THE INVASION OF SAURIDA UNDOSQUAMIS (RICHARDSON) INTO 



THE LEVANT BASIN - AN EXAMPLE OF 

 BIOLOGICAL EFFECT OF INTEROCEANIC CANALS 



M. Ben-Yami' and T. Glaser2 



ABSTRACT 



The Red Sea lizardfish, Saurida undosquamis (Richardson), invaded the Levant Basin and established 

 a population of considerable commercial importance. Its expansion came at the expense of other 

 commercial fishes on which it preys and with which it competes. The explosion of the Red Sea lizardfish 

 population in the Levant Basin was made possible by a combination of changes in the environmental 

 conditions (abiotic and biotic), one of these being the retreat of, or the recession in, the native hake 

 population. The dynamic coexistence between the lizardfish and the hake, its main competitor, is 

 affected by fluctuations in the abiotic conditions to which the hake seems to be more sensitive than the 

 lizardfish. 



A faunistic, zoogeographical approach to the 

 marine animal migration through the Suez Canal 

 is common to most investigators of the canal's 

 influence. Animal species native to one sea and 

 found in the other after the opening of the canal 

 serve as main indicators of its biological influence 

 and of its effectivity as a link to the migrant 

 species and as a barrier to others (Ben-Tuvia, 

 1966, in press; Kimor, 19703; Por, 1971; Steinitz, 

 H., 1968; Steinitz, W., 1929; Thorson, 1971). Many 

 authors listed and described migrant species 

 (Barash and Danin, 1971-*; Ben-Tuvia, 1953; Col- 

 lette, 1970; Gilat, 1964; Gohar, 1954; Gordin, 

 19665; Holthuis and Gottlieb, 1958; Kosswig, 

 1951; Steinitz, H., 1967; Tortonese, 1953). 



Some authors have discussed the Red Sea- 

 Mediterranean animal migrations in relation to 

 ecological conditions in the canal and in the adja- 

 cent sea areas (Gilat, 1966^ 1969^; Oren, 1969, 



'Fisheries Technology Unit, P.O.B. 699, Haifa, Israel. 



^Kibbutz Ma'agan Mikhael, D.N.Hof Hacarmel. Israel. 



^Kimor, B. 1970. The Suez Canal as a link and a barrier in 

 the migration of planktonic organisms. Submitted to the Ocean 

 World-Joint Oceanographic Assembly, Tokyo, 13-25 Sept. 

 1970, 20 p. 



■'Barash, A., and Z. Danin. 1971. Indo-Pacific species of Mol- 

 lusca in the Mediterranean. Appendix to Progress Report 

 1970/1971. The Hebrev/ University - Smithsonian Institution 

 Joint Project "Biota of the Red Sea and the Eastern Mediterra- 

 nean," 8 p. [Processed.] 



*Gordin, H. 1966. Migration of fishes through the Suez Canal 

 Ms. in files of Fish. Technol. Unit, Haifa, Israel. 



^Gilat, E. 1966. The animal bottom communities in the Le- 

 vant Basin of the Mediterranean Sea. 9 p. In files of Fish. Tech 

 Unit, Haifa. [Processed.] 



'Gilat, E. 1969. The macrobenthic communities of the level 

 bottom in the Eastern Mediterranean. In Interim Report, Joint 

 Research Project "Biota of the Red Sea and the Eastern Mediter- 

 ranean," p. 82-89. The Hebrew University of Jerusalem and the 

 Smithsonian Institution, Washington, D.C. [Processed.] 



1970; Por, 1969«, 197P), suggesting that the 

 mechanism of the penetration of some species 

 through the canal and their expansion in the 

 Mediterranean is associated with environmental 

 conditions (salinity, currents, nature of substrate, 

 etc.). 



In this paper we discuss the ecology of the mi- 

 gration and expansion in the new habitat of an 

 important commercial fish. We examine its 

 dynamic coexistence with its native competitor in 

 view of the changing environmental conditions. 



The Relative Importance of Species 



It is a well-known fact that, while some of the 

 migrant species have established themselves in 

 the new environment, creating populations with a 

 significant impact on the ecosystem, other species 

 may just survive under the new and, perhaps, 

 hostile conditions. 



The relative importance of a species in terms of 

 biomass and its role and weight in the food chain is 

 often neglected when two species are listed as 

 "common" or "abundant." One of them may be an 

 important commercial fish with a biomass of an 

 order of tens of thousands of tons or more, and the 



8Por, F. D. 1969. The Canuellidae (Copepoda Harpacticoida) 

 in the waters around the Sinai Peninsula and the problem of 

 Lessepsian migration in this family. In Interim Report, Joint 

 Research Project "Biota of the Red Sea and the Eastern Mediter- 

 ranean," p. 34-40. The Hebrew University of Jerusalem and the 

 Smithsonian Institution, Washington, D.C. [Processed.] 



^Por. F. D. 1970. The nature of the Lessepsian migration 

 through the Suez Canal. Paper presented at the XXIIe Congres 

 Assemblee Pleniere de la C.I.E.S.M., Rome. 



Manuscript accepted September 1973. 

 FISHERY BULLETIN: VOL. 72. NO. 



1974. 



359 



