INFORMATION COLLECTED AT THE HYDROBIOLOGICAL STATION OF RHODES (GREECE) ON LESSEPSIAN MIGRANT FISHES Maria CORSINI & Stamatis STAMATELLOS National Centre for Marine Research/Hydrobiological Station of Rhodes, Cos Street, GR-85100 Rhodes ABSTRACT Lessepsian fishes species were recorded in Greek Seas (Economidis, 1973, Papaconstantinou, 1990). In this work information collected at the Hydrobiological Station of Rhodes on Lessepsian fishes species previously observed in the marine region of Rhodes and on two Lessepsian fishes recently occurred in the same area (Corsini & Economidis, 1998, in press) are given, with the aim to contribute to enrich the knowledge on their distribution. Observations on the maintenance of some of these species in the Aquarium are furthermore described. INTRODUCTION Por used the term Lessepsian migration to describe the immigration of Red Sea biota into the Mediterranean after the opening of the Suez Canal in 1869: Lessepsian migration is a phenomen of unidirectional and successful biotic advance from Red Sea to the eastern Mediterranean (POR, 1978). As previously reviewed, the migrant species belong to mollusks, fishes, Polychaeta, Crustacea Decapoda, meduses, fish parasites and to other groups (POR, 1978; 1990). New records of migrant species are continuously reported and described. The Lessepsian migrants are most successful at intermediary depths, between -40 m, on mixed sandymuddy bottom, showing a depth limit of 70-80 m (about 18 C) for the distribution of organisms of tropical origin (POR, 1978, GOLANI & Ben-TUVIA, 1989). The fish assemblage in the source habitat (Red Sea) was investigated and a preadaptation of the Lessepsian migrants to sandy habitats, enabling successful colonization of these habitats in the Eastern Mediterranean, was suggested (GOLANI, 1993 b). For potentially competitive species (local and immigrant) it was observed a displacement of the local species to deeper (and colder) layers, while the immigrant occupied the shallower (and warmer) parts of a depth previously occupied by the local species (POR, 1978, GOLANI, 1993 a). Several studies on biological and ecological aspects of migrant species in the new environment as well as of the indigenous and immigrant populations were carried out. As underlined by POR (1978), the gradual longshore advance of the Lessepsian migrants along the Asiatic coast is well documented. Since the Lessepsian migrants constitute about the 10% of the biota of the Levant Sea (POR, 1978), it was proposed the delimitation of a biogeographic province within the Mediterranean, the Lessepsian Province (POR, 1990). According to POR (1990), the marine region around the island of Rhodes (Dodecanese islands, South Aegean Sea) belongs to the Lessepsian Province. The island of Rhodes, in particular, is located in a peculiar oceanographic position among the South Aegean Sea and the Levantine basin. Water masses of this area are characterized by high temperature and salinity values, even in deep waters (PANCUCCI- PAPADOPULOU et al., 1992). The surface temperature varies from 17.6 C (February) to 26.4 C (August), while under the thermocline the temperature is always higher than 14.7 C (SIOKOU- FRANGOU & PAPATHANASSIOU, 1989). The salinity is about 39PSU in all seasons. - 35 -
Considering migrant fishes, long ago a number of 9 Lessepsian migrant fish species have been recorded in the SE Aegean Sea (ECONOMIDIS, 1973). As described in PAPACONSTANTINOU, (1990), the list of Lessepsian migrants fished in Greek seas enlarged to 11 fish species (Table 1). Table 1. List of Lessepsian migrants fished in Greek seas (from PAPACONSTANTINOU, 1990). Sargocentron rubrum (Forsskål, 1775) Siganus rivulatus (Forsskål, 1775) Siganus luridus (Ruppell, 1828) Lagocephalus spadiceus (Richardson, 1844) Stephanolepis diaspros Fraser-Brunner, 1940 Upeneus moluccensis (Bleeker, 1855) Leiognathus klunzingeri (Steindachner, 1898) Saurida undosquamis (Richardson, 1848) Pempheris vanicolensis Cuvier, 1831 Hemiramphus far (Forsskål, 1775) Parexocoetus mento (Valenciennes, 1846) OBSERVATIONS AND NEW RECORDS Some of the species of fishes listed in Table 1 were collected in the area of Rhodes and they are exhibited in the small marine museum of the Hydrobiological Station of Rhodes. They are: Sargocentron rubrum, Siganus rivulatus, Siganus luridus, Stephanolepis diaspros, Upeneus moluccensis, Saurida undosquamis, Pempheris vanicolensis. Other two Lessepsian fishes, Pteragogus pelycus (Labridae) (RANDALL, 1981, GOLANI & SONIN, 1992) and Sphyraena chrysotaenia (Sphyraenidae) (Ben-TUVIA, 1986), were recorded recently for the first time in the area of Rhodes (CORSINI & ECONOMIDIS, 1998, in press) and are to be added to the species mentioned above. As previously reported (CORSINI & SIOULAS, 1993), the major part of the incoming fish for the enrichment of the aquarium, comprehending also some Lessepsian species, is collected by trawl-net, generally from the surface to -30 m depth. The sampling station, named A, is located near the Aquarium, at the top of the island, along the eastern coast, 100-400 m far from the beach of the city (Fig. 1). Fig. 1: Map of the top North-eastern coasts of Rhodes town. ( = Station A, - 36 - = Aquarium).
To have an indicative idea about the temperature and salinity values in the area in which some Lessepsian species are caught, the profiles of these parameter, obtained in different seasons during 1997 by a CTD recorder, are shown in Fig. 2 (a, b, c). It may be observed that in the deeper layers, under the thermocline, the seawater temperature was around 16.5-17.5 C both in May, during the formation of thermocline (Fig. 2a), and in August, when the thermocline was completely produced (Fig. 2b). The minimum mean seawater temperatures (16 C) in the Aquarium of the H. S. R. where the species are maintained, are reached in February and March, while the mean maximum values (23.8 C) are in August and September (Fig. 3) (the seawater incomes from a surface well, at 3 m depth). 0 Temperature (deg. C) 15 17 19 21 23 0 Temperature (deg. C) 15 17 19 21 23 25 27 0 Temperature (deg. C) 19,0 19,5,0 10 10 10 Depth (m) 30 40 50 60 70 a. T S Depth (m) 30 40 50 60 70 b. T S Depth (m) 30 40 50 60 c. 70 T S Salinity (psu) Salinity (psu) Salinity (psu) Fig. 2: Temperature and salinity profiles obtained from Station A during May (a), August (b) and December (c) 1997. Temperature (Deg. C) 26 24 22 18 16 14 January February March April May June Month July August September October November December Fig. 3: Main temperatures of the seawater in the Aquarium of Rhodes (1985-1997). Individuals of six Lessepsian fish species are collected enough regularly in station A (Table 2). Table 2. Lessepsian fishes collected in Station A. Siganus rivulatus (Forsskål, 1775) Siganus luridus (Ruppell, 1828) Stephanolepis diaspros Fraser-Brunner, 1940 Upeneus moluccensis (Bleeker, 1855) Pteragogus pelycus nom. nov. Sphyraena chrysotaenia Klunzinger, 1884-37 -
Although a school of Pempheris vanicolensis was photographed at 3 m depth among rocks, in the west of the island, not far from the Station, living specimens were never collected. The specimens of U. moluccensis and of S. chrysotaenia don t survive longer than a few hours, since the fishing method used causes serious external damages. The number of specimens of U. moluccensis is generally low in relation to Mullus surmuletus, which is common in the area. The specimens of S. chrysotaenia are caught in large number, swimming these fishes in schools mixed sometimes with individuals of Sphyraena viridensis. On the other hand, it is a long time that the Lessepsian species Siganus luridus (Fig. 4), Siganus rivulatus (Fig. 5) and Stephanolepis diaspros (Fig. 6) are normally exhibited in the open seawater system of the Aquarium. It is not easy to have more than 2-3 individuals for each one species, being their number very low in the trawl net, in relation to the species Spicara sp., Boops boops, Oblada melanura, Pagrus pagrus, Serranus scriba, Serranus cabrilla, some Labrids and others, usually more abundant in the area. The three migrant species mentioned above live in the tanks with individuals of the species caught together in the field. The maintenance of Stephanolepis diaspros doesn t appear difficult, appreciating a carnivorous diet, while more difficulties are encountered for maintaining the two species of Siganus, being their regime herbivorous. They feed generally on algae growing on the rocks of the tanks. It was observed that they appreciate the brown alga Padina pavonica which is easy to collect in the field. These three Lessepsian species seem to be sensible to the Cryptocaryon sp. infections which appear regularly, during summer, in the last years in the Aquarium of the H. S. R. (CORSINI & STAMATELLOS, 1996). Considering the newly recorded P. pelycus (Fig. 7), the adults generally appeared in a few number of individuals (1 to 3) in the trawl net, but the most recent trawlings showed an increase of its presence, also with young individuals. It presents a reddish-brown color with black spots in dorsal fin. The male differs from the female for the prolongation of the first soft ray of pelvic fins. Two of the first living samples were taken in a closed system tank (0 lit. volume) at environment temperature, in the underground of the Station. During winter, the environment temperature decreased to 12 C and the fishes didn t survive, probably due to the low temperature. Successively, other samples were maintained for a longtime without problem either a) in a closed system tank (100 lit) at C constant temperature, either b) in a closed system tank (100 lit) at environment temperature ranging from 17 C to 28 C either c) in a small tank of the open seawater system (15-24 C). It likes to hide itself, passing the major part of the time in the darker places of the tank and coming out only for food especially at lower temperatures, while, increasing the temperature, it passes longer time outside the refuges and swims more time. Although it was observed that the male appeared initially enough aggressive against females newly introduced in the tank, they successively live together without problem. In the small aquariums in which this species is maintained, with sand, small rocks and the green alga Caulerpa prolifera on the bottom, it lives easy with various other species as Serranus scriba, Diplodus sp., Labrids. This species appears to be voracious and to appreciate a carnivorous diet, including shrimps, mussels, pieces of squids and fishes. ACKNOWLEDGMENTS Authors are grateful to Prof. P. S. ECONOMIDIS (Arstotelian University of Thessalonikis) for his helpful suggestion and advice and for his support and encouragement throughout this study. - 38 -
Fig. 4. Siganus luridus Fig. 5. Siganus rivulatus Fig. 6. Stephanolepis diaspros Fig. 7. Pteragogus pelycus - 39 -
REFERENCES Ben-TUVIA, A., 1986. Sphyraenidae. In Fishes of the North-eastern Atlantic and the Mediterranean (Whitehead P. j. P., M.-L. Bauchot, J.-C. Hureau, J. Nielsen, E. Tortonese, eds). Vol. 3, 1194-1196. Paris. UNESCO. CORSINI, M. & P. S. ECONOMIDIS, 1998. New Lessepsian migrants from the marine area of the Island of Rhodes (Aegean Sea, Greece). In press. CORSINI, M. & A. SIOULAS, 1993. The Aquarium of Rhodes: Operation and Activities. Proceedings of the European Union of Aquarium Curators Meeting, Naples, Oct. 1992. Mémoires Inst. Océanographique Paul Ricard, 93-96. CORSINI, M. & S. STAMATELLOS, 1997. Handling pathogenic ciliates Cryptocaryon-like in the Aquarium of Rhodes. Proceedings 5 th Hellenic Symp. on Oceanography & Fisheries, Kavala, Greece, April 15-18, 1997. Vol. I, 457-460 (in Greek). ECONOMIDIS, P. S., 1973. Catalogue des poissons de la Grèce. Hellenic Oceanology and Limnology, 11: 421-598 (in Greek). GOLANI, D. & A Ben-TUVIA, 1989. Characterization of Lessepsian (Suez canal) fish migrants. Environmental Quality and Ecosystem Stability (ed. By E. Spanier, Y. Steinberger and M. Luria), pp. 235-243, Vol. IV B. ISEEQS Pub. Jerusalem, Israel. GOLANI, D. & O. SONIN, 1992. New records of the Red Sea, Pterois miles (Scorpaenidae) and Pteragogus pelycus (Labridae) from the Eastern Mediterranean Sea. Jap. J. Ichthyol., 39 (2): 167-169. GOLANI, D., 1993 a. Trophic adaptation of Red Sea fishes to the Eastern Mediterranean environment Review and new data. Israel Journal of Zoology, 39: 391-402. GOLANI, D., 1993 b. The sandy shore of the Red Sea lauching pad for Lessepsian (Suez Canal) migrant fish colonizers of the eastern Mediterranean. Journal of Biogeography, : 579-585. PANCUCCI-PAPADOPOULOU, M.-A., I., SIOKOU-FRANGOU, A. THEODORAKIS, & D. GEORGOPOULOS, 1992. Zooplankton vertical distribution in relation to the hydrology in the NW Levantine and SE Aegean seas (spring 1986). Oceanologica Acta, 15 (4): 365-381. PAPACONSTANTINOU, C., 1990. The spreading of Lessepsian fish migrants into the Aegean Sea (Greece). Sci. Mar., 54 (4):313-316. POR, F. D., 1978. Lessepsian Migration. The Influx of Red Sea Biota into the Mediterranean by way of the Suez Canal. Ecological Studies 23. Springer-Verlag, Berlin. Pp. 228. POR, F. D., 1990. Lessepsian migration. An appraisal and new data. Bull. Inst. Océanog. Monaco. Special, 7, 1-10. RANDALL, J. E., 1981. Two New Species and Six New Records of Labrid Fishes from the Red Sea. Senckenbergiana marit., 13 (1/3): 79-109. SIOUKOU-FRANGOU, I. & E. PAPATHANASSIOU, 1989. Aspects du zooplancton côtier de l île de Rhodes (Mer Egée), Vie Milieu, 39 (2): 77-85. - 40 -