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Simbine L.,National Fisheries Research Institute | Viana da Silva J.,Mogi Das Cruzes University | Hilsdorf A.W.S.,Mogi Das Cruzes University
Journal of Applied Ichthyology | Year: 2014

Tilapia is native to Africa, and one of the most cultivated fish in the world. The goal of this research was to evaluate the genetic diversity of tilapia Oreochromis mossambicus from the Limpopo, Incomati, Umbeluzi and Sabié rivers in Mozambique. Microsatellite markers were used to assess the genetic structure and to compare the genetic variability of wild populations of O. mossambicus. DNA samples from 200 specimens were analyzed. All five loci (UNH104, UNH129, UNH142, UNH222 and UNH231) used in this study were polymorphic, with observed heterozygosity ranging from 0.940 to 1.000 and the allelic richness average (Ar) ranging from 8.937 to 15.751. All of the stocks exhibited a remarkably significant excess of heterozygosity relative to the Hardy-Weinberg Equilibrium. Evidence of a genetic bottleneck was found in the four populations evaluated herein. The genetic structure of the population was investigated using the analogues FST and DEST. The most genetic variability occurred within populations. Differentiation among populations ranged from low to moderate levels. No significant correlation was found between geographic and genetic distances. Implications of these findings for management and conservation of O. mossambicus stocks are discussed. © 2013 Blackwell Verlag GmbH. Source

Nam K.-W.,Kunsan National University | Shin Y.-K.,National Fisheries Research Institute | Park K.-I.,Kunsan National University
Parasites and Vectors | Year: 2015

Background: Recent studies have reported that soft tunic syndrome (STS) in the edible ascidian Halocynthia roretzi is caused by the kinetoplastid parasite Azumiobodo hoyamushi. In this study, we attempted to detect and quantify the pathogen in benthic animals. Methods: Four species of ascidians, three species of echinoderms, two species of bivalves, one species each of sponge and algae, as well as seawater, were collected in 2014 and 2015 from an ascidian farm on the southern coast of Korea by SCUBA diving. Samples were collected from ascidian hanging culture ropes or the sea bottom. Inhalent siphons were excised for the analysis of ascidians, and soft body tissues were excised from the other species. Membrane filters were used to filter collected seawater. Tissues and membrane filters were analysed using culture testing, PCR testing, and qPCR diagnoses. Results: Only organisms belonging to Ascidiacea are susceptible to A. hoyamushi infection. The infection rate (% infected of the total number collected) and infection intensity (number of cells infected/g tissue wet weight) varied depending on the seasonal variation in seawater temperatures. Most ascidians examined were infected with A. hoyamushi and showed higher infection intensity in cold water seasons (April 2014 and February 2015), followed by a dramatic drop during warm water seasons (August and November, 2014). In addition, infection intensity of A. hoyamushi during the warm water period was higher in ascidians from the sea bottom than those from the hanging culture rope. Conclusions: Among benthic organisms that inhabit the southern coast of Korea, most ascidians are susceptible to A. hoyamushi infection. Seasonal cycle of infection rates and intensities of the pathogen correspond well with the STS disappearance and onset cycle observed in ascidian farms. The high intensity of A. hoyamushi infection in the ascidians on the sea bottom of ascidian farms during summer suggest further studies on the role of the pathogen in resumption of STS occurrence in late fall or early winter in the southern coast of Korea. © 2015 Nam et al. Source

Kim Y.S.,East Sea Fisheries Research Institute of NFRDI | Jeong C.S.,South Sea Fisheries Research Institute of NFRDI | Seong G.T.,National Fisheries Research Institute | Han I.S.,National Fisheries Research Institute | Lee Y.S.,South Sea Fisheries Research Institute of NFRDI
Journal of Environmental Biology | Year: 2010

The diurnal vertical migration of Cochlodinium polykrikoides (C. polykrikoides), which caused a red tide in the Korean coastal waters of the East Sea/Sea of Japan in September 2003, was examined by determining the time-dependent changes in the density of living cells in relation to the depth of the water column. The ascent of this species into the surface layer (depth of water, 2 m) occurred during 1400-1500. The descent started at 1600 and a high distribution rate (86%) at 15-20 m was observed at 0300. During the ascent, the cells were widely distributed at each depth level from 0600 hr and at 0800-1100, the cells were primarily distributed in the middle layer (0-6 m). The concentration of dissolved inorganic nitrogen was generally ≤ 2.86 μmol l-1, but at 1400-1500, the concentration in the surface layer reduced to ≤0.14 μmol l -1. Moreover, the concentration gradually increased as the depth increased to ≥5m. These results showed that the nutrientconsumption rate associated with the proliferation of C. polykrikoides during a red tide is more influenced by the inorganic-nitrogen resources rather than the inorganic-phosphorus compounds. © Triveni Enterprises, Lucknow (India). Source

Cardinale M.,Swedish University of Agricultural Sciences | Chacate O.,National Fisheries Research Institute | Casini M.,Swedish University of Agricultural Sciences | Chauca I.,National Fisheries Research Institute | Volstad J.H.,Norwegian Institute of Marine Research
Scientia Marina | Year: 2014

Artisanal fisheries are often overlooked by fisheries management agencies despite their great importance for food security and livelihoods. The assessment and management of those fisheries is often rare, especially in developing countries. In Mozambique, a probability-based survey for the monitoring of the small-scale fisheries has been conducted in several coastal provinces since the late 1990's. Here we used the Mozambican on-shore data collection programme to illustrate both the difficulties and possibilities of estimating trends in catch per unit of effort (CPUE in kg day-1) for stocks when data is limited in both quantity and quality, as is often the case for artisanal fisheries. Data on catch and effort collected between 1998 and 2009 from four regions along the Mozambican coast and two different gears were used to assess the status of two species (Hilsa kelee and Thryssa vitrirostris) exploited by the artisanal fisheries. The results showed that standardized CPUE have declined for some of the regions and gears analysed, whereas for others the trend has been stable or has even increased during the last 12 years. However, when CPUE is scaled for the increase in net length, most of the times series show a declining trend. © 2014 CSIC. Source

Baali A.,Mohammed V University | Yahyaoui A.,Mohammed V University | Amenzoui K.,National Fisheries Research Institute | Manchih K.,National Fisheries Research Institute | Abderrazik W.,Hassan 2 University
AACL Bioflux | Year: 2015

The round sardinella, Sardinella aurita (Valenciennes, 1847), was sampled from ship research Al Amir Mouley Abdellah in the period between June and July 2015 (southern Atlantic sea, Morocco) in the area between Cape Boujdor and Cape Blanc. The present study is about reproduction, age and growth of the round sardinella. The sex ratio varies with length. Females are more numerous than males especially for the high size (>34.5). The estimated lengths of fish of which 50% were mature, were 25.54 and 23.73 cm for males and females respectively. Growth parameters estimated, using direct method of Von Bertalanffy, gave asymptotic length, L∞, 33.72 and 33.66 cm and curvature parameter, K, of 0.83 and 0.97 per year for females and males respectively. The comparison of growth parameters for round sardinella, from Mediterranean and Atlantic waters, indicated different growth patterns between the two areas. We determined that the growth of S. Aurita is fast, reaching the size of 19 cm in the first year. © 2015, BIOFLUX SRL. All rights reserved. Source

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