538 



Fishery Bulletin 97(3), 1999 



populations of L. louisiarjensis from the northern Gulf 

 of Mexico (Felder and Lovett, 1989). In relative 

 growth parameters of the major chela, when scaled 

 to carapace length, males and females of both 

 Lepidophthalmus species are much more similar to 

 one another at sizes below transition points than at 

 sizes exceeding those points. 



The estimated maturational transition size in male 

 L. sinuensis ranges from 11.0 to 11.3 mm CL, whether 

 based upon regression analysis of relative gi'owth in 

 chela width, chela height, or wet weight. The range 

 of these values is markedly less than that reported 

 in L. louisianensis (>15.5 mm CL), a warm-temper- 

 ate congener (Felder and Lovett, 1989). In all of these 

 measures, postmaturation growth rate in males is 

 more positively allometric and significantly greater 

 than postmaturation growth rate in females, as has 

 been shown in many other decapods (Hartnoll, 1978, 

 1982 ). Although relative weight increases were posi- 

 tively allometric in both males and females of ma- 

 ture size, the positive allometry of growth in size of 

 the major chela, accompanied by sex-dependent 

 changes in its shape, appears to account for postma- 

 turation rates of weight increase in males that sig- 

 nificantly exceeding those of females. Weight ac- 

 cumulation due to massive but episodic development 

 of ovaries in maturing females would appear to be 

 somewhat offset by the simultaneous trend toward 

 negative allometric growth of the major chela. 



Estimated from the major chela measurements, the 

 mean maturational size in female L. sinuensis ranges 

 from 10.8 to 11.2 mm CL, or slightly less than that of 

 males but very near the values reported for females 

 of L. louisianensis, which ranged from 10.7 to 11.0 

 mm CL ( Felder and Lovett, 1989). Because over 99% 

 of the ovigerous females we collected were >11.0 mm 

 CL, the general validity of this mean size estimate 

 for maturation appears to be confirmed on an inde- 

 pendent basis, even though two atypically small 

 ovigerous females <10.0 mm CL, were collected (Fig. 

 4). Our regression analysis of wet weight indicated 

 that the transitional maturation point for females 

 fell near 9.8 mm CL, but error appeared to be high 

 in values surrounding this point. A relatively large 

 range and error in this weight-dependent value 

 should perhaps be expected because two variables, 

 negative allometry of the major chela and growth of 

 the ovaries, are likely influencing it in opposite ways. 

 We suggest that the aforementioned annual salinity 

 variations and the simultaneous effects on nutrient 

 loading may seasonally alter rates of ovarian growth. 

 This could in turn contribute to the range of weight 

 dependent values for maturation or account for oc- 

 casional occurrences of small egg-bearing females by 

 favoring early maturation of young cohorts. 



Management summary 



Those penaeid culture ponds on the Caribbean coast 

 of Colombia that operate at higher salinities than 

 those near the Rio Sinu have not been found to har- 

 bor detrimental infestations of Lepidophthalmus. 

 However, nutrient-rich, estuarine waters are believed 

 to yield high rates of penaeid production, promoting 

 location of several major penaeid farms in oligohaline 

 habitats that harbor natural populations of L. 

 sinuensis. This pest is introduced to culture ponds 

 by pumping in larvae and perhaps migrant juveniles 

 from the estuary. Although filtration of influent wa- 

 ter should serve to limit entry of any migrant juve- 

 niles, it is practical to limit entry of much smaller 

 planktonic lai-vae only by carefully avoiding pump- 

 ing in of waters from the estuary during nocturnal 

 hours of peak larval activity in the water column 

 ( Nates et al. , 1997 ). Because we herein document that 

 L. sinuensis reproduces year-round, this diel restric- 

 tion of pumping schedules cannot be limited solely 

 to the first annual quarter of elevated salinity when 

 peak abundances of ovigerous females suggest that 

 high densities of larvae might be present among noc- 

 turnal plankton. However, such periods would almost 

 certainly present the greatest risk of larval intro- 

 ductions to culture ponds. 



Although controlling water influx may limit colo- 

 nization of ponds from surrounding environments, 

 Lepidophthalmus will almost certainly over time 

 succeed in becoming established in estuarine ponds 

 that provide it with both richly organic muddy sub- 

 strates and annual cycles of water quality that favor 

 reproduction. Detrimental effects become obvious when 

 densities in ponds exceed 200 burrow openings/m-^ or 

 66 animals/m- (Nates and Felder, 1998), levels we 

 have never found in natural settings on in the Rio Sinii 

 estuary. Explosive reproduction within the ponds 

 appears to immediately precede problem levels of 

 infestation, and measurements of the sex ratios and 

 CL of the population may serve to forecast the po- 

 tential for such an event. Because attainment of a 

 strongly female-biased sex ratio is roughly coincident 

 with previously reported exponential population 

 growth (Nates and Felder, 1998), both sex ratio and 

 density of mature females may prove useful predic- 

 tors of population growth potential. Maturity of both 

 males and females can be determined by measures 

 of CL and cheliped dimensions, or by inference from 

 burrow diameters, and immediately pending episodes 

 of egg deposition can be predicted by monitoring the 

 ovarian index. 



Dense infestations of Lepidophthalmus in Colom- 

 bian shrimp culture ponds have to date been treated 

 periodically by farm operators with the carbaryl pes- 



