Faiince et a\ Age, growth, and mortality of Cich/nsomn iimphthalrmis 



47 



visible on the otoliths. The annulus corresponding to the 

 first year's growth was not consistently clear to the read- 

 ers, which has been observed in thin-sectioned otoliths of 

 other fish species in Florida. Murphy and Taylor (1994) 

 found that the first annulus was visible only in certain 

 individuals of spotted seatrout, Cynoscion nebulosus. Sim- 

 ilarly, Murphy and Taylor (1990) found that the annulus 

 corresponding to the first winter or spring was absent in 

 red drum, Sciaenops ocellatiis. Direct validation of marked 

 otoliths is needed to confirm the presence and location of 

 the first annulus on the otolith of Mayan cichlids. 



We obsen'ed differences in the growth patterns of males 

 and females that are likely linked to reproduction. Males 

 were larger than females and did not appreciably slow 

 their growth with age. The nearly linear growth of males 

 resulted in a theoretical maximum size (L. i of 263.6 mm, 

 well above the -200 mm commonly observed for this spe- 

 cies (Loftus, 1987; Martinez-Palacios and Ross, 1992; pres- 

 ent study). Larger males are common in riverine and la- 

 goonal populations of tilapias (Cichlidae) and may have a 

 selective advantage during the reproductive season if they 

 can defend a spawning pit or brood against potential pred- 

 ators (Lowe-McConnell, 1982). Because sperm production 

 requires less energy than egg production ( Jalabort and Zo- 

 har, 1982), the slowed growth observed in females com- 

 pared with that for males is likely due to differences in 

 energy budgets during the reproductive season. 



No significant differences were found by ANCOVA in 

 the slopes of sex-specific length-weight relationships, but 

 there were significant differences in the intercepts of those 

 lines. Because the actual difference between the y-in- 

 tercepts (weight) of each length-weight relationship was 

 <0.001g, we attribute no biological meaning to the statis- 



tical difference and consider the length-weight relation- 

 ships for both sexes to be equal. 



Mayan cichlids in Florida were much smaller at a given 

 age than those reported by Martinez-Palacios and Ross 

 (1992) in Mexico. One-year-olds were 33-66 mm in Florida 

 vs. 70-130 mm in Mexico, and age-2 fish were 44-130 mm 



