Data/hora: 10/06/2024 19:05:48

Provedor de dados: | 5
País: | France
Título: | Effet des conditions environnementales sur le développement des pathologies à Vibrio dans les élevages de crevettes en Nouvelle-Calédonie
Autores: | Lemonnier, Hugues.
Data: | 2007-05-09
Ano: | 2007
Palavras-chave: | New Caledonia; Risk factors; Environmental stress; Vibriosis; Epizooty; Pond management; Eutrophication; Pond health; Shrimp; Litopenaeus stylirostris; Peneids; Aquaculture; Nouvelle  Calédonie; Facteur de risque; Stress environnemental; Vibrioses; Pratiques d'élevage; Eutrophisation; Santé de l'écosystème bassin; Crevette; Litopenaeus stylirostris; Pénéides; Aquacultre.
Resumo: | Shrimp aquaculture in New Caledonia is a developing industry, exclusively based on the species Litopenaeus stylirostris. However, it is subject to mortalities during grow out as observed all over the world. Since 1993, shrimp reared during the cold period are affected by a disease named "syndrome 93". As a consequence, the whole industry has become seasonal and produces essentially during the warm season. The climatic conditions during the periods of transition between the two main seasons could be responsible for an environmental stress and the origin reason for mortality outbreaks. Stocking density is the main risk factor. It increases the probability of the appearance and development of the epizooty in the pond. The "Summer Syndrome", a septicemic vibriosis caused by Vibrio nigripulchritudo, was identified for the first time in December 1997 in an intensive shrimp farm (DF). It has become enzootic ever since and is expressed after 50d of rearing. Since 2003, two others farms located near DF have developed the disease. As a consequence, the summer syndrome is considered to be a potential threat for all the industry. Between 1991 and 2005, the increase of feed input and nitrogen levels in feed has led to a significant increase in the growth rate over the years in the farms affected by the disease. In consequence, an early eutrophication of the water is observed, which is concomitant with the beginning of the mortality outbreaks. An early eutrophication and the virulence level of the pathogen are considered as the main risk factors of the disease. Factors may act synergistically to explain the summer syndrome. As part of a multidisciplinary approach (pathology – physiology – environment), two high-frequency surveys were carried out to analyse the pond ecosystem. Since the feed quantity increases with the biomass of shrimp, the eutrophication level of the pond ecosystem will also tend to increase with the duration of rearing. During the first part of the rearing, the abundance of each picoplankton type is exceptionally high and picophytoplankton dominated the autotrophic compartment. The nanophytoplankton dominated the second part of the rearing and was more unstable. The shift from pico to nanophytoplankton could be considered as an environmental stress and was observed in relation to the beginning of the mortalities, whatever the disease. Shift intensity could play a role by inducing directly or indirectly a stress for shrimp and/or a growth and/or virulence factors of the pathogen. Results from sediment studies show that mortality was best characterized by TAN concentration in pore water and even more when the TAN concentration was high. TAN and pH are potential stress factors for shrimp reared in ponds affected by these diseases.
Tipo: | Text
Idioma: | Francês
Identificador: | http://archimer.ifremer.fr/doc/2007/these-2643.pdf
Editor: | Université de La Rochelle
Relação: | http://archimer.ifremer.fr/doc/00000/2643/
Formato: | application/pdf