Predominant bacteria associated with black rockcod (Notothenia coriiceps, Richardson 1844) from King George Island, Antarctica

The present study isolated bacteria from black rockcod Notothenia coriiceps (Richardson, 1844) to determine if the relative proximity of salmon farms to natural habitats has resulted in the spread of known salmon pathogens. For this, bacteria were isolated from 60 N. coriiceps collected from seven sites along Fildes Bay, Antarctica (62°12 ́S, 58°57 ́W). Bacterial cultures were obtained from the kidney, liver, and spleen. The predominant bacterium of each culture was 16S rRNA gene sequenced, with 35 isolates obtained from 14 specimens. The predominant genera were Pseudomonas (9), Psychrobacter (7), and Staphylococcus (7), followed by Sporosarcina (4), and Bacillus (3). Notably, the Aliivibrio sp. (99.85% similarity with A. logei) and Chryseobacterium scophthalmus isolates were found and subsequently used to challenge rainbow trout (Oncorhynchus mykiss) and fine flounder (Paralichthys adspersus) species, which showed no clinical signs of disease nor death. Although kidney and skin lesion isolates were recovered (10 and 8 isolates, respectively), N. coriiceps challenges are needed to assess real infection risks. To our knowledge, this is the first description of these bacterial microorganisms from N. coriiceps. Introduction Over the last decade, the Chilean aquaculture industry has rapidly grown due to favorable geography and climate. Initially, fresh and seawater salmonids were farmed in the Los Lagos Region of southern Chile. However, the infectious salmon anemia virus crisis in the mid-2000s resulted in many production centers relocating farther south to the Magallanes and Chilean Antarctic Regions (Ibieta et al., 2011). Antarctica is relatively close to Chile, and the southernmost aquaculture center is only 950 km from the Chilean Antarctic Professor Julio Escudero Base on King George Island. Bull. Eur. Ass. Fish Pathol. , 36(6) 2016, 247 Most farmed fish are transported, often longdistance, during production (Avendaño-Herrera et al., 2014). This increases the risk of introducing bacterial or viral pathogens to wild species susceptible to disease or to becoming natural reservoirs. For example, Streptococcus phocae, the etiological agent of warm water streptococcosis, was related to Atlantic salmon (Salmo salar) mortalities at a farm near Puerto Natales in the Magallanes Region, where water temperatures are < 10°C (Yáñez et al., 2013). Most southern Chile/Antarctic fauna are perciform Notothenioidei fish (Eastman, 1993). While Notothenioidei fish have been studied in relation to global climate change in polar ecosystems (Huth and Place, 2013), there is little information regarding the potential of Antarctic fish species acting as bacterial pathogen carriers. Therefore, the present study sampled different organs from the abundant and widespread Antarctic black rockcod (Notothenia coriiceps), which was captured with species-specialised, environmentally friendly equipment during the 2014 ECA-50 expedition to Chile’s Antarctic base (62°12 ́S, 58°57 ́W). Predominant bacteria were identified from N. coriiceps tissues and compared against known salmonid pathogens to determine incidence in this wild fish. Materials and methods