Pacific oysters (Crassostrea gigas) have been introduced worldwide for aquaculture, which can benefit food sovereignty and economic development; however, established non‐native populations may present risks for local organisms and habitats. We reviewed the documented introductions of C. gigas by country to evaluate factors related to introduction, establishment and production, and to determine impacts of feral populations. To date, C. gigas has been introduced in 64 countries and 10 territories, has been established in 32 and contributes to cupped oyster production in 36 (additionally, three native range countries). Oysters were more likely to be introduced and to establish in higher‐latitude countries, but the economic factor of per capita Gross Domestic Product per capita (GDPpc) served as a stronger explanatory variable than latitude for introduction. Earlier introduction and the use for extended periods in aquaculture, not just in trials, further increased establishment. Commercial production increased with coastline length and when established populations were present, but in contrast to establishment, declined at higher latitude. Effects of feral populations have been studied in 11 countries, spanning a range from negative to facilitative as expected for an ecosystem engineer, while reaching levels of concern warranting removal from coastlines in the UK, Norway, Sweden Australia and South Africa. The use of GDPpc in analyses revealed a widespread inequity in terms of low investment in Pacific oyster aquaculture in poorer countries, while richer countries were able to invest not only in aquaculture but also in studies of environmental impacts of feral oysters.
1. The Yaqui catfish, Ictalurus pricei, is the only native ictalurid species described from north-west México and south-west USA. It is an endangered species owing to the decline and loss of most of its historical populations, mainly because of competition and hybridization with the non-native channel catfish, Ictalurus punctatus. The Arroyo Caj on Bonito is one of the few remnant populations of Yaqui catfish in the Yaqui River basin, and it is threatened by the presence of channel catfish that escaped from private culture facilities.2. Phylogenetic analysis of two mitochondrial and two nuclear genes was used to detect evidence of hybridization with channel catfish in a collection of 20 catfish from Arroyo Caj on Bonito. Fourteen putatively pure Yaqui catfishes, five hybrids and one channel catfish were detected.3. This study further highlights hybridization between channel and Yaqui catfish as the main threat to the remaining Yaqui catfish populations. We recommend urgent evaluation of the remnant populations of native catfish elsewhere and their current conservation status.
In bivalve mollusk aquaculture, massive disease outbreaks with high mortality and large economic losses can occur, as in northwest Mexico in the 1990s. A range of pathogens can affect bivalves; one of great concern is ostreid herpesvirus 1 (OsHV-1), of which there are several strains. This virus has been detected in the Gulf of California in occasional or sporadic samplings, but to date, there have been few systematic studies. Monthly samples of Crassostrea gigas, water, and sediment were taken in the La Cruz coastal lagoon and analyzed by PCR. The native mollusk, Dosinia ponderosa, which lives outside the lagoon, was sampled as a control. The virus was found throughout the year only in C. gigas, with prevalence up to 60%. In total, 9 genotype variants were detected, and genetic analysis suggests that linear genotypic evolution has occurred from strain JF894308, present in La Cruz in 2011. There has been no evidence of the entry of new viral genotypes in the recent past, thus confinement of the virus within the lagoons of the Gulf of California could promote a native genotypic diversity in the short term.
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