Although a large number of fish species have been introduced into Guangdong Province in Southern China, a few species, such as tilapia (Tilapia spp.), North African catfish Clarias gariepinus Burchell, mrigal carp, Cirrhinus mrigala (Bloch) and the sucker mouth catfish (Hypostomus sp.), have established natural populations and can be considered “successful invaders” in large rivers. The specific mechanisms underlying these contrasting results among different introduced fish species remain understudied. The relationship between multiple abiotic–biotic factors and the success of four invasive species was investigated using survey data for the Guangdong Province river ecosystem. In contrast to previous studies that have considered species‐specific traits, the focus was on economic, ecological and anthropogenic factors to predict invasion success. Four main predictive indicators were found: (1) successful invaders were of low or no commercial value; (2) successful invaders tolerated a wide range of environmental conditions, including poor water quality; (3) biodiversity loss accelerated the growth of non‐native populations; (4) human disturbance facilitated population growth and spread of invasive fish species. To lessen the impacts of invasive fish species, the selection of breeding species and breeding areas, maintenance of water quality and reduction in water pollution, protection of the diversity of fish species and reduction of human interference should be addressed.
Tilapia is one of the groups of fish species most widely cultured globally. China has been the largest producer of tilapia in the world since 1990s. Guangdong Province produces almost 40% of all tilapia in China because of its suitable geography and weather conditions, and tilapia culture has brought considerable economic benefits. Unfortunately, many of the biological traits that make tilapia popular for culture also contribute to its success as an invader. Tilapia has invaded natural waters and has become the dominant fish in many rivers of Guangdong Province, causing economic loss in capture fisheries, and affecting native fish species, biodiversity and aquatic ecosystems. Poor fishery management, water quality degradation and biodiversity loss have all facilitated the tilapia invasion. Tilapia have filled the niches left vacant by now locally extinct native species resulting from environmental changes in freshwater ecosystems of the province. The introduction of tilapia has both advantages and disadvantages, which should be managed to use effectively the various tilapia species in aquaculture while controlling their spread in natural waters.
Key-words:Nile tilapia (Oreochromis niloticus), biodiversity resistance, biological invasion, species richness, biomass Nile tilapia (Oreochromis niloticus) is one of the most widely cultured species globally and has successfully colonized much of the world. Despite numerous studies of this exotic species, how differences in native communities mitigate the consequences of Nile tilapia invasion is unknown. Theory predicts that communities that are more diverse should be more resistant to exotic species, an effect that is referred to as "biotic resistance", but these effects are spatially dependent and organismspecific. Field surveys and laboratory experiments were conducted to test the theory of "biotic resistance" and ascertain the relationship between native species richness and the invasion of Nile tilapia. In the field, we found that as native species richness increased, the biomass of Nile tilapia was significantly reduced. Consistent with results from the field, our manipulative experiment indicated that the growth of Nile tilapia was negatively related to native species richness. Thus, our study supports the theory of "biotic resistance" and suggests that species biodiversity represents an important defense against the invasion of Nile tilapia. RÉSUMÉLa diversité des espèces protège contre l'invasion du tilapia du Nil (Oreochromis niloticus) Le tilapia du Nil (Oreochromis niloticus) est l'une des espèces les plus largement élevées à l'échelle mondiale et il a colonisé avec succès la plupart des pays. Malgré de nombreuses études de cette espèce exotique, comment les diffé-rences dans les communautés indigènes influencent les conséquences de l'invasion du tilapia du Nil est une donnée inconnue. La théorie prédit que les communautés qui sont plus variées devraient être plus résistantes aux espèces exotiques, un effet qui est dénommé « résistance au stress biotique », mais ces effets sont spatialement dépendants et propres à chaque organisme. Des études de terrain et des expériences de laboratoire ont été menées afin de tester la théorie de la « résistance au stress biotique » et de détermi-ner la relation entre la richesse des espèces indigènes et l'invasion du tilapia du Nil. Sur le terrain, nous avons constaté que, quand la richesse des espèces indigènes augmente, la biomasse du tilapia du Nil est considéra-blement réduite. Conformément aux résultats sur le terrain, notre expérience de manipulation indique que la croissance du tilapia du Nil est négativement associée à la richesse des espèces indigènes. Ainsi, notre étude confirme la théorie de la « résistance au stress biotique » et suggère que la biodiversité des espèces représente un important moyen de défense contre l'invasion du tilapia du Nil. Mots-clés :
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