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Reproductive and feeding ecology of red swamp crayfish procambarus clarkii (Girard, 1852) in China

Abstract : Aquaculture has developed rapidly in recent years and has become one of the primary contributors to food supply worldwide. However, the immense fishing pressure on wild and commercial-farmed populations has caused population depletion. Furthermore, limited juvenile crayfish production for aquaculture and suboptimal feeding strategies (such as high inputs of artificial diets) has hindered the development of sustainable aquaculture industry. Improving fisheries management is now necessary, based on a better scientific knowledge of population dynamics, reproductive ecology, and optimal feeding strategies, in particular by determining optimal environmental parameters for reproduction and refining artificial diets inputs. In this thesis, we focused on three main questions. First (1) what is the population and reproduction dynamics of adult crayfish living in commercial ponds and how should we adjust the aquaculture management? Second (2) what are the optimal temperatures for artificial reproduction and embryonic development? And third (3) what are the optimal levels of feeding and protein composition of artificial food for crayfish growth? For the first question (1), we studied the population dynamics and reproductive pattern of red swamp crayfish (Procambarus clarkii) by estimating growth, mortality rates, and exploitation rate of a commercial population, as well their reproductive parameters (GSI, HSI, ovarian development, and fecundity). Results showed that spawning activities took place from September to November, with a mean fecundity of 429 ± 9 eggs per female, and two recruitments yearly. There were five growth cohorts and male P. clarkii were overexploited. We thus suggest reducing fishing intensity on immature crayfish and avoid sex selection during the reproductive period to improve the overall sustainability of commercial P. clarkii populations. For the second question (2), we experimentally tested the effects of water temperature to improve reproductive outputs and embryonic development. Results showed that manipulating water temperature was an effective way to induce spawning in females and optimize embryonic development to improve juvenile production, with optimal temperatures of 21 - 25°C and 25°C, respectively. We also built a temperature-dependent developmental model for P. clarkii, D (developmental time, days) = 3140837(T-2.03)-3.76. Finally, for the third question (3), we experimentally tested the effects of five different feeding levels and reduced dietary protein levels (2 experiments) on growth performance and muscle composition of juvenile P. clarkii with natural food Hydrilla verticillata. Results showed that reducing the amounts of an artificial diet to 60% satiation and/or reducing the dietary protein level of the artificial diet to a level of 26% did not significantly affect the growth performance and muscle composition of P. clarkii. Stable isotope analysis suggested that crayfish switched diets to easily available H. verticillata when feeding levels or dietary protein levels decreased. This thesis thus explored new alternatives to traditional crayfish aquaculture by adjusting fishing effort and season, manipulating crayfish culture temperature, and refining feeding strategies to reduce production costs while improving the productivity and sustainability of crayfish aquaculture.
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Shiyu Jin. Reproductive and feeding ecology of red swamp crayfish procambarus clarkii (Girard, 1852) in China. Biodiversity and Ecology. Université Paul Sabatier - Toulouse III, 2019. English. ⟨NNT : 2019TOU30114⟩. ⟨tel-02879974⟩

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