FISHERY BULLETIN: VOL. 80, NO. 2 



Table 3.— Otoliths are from Fundulus heteroclitus 

 larvae. Embryos were incubated on a L12:D12 cycle 

 and the larvae transferred to constant darkness at 

 24 °C immediately after hatching. 



Age 







6 



9 



16 



in EL12:D12 (Table 1), sagitta of LaD24 had re- 

 duced increment numbers after day 6 and sagitta 

 diameters in experimental fish were smaller 

 than those found in the control (LaL12:D12). 



Some groups that had increment formation 

 (LaD24 and LaL6:D6) during the first 6 d had in- 

 crements formed after day 6 that were unclear 

 and it was difficult to differentiate the D and I in 

 the outer areas. However, the LaL12:D12 group 

 showed distinct increments beyond day 6. 



The ED24 group larvae were sluggish upon 

 hatching as were the ED24+L group. The larvae 

 appeared to be normal in every other fashion 

 except that the yolk sacs were notably smaller 

 than the 12L:12D group. 



Effect of Temperature and 



Body Growth on Otolith 



Formation in Larvae 



An increase in temperature caused an increase 

 in the growth rate in the larvae (Fig. 6a). The 

 30°C group grew significantly faster than the 

 24°C group (P<0.05). 



The 30°C larvae, also formed otoliths (Fig. 6b) 

 which were significantly larger (P<0.05) in di- 

 ameters than those in fish held at24°C. However, 

 the difference in growth rates had no effect on 

 the increment counts from either group (Fig. 6c). 

 Both showed daily increment formation in their 

 otoliths but the faster growing otoliths had wider 

 daily increments, which accounted for the in- 

 creased diameter measurements. When the oto- 

 lith diameter data were pooled and compared 

 with length data, the relationship was highly 

 correlated (r = 0.95; Fig. 7). 



Estimation of Age of 

 Wild Fish 



It is difficult to gain any insight into the age 

 structure of the wild population from the length- 

 frequency histograms, e.g., larvae collected 9 

 June 1977 had a standard length-frequency 



x 

 t- 

 o 



-z. 



UJ 



35r 

 30 



25 



20 



15 



10 



5 



30°C Y=6.I7 + .83X '' 

 r=.99 



,'/ 24°C Y = 6.26 +.66X 

 r=.99 



J L 



J I 



0.7- 







35 

 30 



w 25 



i- 



lu 20 



UJ IK 



en 15 

 o 



^ 10 

 5 

 0. 



B 



30°C Y = .I25 +.0I9X ,' 

 r=.98 



/ 



24°C Y = .131 + .0I5X 

 r = .98 



J i 



30 U C Y=2.82 + IX 

 hr = .99 



24°C Y=2.58 +IX 

 r=.99 



-L 



-L 



J 



10 15 20 25 30 

 AGE (DAYS) 



Figure 6.— A regression plot of A) standard length (SL), B)the 

 diameter of the sagitta, and C) the numbers of increments of 

 the sagitta of Fundvlus heteroclitus reared at 24°C and 30°C 

 plotted against age of the fish. 



210 



