In accordance with the terms of reference, conclusions and recommendations will be devoted to carp and eel.
The gradual decline in carp catches from the lake apparently began after reclamation work was initiated in 1958 (Table 1). This is most probably related to the disappearance of the Laspista area which served as a spawning/nursing area as well as a feeding area for the carp population of the main lake.
The disappearance of some of the feeding areas, and the crowding of the carp population in the remaining lake area, appear to have resulted in retarded growth. It was noted that carp were very slender, with lower depth of body in relation to body length and excessive visceral fat deposits. It is difficult, in the absence of data on growth, to determine whether this is due to a genetic deterioration of the original stock or unfavourable feeding conditions and other environmental stresses. It should be noted, however, that Ioannina carp appear to be free from disease.
To compensate for the decline in carp production as brought about by breeding limitations and predation by the droumitsa population, it is recommended that adult carp broodstock be collected from the lake and held in existing or newly constructed ponds in the vicinity of the lake. These fish should be artificially spawned and the fingerlings produced observed for growth rate under controlled conditions. If growth rates are found to be satisfactory then the captive broodstock should be expanded and fingerling production increased for stocking the lake. Stocking will have to be continued annually as long as no measures are taken to provide additional natural breeding grounds for carp in the lake. Alternatively, or in addition, shallow breeding areas with adequate growth of vegetation can be established in suitable locations in the lake.
If outside assistance is required by the country for the implementation of these recommendations, particularly for the establishment of fingerling production through artificial breeding, it is suggested that this be done on the basis of short-term consultancies. Since no trained personnel are available locally, the government may also wish to send suitable candidates for training in this special field.
It is obvious that the re-establishment of an exploitable stock of eel in Lake Ioannina could only be expected if a sufficient number of elvers would annually gain access to the lake. 1Therefore a survey should be initiated to assess the number of elvers which may eventually pass the recently established dampass and sinkhole which drains part of the excess water of the lake. It is suggested that the military post near the dam sites participates survey by informing the agricultural service at cannina whenever elver migration is observed at the pass.
Should it become obvious during the sea survey that elvers do occur in the river but do not ascend the pass it may be advisable to enlarge the sea water flow at the entrance of the pass.
An additional supply of 5 l/sec through a syphon would seem to meet this demand in one of the irrigation ohannels located close to the pass. It is believed that this auxiliary device would increase the effectiveness of the pass.
Should the survey lead to the conclusion that elvers although successfully ascending the pass cannot reach the lake then a stocking programme should be initiated. The stocking material would either have to be collected from the estuary of the River Kalamas and/or be taken from the pass and transported to the lake. Since tracing of elvers and their capture would require skilled personnel the Government may wish to receive technical assistance or send a suitable candidate for training abroad (in France, Italy, Germany) within the fellowships provided in this project.
1 Although the pass was visited three times during the consultant's mission, no indication of elver migration was noted either within the pass or within the river between the estuary and the dam. Since the exact date of migration of elvers is not yet known, the above observations, especially with regard to the effectiveness of the pass, are inconclusive.
LIST OF COMMON SPECIES OF FISH IN LAKE IOANNINA TOGETHER WITH SOME BIOLOGICAL, ECOLOGICAL AND HISTORICAL REMARKS
|Anguilla (LINNAEUS, 1758)||The eel is said to have disappeared from the catches since approx. 1971. No specimen could be obtained during the author's mission.|
|Local name: Cheli.|
|B. albanicus STEINDACHNER, 1895||Maximum size observed: 32 cm (tl). Spawning time: V-males above 22 cm with clearly developed “spawn corpuscles” on forehead. Spawning grounds: vegetation belt (littoral).|
|Local name: MARITSA.|
|C. carpio LINNAEUS, 1758||This species was introduced from Italy in 1928. There are two varieties present: a) the scaled type and b) the mirror type with either irregularly distributed large scales or with three to four scale rows on each side. It is not unlikely that the former was derived from Yugoslav river carp stocks and later transplanted to Lake Ozeros, during 1960 to 1966. Maximum size observed (mirror type): 36 cm (tl), average size: 24 cm. Spawning time: V/VI.|
|Local names: Kyprinos (Carpa)|
|L. cabeda pamvoticus (STEPHANIDIS, 1939)||Most likely identical with L. cephalus (LINNAEUS, 1758) which is widely distributed in Greece. Only one specimen could be obtained (female, tl 28 cm, development of ovaries: IV stage pointing at spawning in VI). According to fishermen this species rarely occurs.|
|Local name: TSEROUKLA|
|P. epiroticus STEINDACHNER 1896|
P. epiroticus epiroticus STEINDACHNER 1896
|The latter is most likely an ecotype of the former since all specimen observed (30) did have the same meristic and nonmeristic characteristics (throat teeth formula: 5-5; number of scales in lateral line: 54–55; 11 gillrakers).|
Maximum size observed: 9 cm.
Spawning time: V
Spawning grounds: littoral vegetation.
|Local names: Tsima, Tsimes.|
Mainly used as trout feed (see Droumitsa); only occasionally on the market.
|R. rutilus rubella (BONAPARTE, 1832/41)||Maximum size observed: 19 cm (tl). Spawning time: V.|
Spawning grounds: almost exclusively in the litoral springs (of the lake) whose temperatures are 4° to 5° C below the average lake temperature.
Eggs are deposited on stones and rocky walls of spring mouths.
Schooling of postlarvae recruits at the the place of hatching; later on schools migrate towards the marginal plant associations. 80% of the catch is sold to trout farmers as trout feed.
This species is said to have been introduced soon after the second World War from Lake Ozeros. No explanation for the reason for this transplantation could be obtained.
|Local name: Droumitsa.|
|P. aristotelis (AGASSIZ, 1856)||Introduced from Lake Ozeros soon after second World War.|
Maximum size observed: 18 cm; according to fishermen's opinion, this species would not thrive well in Lake Ioannina. Specimen observed by the author in Lake Ozeros seemed also not to be well adapted to the prevailing conditions of the lake, their maximum length was below 25 cm whereas it is is reported to reach a maximum tl of more than 50 cm in other lakes of Etolia and Akarnania.
|Local names: Glanidi, Glavos.|
|T. tinca (LINNAEUS 1758)||For introduction: see carp maximum size observed: 19 cm|
Spawning time: see carp.
|Local name: Glynia|
Not included in the list is the crayfish Astacus fluviatilis the catch of which is almost exclusively shipped alive (by plane) to France. Local consumption is negligible. The average weight of single specimen varies between 64 and 91 g. During survey females carried eggs (between 32 and 46 females).
COMPOSITION OF CATCH AND TOTAL CATCH REPORTED FOR LAKE IOANNINA COVERING BOTH THE PERIODS 1945–51 AND 1967–72
|Year||Catch as per Species||Total catch|
Remarks: -: Nil; all figures “rounded”.
All figures obtained from the Greek Bank of Agriculture, Ioannina Branch and/or the Fishermen's Cooperative on Lake Ioannina Island.
Figures covering the period from 1952 to 1966 could not be made available because at that time fisheries rested within the Ministry of Industry of which no branch exists at Ioannina.
There are no statistics covering the production of crayfish. In 1972 a catch of approx. 1 metric ton was reported by the Head of the Cooperative.
There was no breakdown as to species carp/tench available for the period 1945–51.
PERCENTAGE SHARE OF CARP AND TENCH CATCH AS TO TOTAL CATCH
|Year||Percentage share of carp and tench as to total catch of lake fish|
Remarks: figures “rounded”.
NUMBER OF FISHERMEN AND AVERAGE ANNUAL CATCH PER FISHERMAN IN METRIC TONS
|Year||Number of Fishermen||Total Annual Catch as per Fisherman (metric tons)|
Remarks: figures “rounded”;
numbers of fishermen include from 10 to 15 % part-time fishermen.
DEVELOPMENT OF FISH PRICES RECEIVED BY FISHERMEN AT IOANNINA FOR THE PERIOD 1971–1974
|Year||Prices Received for 1 kg (Drachmai) by Fishermen|
Remarks: ? unknown;
figures for 1974 cover the period January-May.
Figures cited derived from market observations and information given by fishermen as well as by local consumers.
It is strongly anticipated that prices will increase by 15 % during 1974.