An evaluation of the role and impacts of alien finfish in Asian inland aquaculture

Abstract

Asia dominates global aquaculture production accounting for over 80% of the total and the mainstay in Asian aquaculture is ¢n¢sh. Over the years, Asia has experienced a number of inter-continental and intra-continental transfers/introductions/translocation of ¢n¢sh species, between nations and watersheds, beyond their natural range of distribution, primarily for aquaculture development. In this article all such species are referred to as alien species. An attempt is made to evaluate the importance of the production of alien species in selected Asian nations, using statistics of the Food and Agriculture Organization. Also, negative e¡ects, if any, based on literature surveys, of alien species in relation to displacement of indigenous species, and on biodiversity and/or genetic diversity together with associated pathogen transfers are evaluated. The major alien species, based on their signi¢cance to Asian inland aquaculture considered, are the tilapias, cat¢sh, Chinese and Indian major carps and common carp. It is estimated that currently alien species account for nearly 12% of the cultured ¢n¢sh production (2.6 million tonnes) in Asia, valued at US$ 2.59 billion, and the contribution exceeds 40% when Asian countries excluding China are taken into consideration. Inland ¢n¢sh aquaculture in some Asian nations, such as Indonesia and the Philippines, is predominated by alien species, and in some others, e.g. Bangladesh and India, the contribution from alien species has been increasing steadily. It is suggested that overall alien ¢n¢sh species have done little ecological harm to native £ora and fauna. However, in the wake of increasing anthropogenic development taking place in watersheds the resulting environments are often made unconducive to indigenous species but not to some alien species, thereby potentially and indirectly making the latter invasive.

Production of red tilapia (Oreochromis spp.) in floating cages in the Mekong Delta, Vietnam: mortality and health management

“…Tilapia are popular fish for culture because of their hardiness, breeding success, short grow-out cycles, tolerance to a wide range of environmental factors, including fresh and brackish water, resistance to disease, easy handling, and appealing flavor (El-Sayed 2006, Silva et al 2006. Over 90% of farmed tilapia are produced in developing countries, mainly in Asia (El-Sayed 2006).…”

Invasion of an Exotic Fish—Common Carp, <I>Cyprinus Carpio</I> L. (Actinopterygii: Cypriniformes: Cyprinidae) in the Ganga River, India and its Impacts

“…The results of this study highlights that the common carp has established in the Ganga River as a pest through naturally breeding populations which is now becoming the source for secondary invasions at other places. Impacts of exotic fish in the Ganga have been found to be mild at present but it may cause habitat alteration, trophic structure alteration, and hybridization in due course of time (De Silva et al 2006, García-Berthou 2007, Lakra et al 2008. Gut content analysis, the diet breadth, and the gut repetitive index showed similar pattern at all the sampling stations.…”

“…Exotic fish introductions have been reported to impact the fish biodiversity and have provided significant warnings of the various effects on environment posing threats to the community trophic structure disrupting biological integrity (Casal 2006, De Silva et al 2006, García--Berthou 2007, Rowe 2007, Lakra et al 2008). It has also been realized that the nature and extent of such changes being complex remains unpredictable.…”

“…The common carp, Cyprinus carpio L., is extensively translocated species around the world (Sivakumaran et al 2003, De Silva et al 2006, Lakra et al 2008 including India where it was introduced in 1959 for aquaculture purpose (Singh and Lakra 2006). In India, it was studied for more than a decade under All India Coordinated Research Project for developing it as a species under composite fish culture.…”

Tradeoffs among Ecosystem Services Associated with Global Tilapia Introductions

“…Examples of phrases that led to a score of "negative" included: "We therefore consider that O. niloticus poses an unacceptable risk to its congenerics in the Limpopo River system" (Zengeya et al, 2012), and "The species have become widely established, with a range of negative consequences for the rich natural fish fauna of this Central American country" (McCrary et al, 2007). Statements scored as "positive" included: "The general importance of tilapias to the Asian region is evident from the fact that the first ever, multination, selective breeding programme on a cultured finfish species in Asia was on O. niloticus" (De Silva et al, 2006) and "Use of these non-native tilapia and carp species in fisheries enhancement in mainland SE Asia supported substantial increases in harvestable biomass while having only mild impacts on native fish communities" (Arthur et al, 2010). In contrast, where authors acknowledged both significant benefits and harms, "both" was assigned.…”