Abstract. - Growth of the deep 

 slope snapper Etelis earbunculus 

 was evaluated from the density of 

 daily increments in sagittal otoliths 

 collected from Hawaii, the Common- 

 wealth of the Northern Marianas 

 Islands (NMI), French Polynesia, 

 and Vanuatu. The rate of otolith 

 growth (><m/day) as a function of oto- 

 lith radius was fit by regression to 

 a modified Gompertz rate curve and 

 the age of fish estimated by integrat- 

 ing the equation. There were slight 

 regional differences between the es- 

 timated values of each of the three 

 otolith growth rate parameters, 

 which may be attributable in part to 

 random sampling differences. How- 

 ever, integrated estimates of fish age 

 versus otolith radius varied little be- 

 tween sites because of the compen- 

 satory relationship between two of 

 the three estimated parameters 

 which together determine the rate of 

 dampening of the otolith growth 

 function. There were significant re- 

 gional differences in average otolith 

 radius, and thus in estimated age, as 

 a function of fish length. Fish from 

 Vanuatu and NMI were younger at 

 a given length than those from the 

 other two regions. However, fish as 

 large as those at Vanuatu are not 

 found at NMI, suggesting there may 

 be regional differences in mortality. 

 Regional age-at-length data were fit 

 to a von Bertalanffy growth curve, 

 both unconstrained and held to a 

 value of asymptotic length (L^) ob- 

 tained from the literature. Estimates 

 of natural mortality for each region 

 are discussed, based on the regional 

 values obtained for the von Berta- 

 lanffy growth constant (K). These 

 results should be confirmed using 

 data obtained from a wider range of 

 fish sizes. 



Estimates of Age and Growth 

 of Ehu Etelis earbunculus in Four 

 Regions of the Pacific from Density 

 of Daily Increments in Otoliths 



M. Kimberly Smith 



Honolulu Laboratory, Southwest Fisheries Science Center 

 National Marine Fisheries Service. NOAA 

 2570 Dole Street, Honolulu, Hawaii 96822-2396 



Present address: State of Hawaii, Department of Land & Natural Resources 

 Division of Aquatic Resources, 1151 Punchbowl St., Rm. 330, Honolulu, Hawaii 968 1 3 



Eric Kostlan 



Department of Mathematics. University of Hawaii 

 Manoa Campus. Honolulu, Hawaii 96822 



Manuscript accepted 11 February 1991. 

 Fishery Bulletin, U.S. 89:461-472 (1991). 



The observation of microscopic mark- 

 ings in thin sections of the otoliths of 

 fishes, with evidence that these marks 

 present a record of daily growth 

 (Panella 1971, 1974), provided an 

 alternative means of ageing tropical 

 species for which seasonal and annual 

 growth rings are often hard to inter- 

 pret. These marks are produced in 

 many fishes (Brothers et al. 1976, 

 Struhsaker and Uchiyama 1976, Wild 

 and Foreman 1980, Neilson et al. 

 1985, Jones and Brothers 1987, and 

 others). Counting otolith microincre- 

 ments has proved useful in estimat- 

 ing the growth of juvenile and larval 

 fishes (Barkman 1978, Methot 1981, 

 McGurk 1984, Jones 1986, Geffen 

 1986), because they have small and 

 transparent otoliths with readily in- 

 terpretable microincrements. While 

 offering the opportunity to detect 

 growth on a more sensitive scale, the 

 laborious process of enumerating all 

 the daily increments in the otoliths of 

 older organisms has limited the wide- 

 spread use of this technique (Ralston 

 and Williams 1988a). 



From the late 1970s through the 

 mid- and late 1980s, Ralston and col- 

 leagues (Ralston 1976, 1981, 1985; 

 Ralston and Miyamoto 1981, 1983; 

 Ralston and Williams 1988a) devel- 

 oped a labor-efficient method of esti- 



mating the age and growth rate of 

 fishes using microincrement data 

 from otoliths. This method, based 

 on numerical integration of otolith 

 growth rates from the density of 

 presumptive daily increments, was 

 applied by S. Ralston and H.A. Wil- 

 liams (Honolulu Lab., NMFS South- 

 west Fish. Sci. Cent., Honolulu, HI, 

 unpubl. data) to a number of Pacific 

 Ocean commercial species. It pro- 

 vided an estimate of the von Berta- 

 lanffy (1957) growth curve for which 

 the asymptotic length (L^), growth 

 constant (K), and age at zero length 

 (t ) were within the range of previ- 

 ous regional estimates for many of 

 the 24 species for which the method 

 was tested. 



However, three out of four growth 

 curves estimated by this method for 

 the deep slope "red" snapper Etelis 

 earbunculus Otnown as ehu in Hawaii), 

 did not reach an asymptotic length, 

 instead having the form of a straight 

 line with positive slope. These results 

 were considered to be anomalous, 

 since collections included fish at or 

 near the regionally estimated values 

 of asymptotic length (although the 

 sample size for some regions was 

 very small). Otolith collections for 

 this species came from Hawaii, Va- 

 nuatu, French Polynesia, and the 



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