SMITH and DAIBER: BIOLOGY OF SUMMER FLOUNDER 



1966-68. Upon removal, they were cleaned in 

 water and stored dry. Prior to examination, 

 otoliths were soaked for 30 min in a 2 c /c solution of 

 the plant enzyme, papain, according to the 

 technique of Pruter and Alverson ( 1962) for clean- 

 ing and clearing. Annuli were visible before soak- 

 ing and it is doubtful this clearing process helped. 



For examination, otoliths were placed in distil- 

 led water in the wells of a Coor's 3 black porcelain 

 spot plate. They were measured with an ocular 

 micrometer to the nearest 0. 1 mm for radial length 

 and annuli lengths with the concave surface up. 

 All otoliths were read twice, and those very 

 difficult to interpret a third time. Approximately 

 20% of the otoliths were discarded because of ir- 

 regular shape or indistinct annuli, leaving 319 

 used in the age analysis. Mean annuli lengths are 

 given in Table 1. No age-group 6 males were col- 

 lected in this study. 



There was a linear relationship between total 

 length (TL in millimeters) and otolith radial 

 length in millimeters, and this relationship was 

 best described by: 



Otolith radial length = 0.012(TL) 



Correlation coefficient = 0.998 

 Standard error of estimate = 0.336 



This equation applied to both sexes. 



Fish length at time of annulus formation or 

 back-calculated length was calculated as de- 

 scribed in Rounsefell and Everhart (1953), and 

 these lengths for males and females are given in 



3 Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



Tables 2 and 3, respectively. No correction factor 

 was used in the calculation because: 1) the line 

 best representing the total length-otolith radial 

 length relationship had a zero origin and 2) correc- 

 tion factors obtained were not reasonable because 

 they gave the fish a negative length at time of 

 otolith formation. According to Rugh (1962), who 

 used Fundulus heteroclitus as an example of a 

 typical teleost, otoliths start to form in the first 

 quarter of development. Therefore, fish length at 

 time of otolith first formation could be considered 

 negligible when compared with fish length at 1 yr. 



The observed 17 cm length at 1 yr as reported by 

 Eldridge (1962) is far above a 12 cm length we 

 back-calculated using the otolith core edge as the 

 first annulus. We assumed the first annulus was 

 located at the core edge (radial length from 1.1 to 

 1.5 mm) because typically the first well-defined 

 annulus away from the core (approximately 3.3 

 mm radial length, Table 1) was only present in 

 otoliths from fish larger than 27 cm, fish we be- 

 lieved too large to be in age-group 1 (fish 1 or 1 + yr 

 old). Supporting our belief is Eldridge's reported 

 length frequency at 1 yr and our subsequent cap- 

 ture (1973) of Delaware Bay flounder during 

 winter in the 15-20 cm size range. A few otoliths 

 we examined had faint rings at radial lengths of 

 2.0 to 2.6 mm, but we thought these represented a 

 false annulus. Probably these faint rings were 

 true first annuli and they were not observed in 

 most otoliths. 



The primary reason for the difference between 

 our back-calculated fish lengths and those given 

 by Poole ( 1961 ) and Eldridge ( 1962), Tables 2 and 

 3, is the interpretation of age at the first annulus 

 used. Examination of Poole's calculated length at 

 1 yr plus his photographs of otoliths indicated he 

 considered the first well-defined annulus as being 



TABLE 1. — Mean radial distance ± 1 standard deviation of annuli on otoliths from 

 summer flounder taken in Delaware Bay during 1966-68. (No suitable first annulus was 

 found.) 



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