During the research programme conducted on the OV Puerto Deseado in the summers of 2011 and 2013, 36 stations were sampled using a demersal net at depths between 53–590 m in the Antarctic Peninsula and South Shetland Islands. A total 3378 fish specimens belonging to 36 species were recorded. Notothenidae was the best-represented family in species number, with Lepidonotothen nudifrons, L. larseni and Trematomus scotti being the most numerous species. Of the fish assemblages, 20% of the species were considered as dominant, 10% as common, 13% as occasional and 57% as rare. Six groups (and two sub-groups) were obtained by the ordination diagram based on geographical location: group 1=Gerlache Strait, group 2=Deception Islands, group 3=Biscoe Island, group 4=between Elephant and King George islands, group 5=northern Antarctic Peninsula, and group 6=South Shetland Islands, with sub-groups 6a shallower South Shetland Islands and 6b deeper South Shetland Islands. Sampling depth and water temperature significantly explained the spatial pattern. A latitudinal pattern of decreasing abundance from north-east to south-west was found in L. larseni and the opposite in T. scotti. The predictability of fish composition in the assemblages’ areas could be a useful tool for ecosystem-based management.

The RV Nathaniel B. Palmer was used for bottom trawling at depths of 100–1200 m during two recent cruises in the south-western Ross Sea. Although only 10 of 20 trawls were completely successful, a diverse collection of 979 specimens was obtained representing 47 species (36 notothenioids and 11 nonnotothenioids) and eight families. The collection included four new species, a new colour morph of a known species and eight rare species. The collection also established four new locality records, three second occurrences, three most southerly records and eleven new depth records for fish in the Ross Sea. Good taxonomic coverage for some groups was indicated by collection of all four species of Artedidraco, nine of ten bathydraconids and seven of eight channichthyids occurring in East Antarctica. The most abundant species were Trematomus scotti (29.7%), Bathydraco marri (10.4%), Trematomus eulepidotus (8.7%) and Dolloidraco longedorsalis (6.1%). Fish biomass was determined at two stations. The fish fauna of the Ross Sea south of the 1000-m isobath includes at least 80 species – 54 notothenioids and 26 non-notothenioids, approximately the same number as the Weddell Sea. Species diversity (H′ = 1.88) was higher than both the Weddell Sea and boreal regions. This collection indicates that, even in relatively shallow water, knowledge of specific and intraspecific diversity in the Ross Sea fauna is incomplete.

Antarctica is a continental island and the waters of its shelf and upper slope are an insular evolutionary site. The shelf waters resemble a closed basin in the Southern Ocean, separated from other continents by distance, current patterns and subzero temperatures. The benthic fish fauna of the shelf and upper slope of the Antarctic Region includes 213 species with higher taxonomic diversity confined to 18 families. Ninety-six notothenioids, 67 liparids and 23 zoarcids comprise 45%, 32% and 11% of the fauna, a combined total of 88%. In high latitude (71–78°S) shelf areas notothenioids dominate abundance and biomass at levels of 90–95%. Notothenioids are also morphologically and ecologically diverse. Although they lack a swim bladder, the hallmark of the notothenioid radiation has been repeated diversification into water column habitats. There are pelagic, semipelagic, cryopelagic and epibenthic species. Notothenioids exhibit the disproportionate speciosity and high endemism characteristic of fish species flock. Antifreeze glycopeptides originating from a transformed trypsinogen gene are a key innovation. It is not known when the modern Antarctic shelf fauna assumed its current taxonomic composition. A late Eocene fossil fauna was taxonomically diverse and cosmopolitan. There was a subsequent faunal replacement with little carryover of families into the modern fauna. Basal notothenioid clades probably diverged in Gondwanan shelf locations during the early Tertiary. Dates inferred from molecular sequences suggest that phyletically derived Antarctic clades arose 15–5 m.y.a.

Fish catches around the Great Lake, Tonle Sap river and the transitional zone between the lake and the river were studied by professional ‘fishing lot' (i.e. fishing zone) from 1995 to 1997. One hundred and twenty species of fish, belonging to 26 families and nine different orders were recorded. Compared to previous studies (1936–1976), only 53 % of families, 32 % of genera and 54 % of species were collected by professional fishing lot. This important loss in biodiversity could have several causes: bias of sampling procedures between professional fishing and research sampling, overfishing, modification of the floodplain by deforestation, etc. The professional fishing data showed that Cypriniformes accounted for 41.6 % of the total number of individuals caught, the Cyprinidae family alone represented 40 species. Siluriformes made up 21.6 %, Perciformes 13.3 %, with six other orders represented by smaller numbers. Eighty-seven percent of the recorded species occur in both habitats depending on the season. Migration takes place from the Mekong river to the Great Lake through the Tonle Sap river at the beginning of the rainy season (May–October), and in the reverse direction at the start of the dry season (November–February). The majority of the species reproduce at the start of the rainy season (May–June) in the flooded plain and the forest floodplain of the Great Lake; the period, the place and the means of reproduction have not been closely studied, particularly for the Belontiformes, Clupeiformes, Synbranchiformes, Pleuronectiformes and Tetraodontiformes. Multivariate analysis of fishing data (November–February) shows three distinct communities: that of the lake (Perciformes and Siluriformes), of the river (Pleuronectiformes, Cypriniformes, Clupeiformes and Siluriformes), and of the transitional zone formed from the principal channel, the old river channel and the oxbow lakes (Cypriniformes, Siluriformes and Osteoglossiformes).