Por:
William Camargo Navarro
|
Fecha:
2002
The series of studies accomplished and compiled in the present thesis had as a main objective the evaluation of the suitability of the Colombian Artemia franciscana for the aquaculture industry. Further, an evaluation of six newly reported populations (Salina Cero, Kangarú, Tayrona, Bahía Hondita, Pusheo and Warrego) is included. In addition to the description of biotypes, physicochemical parameters were recorded for each population studied. The habitats where Artemia has actually been registered in Colombia are of marine (thalassohaline) origin, thus they are sodium and chloride rich. The application of biometric tools to determine possible cyst and nauplius size differences among the different Colombian populations has been successful at further separating some of the most promising Artemia populations of potential aquaculture use.
Further, cysts from Tayrona show the smallest size, followed by Galerazamba, Kangarú, Manaure, Salina Cero and Pozos Colorados. Galerazamba has the thinnest chorion, followed by Tayrona, Salina Cero, Manaure, Pozos Colorados and Kangarú. Additionally, nauplii from Galerazamba present a small size followed by Manaure, Salina Cero, Pozos Colorados and Tayrona. The determination of FAME from Manaure, Galerazamba, Salina Cero and Tayrona, suggested high EPAs but low DHAs. Hence, all four populations sampled are not considered suitable for marine aquaculture unless fortified with DHA rich emulsions, according to actual aquaculture quality standards. The cyst quality study, conducted on cysts batches, shows that cyst collection and processing techniques need to be improved in order for them to be suitable for the growing Colombian aquaculture industry.
The outcome of the population distribution study, shows Manaure, Galerazamba and Salina Cero as having a stable mean population distribution with a balanced adult (38%, 36% and 19%, respectively) to juvenile+nauplius proportion (62%, 64% and 81%, respectively), as well as a stable female:male sex ratio (1:0.84, 1:0.88 and 1:0.84, respectively). In contrast, Tayrona exhibits an unstable population distribution with a high proportion of adults (82%) and low juvenile+nauplius (18%) and female:male ratio (0.88:1), thus recruitment of the juvenile and nauplius cohort to assure continuity of the species in this biotope is below sustainable levels. The results for the reproductive experiments (mean cyst production per female) do not entirely agree with the estimated cyst production potential at each site (field work results).
These results difference is likely to be due to the interaction in the field among the three parameters (salinity, percent O2 saturation, and nitrate) on cyst production, particularly in the case of Salina Cero. Similarly, nitrate levels might have been affected by salinity. The latter may be supported, in part, by the observation of low nitrate levels during the peak of cyst production during this study. The genetic study on some Caribbean Artemia franciscana strains based on RAPDs generated two similar dendrograms with the same separation for the two Caribbean population clusters (middle Caribbean: Pozos Colorados, Tayrona, Manaure, Venezuela-PAV, Bonaire and Curaçao and lower Caribbean: Galerazamba and Salina Cero). Moreover, the clustering pattern obtained suggests that the populations in these two clusters are not genetically identical.
Further, the splitting of the Artemia populations coincides with the existence of a geographical barrier in Colombia named the Sierra Nevada de Santa Marta. The Sierra Nevada might constitute a geographic barrier to shorebirds and hence Artemia cyst dispersal further south. The discriminant analysis based on morphometric characters, assigns male and female individuals into their proper population group (North American and Caribbean coast) to which they belong by only one discriminant function (100% confidence). However, male morphometric characters separate better population groups than the female characters, since all Colombian populations are correctly clustered in the Caribbean coast whereas the SFB population fall into the North American group, with no overlapping between both, as it happens with females.
Similarly, for Artemia populations classified by their geographic origin, male and female individuals again separate the Colombian populations from the North American (SFB) populations. According to the analysis, Salina Cero male population is similar to its neighboring Galerazamba population and is also related to the other Colombian populations, and this is consistent with the previous findings using RAPDs and also likely to be explained by the existence of a geographic barrier (Sierra Nevada de Santa Marta). Apparently, as deduced from the influence of lunar cycles and sampling time study the conglomerates formed by brine shrimp are asynchronous. Finally, it is recommended to conduct Artemia surveys preferably late in the evening or alternatively during early morning since Artemia tends to distribute more uniformly during the evening (dark and cool), when water temperature is lower, particularly in saltworks, where the evaporation basins are shallow.
Fuente:
Biblioteca Virtual Banco de la República
Formatos de contenido:
Tesis
