BEN-YAMI and GLASER: INVASION OF SAURIDA UNDOSQUAMIS 



the other is the Indo-Pacific species greater 

 lizardfish, Saurida tumbil (Bloch). The first is a 

 quantitatively insignificant and hence noncom- 

 mercial demersal predator in the Levant Basin. 

 Although a natural competitor to the latter, the 

 native S. saurus was superseded by the invader, 

 being now as rare as ever. 



Saurida tumbil is one of the main commercial 

 fishes and dominates in the south Red Sea trawl 

 fishery. Another species, S. undosquamis , is the 

 "underdog" there, though not as rare as Synodus 

 saurus is in the Levant Basin. Saurida undo- 

 squamis holds ground only in deeper and, evi- 

 dently, cooler waters, while S. tumbil dominates 

 over most of the trawling grounds (Ben-Tuvia, 

 1966). On the other hand, it is S. undosquamis, 

 probably the euryecous of the two, which spread 

 into the northern Red Sea, becoming the only sig- 

 nificant lizardfish in the Gulf of Suez and the Le- 

 vant Basin. 



Feeding in Israel Waters 



Shmida (1964)^2 investigated 76 stomachs of 

 which 49 contained food. The fish were from 

 catches taken in summer and spring. While the 

 bulk of the food taken in spring consisted of crus- 

 taceans (mostly Decapoda, Macrura), the food of 

 hake caught in summer was mostly fish. Shmida 

 concludes that, in general, the food in terms of 

 weight was half crustaceans and half fish. All 

 identifiable fish were anchovy. Unfortunately, 

 Shmida had at his disposal only small individuals, 

 less than 27 cm long. Larger, faster, and stronger 

 hake may have a different diet in which the pro- 

 portion offish may be higher. This was indicated 

 by a slight trend of more fish in the stomachs of the 

 larger hake, even within the narrow length range 

 investigated (Shmida, 1964). 



Habitat 



HAKE 



Another important commercial fish whose 

 habitat and food in the Levant Basin indicate that 

 it is the main competitor of the lizardfish is the 

 hake, Merluccius merluccius. This is an eastern 

 Atlantic species which is also native to these wa- 

 ters (Ben-Tuvia, 1953), and whose biology and 

 habits in the Levant Basin still remain to be 

 studied. 



In the Atlantic Ocean the hake is known as a 

 voracious predator, feeding during the day at the 

 bottom and rising at night into higher water 

 layers. It is known as a deepwater species caught 

 at depths down to 400 fm. Off the British Isles, it 

 seems to prefer water temperatures of around 

 lOT. 



Spawning and Growth 



Near the British Isles, the hake spawns mostly 

 at or near areas over the 100-fm isobath. Females 

 spawn up to a million eggs each. The eggs are 

 pelagic, floating on the sea surface. Before hatch- 

 ing, which occurs within a fortnight, the eggs de- 

 scend to midwater, where the larvae hatch and 

 develop. The yolk is absorbed within 3 to 4 wk 

 after which the postlarvae feed on zooplankton. 

 The fry descend to the bottom, where hake 3 to 4 

 cm long were taken. They reach 10 cm at the year's 

 end and become mature at 20 cm (Marshall, 1965; 

 Travis Jenkins, 1954). 



The hake prefers cool water. This is evident 

 from its occurring over the shallow trawling 

 grounds only during the cooler season of the year. 

 Its proportion in trawl catches can be consider- 

 able, even at depths less than 20 fm, if the water is 

 cold enough. With the approach of the warm sea- 

 son, the hake retreats to the deepwater regions 

 where it remains available to trawls at depths 

 over 100 fm throughout the season (Ben-Yami, 

 1971). Figure 6 illustrates the relative distribu- 

 tion of the lizardfish and the hake over the Israeli 

 continental shelf and their overlapping habitats. 



RED SEA MIGRANTS AS PREY 



OF THE HAKE 



AND THE LIZARDFISH 



As mentioned above, both our predators feed 

 extensively on anchovy. It seems, nevertheless, 

 that the hake competes with the lizardfish also for 

 other fish, some of them Red Sea migrants. Ben- 

 Tuvia (1966) reports that two of them, Leio- 

 gnathus klunzingeri and a Red Sea goatfish, Upe- 

 neus asymmetricus Lachner (reported previously 

 as U. tragula Richardson), are components of the 

 food of both the lizardfish and the hake. Leio- 

 gnathus, a trash fish in trawl catches, has been, 

 undoubtedly, of major importance in the food 



i^Shmida, A. 1964. T'zunat dagim b'Yam Tikohn uv'Yam 

 Suf (Food of fishes in the Mediterranean and the Red Sea). [In 

 Hebrew.] Unpubl. manuscr. In files of the Isr. Sea Fish. Res. 

 Stn., Haifa. 



367 



