Luis A. Soto

Effect of salinity on survival, growth, and oxygen consumption of postlarvae (PL10-PL21) of Litopenaeus setiferus

The present study was done to establish the lethal salinity (LCsO) and the effects of an abrupt change in the salinity on the oxygen consumption and the growth of postlarvae (PL10-PL21) of Litopenaeus setiferus, and their integration as assimilated energy. Postlarvae of L. setiferus presented a mean LC50 at 8%o, and a time of response of 2 h. Thereafter, LC50 remained constant for the next 96 h. The effect of salinity on oxygen consumption and growth rate changed with the age of postlarvae. From PL10 to PL15, the highest oxygen consumption was obtained at 10%o and the lowest at 40%o. During this time, growth rate increased with salinity with the maximum value in 40%o and lowest at 10%o. From PL15 to PL21, the highest oxygen consumption was obtained at 30 and 40%o. In 30 and 40%0, the growth rate was lower than that observed in animals maintained in 10%o. The assimilation-salinity relationship changed with the age of the organisms. From PL10 to PL15, assimilated energy increased with a decrease in the salinity, and from PL15 to PL21, assimilation increased directly with an increase in the salinity. The inverse relationship between oxygen consumption and growth has been observed in other estuarine organisms and suggests that, when animals are found in an osmotically favorable medium, the processes of capture and distribution of the ingested energy are more efficient. These mechanisms change with age. From PL15 to PL21, an increase in the salinity produced an increase in the assimilation. This was a result of an increase in the respiratory efficiency and, as a consequence, a reduction of the net growth efficiency.

Feeding schedule for Penaeus setiferus larvae based on diatoms (Chaetoceros ceratosporum), flagellates (Tetraselmis chuii) and Artemia nauplii

Abstract This paper is the first to present a basic feeding schedule for Penaeus setiferus larvae based on diatoms ( Chaetoceros ceratosporum ), flagellates ( Tetraselmis chuii ) and Artemia nauplii. Growth rate (μm/day), rate of metamorphosis and survival of larvae fed 5 different concentrations of diatoms, flagellates and Artemia nauplii were measured. Survival associated with sudden changes in salinity (quality index QI) of the postlarvae harvested from each treatment was measured. A performance index was calculated from the growth rate, survival and QI. Considering all responses, a feeding schedule for P. setiferus larvae is recommended including a progressive increase in the concentration of diatoms (between protozoea and mysis; 30 and 40 × 10 3 cells/ml, respectively), flagellates (between protozoea and mysis; 2 × 10 3 cells/ml, respectively) and Artemia nauplii (0.5, 1.0 and 1.5 between PZ 3 -M 1 , M 1 -M 2 and M 2 -M 3 , respectively). The increase in concentration of algae and Artemia indicates a pattern of development of the digestive system associated with development of the larvae. This pattern must be considered to improve the production of larvae of this species under controlled conditions.

Critical dissolved oxygen level to Penaeus setiferus and Penaeus schmitti postlarvae (PL10–18) exposed to salinity changes

Abstract Dissolved oxygen is the most important limiting factor in the intensive cultivation of shrimp species. The critical oxygen level and its effects upon the energy metabolism of postlarvae (PL 10–18 ) of Penaeus setiferus and Penaeus schmitti exposed to diverse salinities were estimated. In both species the critical oxygen level (COL; estimated as the point of inflection of the curve obtained from the relation between the oxygen consumption and the oxygen concentration) was affected by salinity concentration. In P. schmitti , the COL was 5 mg l −1 for salinities of 38, 30, 20 and 15%., and 4.5 mg l −1 for animals kept at 25%. salinity. In P. setiferus , the COL was 5.0 mg l −1 in 37, 30, 25, 20 and 10%. salinities and 4.5 mg l −1 in 15, 5 and 1%. salinities. The energy deficit (END; deficit of metabolic energy) caused by the metabolic oxygen critical concentration was in P. schmitti 13.9% (38%. salinity) and 26.3% (30%. salinity), with intermediate values of 17.2, 22.7 and 24.7% in 25, 20 and 15%. salinities, respectively. For P. setiferus , the END was between 9.1% (l%. salinity) and 25.1% (30%. salinity), with intermediate values for the remaining salinities. Based on these data, the optimum salinity for P. setiferus postlarvae was between 5%. and 15%., and was 25%. for P. schmitti postlarvae. At these salinities the tolerance for the decrease in the oxygen concentration was greater than in the rest of the salinities. The high COL obtained for the postlarvae of both species indicates that the culture conditions must be carefully maintained at this developmental stage to obtain the maximum metabolic performance of the shrimp.

C:N:P Molar Ratios, Sources and 14C Dating of Surficial Sediments from the NW Slope of Cuba.

The surficial sediments recovered from 12 sites located near the channel axis of the Florida Straits and the lower slope off NW Cuba were analyzed for total organic carbon (TOC), nitrogen (TN), phosphorus (TP), elemental C:N:P ratios, C and N isotopic values, and 14C dating. The depth profiles of TOC, TN, and TP (0-18 cm) displayed a downcore trend and a significant variation. The TOC values were low (0.15 to 0.62%; 66 to 516 µmol g-1). Sites near the island’s lower slope had lower TOC average concentrations (158-333 µmol g-1) than those closer to the channel axis (averaging 341-516 µmol g-1; p <0.05). The TN concentrations near the lower slope attained 0.11% (80 µmol g-1), whereas, towards the channel axis, they decreased to 0.07% (55 µmol g-1; p<0.05). The C:N ratios ranged from 1.9 to 10.2. The mean molar C:N ratio (5.4) indicated a marine hemipelagic deposition. The TP was lower at sites near the lower slope (38.4 to 50.0 µmol g-1; 0.12% to 0.16%) than those near the channel axis (50.0 to 66 µmol g-1; 0.15 to 0.21%). C:P fluctuated from 7.7 to 14.1 in the surficial sediment layer. The bulk organic δ13Corg and δ15N values confirmed pelagic organic sources, and the 14C dating revealed that the sediments were deposited during the Holocene (1000-5000 yr BP). We suggest that the hydrodynamic conditions in the Straits influence vertical and advective fluxes of particulate organic material trapped in the mixed-layer, which reduces the particulate matter flux to the seabed.

Analisis ecológico de los productores primarios en la Laguna de Términos, Campeche, México

La laguna de Terminos, ubicada al Sur del Golfo de Mexico, ha sido objeto de un buen numero de investigaciones en las cuales se ha reconocido amplamente su papel ecologico como area de crianza y alimentacion para recursos bioticos de interes comercial. Para obtener el articulo completo pueden contactar al Editor de la Revista Ecosistemas y Recursos Agropecuarios en el siguiente correo electronico era@ujat.mx y se les enviara sin algun costo.