FISHERY BULLETIN: VOL. 87, NO. 1 



growth increments, specifically with stock-assess- 

 ment applications in mind. In this regard, the von 

 Bertalanffy growth equation (Ricker 1979) is of fun- 

 damental importance. Due to its widespread use in 

 assessment models (e.g., the Beverton and Holt 

 [1957] yield formulation), parameter estimates for 

 this equation provide an ideal complement to many 

 of the length-based methods that are currently in 

 use (e.g., Morgan 1987). The ultimate goal of this 

 study was, therefore, to develop a methodology to 

 estimate the von Bertalanffy growth parameters K 

 and L„ from the study of daily increments. Ideal- 

 ly, the approach developed should be general in its 

 application, easy to implement, simple in its tech- 

 nical requirements, and cost effective. Were such 

 a uniform framework to the study of age and growth 

 of exploited tropical species developed, it would 

 assist routine assessment work greatly. 



MATERIALS AND METHODS 



As part of a larger program to assess stocks of 

 deep slope fishes in the Mariana Archipelago (Polo- 

 vina 1985; Polovina and Ralston 1986; Ralston in 

 press b), a study of the age and growth of gindai, 

 Pristipomoides zotmtus, was initiated. This commer- 

 cially important eteline snapper (Lutjanidae) is wide- 

 ly distributed in the Indo-Pacific region (Allen 1985) 

 and is the most commonly caught species in Guam's 

 deepwater hook-and-line fishery (Polovina 1986). 



Field sampling for gindai specimens was con- 

 ducted from the NOAA ship Townsend Cromwell 

 during the 2 yr period spanning April 1982 to May 

 1984. During this time, six 40 d cruises were com- 

 pleted, such that samples of gindai were obtained 

 during all months of the year except March, Sep- 

 tember, and October. 



All gindai were caught during daylight hours by 

 using hydraulic fishing reels equipped with circle fish 

 hooks. When landed, fish were measured to the 

 nearest millimeter fork length (FL) with a measur- 

 ing board and weighed to the nearest 0.01 kg on a 

 beam balance. 



Specimens were sexed at the time of capture by 

 gross examination of the gonads. In addition, a rep- 

 resentative selection of the gonads was frozen for 

 more detailed examination in the laboratory. There, 

 they were preserved in a solution of 10% buffered 

 formalin and weighed to the nearest 0.1 mg. Ova- 

 ries were staged with the classification of Everson 

 (1984), developed for Etelis carbunculus. a related 

 deepwater eteline lutjanid. His classification recog- 

 nizes seven stages based on egg size, shape, and yolk 

 content, i.e., (I) primordial, (II) early developing, (III) 



developing, (IV) advanced developing, (V) early ripe, 

 (VI) ripe, and (VII) residual. Gonadosomatic indexes 

 (gonad weight expressed as a percentage of body 

 weight) also were calculated where possible. 



Otoliths 



At the time of capture, sagittal otoliths were col- 

 lected, by frontal section through the cranium, from 

 certain individuals sampled uniformly from the full 

 size range of gindai captured. The otoliths were 

 rinsed in fresh water to remove adhering mem- 

 branes and endolymph and were stored dry in glass 

 vials. Later in the laboratory, they were examined 

 with a dissecting microscope for the presence of 

 hyaline (i.e., translucent) and opaque markings while 

 illuminated with reflected light against a dark back- 

 ground. When markings were present, the distance 

 from the focus to the beginning of each opaque zone 

 was measured along the postrostral growth axis by 

 using a calibrated ocular micrometer. Total otolith 

 length (focus to postrostrum) also was recorded. 



A random subsample of gindai otoliths was taken, 

 and their microstructure examined for the presence 

 of daily increments (Campana and Neilson 1985). To 

 prepare the otoliths, they were first embedded in 

 casting resin, which was allowed to harden com- 

 pletely. Cast otoliths were sectioned on a Buehler^ 

 ISOMET low speed jewelry saw. Thin (0.70 mm) sec- 

 tions were made through the focus along a frontal 

 plane to the most distal portion of the postrostrum. 

 Sections were polished sequentially on a Buehler 

 ECOMET polisher/grinder with 180 and 600 grit 

 abrasive disks. Samples were then briefly etched for 

 5-30 seconds in a dilute solution of 1% HCl, washed 

 in water, and dried. Prepared sections were 

 mounted on glass slides with Euparol or Flotexx and 

 cover slips and allowed to clear and harden com- 

 pletely prior to viewing (approximately 2 weeks). 



Mounted otolith sections were examined with a 

 compound binocular microscope by using trans- 

 mitted light at a magnification of 200 or 400 x . Total 

 lengths of the otoliths (i.e., the distance in micro- 

 meters between the focus and the postrostral 

 margin) were measured (N = 94) and individual 

 readings were made at selected points along the 

 postrostral growth axis, v/herever it was possible 

 to distinguish the characteristic bipartite structure 

 of daily increments. At each site sampled the aver- 

 age width of presumptive daily growth increments 

 was determined by counting a small number (me- 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service. NOAA. 



