AGE AND GROWTH OF THE NEHU, STOLEPHORUS PURPUREUS 

 (PISCES: ENGRAULIDAE), FROM THE HAWAIIAN ISLANDS AS 

 INDICATED BY DAILY GROWTH INCREMENTS OF SAGITTAE 



Paul Struhsaker and James H. Uchiyamai 



ABSTRACT 



Direct evidence is presented that the sagittae of nehu, Stolephorus purpureas, grow by discernible 

 daily increments. Aging by daily growth increments provides the means to establish a general growth 

 curve for the first 6 mo of life for this species. Adult nehu exhibit nearly linear growth between 30 and 

 60 mm standard length. Preliminary evidence is presented that the nehu population of Pearl Harbor 

 may grow more rapidly than that of Kaneohe Bay. 



Attempts to age tropical fishes by conventional 

 methods have generally been thwarted by the 

 absence of well-defined annuli in calcarious 

 structures and protracted spawning periods 

 which make length-frequency mode progression 

 analyses difficult. Recognizing that exceptions 

 to the above statement exist, Pannella's work 

 (1971) providing indirect evidence of the pres- 

 ence of daily growth layers and periodical 

 deposition patterns in the sagittae (otoliths) of 

 three species of boreal fishes from the western 

 North Atlantic suggested a means for conducting 

 age and growth studies of tropical species. He 

 concluded in that report: "Preliminary observa- 

 tion of growth patterns in sagittae of other 

 species, living at various depths and different 

 climates, appears to support the idea that daily 

 growth may be a universal feature of fish oto- 

 liths." Pannella's (1974) later work in Puerto Rico 

 provided circumstantial evidence of daily growth 

 layers in sagittae of several species of tropical 

 fishes. 



To gain direct evidence that daily growth incre- 

 ments exist in tropical fishes we studied the nehu, 

 Stolephorus purpureas Fowler, a small engraulid 

 endemic to the Hawaiian Islands. The nehu is the 

 basis of a live-bait fishery producing about 4,000 

 metric tons annually of skipjack tuna, Katsu- 

 wonus pelamis (Linnaeus), from the vicinity of the 

 Hawaiian Islands. Stolephorus purpureus is a 

 short-lived species (less than 1 yr) and has been 

 the subject of relatively numerous studies: Naka- 

 mura (1970) has summarized the biological 



'Southwest Fisheries Center, Honolulu Laboratory, National 

 Marine Fisheries Service, NOAA, Honolulu, HI 96812. 



knowledge of this species available through 1965. 

 Our work provides evidence of the presence of 

 daily growth increments in the sagittae of nehu 

 and permits the assembly of a growth curve for the 

 first 6 mo of life for this species. 



Brothers et al. (1976) have recently demon- 

 strated the presence of daily growth increments in 

 larval Engraulis mordax Girard and Leuresthes 

 tenuis (Ayres) and presented evidence that the 

 phenomenon occurs in several other species of 

 California fishes. 



METHODS AND MATERIALS 



The nehu samples were taken with three types 

 of gear in Pearl Harbor and the southeastern end 

 of Kaneohe Bay, Oahu, Hawaiian Islands. Adults 

 and juveniles (> about 30 mm standard length 

 (SL) ) were sampled with commercial bait seines 

 (square mesh measuring 3.2 mm to a bar) in Pearl 

 Harbor. Postlarvae (about ^ 20 mm SL), juveniles, 

 and adults were obtained in Kaneohe Bay by a 

 similar seine having a bar mesh measurement of 

 1.6 mm. Larvae (< 20 mm SL) were obtained near 

 Coconut Island by personnel of the Hawaii Insti- 

 tute of Marine Biology with 0.5-m ring nets with 

 mesh sizes of 550 /um. 



Three separate holding experiments were con- 

 ducted to test the hypothesis that the sagittae of 

 nehu grow by discernible daily increments. All 

 animals for these experiments were collected in 

 Pearl Harbor and held in tanks of 38-kl capacity 

 at the National Marine Fisheries Service (NMFS) 

 Kewalo Basin Facility. The tanks were supplied 

 with well sea water of 23°-24°C and 33-35%o salin- 

 ity at a rate of about 300 liters/min. The nehu 



Manuscript accepted August 1975. 

 FISHERY BULLETIN: VOL. 74, NO. 1, 1976. 



