Scavenging crustacean fauna in the Chilean Patagonian Sea

Abstract

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.

Decapods Associated with the Southern King Crab (<em>Lithodes santolla</em>) Fishery in Central Patagonia (44º S, Chile).

“…The study was carried out in the Magdalena Sound, which is a fjord located in the Puyuhuapi Channel in the Aysén region of Chile (Figure 1). The Magdalena Sound is in front of the town of Puerto Cisnes on Magdalena Island, and is the deepest branch of the Puyuhuapi Channel, approximately 14 km long, 350 m deep and comprised mostly of vertical stone walls [14,15]. The area contains high amounts of dissolved organic matter, both of autochthonous (i.e., primary production) and allochthonous origin (i.e., discharge from rivers and aquaculture activities), and is influenced by the interaction of fresh water and seawater.…”

“…The area contains high amounts of dissolved organic matter, both of autochthonous (i.e., primary production) and allochthonous origin (i.e., discharge from rivers and aquaculture activities), and is influenced by the interaction of fresh water and seawater. This generates estuarine stratification, with the first layer (0-10 m deep) composed of brackish water and the deeper layers composed of seawater of sub-Antarctic origin [14,15]. Data analysis: Bathymetric patterns -The bathymetric patterns of abundance by species were analysed through a correlation analysis between depth strata and abundance of each species and total species [16,17].…”

“…Nevertheless, ecological studies are scarce due to the difficulty of accessing southern Chilean Patagonia [2,[10][11][12]. Previous studies were mainly conducted on intertidal and subtidal populations and communities in central and northern Patagonian inner seas [2,8,10] by studying the stomach contents of coastal fish for which decapods represent an important food source [10,13] as well as communities in deep seas [14]. Nevertheless, these studies were mainly based on first reports of decapod species and communities taken during short sampling periods.…”

“…The fishing gear used to catch Southern king crab (bait trap) and its operation at different depths over several months [3] provides the opportunity to use the information collected (relative abundance) from the catches of both the target species and its associated fauna to study the biodiversity and ecology of scavenging decapod crustaceans [14].…”

“…Additionally, due to the stratification and seasonal variations of the physicochemical parameters presented by the fjords of Patagonia [14,15], the relative abundance data obtained can be used to determine relevant ecological information such as bathymetric patterns of abundance by species, to model the abundance by season, and to determine the structuring pattern of the scavenging decapod crustacean assemblage.…”