544 



Effect of type of otolith and preparation technique 

 on age estimation of larval and juvenile spot 

 (Leiostomus xanthurus) 



Dariusz P. Fey 



Sea Fisheries Institute 



Dept. of Fisheries Oceanography and Marine Ecology 



ul Kollataja 1 



81-332 Gdynia, Poland 



E-mail address dfeyig mirgdynia pi 



Gretchen E. Bath Martin 



James A. Morris 



Jonathan A. Hare 



NOAA National Ocean Service 



Center for Coastal Fisheries and Habitat Research 



101 Pivers Island Road 



Beaufort, North Carolina 28516-9722 



Otoliths of larval and juvenile fish 

 provide a record of age, size, growth, 

 and development (Campana and Neil- 

 son, 1985; Thorrold and Hare, 2002). 

 However, determining the time of 

 first increment formation in otoliths 

 (Campana, 2001) and assessing the 

 accuracy (deviation from real age) 

 and precision (repeatability of incre- 

 ment counts from the same otolith) 

 of increment counts are prerequisites 

 for using otoliths to study the life his- 

 tory offish (Campana and Moksness, 

 1991). For most fish species, first 

 increment deposition occurs either 

 at hatching, a day after hatching, or 

 after first feeding and yolksac absorp- 

 tion (Jones, 1986; Thorrold and Hare, 

 2002). Increment deposition before 

 hatching also occurs (Barkmann 

 and Beck, 1976; Radtke and Dean, 

 1982). If first increment deposition 

 does not occur at hatching, the stan- 

 dard procedure is to add a predeter- 

 mined number to increment counts 

 to estimate fish age (Campana and 

 Neilson, 1985). 



Accuracy and precision of incre- 

 ment counts is in part determined 

 by the increment formation rate, 

 which has been reviewed elsewhere 

 (Campana and Neilson, 1985; Jones, 

 1986; Geffen, 1987), and by the type 

 of otolith (asteriscus, sagitta, or la- 

 pillus) and the preparation tech- 



nique used for aging. In most age 

 and growth studies of larval and 

 juvenile fish, the sagitta, the larg- 

 est of the three otoliths, has been 

 used (Campana and Neilson, 1985), 

 but there are many examples of fish 

 species that can be aged accurately 

 by using the lapillus (e.g., Hoff et 

 al., 1997; Bestgen and Bundy, 1998; 

 Escot and Granado-Lorencio, 1998; 

 Morioka and Machinandiarena, 

 2001). Although infrequently used, 

 the asteriscus has provided age in- 

 formation with similar or even bet- 

 ter precision and accuracy than the 

 sagitta and lapillus (David et al., 

 1994). However, the microstructure 

 of asterisci is usually not as clear 

 as that of sagittae or lapilli, and the 

 extraction of asterisci is relatively 

 time consuming and laborious (Cam- 

 pana and Neilson. 1985; Neilson and 

 Geen, 1985). As for otolith prepa- 

 ration, two general techniques are 

 common: 1) polishing of one or both 

 sides of a sectioned otolith in trans- 

 verse view, and 2) polishing of one 

 side of the whole sagitta (Secor et 

 al., 1992). Sagittae and lapilli pro- 

 vide the same accuracy and preci- 

 sion for age estimation; however, la- 

 pilli may be easier to process for age 

 determination and may not require 

 processing at all (e.g., Ichimaru and 

 Katsunori, 1995). 



Spot (Leiostomus xanthurus) is an 

 important fishery species along the 

 southeast coast of the United States 

 (Mercer, 1987) and is a dominant 

 species in coastal ecosystems owing 

 to its abundance (Walter and Aus- 

 tin, 2003). Studies of spot have il- 

 luminated processes that affect the 

 abundance of estuarine-dependent 

 species ( Warlen and Chester, 1985; 

 Flores-Coto and Warlen, 1993; Ross. 

 2003). Further, spot has been used 

 as an experimental organism for ex- 

 amining larval ecology (Govoni et al., 

 1985; Govoni and Hoss, 2001) and 

 otolith chemistry (Bath Martin et al., 

 2000, 2004; Bath-Martin and Thor- 

 rold, 2005). Although spot has been 

 widely studied and is an important 

 ecological and fishery species, basic 

 information necessary for otolith 

 analyses is not available. 



Our goal was to provide a founda- 

 tion for the use of otolith increment 

 counts in examining the ecology of 

 larval and juvenile spot. Our specific 

 objectives were 1) to determine the 

 timing of first-increment formation of 

 spot (Leiostomus xanthurus) and 2) to 

 assess the accuracy and precision of 

 age estimates from increment counts 

 made with different combinations 

 otoliths and preparation techniques. 

 Specifically, four combinations of oto- 

 liths (sagittae and lapilli) and prepa- 

 ration techniques were compared: 1) 

 a transverse section of the sagitta 

 (polished on one side TSS-1); 2) a 

 transverse section of the sagitta (pol- 

 ished on two sides TSS-2); 3) a whole 

 sagitta (polished on one side WS-1); 

 and 4) a whole lapillus (polished on 

 one side WL-1). 



Materials and methods 



First increment formation 



Six male and six female spot were 

 induced to spawn by injection of 

 human chorionic gonadotropin (HCG) 

 hormone at the NOAA Beaufort Labo- 

 ratory. Eggs were incubated in a 100-L 



Manuscript submitted 14 May 2004 to the 

 Scientific Editors Office. 



Manuscript approved for publication 

 29 March 2005 by the Scientific Editor. 



Fish. Bull. 103:544-552 (2005). 



