The marine ecosystem of the Chilean Patagonia is considered structurally and functionally unique, because it is the transition area between the Antarctic climate and the more temperate Pacific region. However, due to its remoteness, there is little information about Patagonian marine biodiversity, which is a problem in the face of the increasing anthropogenic activity in the area. The aim of this study was to analyze community patterns and environmental characteristics of scavenging crustaceans in the Chilean Patagonian Sea, as a basis for comparison with future situations where these organisms may be affected by anthropogenic activities. These organisms play a key ecological role in marine ecosystems and constitute a main food for fish and dolphins, which are recognized as one of the main tourist attractions in the study area. We sampled two sites (Puerto Cisnes bay and Magdalena sound) at four different bathymetric strata, recording a total of 14 taxa that included 7 Decapoda, 5 Amphipoda, 1 Isopoda and 1 Leptostraca. Taxon richness was low, compared to other areas, but similar to other records in the Patagonian region. The crustacean community presented an evident differentiation between the first stratum (0-50 m) and the deepest area in Magdalena sound, mostly influenced by Pseudorchomene sp. and a marked environmental stratification. This species and Isaeopsis sp. are two new records for science. The discovery of undescribed species evidences that this region needs further studies exploring its biodiversity, which is most likely being already impacted by anthropogenic pressure. The Chilean Patagonian region, located between 41°20′S and 55°58′S of latitude in South America, includes one of the most complex systems of channels and fjords of the planet and holds some of the largest estuarine areas of the world 1. It contains approximately 1,600 km of shoreline and a surface of 2,400 km 2 , being a transition zone of climatological, biogeographical and biological conditions between the Antarctic and the temperate Pacific regions 2. This situation produces an ecosystem that can be considered structurally and functionally unique 3. The ecological and physicochemical characteristics of a fjord are mainly controlled by the interaction of fresh water flowing from the rivers and the entrance of sea water depending on marine currents and tides 4. This creates a strong vertical gradient characterized by a halocline (i.e., a rapid vertical change in salinity), with brackish surface waters and saline intermediate and deep waters. Such marked stratification creates specific environmental conditions that often determine the presence of different species assemblages 5. Within the Chilean Patagonia, the Aysén region is subjected to different anthropogenic activities that have the potential to affect the marine biodiversity.

Our knowledge on the status of Hemigrapsus crenulatus (H. Milne Edwards, 1837) populations along the Chilean coast is scarce. The aim of the present study was to quantitatively estimate the spatial distribution and abundance of Hemigrapsus crenulatus in the Puerto Cisnes estuary (44°S, Aysen region, Chilean Patagonia). The spatial distribution appeared to be aggregated, with 3.64 ± 7.99 ind/m2 as gross density, and 10.50 ± 10.62 ind/m2 as a potential ecological density, i.e., if the quadrants with zero individuals are not taken into consideration. The equation of the negative binomial distribution was: where: . The average density of Hemigrapsus crenulatus under stones is lower if all beach surfaces are considered. Its abundance or dominance on estuarine beaches probably would be due to the fact that this species is one of the crustaceans of the lower intertidal level that can survive under a wide range of salinity values.

The intertidal crustaceans on the Chilean coast are characterized by high diversity and niche specialization. The present study applied a size overlap null model for intertidal decapod communities at four different sites on the Chilean coast. The results revealed that there is a size overlap for the four sites, though body size is significantly different for each location. This means that the reported species would share their ecological niches. The results agree with the first classic environmental descriptions for Chilean intertidal decapods at a local scale and support the observations for similar species on the southern Pacific and southern Atlantic coasts.

The Patagonian blenny (Eleginops maclovinus) is species endemic to South America with physiological characteristics that would facilitate its incorporation into Chilean aquaculture. However, there is currently no specific artificial food that can be used to raise E. maclovinus. In light of this problem, this study describes the proximal composition and fatty acid profile of the crab Hemigrapsus crenulatus, one of the main foods of E. maclovinus. The purpose of the study is to serve as basic information for the development of a specific artificial diet for juveniles of this fish species. The proximal analysis of the complete body of H. crenulatus indicates that it is mainly composed of ash (35.9%), proteins (32.2%), glucides (19.8%) and minor lipids (3.6%). The fatty acid profile is 40.7% PUFAs, 29.7% MUFAs and 29.5% SAFAs, and the most abundant acids are Eicosapentaenoic (18.8%), Oleic (6.8%) and Palmitic (16.6%), respectively. H. crenulatus has highest level of proteins, lipids and PUFAs among the species of the Brachyura infraorder.

Galaxias maculatus is an osmeriform native fish of the Southern Hemisphere, in which the crystalline larvae is considered as a luxury delicacy, for this reason, it has been commercially exploited in Chile, Argentina and New Zealand. However, the fisheries have been rapidly decreasing due to the overexploitation and the predation of introduced species. Because of these events, there is a need to determine a carrying capacity for an intensive fish culture. In order to optimize stocking densities for fish culture, this paper proposes objectives to determine oxygen consumption (OC) rates, dissolved oxygen concentrations that produce signs of hypoxia and the average time elapsed between food intake and peak OC in G. maculatus. In the oxygen experiments under routine metabolism conditions, we found that G. maculatus adults and whitebait showed signs of asphyxia at dissolved oxygen concentrations between 1.3 and 2.2 mg L−1 and that adults tolerated dissolved oxygen levels as low as 1.3 mg L−1. The results showed that G. maculatus individuals with an average weight of 0.04 g consumed 0.048 mg O2 h−1, whereas individuals with an average weight of 1.4 g consumed 0.345 mg O2 h−1. Galaxias maculatus increased the OC rate by 31%, from 0.39 to 0.51 mg O2 h−1 g−1, occurring 14 min after food intake. The carrying capacities for industrial cultures of G. maculatus, were estimated using an allometric equation (OC=0.2363 ×W0.612), a water flow rate of 1 m3 h−1 and an input oxygen concentration of 10 mg L−1 at 12 °C. The density culture of whitebait (4 g) can be allowed to reach 8–11 kg m−3; therefore, these stocking densities reduce the risk of hypoxia and mortality, ensuring the appropriate growth and feed conversion rates.