scholarly journals Age, growth, mortality and condition index of an unexploited Ruditapes decussatus population from El Mellah lagoon Algeria

2017 ◽  
Vol 11 (1) ◽  
pp. 436-442
2021 ◽  
Author(s):  
Anam Tsear

The grooved carpet shell clam (Ruditapes decussatus) is one of the most economically essential mollusks in Mediterranean lagoons and sandy beaches, with fisheries and aquaculture both contributing to its abundance. The goal of this research is to see how varying amounts of acidity affect this calcifying organism. 420 ppm (ambient control), 550 ppm, 750 ppm, and 1050 ppm were used to incubate juvenile clams in CO2  enriched saltwater. With increasing pCO2 , the biological parameters evaluated revealed a small decline. Differences, however, were not substantial. In terms of overall weight, the reduction was greatest at 550 and 1050 ppm. Furthermore, clams kept at 550 parts per million had the lowest condition index and the greatest mortality rate of 8%. Both the 550 ppm and the control 420 ppm groups demonstrated an increase in metabolic rate and ammonia excretion in the physiological response testing. With increasing acidification, the algal feed clearance rate declined, with the highest average value in the control (420 ppm) group and the lowest average value in the extremely high pCO2 (1050 ppm) group. Ocean acidification may put further strain on R. decussatus' health and economic value by the end of the century


Author(s):  
F. Laruelle ◽  
J. Guillou ◽  
Y.M. Paulet

Since the introduction of the Manila clam Ruditapes philippinarum (Mollusca: Bivalvia) to aquaculture clam beds, this species has spread to several sites. As a result, an extensive fishery has developed around this species. Its reproductive cycle and that of a native clam species, Ruditapes decussatus (Mollusca: Bivalvia) from two Brittany sites are examined here and the seasonal variations in the condition index, the scale of maturation stages, the histology and the oocyte size-frequencies of both species are compared. The differences observed between the species and between sites were attributed to environmental conditions. Ruditapes philippinarum showed a more extended breeding period and a greater number of spawning events than R. decussatus. In the Morbihan Gulf, the reproductive activity of R. philippinarum appeared particularly great in terms of number of spawning events, and speed of maturation. For both species, synchronism was more apparent during the first maturation, while spawning, and particularly partial spawning, tended to decrease the level of synchronization.


2017 ◽  
Vol 81 (2) ◽  
pp. 229 ◽  
Author(s):  
Maria João Botelho ◽  
Sara T. Costa ◽  
Domitília Matias ◽  
Florbela Soares ◽  
Sandra Joaquim ◽  
...  

To examine the extent to which human activities near the Ria Formosa coastal lagoon influence the accumulation of trace elements (TE) in Ruditapes decussatus, individuals were transplanted from a natural bank located in the lower lagoon to three sites located in clam growth grounds under the influence of a small city (Faro), a fish farming centre (Olhão) and a site near the lagoon inlet (Lavajo). Concentrations were determined in substrate of the clam grounds and in the digestive gland, gills, mantle plus siphons, and remaining tissues of clams in four periods of the year. These measurements were accomplished with the monthly survey of the gametogenic stages, condition index, proteins, glycogen, total lipids, pH and osmolarity of hemolymph. Arsenic, Cu, Mn, V, Cr and Pb were preferentially linked to the digestive gland, while Cd was linked to the gills. TE concentrations in the digestive gland and remaining tissues were higher in winter, most likely reflecting additional inputs associated with rain. The lack of disruptions in biological parameters and the prolonged period of spawning and gonad recovery in clams suggest that the current TE availability in the lagoon has a minor influence on the reproductive cycle and hence on clam production.


2021 ◽  
Vol 02 (02) ◽  
pp. 1-1
Author(s):  
Sofia Silva ◽  
◽  
Alexandra Cravo ◽  
João Rodrigues ◽  
Cátia Correia ◽  
...  

The use of biomarkers in bivalves has gained significance as a reliable method for the assessment of the presence and effect of contaminants in aquatic ecosystems. However, it is important to note that the biomarkers respond not only to contaminant loadings and bioavailability but also to environmental stress. Therefore, the association between biomarkers and contamination/pollution should be conducted cautiously as the environmental factors also affect their response. These factors should be integrated into the assessment of the response of the biomarkers. The potential impact of effluents from an urban wastewater treatment plant (UWWTP) on the Ruditapes decussatus clam specimens located 1.5 Km away in a surrounding area was evaluated. After one month of exposure, three biomarkers were analyzed, namely lipid peroxidation (LPO), acetylcholinesterase (AChE) and electron transport system (ETS). These parameters were also determined for a control group purchased from a local nursery, which had no influence from UWWTP, in order to compare the results obtained from both groups. The in situ physicochemical characterization of the exposure site (temperature, salinity, pH and dissolved oxygen) was evaluated together with nutritional parameters, morphometric measurements and condition index. The biochemical analysis showed that the activity levels of AChE fluctuated from 4.0 to 4.6 nmol/min g protein and that of LPO from 101.5 to 248.9 nmol MDA/g protein. Also, the ETS activity levels were in the range of 27.2 to 30.2 nmol O2/min g protein. The lipid peroxidation was found to be the most responsive biomarker toward the damage caused by environmental conditions on the clams.


2018 ◽  
Vol 09 (02) ◽  
pp. 139-151
Author(s):  
Hussein Ewadh ◽  
◽  
Raid Almuhanna ◽  
Saja Alasadi ◽  
◽  
...  

Buildings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 156
Author(s):  
Deniz Besiktepe ◽  
Mehmet E. Ozbek ◽  
Rebecca A. Atadero

Condition information is essential to develop effective facility management (FM) strategies. Visual inspections and walk-through surveys are common practices of condition assessment (CA), generally resulting in qualitative and subjective outcomes such as “poor”, “good”, etc. Furthermore, limited resources of the FM process demand that CA practices be efficient. Given these, the purpose of this study is to develop a resource efficient quantitative CA framework that can be less subjective in establishing a condition rating. The condition variables of the study—mean time between failures, age-based obsolescence, facility condition index, occupant feedback, and preventive maintenance cycle—are identified through different sources, such as a computerized maintenance management system, expert opinions, occupants, and industry standards. These variables provide proxy measures for determining the condition of equipment with the implementation example for heating, ventilating, and air conditioning equipment. Fuzzy sets theory is utilized to obtain a quantitative condition rating while minimizing subjectivity, as fuzzy sets theory deals with imprecise, uncertain, and ambiguous judgments with membership relations. The proposed CA framework does not require additional resources, and the obtained condition rating value supports decision-making for building maintenance management and strategic planning in FM, with a comprehensive and less subjective understanding of condition.


2021 ◽  
pp. 101888
Author(s):  
Zineb Amane ◽  
Lina Tazi ◽  
Yassine Ouagajjou ◽  
Khalil Chahdi Ouazzani ◽  
Ahmed Nabich ◽  
...  

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