Evaluación de algunos parámetros de calidad del agua en un sistema cerrado de recirculación para la acuicultura, sometido a diferentes cargas de biomasa de peces

Utilizing different loadings of biomass of the Nile Tilapia Oreochromis niloticus and rainbow trout Oncorhynchus mykiss, some water quality parameters were evaluated in a closed aquaculture recirculating system. The systems is integrated by six culture tanks, a sedimentation cistern, two submerged bio-filters, a fast sand filter, two pumps, a reconditioning-water reservoir and a unit of ultraviolet light lamps. Fishes were fed twice a day for 120 days with 2% of their total biomass. The following water quality parameters were recorded: water temperature, dissolved oxygen, pH, total ammonium nitrogen (TAN), ammonia, nitrate and chemical oxygen demand. The data were analyzed with a one-way ANOVA to determine statistical differences in the components of the system. The average values of TAN and nitrate indicated a high efficiency of the nitrification process at different fish loading of biomass. About 50% of TAN and more than 90% of ammonia was stripped into the atmosphere and this explains the low levels measured in the other components of the system. Other causes that contribute to the removal of nitrogen compounds were the assimilation by microorganism accumulated in the bottom of the sedimentation tank and the absorption and adsorption by the sludge. Results showed that the water quality parameters were satisfactory for 99% survivorship and an acceptable growth rate for both fish species.El objetivo de este estudio, fue evaluar algunos parámetros de calidad del agua en un sistema cerrado de recirculación utilizado en la acuicultura, sometido a distintas cargas de biomasa de Tilapia del NiloOreochromis niloticus y de trucha arco iris Oncorhynchus mykiss. El sistema consiste de seis estanques de cultivo, una cisterna de sedimentación, dos piletas con biofiltros sumergidos, un filtro de arena rápido, dos bombas, una pileta de reacondicionamiento y una unidad de lámparas de luz ultravioleta. Los peces fueron alimentados durante 120 días dos veces al día con el 2% de su biomasa total. Se registraron los siguientes parámetros de calidad del agua: temperatura, oxígeno disuelto, pH, nitrógeno amoniacal total (NAT), amoniaco, nitrato y demanda química de oxígeno. Los datos se analizaron con un ANDEVA de una sola vía para detectar diferencias significativas entre los componentes del sistema. Los valores promedio de NAT y nitrato indicaron una alta eficiencia en los procesos de nitrificación, aún cuando el sistema fue sometido a diferentes cargas de biomasa de peces. Los bajos valores detectados de NAT y amoniaco se debieron al arrastre eficiente hacia la atmósfera (50% NAT y más del 90% respectivamente). Otras posibles causas que contribuyeron a la eliminación de los compuestos nitrogenados, fueron la asimilación por microorganismos presentes en los lodos acumulados en la cisterna de sedimentación, además de la absorción y la adsorción por los lodos. Los resultados mostraron que la calidad del agua mantenida en el sistema permitió el 99% de sobrevivencia de ambas especies y una tasa de crecimiento aceptable

Role of oceanography in shaping the genetic structure in the North Pacific hake <i>Merluccius productus</i>

<div><p>Determining the relative influence of biotic and abiotic factors on genetic connectivity among populations remains a major challenge in evolutionary biology and in the management and conservation of species. North Pacific hake (<i>Merluccius productus</i>) inhabits upwelling regions in the California Current ecosystem from the Gulf of California to the Gulf of Alaska. In this study, we examined mitochondrial DNA (mtDNA) and microsatellite variation to estimate levels of genetic differentiation of <i>M</i>. <i>productus</i> in relation to the role of oceanographic features as potential barriers to gene flow. Samples were obtained from nine sites spanning a large part of the geographic range of the species, from Puget Sound, Washington to Costa Rica. The microsatellite results revealed three genetically discrete populations: one spanning the eastern Pacific coast, and two apparently resident populations circumscribed to the Puget Sound and the northern Gulf of California (F_ST = 0.032, p = 0.036). Cytochrome b sequence data indicated that isolation between the Puget Sound and northern Gulf of California populations from the coastal Pacific were recent phenomena (18.5 kyr for Puget Sound and 40 kyr for the northern Gulf of California). Oceanographic data obtained from the Gulf of California support the hypothesis that permanent fronts within the region, and strong gradients at the entrance to the Gulf of California act as barriers to gene flow. A seascape genetics approach found significant genetic–environment associations, where the daytime sea surface temperature and chlorophyll concentrations were the best predictive variables for the observed genetic differentiation. Considering the potential causes of genetic isolation among the three populations, e.g. spawning areas in different latitudes associated with upwelling processes, oceanographic barriers, asymmetric migration and specialized diet, oceanographic barriers appear to be a likely mechanism restricting gene flow.</p></div

Relaxed Bayesian topology with the estimated divergence times based on CYTB sequences for populations of <i>Merluccius productus</i> obtained with BEAST [65].

<p>Numbers at nodes indicate divergence time in millions of years. Blue bars correspond to the 95% highest posterior density (HPD) intervals. For clarity, samples from the NGC, PC and PS were collapsed into triangles.</p

Redundancy analysis (RDA) for the association of oceanographic variables obtained from Ocean Color Web, and the ancestry coefficients of the three populations.

<p>Puget Sound (PS), Pacific Coast (PC) and Northern Gulf of California (NGC) generated in STRUCTURE. Chlorophyll <i>a</i> concentration (CHL) and sea day time surface temperature (SSTd).</p

Pairwise F_<i>ST</i> values (below diagonal) and ϕ_<i>ST</i> (above diagonal) for <i>Merluccius productus</i>.

<p>Location abbreviations as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0194646#pone.0194646.t001" target="_blank">Table 1</a>.</p

Role of oceanography in shaping the genetic structure in the North Pacific hake <i>Merluccius productus</i> - Fig 4

<p><b>Genetic barriers detected using pairwise population differentiation indices for <i>Merluccius productus</i>: a) mtDNA and b) microsatellite data.</b> Red lines indicate genetic barriers. Voronoï tessellation shown in blue and the corresponding Delaunay triangulation of samples in green. Numbers in parentheses indicate bootstrap percentages. Abbreviations are as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0194646#pone.0194646.t001" target="_blank">Table 1</a>.</p

Satellite and hydrographic data.

<p>Climatology of February of the Gulf of California (2002–2010) from the MODIS-Aqua satellites: sea surface temperature (SST) °C. Midriff archipelago region (MAR), northern Gulf of California (NGC), south of the Gulf of California (SGC), and entrance of Gulf of California (EGC).</p

Hierarchical analysis of molecular variance (AMOVA) of genetic variation of <i>Merluccius productus</i> for mitochondrial DNA (mtDNA) and microsatellite loci (M).

<p>Hierarchical analysis of molecular variance (AMOVA) of genetic variation of <i>Merluccius productus</i> for mitochondrial DNA (mtDNA) and microsatellite loci (M).</p

Temperature and salinity profiles.

<p>(a) and (c) depict temperature and salinity distributions across the front located south of the Midriff Archipelago Region (MAR). (b) and (d) depict temperature and salinity distributions across the entrance of the Gulf of California.</p

Parameters of the mismatch distribution and neutrality test (Tajima’s <i>D</i>, Fu’s <i>Fs</i>) for populations of <i>Merluccius productus</i> based on mtDNA data.

<p>Parameters of the mismatch distribution and neutrality test (Tajima’s <i>D</i>, Fu’s <i>Fs</i>) for populations of <i>Merluccius productus</i> based on mtDNA data.</p