MAJOR ASPECTS OF ECOLOGY OF STRIPED MULLET 



higher but more uniform salinities and lower but 

 more uniform temperatures than areas in which 

 fish <50 mm SL were generally found. 



At high tide, water temperature and salinity 

 values were nearly uniform throughout a given 

 location. Mullet <50 mm SL were concentrated 

 along the tide line on the beach or along the sides 

 of rivers in the shallowest water available. Schools 

 were dense and often composed of more individu- 

 als than found in schools at low tide in the same 

 area. Little feeding occurred; evasion of predators 

 was seen more commonly. At high tide, schools of 

 mullet with individuals >50 mm SL moved into 

 the former tide line and tide pool areas, and were 

 observed feeding in the areas from which the 

 smaller mullet retreated. 



The results of the experiments and field obser- 

 vations demonstrate that dynamic differences 

 occur in the behavior and distribution of schools of 

 mullet composed of individuals generally <50 mm 

 SL as compared with schools with juveniles of 

 greater length. In the field young mullet <50 mm 

 SL prefer and select areas characterized by mini- 

 mal water depth, tide pool formation, relatively 

 high fluctuating temperatures, and relatively low 

 fluctuating salinities. Juveniles &50 mm SL, on 

 the other hand, seek somewhat deeper water and 

 tide pools with lower more uniform temperatures 

 and higher more uniform salinities. 



Experimentally, a wide range of temperature 

 values ( 13°-40.8°C) was available to the fish. How- 

 ever, mullet <50 mm SL tended to concentrate in 

 water of higher temperature near the surface of 

 the tank and fish >50 mm SL tended to occur 

 deeper in the tank at lower temperatures for each 

 test salinity. Although the experimental tank al- 



lowed fish a means of behaviorally escaping lethal 

 or near lethal conditions (as presumably did 

 deeper tide pools for mullet >50 mm SL in the 

 field), entrapment in shallow intertidal tide pools 

 in the field did not. Fish <50 mm SL appeared to 

 actively seek such near lethal conditions in the 

 field (and experimentally), and as observed in a 

 Kuapa Pond stream culvert, occasionally perished 

 as a result. 



Predators 



Most predators observed interacting with mul- 

 let during this study were solitary stalking or 

 stationary "sit-and-wait" species (Table 3). At- 

 tacks by predators upon schools of mullet with 

 individuals <50 mm SL were almost nonexistant 

 at low tide. 



Where deeper water was immediately contigu- 

 ous with a shallow water shelf (e.g., along Kahana 

 River), predators (e.g., barracuda) in the deeper 

 water were observed orienting towards and paral- 

 leling the movements of schools of the small mul- 

 let feeding in the shallower water. When mullet 

 strayed off the shelf into deeper water, they were 

 attacked. Predation upon mullet &50 mm SL dur- 

 ing low tide was occasionally observed as schools 

 moved and fed in the deeper intertidal region. 



At high tide, schools of these larger mullet con- 

 tinued to be attacked by predators, as they were at 

 low tide. Similarly, during high tides and ebb and 

 flood periods, predators attacked mullet schools 

 with individuals <50 mm SL. 



At night, along Wailupe Beach and the Kahana 

 River (Table 2), mullet schools broke up and indi- 

 viduals spread out and remained relatively mo- 

 tionless near the bottom. The fish slowly moved 



Table 3. — Predatory fish observed interacting with schools of mullet. 



Location 



Species 



Standard 

 length 

 (mm) 



Water 

 depth 

 (cm) 



Tide 



Remarks 



Eleotris sandwichensis 



78 



7 5-30 



Low 



In tide pools with open connections and channels to deeper 



water Attacked and chased juveniles of all sizes. 

 A possible predator, moved in with flood tide Observed 



following schools of mullet near surface. 

 Moved inshore with flood tide; attacked and chased individuals of 



all sizes in schools Followed feeding individuals in 



schools. Swam slowly along the shoreline at high tide 

 tvlullet <50 mm SL usually in shallowest water 1.8-75 cm deep. 



Barracuda in deeper water followed or paralleled movements 



of mullet in shallow water and attacked when the mullet 



strayed into deeper water 

 Moved in with flood tide Water turbid: caught in seines with 



juvenile mullet No mullet found in stomach 



contents 

 At low tide mullet • 50 mm SL in shallowest water 15 cm 



deep, barracuda followed (paralleled) schools cf mullet 



In shallower water (see above). 

 Single unsuccessful attack on school of mullet of 



individuals about 40 mm SL. Caught after attack. 



307 



