand, S. Ghasemi
Iranian Fisheries Research Organization and Department of the
Environment, I. R. Iran
Background
Recent findings show that the invasive
Comb Jelly Mnemiopsis leidyi has appeared in the Caspian Sea in considerable
numbers. The jellyfish Aurelia aurita also is observed in the Caspian. Presence of
these species stresses that there is still the possibility of invasion by other species.
Presence of the Comb Jelly Mnemiopsis
leidyi in the Caspian Sea was recognized for the first time by Iranian Fisheries
Research Organization in 1995 and warning letters were issued in this regard. Researchers
from Tarbiat Modarres University also reported occurrence of this species in large numbers
(Esmaili et al, 1999). Today after almost 6 years this species has increased in numbers
and a reduction in the catch of Kilka has been linked with the presence of this Comb
Jelly. However more investigation is needed to prove the impact of Mnemiopsis on
Kilka stocks in South Caspian Sea. It is also reported that Mnemiopsis has been
found in Funnel nets in large numbers.
Following observation of Aurelia
aurita in the Caspian IFRO and Tarbiat Modarres University are running a combined
research on biomass and distribution and biology of this species.
Parallel to this Iranian Fisheries
Research Organization is conducting a research study on abundance, distribution and
possible control of Mnemiopsis populations in southern Caspian Sea.
Present information on Mnemiopsis in
South Caspian Sea
Two pilot studies were conducted in
southern Caspian and the results of which showed that in winter 2000 maximum biomass of
Ctenophore in south Caspian Sea, was 125 g/m2 in Khazarabad region and a
minimum of 0 was observed in surface waters of Amirabad (Table 1).
Meanwhile in summer 2000, there were an
increase with depth in most sites with a maximum of 470 g/m2 in 20metre depth.
However, Gorgan showed a maximum in 5 meter depth.(93.7 g/m2) (Table 2).
This data indicates that Ctenophore
biomass in different sampling sites tends to increase from surface to bottom.
Possible effects on the Caspian
The follow up of invasive effects of M.
on Black Sea, considering the same situation in the Caspian Sea (there are about 400
endemic species in the Caspian), would lead us to postulate that a similar thing is most
likely to happen in this area. It seems that this has already started, bearing in mind
that this is a different environment these effects could be categorized as follows:
A decline in the population of endemic
mostly pelagic, benthic or semi-benthic species such as crustaceans of the orders
Amphipoda, Mysidacea, Cumacea, Copepoda and Onychopoda (Zaittsev and Mameav 1997 sited in
Ivanov et al. 2000).
A reduction in pelagic fish larvae and
eggs (as in Black Sea). The main stock of pelagic fish in the Caspian is Kilka (small
Clupeids) with 3 species constituting the main fishery in southern Caspian. Kilka feeds
exclusively on zooplankton, mostly copepods(55-77% by weight), cladocerans and
meroplankton. A reduction in zooplankton and fish eggs and larvae has most probably
resulted to a 18000 tons decline in Kilka fisheries of Iran in a course of one year (Table
3).
A possible impact on top predators of
the Caspian, sturgeon fishes and the Caspian seal as a result of a reduction in their food
(Kilka).
The presence of Mnemiopsis in
the Caspian may produce a great change in the food chain and influence the entire fish
populations.
Recommendations
It is obvious that the invasion problem
in the Caspian Sea is a regional problem and all neighboring countries should be involved
when proposing any action plan or policy. It is proposed that a working committee
consisting of a group of scientists from all member states of CEP should be established
and concentrate on the followings:
assess abundance, distribution and
impacts of Mnemiopsis in the Caspian Sea.
investigate means by which this species
has been introduced to the Caspian and evaluate extent of damages caused.
conduct experimental studies on
effective control mechanisms, possibly using endemic predators (GESAMP 1997).
develop a strategy and recommend
measures to overcome the outbreak of this invading species.
enhance co-operation among national
research centers and stakeholders.
improve co-ordination among
institutions, national and international programs in the areas of scientific research,
monitoring and control measures.
Table.1.Biomass of
Ctenophore (g/m2) in winter 2000
Site |
Depths(m) |
Surface |
5(m) |
10(m) |
20(m) |
Khazarabad |
5 |
9.30 |
11.35 |
0 |
0 |
10 |
15.55 |
30.20 |
124.85 |
0 |
20 |
12.35 |
15.30 |
6.60 |
16.95 |
Amirabad |
5 |
0 |
24.25 |
0 |
0 |
10 |
15.25 |
65.75 |
105.45 |
0 |
20 |
25.35 |
17.85 |
25.85 |
35.45 |
Babolsar |
5 |
0 |
0.50 |
0 |
0 |
10 |
0.67 |
3.65 |
55.45 |
0 |
20 |
0 |
0.70 |
9.86 |
4.50 |
Table.2.Biomass of
Ctenophore (g/m2) in Summer 2000
Site |
Depth(m) |
Surface |
5m |
10m |
20m |
Khazarabad |
5 |
0 |
26.7 |
0 |
0 |
10 |
51.90 |
203.1 |
237.7 |
0 |
20 |
55.90 |
59.1 |
180.8 |
62.8 |
Amirabad |
5 |
0 |
10.5 |
0 |
0 |
10 |
0 |
7.2 |
1.5 |
0 |
20 |
0 |
5 |
50 |
10.5 |
Turkmen |
5 |
75.24 |
11.3 |
0 |
0 |
10 |
231.96 |
134 |
129.9 |
0 |
20 |
30.60 |
70.1 |
112.5 |
470.3 |
Gomishan |
5 |
60 |
20 |
0 |
0 |
10 |
10 |
240.4 |
280.5 |
0 |
20 |
30.50 |
240.2 |
245.1 |
470.4 |
Gorgan |
5 |
4.60 |
93.7 |
0 |
0 |
Table.3. Kilka
landings at Iranian Ports of the Caspian Sea
Fishing
season |
Catch (Tons) |
1998/1999 |
82100 |
1999/2000 |
83000 |
2000/2001 |
65000 |
References
Ivanov, V. P. et al., 2000. Invasion of
the Caspian Sea by the Comb Jellyfish Mnemiopsis leidyi (Ctenephora). Biological Invasion
2: 255-258, 2000.
Esmaeili Sari, B. et al., 1999. First
report on occurrence of a combjelly in the Caspian Sea. Journal of Environmental Sciences
and Technology, No.3, Islamic Azad University.
GESAMP, 1997. Opportunistic settlers and
the problem of ctenophores Mnemiopsis leidyi invasion in the Black Sea, GESAMP Report and
Studies No. 58.
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