1. INTRODUCTION

This joint report provides a brief overview of the status of the project at the end of the second mission of both consultants (7 August to 14 September 1990). More details are to be found in the Project Performance Report.

The second mission of the Technical Adviser was originally scheduled for March 1990. However, due to political events in Czechoslovakia, the home country of the Technical Adviser, his mission was postponed to August 1990.

2. TERMS OF REFERENCE

The terms of reference of the Technical Adviser and the Aquatic Pollution Consultant during their mission were:

With the National Project Director, they were responsible for the execution of the project, especially to:

• monitor the progress of all scheduled investigations for the purpose of identifying any shortcomings and recommending adjustments;

• ensure that investigatory efforts are correctly and effectively directed;

• provide technical guidance and on-the-job training to technical personnel of the project;

• coordinate the field activities of the Technical Adviser and the Aquatic Pollution Consultant and of the project itself in close cooperation with the National Project Director;

• the Aquatic Pollution Consultant should produce a mission and technical report and project performance report on the contribution of the consultants to the project.

3. ITINERARY

The Technical Adviser and Aquatic Pollution Consultant visited Iran from 8 August to 13 September 1990, with the following itinerary:

3.1 Persons Met

Mr. Per H. Janvid, UNDP Resident Representative
Mr. M.M. Humayun Kabir, Deputy Resident Representative, UNDP
Dr. H.R. Ghaffarzadeh, Programme Officer, UNDP
Mr. V. Haghpanah, Director, Shilat Fisheries Research Organization (SFRO) in Bandar Anzali
Mr. B. Razavi, Deputy Director, SFRO
Mr. M.R. Noi, Head, Biological Department (BD), SFRO
Mr. E. Mirzai, Biologist, (BD), SFRO
Mr. A. Mellatparast, Head, Department of Limnology (DL), SFRO
Mrs. T. Mohammadjanii, Head, Phyto and Zooplankton Section, SFRO
Mr. S.H. Khodaparast, Head, Jehad Chemical Laboratory (JCL)
Mr. M. Estaki, Chemist, JCL
Mr. A. Nezami, Chemist, JCL
Mrs. L. Rastad, Biologist, BD, SFRO
Mr. N. Goouhi, Head, Experimental Hatchery, SFRO
Mr. N. Hosseinpour, National Project Director
Mr. M. Karimpour, National Project Staff (NPS)
Mr. D. Haghighi, NPS
Mr. A. Mohammed, Hydrologist, North Water and Power Organization, Rasht

4. SUMMARY OF OBSERVATIONS FOR THE PERIOD NOVEMBER 1989 – SEPTEMBER 1990

4.1 Status of the Anzali Lagoon

Observations and preliminary analyses of chemical and biological samples collected during the first year of the project revealed that the Anzali Lagoon in its present stage belongs to water bodies with low fishery value. Its biological productivity is high; however the bulk of nutrients is utilized by aquatic macrophytes and only a fraction is channeled to fish through the food chain.

Its open water surface, divided into three more or less separate basins, is now about 108 km², which is slightly less than 50% of its surface in 1966 (218 km²). From a fishery point of view the only utilizable part is the western basin (68.2 km²). Southern and eastern basins represent a marsh dominated by emergent weeds (Phragmites and Scirpus). Dissolved oxygen content in the western basin varies from 4.12 to 11.0 mg.1^-1 with a mean of about 7–8 mg.1^-1 during the period January – May 1990. This is a favourable dissolved oxygen concentration for most of the fish species living there. pH values fluctuate between 8 and 10 with values above pH 9 being frequent as a result of a heavy cover of bottom by submerged vegetation. Benthic animal community is poor with between 700 and 1 400 animals per square metre. Also phytoplankton shows a low density with an average of around 9 600 cells per litre. Zooplankton shows also low concentrations, especially copepods, cladocerans and rotifers which represent the most important food organisms for young fish. The total average concentrations of these three groups was 7 100, 4 700 and 3 700 organisms per litre respectively in the Western lagoon during the April – June period. Low phyto- and zooplankton densities reflect the high density of aquatic macrophytes which consume the bulk of nutrients entering the Western lagoon.

The lagoon is under the influence of nutrient and sediment loads delivered to it by ten inflowing rivers. Pesticide and industrial pollution loads have a minute impact. The lagoon, especially its southern and eastern parts, functions as a sediment and nutrient trap which stimulates the excessive growth of aquatic macrophytes but inhibits plankton. Most parts of the Anzali lagoon produce gas in its sediment and the sediment-water interface is deoxygenated.

4.2 Fish and fisheries

Based on the inspections of fish catch during the catch-and-effort data census and on experimental fishing, a list of 26 fish species was compiled (Appendix 1). Pike-perch (Stizostedion lucioperca) and bream (Abramis brama) known to support significant fisheries in the past were not found.

The fish fauna in the Anzali Lagoon is composed of resident and diadromous species. The first are represented by 16 species, six of which are exotic introduced intentionally or accidentally by man. Common sawbelly, Hemiculter leucisculus deserves special attention as it possibly could become a pest (see also section 6). Eastern and southern basins are poor in fish species, with only Carassius auratus, Esox lucius, Tinca tinca and Proterorhinus marmoratus recorded from channels with slowly running water. Extensive areas covered by dense mats of Trapa natans are inhabited by numerous and dense schools of Gambusia affinis. Other species of fish avoid Trapa and occur mostly only in the western basin. Outflows are inhabited by brackish water species, especially gobiids which also occur in channels connecting the southern basin (Siahdarvishan) with the western basin and they are also present in the lower courses of the Pirbazar and Pasikhan rivers. Young mullets (Liza aurata) occur only in some rogas.

Thanks to catch-and-effort census initiated at the beginning of this year more reliable data on the fishery are now available. The first data show that the lagoon is under an intensive fishing pressure. The western basin is mostly fished by haul seines (up to 16 haul seines daily), followed by gill nets (estimated total length of up to 4.8 km). Most fishermen are artisanal and their activity is limited to winter and early spring months. Their total catch recorded since 21 January until 15 March 1990 was 6.6 metric tons of which 90.3%, 7.8% and 1.9% is shared by haul seines, gill nets and cast nets respectively. The composition of the catch mirrors the environmental conditions of this basin, especially the high pH values. The bulk of the catch by weight is represented by the accidentally introduced goldfish Carassius auratus (77.7%), intentionally introduced silver carp Hypophthalmichthys molitrix (7.8%; most of it is a hybrid H. molitrix x bighead carp Aristichthys nobilis) and by the native pike Esox lucius (5.6%) and common carp Cyprinus carpio (5.9%). The first three species are known to live in waters with pH well above 8 and Carassius auratus may withstand also total anoxia. Caspian shemaya (Chalcalburnus chalcoides) which has been recorded in gill net catches, was probably misidentified and is most probably the accidentally introduced common sawbelly Hemiculter leucisculus. The catch of the herbivorous silver and grass carps and of common carp is low in spite of them being regularly stocked at a rather high stocking rate (930 000 - grass carp, 655 000 - silver and bighead carp and 136 000 common carp per year). As the mean weight of stocked juveniles is only 3 g most juveniles are probably preyed upon by pike and wels (Silurus glanis). To avoid the harsh environmental conditions and shortage of food, part of the stocked juveniles probably migrate to the Caspian Sea.

Migratory species Rutilus frisii kutum, Vimba vimba persa, Barbus brachycephalus, Chalcalburnus chalcoides and Alosa caspia (two subspecies) were not recorded in the western basin although they were abundant there in the past. They occur and are fished in rogas and in the inflowing rivers during late winter and spring months.

4.3 Crayfish

Crayfish stocks were assessed at seven stations on six inflowing rivers and/or channels and in one rogas (outlet) using special traps which were inspected daily. Crayfish were measured and fecundity and standing stock estimated. Preliminary results show crayfish biomass of about 500 kg/ha and yield of about 250 kg/ha. The optimum harvesting time is between the end of May and the second decade of June and from the first decade of September until mid December. Water temperature of 26°C stops the crayfish activity and mass mortality of crayfish takes place at 32°C. The mean fecundity is 211 with the first eggs being recorded on 10 December. Females bear juveniles until 21 May. The crayfish stock in Anzali Lagoon consists of several groups. The total, carapace and orbital carapace length seldom reaches more than 130, 60 and 45 mm respectively. About 48% of the stock is represented by specimens longer than 100 mm in total length.

4.4 Impact of the rising Caspian Sea level

Since 1977 when the Caspian Sea dropped to its lowest level since 1879 when measurements of level were initiated, the constant rise is observed. According to measurements from the Bandar Anzali water gauge the sea level increased from -30.03 m to the present (1989) -28.62 m, i.e. by 1.41 m within 12 years. The rising level has already made an impact on not only the hydrochemical regime of the Anzali Lagoon, but also on its biota. While in 1989 the average chloride concentration in the western region of the Western lagoon was 226.6 mg.1-¹ the average value for the same locality for the period February-June 1990 was 374 mg. 1^-1 (surface) and 407 mg.1-¹ (bottom). At the upper mouth of the Anzali roga connecting the western basin of the lagoon with the sea the mean chloride concentration in the same period of 1990 was 482 and 474 mg.1-¹ at the surface and bottom respectively. This part of the Anzali Lagoon has brackish water fish gobiids, mullet and shad, prawns (Palaemon sp.) and barnacles (Balanus sp.). Balanus is an exotic crustacean which entered the Caspian Sea from the Black Sea via Volga-Don Canal built in 1954–5. It is frequently found on the carapace of crayfish and it has been found also in the lower courses of rivers entering the Anzali Lagoon. As a result of the increasing salinity the submerged and floating vegetation mats in the western basin of the lagoon were found to be much less dense in the summer of 1990 than in corresponding periods of the past year. If the Caspian Sea level increases further or if it stabilizes one can expect further changes in the hydrochemical regime and in the biota composition of the Anzali Lagoon. Under the new conditions the restoration of fishery in the Anzali Lagoon would then become easier.

5. STATUS OF THE PROJECT ELEMENTS

5.1 Project Timetable for 1989–1990 (Fig. 1)

5.2 Equipment

Although the list of equipment needed for the project performance was prepared, submitted to the UNDP Project Officer and then ordered by FAO HQs in time (November 1989 to May 1990), no equipment had been received in Bandar Anzali by the end of the mission. This has hampered both the field sampling and laboratory analyses, especially of biological samples and it may delay completion of the project.

5.3 Aquatic pollution survey

The national laboratory has carried out monthly sampling and analyses of the TSS, COD, total N, NH4-N, NO3-N, total P, PO4-P in rivers entering the Anzali Lagoon. In accordance with recommendations of the APC during his first visit in March, the NPS took bi-weekly samples of aquatic insects in the Masuleh River. These investigations were extended also to Pasikhan River with samples being taken by both the APC and NPS.

Performance on river load survey and progress on the quantification of load processing in the lagoon have been evaluated. Additional parameters with method, sampling sites and schedule were suggested to be included in a year-round work plan (Appendix 2).

5.4 Physico-chemical water analyses of the lagoon

Water sampling for chemical analysis of the lagoon water is being performed according to the work plan. The gross primary production and the chlorophyl a measurements began in August.

5.5 Hydrobiological sampling

Sampling of phyto- and zooplankton started in April. Sampling of benthic animals was carried out according to the schedule. The sampling faced some shortcomings and had to be adjusted. Instead of three subsamples only one was collected from each station. This has reduced the sampling reliability and thus the possibility for statistical evaluation of the data collected between January and July. The main groups of phytoplankton, zooplankton and macrozoobenthos were identified.

5.6 Crayfish stock assessment

Daily crayfish samples have been collected from seven stations in six rivers. Biometrical data have been collected and the marking of crayfish (by punching) is used to estimate population density and migrations. Critical and lethal temperatures were established and are recorded together with female fecundity. Regression analyses have been computed and relevant nomograms for conversion of some biometric characteristics plotted. Length/Weight relationship has not been calculated as the fine field balances necessary for such work has not yet arrived.

5.7 List of aquatic vegetation

The list of aquatic vegetation found in the Anzali Lagoon and its particular regions has been prepared by the NPS based on the report of YACOM two years ago. However, the up-to-date list could not be prepared as there is no competent botanist in the country to identify the species. An attempt will be made to collect plants and get them identified outside Iran.

5.8 Fish stock assessment

According to the work plan for the purpose of the fish stock assessment, fish were regularly sampled in various sections of the lagoon using haul seine, gillnets, fyke nets, drift nets and cast (lane) nets.

Fyke nets did not prove to be efficient as only a few fish were caught each time. This was because at each station (outlets or rogas from the lagoon) only one fyke net was applied close to the shore. Proposed closing of some rogas by a set of fyke nets laid from shore to shore could not be done because of heavy boat traffic from and to the Anzali Lagoon.

Beach seines were not applied at all as the only two suitable places near the Abkenar and Gluga villages were fenced off by peasants by a barbed wire to prevent the seining.

Nevertheless, collection of catch-and-effort data continues. The inspection of catches and gear of local fishermen started in December 1989 and continued until the beginning of August 1990. The species composition, number and weight of fish catches, fishing gear, number of boats and hours of fishing were recorded. The data will be evaluated during this project.

Fish migration study was hampered by the lack of tagging equipment which has not arrived. Nevertheless, the fyke net catches and information provided by fishermen suggested that some fish are entering the lagoon.

Some samples have already been analyzed for age composition and age-length, age-weight and length-weight relationships.

The Technical Adviser and National Project Staff also sampled fish at two stations on the Pasikhan and Masuleh Rivers.

5.9 Training

On-the-job training in fish species identification, recording, evaluation and interpretation of statistical data was given to the National Project Staff on various occasions.

6. OTHER ACTIVITIES

The Technical Adviser assisted the SFRO Experimental Hatchery in artificial propagation of Barbus brachycephalus, a valuable freshwater fish, the catches of which have been declining. A method of artificial breeding for Barbus barbus, a similar species, was introduced to the counterparts and will continue to be tested with B. brachycephalus. The habitat and ecology of B. barbus and B. brachycephalus are similar.

Among the fish samples from the Anzali Lagoon collected by Mr. Haghighi, the Technical Adviser identified a species not yet recorded in Iran. It is an exotic cyprinid fish, the common sawbelly Hemiculter leucisculus. How this fish appeared in the Anzali Lagoon is not yet known. It must have been transferred accidentally with consignments of the Chinese herbivorous carps from the USSR or from Romania. Because of known competition of this species with native fish in Soviet Uzbekistan, a similar effect may be expected also in Iran. The Technical Adviser prepared a leaflet on this fish (Appendix 3). This leaflet will be distributed to Shilat and Jehad hatcheries and fish farms.

7. TRIPARTITE REVIEW

The project progress was reviewed by a Tripartite Committee on 30 August 1990. Participants of the committee were Mr. M.H. Kabir, Deputy Resident Representative, UNDP, Dr. H.R. Ghaffarzadeh, Programme officer, UNDP, Mr. V. Haghpanah, Deputy Director of the Shilat Research and Training Centre and Director of the SFRO, Mr. N. Hosseinpour, NPS Director, Dr. J. Holcik, FAO Technical Adviser and Dr. J. Olah, FAO Aquatic Pollution Consultant. The project is making good progress, although not yet all field and laboratory work is possible, due to a delay in the delivery of equipment. The UNDP Representative explained that some of the equipment in Tehran Airport still needs to be cleared through customs and that in this respect little can be done by the UNDP office. The UNDP agreed with the proposal of Mr. Haghpanah and the Technical Adviser to extend the mission of Dr. OJah by a further two months to cover additional environmental aspects. FAO HQs should discuss the possibility of such an extension with UNDP and request additional funds. Subject to the availability of funds, two missions are proposed for Dr. Olah, i.e. one in May 1991, the second in October 1991. It is essential that the Shilat Fisheries Research Organization also equips another office for the use by consultants and counterparts, five of which share one room at present.

8. IMPLEMENTATION COMMITTEE

A meeting of the Implementation committee consisting of FAO consultants, NPS director, SHILAT Deputy Director and of the Head of the JEHAD Chemical Laboratory was held on 8 September 1990. Organization and methodological problems were discussed. Consultants requested that diurnal dissolved oxygen measurements be initiated in various parts of the lagoon, to establish the range in dissolved oxygen concentrations and their possible impact on fish distribution. It was recommended that the library be reorganized to efficiently fulfill its function.

Fig.1 Project timetable in 1989–1990

APPENDIX 1

List of fish for the Anzali Lagoon

I = introduced exotic species
* = species resident in the western part of the lagoon

APPENDIX 2

RIVER LOAD SURVEYS

The first mission of the Aquatic Pollution Consultant concluded that the Anzali Lagoon is exposed to heavy domestic nutrient and sediment load. Pesticide and industrial pollution is of secondary importance. As the nutrient and suspended sediment loads were never measured and it is thought that they have a decisive role both on the siltation and on the abundant growth of macrophytes in the Anzali Lagoon, the consultant prepared a monitoring programme for river load measurements. The counterpart chemical laboratory then initiated the measurements of river nutrients and suspended sediment loads. During the second mission of the consultant, additional parameters were introduced into the river survey programme in order to obtain more background information which would assist in the formulation of strategies for the lagoon. An account of the work in progress and additional proposals follow:

1. Monitoring total suspended sediment (TSS) concentrations in inflowing rivers

Monitoring of TSS load received high priority because of the almost complete lack of reliable data. Over the last years, a rapid increase in siltation of the Anzali Lagoon has been taking place, especially in the Siah Khesim and Seygan regions of the lagoon. Regular monitoring has therefore been initiated. As the lowest section of Palaghvar River was not accessible by car, samples were taken 2 km upstream. Samples were also taken at its largest tributary Abater. The filtering procedure was modified during this second mission. The first results show a wide range of fluctuations in rivers and lakes, which emphasize the importance of the bi-weekly sampling schedule. The final assessment and evaluation of the silt load for the lagoon restoration strategy and remedial measures are to be completed by May 1991.

2. Monitoring total organic carbon in rivers entering Anzali Lagoon

Data on the total organic carbon content in the inflowing rivers are scarce and so are some other chemical analyses. The Pirbazar River and its tributaries Goharud and Siard were surveyed during the period 1983–84. In the survey of Pirbazar River, the chemical oxygen demand was measured with permanganate, but permanganate oxidizes only a certain portion of the reduced organic carbon and the results cannot be accepted and used in calculating the total organic carbon budget. After introducing the bichromate oxidation method during the first mission of the consultant, monitoring of the total organic carbon content started in the eleven most important rivers. Preliminary results have been tabulated and evaluated showing several trends. With the snow melting and early rains the organic carbon concentration is diluted. The organic carbon concentration starts to increase again during the low discharge in the summer months. It is not yet clear why a high concentration of total organic carbon was recorded in several rivers which do not drain domestic sewage. To explain this will require all-year-round monitoring.

3. Allochtonous vs. autochtonous organic load in the rivers

The river's organic carbon is of two origins: allochtonous carbon from the dry land and that produced in rivers by photosynthesis as autochtonous carbon. The simplest approach to quantify the magnitude of autochtonous input through photosynthesis is the direct measurement of the chlorophylls. Two complete surveys on eleven rivers carried out during the summer period showed that rivers draining the catchment area of the lagoon have a very low chlorophyll content and therefore river photosynthesis plays a minor role in oxygen production and its contribution to carbon load during the summer is negligible. The rivers examined have a self-purification process relying upon the physical re-aeration which is high in the mountainous and foothill region of the watershed but low along their 20–25 km-long lowland sections.

4. Nitrogen load in the inflowing rivers

NH₄-N and NO₃-N concentration are now monitored on eleven inflowing rivers. The total nitrogen monitoring was initiated during the second mission. This is being done by using the digestion method. Two alternative digestion procedures are now being used in the laboratory.

5. Phosphorus load in the inflowing rivers

PO₄-P and total-P concentrations in the inflowing rivers are now regularly monitored. For this purpose samples are being processed without previous fixation as the total phosphorus content remains fairly constant for several days without fixation. A new method for total phosphorus determination was also introduced which uses single digestion both for nitrogen and phosphorus. The new method will be compared to the previous one using a separate digestion for the total N and the total P. The phosphorus load is an important indication of the level of nutrient inputs into the lagoon and therefore its determination is of high priority. To learn about the annual phosphorus cycle, the monitoring should cover at least a 12-month period.

6. Other indicators of river nutrient load

From meetings between the Technical Adviser and the Aquatic Pollution Specialist and also from conclusions made at the Tripartite Review Meeting held on 30 August it was recommended to include some additional activities into the year-round regular bi-weekly river survey. In order to predict the organic carbon load of rivers, and to prepare a management programme for reducing it, it was decided to expand the monitoring programme as follows:

1. The number and size of sediment traps along the main inflowing rivers will be increased. To quantify nutrients attached to particles and liable to sedimentation in the traps, concentrations of the total particulate phosphorus/TPP, total particulate nitrogen/TPN and total particulate organic carbon/TPOC in the water column of inflowing rivers will be measured separately. Methods already used for total-P, total-N and total organic-C measurements will be applied on filtered river water samples. The same counterpart laboratory staff will measure the additional parameters using the same sampling schedule and at the same sampling stations which were detailed and mapped during the first mission.

2. Organic carbon decomposition and the self-purification capacity in the rivers Pirbazar, Pasikhan and Siahdervisan will be monitored.

7. Load processing in lagoon ecosystems

As the chemical environment determines the community structure of the lagoon, a detailed survey was carried out on the most important chemical variables which influence directly the occurrence, abundance, distribution and species composition of the lagoon fish community. 25 sampling stations were selected in the Siahkeshim and Seygan sectors of the lagoon, and the following field data collected: morning and evening dissolved oxygen concentrations, sediment and water redox condition and gas presence, using portable oxygen and redox meters and gas traps designed by the consultant and manufactured in the Shilat workshop. The measurements were carried out by the counterpart staff and by two Ph.D. students who joined the consultant's mission (Mr. Nezami and Mr. Esteky of Shilat, Jehad). Their contribution was financed partly by the Government of Iran (travel expenses) and partly by Hungary (equipment and material). These additional persons have experience in nutrient analyses, sediment loads and processing of the data. The results of this survey still need to be evaluated. At present it would appear that the lagoon, apart from the open water areas of the Western Basin with a sizeable plankton community, is heavily oxygen-deficient with reduced sediments producing gas. This has a negative impact on fish distribution: the Siahdervishan and Seygan sectors of the lagoon are almost devoid of fish, with only some fish present along the connecting canals. It is recommended to monitor monthly, morning and evening, dissolved oxygen concentrations and sediment gas content, at one station each in the submersed, floating and emergent macrophyte community regardless of the sector, plus at three stations in the open water areas of the Western Basin, i.e. in the eastern, middle and western part of the basin. The dissolved oxygen values will also be used to calculate primary production and community respiration.

For the purpose of determining the nutrient content in sediments, 74 sediment samples were collected at various sampling stations. The samples will be analysed in Hungary.

Organic mater is reaching the Anzali Lagoon in the form of domestic and agricultural waste, and is being removed through several processes; photosynthesis and chemosynthesis, bacterial decomposition, and through the food chain. In the present project, primary production of submersed, floating and emergent vegetation and of the phytoplankton community was estimated using landsat imagery. A more reliable estimate is still needed. A simple method using three points in situ was introduced to quantify the gross primary production and community respiration. The survey covered 40 stations on inflowing rivers, connecting canals, collecting canals, open waters, submersed, floating and emergent vegetation as well as outlets to the sea. Ranges were tabulated and data are being evaluated. This survey will continue at one station in each of the submersed, floating and emergent macrophyte communities and at one station in the middle of the open water area of the Western Basin. Benthic fish feed organisms utilizing and processing the organic carbon are also being investigated in the open areas. The numbers of macrobenthic animals are well below 1 000/m2. Several thousands, mainly oligochaetes, were present only in the organically polluted outlets from Bandar Anzali.

Most parts of the lagoon have no benthos, but submerged, floating and emergent vegetations are full of animals. This community probably plays a crucial role in load processing. This animal community lives and functions in a highly oxygen deficient environment. Their species composition and abundance were studied in Chara and Ceratophyllum and consists of hemipterans Corixa and Plea, pulmonate gastropods Radix and Planorbis, limnocharid water mites parasitizing on hemipterans, odonats, mayflies and gammarids. Some of these animals utilise atmospheric oxygen and therefore, to some extent, they are not influenced by the oxygen deficient lagoon. Their number may reach enormous densities of around 30 000/m². Monthly surveys are to be carried out on this community in Chara, Ceratophyllum and Trapa.

Nitrogen release to the atmosphere seems to be the dominating pathway for removal of this element from the lagoon. A reliable estimate would require direct measurement of nitrification and denitrification processes in the lagoon which, however, is not the subject of investigations under the present project.

APPENDIX 3

Common Sawbelly (Hemiculter leucisculus (Jordan et Metz, 1913)) - an undesirable fish species in Iran?

An exotic (= not native to Iran) cyprinid fish, the common sawbelly (Hemiculter leucisculus (Jordan et Metz, 1913)) has_been identified from the Anzali Lagoon, Gilan Province. The fish was collected by Mr. D. Haghighi during his regular catch-and-effort census sampling on 24 May 1990 and then again by the consultant in the same locality, on 27 August 1990.

The original distribution of this species is in watersheds of the rivers Kang-tse-kiang, Hoang-ho, Yalu and Amur in China, Korea and the USSR respectively. The species was probably accidentally transferred to Iran with consignments of the Chinese carps (grass carp, silver carp and bighead carp) from the USSR and/or Rumania, where it has also been found. Although not a predator, its occurrence could compete with the native Iranian fish for food. It could also feed on their eggs and hatchlings. Such a situation is known to exist in the Soviet Central Asia where the common sawbelly was also unintentionally introduced with the grass carp and silver carp from the Amur River and rapidly spread afterwards to fish farms and natural water bodies.

The common sawbelly resembles the native Caspian shemaya (Chalcalburnus chalcoides iranicus Svetovidov, 1945). However, it may easily be distinguished from the former by the following characters:

1. its abdomen possesses a marked unscaled sharp keel running from vent to throat. In Shemaya this keel is very short, not reaching even the base of the ventral fins;

2. its lateral line steeply descends between the base of the ventral and the end of the anal fins, running parallel to the lower profile of the body, 1–3 scale rows from the mid ventral line. Then, behind the end of the anal fin, curving upward and running on the caudal peduncle centre. In Shemaya the lateral line is almost straight, running in the centre of the body flanks;

3. the last unbranched ray in its dorsal fin is transfomed into a smooth sharp spine, with a soft tip. In Shemaya this ray is soft;

4. a narrow dark band runs laterally from the end of the head to the tail fin. Such a band is not present in the Caspian shemaya.

Although little can be said about the present impact of this exotic species on the native fauna of the Anzali lagoon and its tributaries, it could possibly have in the future a negative impact rather than a positive one. Therefore, it is recommended to introduce some control over this species already present in the lagoon by destroying any specimens which are captured. Ponds and lakes in Iran, into which Chinese carps have been introduced, should also be checked for the presence of this fish, and wherever found, it should be destroyed. The findings should be reported to Shilat for recording its present distribution.

Any new transfers of Chinese carps and other fish, both within and from outside the country, should be checked for its presence and all specimens found, removed and destroyed.

It is advisable that any future introductions of exotic fish to Iran should adhere to the internationally accepted Codes of Practice. ¹ There is growing evidence that only few introductions bring beneficial results. Some introductions have resulted in an adverse impact, especially on the native fish. A review on introductions by R.L. Welcomme: International Introductions of Inland Aquatic Species (FAO Fisheries Technical Paper No. 294, Rome, 1988) provides more details on the subject.

¹ Codes of Practice and Manual of Procedures for Consideration of Introductions and Transfers of Marine and Freshwater Organisms. EIFAC Occasional Paper No. 23, Rome, 1988