SynopsisWe report the finding of an established population of exotic Chinook salmon spawning in headwaters of the Santa Cruz River system (Argentina), the first for this species in an Atlantic basin of South America. Spawning takes place in the Caterina River, a small tributary of Lake Argentino, located 488.5 km from the ocean. Anadromy was verified by correspondence of N and C stable isotope ratios with those of fish captured by bottom-trawlers in the ocean and those of anadromous rainbow trout from the same river basin. The scale patterns of most fish examined were consistent with a stream-type life cycle (i.e., seaward migration by juveniles after a full year in fresh water). Two potential origins were identified for this population: in situ introductions of fish imported directly from the USA in the early 20th century or fish from two ranching experiments conducted in southern Chile during the 1980s. In the latter case, colonization would have proceeded through the Strait of Magellan, helped by prevailing eastward currents.
The Chinook salmon Oncorhynchus tshawytscha, which was introduced deliberately in Chile four decades ago for sport fishing and aquaculture, represents a rare example of a successful translocation of an anadromous Pacific salmon into the southern Hemisphere, offering a unique opportunity to examine the role of introduction history and genetic variability in invasion success. We used historical information and mitochondrial displacement loop sequences (D-loop) from seven colonized sites in Chile and Argentina and from native and naturalized Chinook salmon populations to determine population sources and to examine levels of genetic diversity associated with the invasion. The analysis revealed that the Chinook salmon invasion in Patagonia originated from multiple population sources from northwestern North America and New Zealand, and admixed in the invaded range generating genetically diverse populations. Genetic analyses further indicated that the colonization of new populations ahead of the invasion front appear to have occurred by noncontiguous dispersal. Dispersal patterns coincided with ocean circulation patterns dominated by the West Wind Drift and the Cape Horn Currents. We conclude that admixture following multiple introductions, as well as long-distance dispersal events may have facilitated the successful invasion and rapid dispersal of Chinook salmon into Patagonia.
Rainbow trout (Oncorhynchus mykiss) was first introduced into Argentinean Patagonia, the southernmost region of South America, from the United States in 1904 and at present constitutes the most conspicuous freshwater fish in lakes and rivers of the region. The Santa Cruz River in Southern Patagonia is the only river in the world where a self-sustained population of introduced rainbow trout is known to have developed an anadromous run. In this study, we examined mtDNA sequence variation to identify the source of Santa Cruz River rainbow trout, providing a historical framework to interpret the processes underlying phenotypic variation and structure of Patagonian populations. The Santa Cruz River may harbor distinct North American stocks of rainbow trout, widely distributed around the world during the late 19th and early 20th centuries, but today threatened after decades of habitat loss, species introduction, and introgression from alien stocks. The mtDNA sequence data revealed that the most likely origin for wild anadromous and nonanadromous fish was the McCloud River in California. Meanwhile, a local hatchery stock, representative of rainbow trout introduced from Denmark after 1950 and widely stocked ever since throughout Patagonia, most probably originated from multiple lineages from western North America, including non-Californian populations.
Aquaculture, which represents 47% of global fish production, is quickly becoming the primary source of fish for human consumption (FAO, 2018). However, aquaculture development faces a number of challenges, such as climate change and increased disease rates (FAO, 2018). Thus, the intensification of culture systems to meet the growing global demand has led to the emergence of bacterial diseases with substantial economic losses for farmers (Hoseinifar, Sun, Wang, & Zhou, 2018). Antibiotics have been widely used in the fight against these infections. However, overreliance on antibiotics as an outbreak prevention and treatment strategy has led to the emergence of antibiotic-resistant bacterial strains and to the accumulation of antibiotics in the tissue of cultured organisms, making them unsuitable for human consumption (Romero, Feijoó, & Navarrete, 2012). An environmentally friendly alternative to antibiotics is the use of beneficial bacteria, namely probiotics. A probiotic is defined as a live
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.