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Master Thesis

Filtration and assimilation efficiency of Ruditapes philippinarum; why do they not keep growing?

Abstract : A lack of growth has been reported in a Ruditapes philippinarum farm in 2011. Growth, clearance rate (CR), ingestion rate (IR) and assimilation efficiency (AE) have been measured in 2012,as environmental parameters, to identify the reasons of the slow-down in growth and to propose solutions. Standardized CR and IR decreased from 8 to 28mm, from respectively 13 500 to 1 000 ml.h-1.gDW-1 and from 0.017 to 0.002 gDW of food.h-1.gDW-1. Both standardized CR and IR dropped when algal concentration reached level under 20 000 particles.ml-1 which is probably the limiting algal concentration threshold previously mentioned in the literature. AE is not affected by environmental parameters but has been found lower at low standardized IR and CR, which excludes the theory of saturated IR to explain low AE. A model performed showed that increasing algae concentration at low algal concentrations is the best way to increase IR. There is a morphological limitation of standardized CR over size, due to the lower increase of inhalant syphon when body size and maintenance costs increase. This limitation added to lower algal concentration and AE in summer is the reason of a slow-down and a stop in growth. The main solution to maintain and accelerate growth is to increase algal production in summer by shifting to other algae species, more adapted, and enrich the culture medium in limiting nutrients. It would also be possible to avoid summertime stressful conditions by growing clams longer in hatcheries, in order to put them larger in ponds in spring.
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Master Thesis
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Submitted on : Tuesday, December 18, 2012 - 9:42:13 AM
Last modification on : Monday, July 6, 2020 - 3:38:21 PM
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Bastien Debeuf. Filtration and assimilation efficiency of Ruditapes philippinarum; why do they not keep growing?. Agricultural sciences. 2012. ⟨dumas-00766290⟩

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