FISHERY BULLETIN: VOL. 72, NO. 2 



Other new records for the Gulf of Elat are 

 Diphyes dispar, L. subtilis, L. subtiloides, S. chuni, 

 S. quadrivalvis, A. eschscholtzi , A. tetragona, E. 

 hyalinum, C. cordiformis, A. rosacea, A. elegans, 

 and A. okeni. These species, except CA. contorta, 

 were only previously observed in either the 

 central and the southern Red Sea or both (Figures 

 1, 2, 4-8). Ch. contorta was previously observed in 

 the Gulf of Elat (Furnestin, 1958). 



The depth of the sill at Bab el Mandeb does not 

 exceed 100 m (Halim, 1969) and consequently 

 meso and bathypelagic species are extensively 

 excluded from the Red Sea. Halim considered 

 the scarcity of species in the Red Sea as due 

 to the "excluding action of the deep outflow over 

 the sill at the southern entrance of the Red Sea 

 on the deep water species; and . . . the effect 

 of the high (21.5°-22°C) minimum tempera- 

 ture of the Red Sea deep water in inhibiting 

 many species. . . ." He also considers excluding 

 features the "high salinity (40.5-41.0''/oo) and the 

 very low oxygen content (below 1 ml/1 in summer 

 and 2 ml/1 at the end of the winter) below 

 sill depth." 



Similar interpretation could be applied for the 

 paucity of the Mediterranean siphonophores as 

 compared with the Atlantic, because of the sill at 

 Gibraltar. 



Thorson (1971) stated that "the physical- 

 chemical conditions for the animals to pass the 

 Canal have improved enormously although 

 there are still obstacles for the migration of many 

 species." 



Seasonal variations in occurrence, abundance 

 and in the distributional pattern presented by the 

 species of siphonophores in both the Levant 

 Mediterranean basin and the Gulf of Elat are to 

 be expected. The various populations may show 

 changes in both location and time of year. These 

 changes may be due to the characteristics of the 

 flow through the Strait of Gibraltar, and Bab el 

 Mandeb respectively, and the characteristics of 

 the circulation in the Mediterranean and the 

 Arabian Sea, as well as the aspects of the vertical 

 migration (Halim, 1969), and the ontogeny of the 

 population. 



Most of the siphonophores, except for a few 

 species as explained above, present a wide 

 almost cosmopolitan distribution (Alvariho, 

 1971). However, species abundant in the western 

 Mediterranean and the Atlantic reaching the 

 easternmost Mediterranean region could be con- 



sidered "indicators" or tracers of the Atlantic 

 waters. This could be similarly applied to some 

 Indo-Pacific or Indian Ocean species reaching 

 the Red Sea. 



SIPHONOPHORES OF 



THE WESTERN CARIBBEAN AND 



THE CENTRAL AMERICAN PACIFIC 



The pairs of closely related species allopatric in 

 distribution, Ch. appendiculata-Ch. contorta, 

 M. atlantica-M. kochi, and L. challengeri- 

 L. fowleri deserve special attention. 



Chelophyes appendiculata inhabits the 

 temperate oceanic regions, and appears scattered 

 along the tropico-equatorial realm, while Ch. 

 contorta presents a distribution restricted to 

 the tropico-equatorial regions (Alvariho, 1971). 



Muggiaea atlantica inhabits the neritic tem- 

 perate eastern Pacific, Transition region (band 

 between the Subarctic and Central Pacific), 

 the Japanese neritic waters and the neritic 

 regions of the temperate Atlantic. Muggiaea 

 kochi occupies the neritic tropico-equatorial 

 Atlantic and the eastern equatorial Pacific (Al- 

 variho, 1971). 



Lensia challengeri is an Indo-Pacific species, 

 and L. fowleri is most probably restricted to the 

 Atlantic waters (Alvariho, 1971). 



However, Ch. appendiculata, M. kochi, and 

 L. fowleri appear widely distributed in the Carib- 

 bean region annex to the Panama Canal and in 

 adjacent regions of the Caribbean, Gulf of Mexico, 

 and western tropical Atlantic. Ch. contorta, 

 M. atlantica, and L. challengeri appear in the 

 Central American Pacific region. Few specimens 

 of Ch. appendiculata and M. kochi were 

 observed at locations near the opening of the 

 Panama Canal in the Pacific, and few specimens 

 of Ch. contorta, M. atlantica, and L. chal- 

 lengeri occurred at locations near the opening 

 of the Panama Canal in the Caribbean. These 

 observations suggest the Caribbean and the 

 Pacific populations may be able to migrate or 

 survive artificial transport via the Panama Canal 

 (Figures 9-11, Table 2). 



The species of siphonophores appearing abun- 

 dantly distributed in the surveyed region in both 

 the Caribbean and the Central American Pacific 

 are Diphyes bojani, D. dispar, Diphyopsis mitra, 

 and A. eschscholtzi. Diphyes bojani occurred at 

 all Caribbean stations, except for the close to 



534 



