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Methodology for the Mnemiopsis Monitoring in the Caspian Sea

A Report Prepared for the Caspian Environment Program, Baku, Azebaijan in December-2001

Ahmet E. Kideys & Tamara Shiganova*
Institute of Marine Sciences, Erdemli, Turkey
*Shirshov Institute of Oceanology, Moscow, Russia

During the conference devoted to Mnemiopsis, invader of Caspian Sea, held in Baku, Azerbaijan, 24 – 26 April 2000, the working group has suggested producing a document describing methods for monitoring Mnemiopsis and other gelatinous macroplankton in the Caspian Sea in order to evaluate their impact on the ecosystem. In this document three types of data collection were suggested to be deployed; these being (1) the basin-wide sampling, (2) coastal monitoring and (3) sightings by volunteers. The document includes detailed sampling and processing methods, too.

Mnemiopsis which was brought in 1980s from coastal waters of the northern America to the Black Sea caused tremendous damage in this new ecosystem (Vinogradov et al, 1989, 1992, Shiganova,1997, 1998; Kideys 1994; Kideys et al. 2000. This ctenophore have now appeared in the Caspian Sea since 1997-1998. At the time of Mnemiopsis invasion, there was also found jellyfish Aurelia aurita in the Caspian Sea, permanent resident of the Black Sea (Ivanov et al, 2000, Shiganova et al, 2001).

By the year 2000 a substantial increase in Mnemiopsis biomass, particularly for the Southern and Mid Caspian was noted with a decline in the biomass of mesozooplankton which adversely changed the nourishment of sprats (Shiganova et al. 2001). Similar results were obtained from the monitoring programs set up in two different coastal regions in the Iran and Azerbaijan coasts of Caspian (Kideys et al. 2001a,b).

During the conference devoted to Mnemiopsis, invader of Caspian Sea, held in Baku, Azerbaijan, 24 – 26 April 2000, the working group has decided to produce a document for “Methods for monitoring Mnemiopsis and other gelatinous macroplankton in the Caspian Sea” for the assessment of their impact on the Caspian ecosystem. Therefore this document has been prepared to guide studies relating gelatinous organisms in the Caspian Sea using a similar methodology.

Should you have any questions regarding this document please do not hesitate to contact Tamara Shiganova ( and Ahmet Kideys (



3.1. Mnemiopsis
Mnemiopsis (Fig.1)
is a lobate ctenophore with two large oral lobes, transparent and a bit whitish. The animal moves by means of cilia on rowing membranes. The cilia are directed towards aboral side, so that ctenophore swims with mouth ahead.

mnem_method1.jpg  mnem_method1.jpg

Fig. 1. Mnemiopsis leidyi. (1) aboral organ, (2) subtentacular row of comb flappers, (3) subsagital row of comb flappers, (4) auriculus, (5) subsagital tube, (6) translobal tube, (7) tentacular tube, (8) lobe (from Shiganova 2000).

The sizes of Mnemiopsis found in the Caspian Sea are much smaller than those found in the Black Sea. For example during the August 2001 cruise in the mid and southern Caspian, The maximum size of the ctenophore was only 41-45 mm and the bulk of individuals (85.5%) were less than 10 mm in length (A. Kideys & M. Moghim, unpublished data). Whereas the individuals found in the Black Sea reach the size of 14-18 cm.

The eggs of Mnemiopsis are round, 0.15-0.3 mm in diameter. The larva has spherical form without lobes, with long catching tentacules and has the size of about 0.15-0.20 mm (Fig 3 A, B); lobes began to evolve when the individual exceeds 10 mm in length. (Fig 2).

mnem_method2.jpg  mnem_method2.jpg

Fig. 2. Early life stages of Mnemiopsis. (A) newly laid egg, (B) embryo with tentacles, about 30 hours old, still within the egg envelope, (C) newly hatched embryo in cydippid stage, (D) embryo about 32 hours old showing muscular strands (from Shiganova 2000).

3.2. Aurelia aurita
The jellyfish A. aurita has a complicated life cycle with several sessile and pelagic stages - planula, scyphistoma, ephyra and finally medusa. The most remarkable and recognizable stage is medusa (Fig 3).

mnem_method31.jpg  mnem_method31.jpg






Fig 3. Aurelia aurita.

Planula - larva stage stays in plankton for about a week and then sink on the bottom. Scyphistoma develops from the sunken planula, which has an appearance similar to polyp with 16-32 feelers. They usually occur in shallow areas, in sublitoral, usually attached to oysters or mussels. Scyphistoma can germinate another larval stage called ephyra which grows into medusa. A. aurita ephyrae has the size of 3-6 mm and may appear in different times in different regions depending on the temperature. Ephyrae appear between December and April in the Black Sea.

3.3. Other gelatinous macroplankton of the Caspian Sea
Ctenophores Pleurobrachia pileus (Fig. 4) and Beroe ovata (Fig. 5) which occur in the Black Sea may appear anytime in the Caspian. Other gelatinous of macroplankton species of the Caspian Sea are hydrozoans Blackfordia virginica, B. pallasi, Maeotica sp, Moerisia pallasi (Fig. 6), Bougainvillia megas, Perigonimus megas.

mnem_method4.jpg  mnem_method4.jpg

Fig. 4. Pleurobrachia pileus

mnem_method5.jpg  mnem_method5.jpg

Fig. 5. Beroe cucumis sensu Mayer, 1912 (# 67) and Beroe ovata sensu Mayer, 1912 (# 68 and 69). Note the extreme flattening of Beroe ovata sensu Mayer, 1912 (# 69) (from R. Harbison).

mnem_method6.jpg  mnem_method6.jpg

Fig. 6. Moerisia pallasi



Three types of monitoring are proposed:

  • a) From basin-wide cruises
  • b) From regular coastal monitoring at selected stations by institutes or scientific establishments of riparian countries
  • c) From observations by volunteers

a) Basin-wide cruises

Cruise Timing
It is reasonable to conduct cruises at least once in a season: in spring (March-April); in summer (August - September); in fall (October-November); and in winter (December – January). The most important sampling materials are obtained in August-September, when, based on Black Sea experience, one can anticipate an intensive reproduction, and consequently maximum abundance and biomass of Mnemiopsis population.

However, since seasonal dynamics of Mnemiopsis in the Caspian Sea is not known yet, it is even more desirable to conduct studies on a monthly basis.

Investigation of Spatial distribution
It is important to conduct studies in all parts of the Caspian due to differences in temperature and salinity regimes as well as hydrochemical characteristics of the Northern, Middle and Southern Caspian.

Vertical Distribution
The investigation of vertical distribution of Mnemiopsis should be implemented at least at two stations (one shallower and one deeper) in each region of the Caspian making use of a closing net. The important parameters to take into account should be the presence of the thermocline and pycnocline; the layer of sampling could be adjusted depending on the position of these layers.

At the first stage it is suggested to sample the following vertical layers: 500-250m, 250-100m, 100-50m, 50-25m and 25-0m. Occurrence of diel vertical migrations are determined by analyzing samples taken at day and night time.

Additional sampling could be performed from the thermocline to the surface, from pycnocline to thermocline. For sound results, each layer should be sampled at least three times. A minimum of two stations (where Mnemiopsis abundances are seemingly high) should be studied for this aim.

b) From regular coastal monitoring at selected stations by institutes or scientific establishments of riparian countries

For monitoring it is desirable to have at least 2-3 stations (optimally 10 stations). The distance between stations should be kept as far as possible. If the institute or other research institution has long term stations already established, they should be used for Mnemiopsis study.

Sampling Interval
It is recommended to take samples biweekly from early March to late November and monthly for the rest of the year.

c) Observation by volunteers
The volunteers can be any inhabitants of coastal towns of riparian states. The best candidates are University or Institutes students, fishermen and oil workers. Due to the presence of only one ctenophore species in the Caspian Sea at present, volunteers could easily categorize gelatinous organisms in two groups: 1) Mnemiopsis and 2) Other gelatinous organisms. If a volunteer wants to be sure if it is a Mnemiopsis or other gelatinous organisms, a scoop could be deployed. An example of “reporting form” is given in Appendix 1.


(To be used during monitoring a and b given above)

For the sampling of Mnemiopsis and other gelatinous organisms it is recommended to deploy a net with wide diameter (=or >50 cm) equipped with net material of 500 micron of mesh size. Information on some nets to be used in monitoring studies are given in Appendix 2.

Sampling is performed by vertical hauls of certain water column from the board of a vessel. The net is lowered by winch equipped with length meter to measure the length of released rope (ropes diameter 4-6mm). The velocity of lifting should be 1 meter per second. Depth of sampling should be corrected with taking into account angle of rope in the process of hauling. In the case of small ship and small depths, if the required equipment (winch, arrows) is absent, it is possible to perform vertical hauls from the board by hands using a suitable net.

5.1. Measurement of Mnemiopsis and other gelatinous organisms
Since the fixation of gelatinous macroplankton is very problematic, various measurements of these organisms should be taken immediately.

In order to measure the total (with lobes) and/or oral-aboral (without lobes) length, ctenophores should be placed individually in a Petri dish with very small volume of water. If there are <50-100 individuals in the sample; all Mnemiopsis will be sorted out to size groups on Petri dish using a ruler and numbers will be counted as follows:

Length Group (mm) Mnemiopsis number
0-5 ….
6-10 ….
11-15 ….
16-20 ….
21-25 ….
26-30 ….

and so on..

Ctenophore’s weight could be calculated by using length-weight equation obtained for Caspian Mnemiopsis as given following (Kideys et al 2001b):

Weight (gr) = 0.0011 Length (mm)2.34, R2=0.65, n=98. The total biomass is assessed as the sum of products of average animal weights in the group and total number of individuals in the group.

If the sample size is not higher than 100 individuals, all animals should be measured individually, otherwise a subsampling could be performed (1/2, 1/3, 1/4, etc. of total), Then a recalculation for the entire sample should be executed.

The Mnemiopsis eggs and larvae should be fixed in 2% buffered formaldehyde along with other mesozooplankton

Jellyfish Aurelia aurita
The jellyfishes can be grouped with 1 cm intervals and then the number of animals for each size group is recorded. The jellyfish A. aurita can be fixed in 2% buffered formaldehyde. We are proposing the following equation for calculation of biomass of A. aurita, which was developed for A. aurita inhabiting in the Black Sea:
W= 0.12 L 2.58 where W- wet weight in grams, L- length in mm;
(measurements range from 6.1 to 151mm)(Mutlu, 2001)

These equations should also be developed for the Caspian population of A. aurita.

5.2. Calculation of abundance and biomass of gelatinous organisms

To assess the abundance and biomass it is necessary to count total number of ctenophores or/and jellyfish in the sample, and then assess total abundance and biomass for the area (i.e. per m2) and/or water volume (per m3 by taking sampling depth into account).

Some investigators use coefficient for the filtering efficiency of the net, whilst some others not. The Institute of Oceanology Russian Academy of Sciences has adopted factor for the non-caught gelatinous organisms for the sampling with BR net in relation to underwater observations (Vinogradov et al, 1989).

For Mnemiopsis

  1. < 10 mm, coefficient k - 2;
  2. 10-45 mm, coefficient, k -2 ;
  3. >45 mm, coefficient –2.3

For A. aurita:

  1. <50 mm, coefficient, k-2 ;
  2. 50-100 mm, coefficient, k-2.3;
  3. >100 mm, coefficient k-3.

If a correction factor is applied, this should be clearly stated in the methods.

Other gelatinous organisms

In case of discovery of any unknown gelatinous organisms, if possible one should take their photograph, measure, describe them and try to preserve them in 2% buffered formaldehyde or glutaraldehyde.

5.3. Basic parameters to be measured in course of monitoring

Hydrophysical parameters:

  1. Temperature (preferably at all depths or at least in the surface waters).
  2. Salinity (preferably at all depths or at least in the surface waters).
  3. Turbidity (Secchi depth).

Hydrochemical parameters:

  1. Nutrients and oxygen samples from selected depths down to the sea bottom.

Biological parameters:

  1. Phytoplankton samples from standard depths (2 liter of seawater from depths of 0, 10, 25, 50 m: for methodology see Kasimov 2000).
  2. Mesozooplankton (including ichthyoplankton) samples (using a vertical net tow from 100 m to the surface for deep stations and from the bottom to the surface for shallow stations). It will be appropriate to use a mesh size of 100 to 200 um (see Kasimov 2000 for methodology) for zooplankton and 500 um for ichthyoplankton . The most optimal net for zooplanlankton sampling is a Juday net and an ichthyoplankton net which are available in the most Institutes of Caspian countries with mesh size equal to 125, 180 or 200 micron for a Juday net. Alternatively a METU Net (designed by Dr Ahmet Kideys) with different mesh sizes of 112-200 micron could also be used. Again some investigators may use coefficients for the filtering afficiency of mesozooplankton (Shirshov Institutse’s coefficient is 2 for mesozooplankton). If any coefficient is used, again, this should be clearly stated.
  3. In addition to phytoplankton samples, sampling for chl-a from phytoplankton sampling depths.

The cruise data recording sheet prepared for the Caspian coasts of Iran could be modified according to aim (see Appendix 3).



  1. Ivanov PI, AM Kamakim, VB Ushivtzev, T. Shiganova, O. Zhukova, N. Aladin, SI Wilson, GR Harbison, HJ Dumont 2000. Invasion of Caspian Sea by the comb jellyfish Mnemiopsis leidyi (Ctenophora). Biological Invasions 2: 255-258.

  2. Kasymov A 2000. Methods of monitoring in Caspian Sea. Gapp-Poligraf Publ., Baku, pp. 26-32.

  3. Kideys AE 1994. Recent dramatic changes in the Black Sea ecosystem: The reason for the sharp decrease in Turkish anchovy fisheries. Journal of Marine Systems 5: 171-181.

  4. Kideys A. E., A. V. Kovalev, G. Shulman, A. Gordina & F. Bingel 2000. A review of zooplankton investigations of the Black Sea over the last decade. J. of Marine Systems, 24:355-371.

  5. Kideys A.E. & Z. Romanova (2001). Distribution of gelatinous macrozooplankton in the southern Black Sea during 1996-1999. Marine Biology 139: 535-547.

  6. Kideys A. E., Shahram Ghasemi, Davood Ghninejad, Abulgaseem Roohi & Siamak Bagheri2001a. Strategy for combatting Mnemiopsis in the Caspian waters of Iran. A report prepared for the Caspian Environment Programme, Baku, Azerbaijan, Final Report, July 2001.

  7. Kideys A. E., F. M. Jafarov, Z. Kuliyev & T. Zarbalieva 2001b. Monitoring Mnemiopsis in the Caspian waters of Azerbaijan. A report prepared for the Caspian Environment Programme, Baku, Azerbaijan, Final Report, August 2001.

  8. Mutlu E. 2001. Distribution and abundance of moon jellyfish (Aurelia aurita) and its zooplankton food in the Black Sea. Marine Biology 138: 329-339.

  9. Shiganova T.A. 1997. Mnemiopsis leidyi abundance in the Black Sea and its impact on the pelagic community. In "Sensivity of the North, Baltic Sea and Black Sea to antropogenic and climatic changes" Sp.Volume. Ed. E. Ozsoy and A.Mikaelyan. Kluwer Acad. Pub.p.117-130.

  10. Shiganova T.A. 1998. Invasion of the Black Sea by the ctenophore Mnemiopsis leidyi and recent chanches in pelagic community structure. Fisheries Oceanography –Globec Special Issue Ed.Steeve Coombs.p.305-310

  11. Shiganova T.A.Kamakin A.M., Zhukova O.P., Ushivtzev V.B., Dulimov A.B.Musaeva E.I. Invader in the Caspian Sea ctenophore Mnemiopsis and initial results of its impact on the pelagic ecosystem. 2001, Oceanology V.41, N 4. Pages 542-549.

  12. Shiganova T.A. Some results of study of Mnemiopsis leidyi biology in the Black Sea // “Ctenophore Mnemiopsis leidyi (A.Agassiz) in the Azov and Black Sea and consequences of its intrusion”. Ed.S.P. Volovik. Rostov –on-Don. 2000 b:.pages 33-75.

  13. Vinogradov M.E., E.A. Shushkina, E.I. Musayeva, P.U.Sirokin. New invader in the Black Sea – ctenophore Mnemiopsis leidyi (Agassiz) // Ocean Science 1989, V. 29, issue 2, pages 293-299.

  14. Vinogradov M.E., V.V. Sapoznikov, E.A. Shushkina. The Ecosystem of the Black Sea, M.Nauka, 1992, page 112.


Appendix 1
Mnemiopsis Reporting Form for Volunteers to obtain data on Mnemiopsis and other gelatinous organisms’

Volunteer’s name:
Volunteer’s occupation (please tick appropriate box):

  • Student
  • Fisherman
  • Seaman
  • Oil Rig Worker
  • Other


  • Less than 1-2 individuals in m3
  • Between 3-10 individuals in m3
  • More than 10 individuals in m3
  • If possible then please indicate size composition and peculiarities of spatial distribution

Other gelatinous organisms:

Short description:
Body shape:
Average quantity in m3


Please forward this information to ...


Appendix 2

Some plankton nets recommended for big boats (BB) and small boats (SB)

Type of net

Diameter (cm)

Mesh Size (um)

Plankton Group




Macro (SB)

Hensen Net



Macro (BB)

Bogorov-Rass net (BR) -13/140



Macro (BB)

Big cone Net



Macro (BB, SB)

Small cone Net


~ 900

Macro (SB)

Juday net-80/113



Meso (BB)

Juday net-37/50



Meso (BB, SB)

Small Cone Net



Meso (SB)




Meso (SB)

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