THORROLD: LIFE HISTORY PARAMETERS IN HERKLOTSICHTHYS CASTELNAUI 



Breakwater Marina 



Cape Cleveland 



y 



10km 



Figure 1.— Map of Australia showing position of Breakwater Marina. Townsville, where sampling 

 was conducted from July to December 1987. Hatching indicates mangrove areas. 



Otolith Preparation 



Standard length of larvae (tip of snout to hypural 

 crease or tip of notochord in preflexion larvae) was 

 measured under a stereo dissecting microscope with 

 an ocular micrometer. Measurement was made to 

 the nearest micrometer unit (0.135 mm at 10 x 

 magnification). Specimens were placed in a drop 

 of water on a microscope slide and otoliths were 

 teased out with electrolytically sharpened tung- 

 sten needles. The larva was removed from the slide, 

 and the otoliths air dried. To ensure dehydration, 

 a drop of 98% ethanol was added to the otoliths 

 and allowed to evaporate. Otoliths were then 

 mounted in immersion oil for microscopic examina- 

 tion. 



Individuals of H. castelnaui have three pairs of 

 otoliths: sagittae, asterisci, and lapUli. Sagittae were 

 the only otoliths found to be deposited during the 



first days of larval life, and subsequently only sagit- 

 tae were considered in the analysis. Growth incre- 

 ments were visible in sagittae from larvae that 

 ranged from 5 to 25 mm SL. These otoliths were 

 viewed for counting under a compound microscope 

 using polarized transmitted light. All counts were 

 made at 1000 x magnification. An Ikegami^ high 

 resolution video camera was mounted on the micro- 

 scope, which was connected in turn to a video 

 screen. Otolith increments were counted on the 

 video screen as the increased contrast made rings 

 easier to read. The system was interfaced with a 

 Commodore Amiga personal computer for measure- 

 ment of otolith radius and growth increment widths 

 (Thorrold, MS in prep.). Otolith radius was measured 

 from the center of the primordium to the outside 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



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