ANALYZING THE WIDTH OF DAILY OTOLITH INCREMENTS TO 

 AGE THE HAWAIIAN SNAPPER, PRISTIPOMOIDES FILAMENTOSUS 



Stephen Ralston 1 and Garret T. Miyamoto 2 



ABSTRACT 



Studies of otolith microstructure in Hawaiian snapper, Pristipomoid.es filamentosus, indicate that growth in- 

 crements are deposited daily in immature fish (<40 cm FL and <3 yrof age). Laboratory experiments with 

 tetracycline- injected fish and analysis of modal progression in size- frequency distributions of field-sampled 

 fish validate this conclusion. Given a 1:1 correspondence between increments and days, one can determine 

 otolith growth rate by measuring increment width. Based on the relationship between otolith growth rate and 

 otolith length, we conclude that increment deposition in mature P. filamentosus is episodic, i.e., 

 interrupted. 



Using regression analysis, a model is developed relating otolith growth rate to otolith length. It is shown that 

 integration of the regression equation provides estimates of the age of individual fish. Assumptions involved 

 in the model are discussed, and it is concluded that this method of aging adequately represents the growth of 

 P. filamentosus when time is measured on a scale of years. Age estimates derived here are entirely consistent 

 with those of related forms (Lutjanidae) reported in the literature. 



Studies of fish otoliths have now revealed that these 

 calcified structures often grow by daily accretion of 

 increments, in a manner analogous to the annual 

 rings of trees. Pannella (197 1, 1974) was the first to 

 demonstrate this, and now many other researchers 

 have substantiated and extended his findings to a 

 wide variety of temperate and tropical species in 

 both marine and freshwater environments (Brothers 

 etal. 1976; StruhsakerandUchiyamal976; Le Guen 

 1976; Ralston 1976; Timola 1977; Taubert and Co- 

 ble 1977; Barkman 1978; Brothers 1978; Methot and 

 Kramer 1979; Dunkelberger et al. 1980; Pannella 

 1980; Schmidt and Fabrizio 1980; Steffensen 1980; 

 Wild and Foreman 1980; Wilson and Larkin 1980; 

 Worthmann 1980; Brothers and McFarland 1981; 

 Mugiya et al. 1981; Uchiyama and Struhsaker 1981; 

 Tanaka et al. 1981; Ralston and Miyamoto 1981; 

 Campana and Neilson 1982; Watabe et al. 1982; 

 Radtke and Dean 1982; Radtke 3 ). Daily growth 

 structures from a wide variety of plant and animal 

 tissues were known for some time prior to Pannella' s 

 discovery (Choe 1963; Neville 1967). In fact, several 

 publications which predate his work presented 

 photographs of otoliths in which typical daily in- 

 crements are evident (Hickling 1931; Morris and Kit- 



1 Southwest Fisheries Center Honolulu Laboratory, National 

 Marine Fisheries Service, NOAA, Honolulu, HI 96812. 



department of Animal Science, University of Hawaii, Honolulu, 

 HI 96822. 



'Radtke, R. L. Scanning electron microscope observations of daily 

 increments and structure in otoliths of the adult tropical fish Pris- 

 tipomoides filamentosus. Manuscr. in prep. Pacific Gamefish Foun- 

 dation, P.O. Box 25115, Honolulu, HI 96825. 



Manuscript accepted February 1983. 

 FISHERY BULLETIN: VOL. 81, NO. 3, 1983 



tleman 1967; Degens et al. 1969), yet their temporal 

 significance was unappreciated at the time. 



We are now developing a more sophisticated un- 

 derstanding of the processes which control the in- 

 cremental growth of otoliths, with multiple factors 

 influencing accretion, including photoperiod, food, 

 and temperature (Hickling 1931; Irie 1960; Degens 

 et al. 1969; Mugiya 1974, 1977; Taubert and Coble 

 1977; Brothers 1978; Dunkelberger etal. 1980; Pan- 

 nella 1980; Mugiya et al. 1981; Tanaka et al. 1981; 

 Watabe et al. 1982; but see Campana and Neilson 

 1982). Furthermore, some studies have revealed the 

 existence of subdaily increments (Taubert and Coble 

 1977; Brothers 1978; Pannella 1980; Wilson and 

 Larkin 1980; Campana and Neilson 1982) which 

 complicates considerably the temporal interpreta- 

 tion of increment periodicities. 



A powerful application of daily increment research 

 has been the use of increment width as a measure of 

 otolith and somatic growth rate. Pannella (1974) first 

 presented this view when he stated, "Increment 

 thickness is the spatial expression of time" and 

 "... is the faithful expression of the conditions and 

 rate of growth." In substantiating this claim, 

 Struhsaker and Uchiyama (1976), Taubert and Coble 

 (1977), and Barkman (1978) showed that otolith ring 

 counts depend purely on specimen age and not 

 otolith size. Slow-growing fish had small otoliths, 

 while in comparably aged fast-growing fish the 

 otoliths were larger but contained no more in- 

 crements. Moreover, Wild and Foreman (1980) used 

 the change in otolith dimension subsequent to mark- 



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