Abstract
Hydromedusae collected in epipelagic waters of the channels in southern Chile, between the Corcovado Gulf and the Pulluche-Chacabuco channels, were analysed. A total of 23 species were identified and recorded for the first time in this region. The most abundant species were Hydractinia minuta (44.4%), Clytia spp. (21.0%), Solmundella bitentaculata (14.5%), and Amphogona apicata (9.8%). H. minuta was the only species whose maximum abundance occurred in interior, low temperature, low salinity waters. Most of the species identified in the southern channels are common inhabitants of the Humboldt Current System, although a rare species ( Heterotiara minor ) was recorded for the first time in Chilean waters. High-diversity values (> 2.5 bits) were recorded in the oceanic waters of the adjacent Pacific Ocean.
Highlights
Hydromedusae are common to all the oceans, no information is available regarding these conspicuous gelatinous organisms in this extensive southern channel region except for the work of Pagès and Orejas (1999), which describes the presence of 17 species around the Strait of Magellan
The geographic distribution of the medusae was analysed according to the dominant species, which were considered to be those whose abundance was greater than 5% of the total collected specimens
The vertical temperature distribution was very homogenous between the Corcovado Gulf and the Chacabuco Channel (Fig. 2)
Summary
Over the last ten years, a systematic research programme has been carried out in southern Chile, in the interior waters of the fjords and channels, resulting in significantly increased knowledge and understanding of the oceanographic and zooplankton characteristics of the interior waters between Puerto Montt and Cape Horn (Palma and Silva, 2004).Zooplankton studies in Chile’s southern fjords and channels have focused on chitinous organisms such as copepods, euphausiids, and the larvae of decapod crustaceans (Guglielmo and Ianora, 1995, 1997; Mujica and Medina, 1997, 2000; Palma et al, 1999; Marín and Delgado, 2001; Palma and Aravena, 2001) and some gelatinous (siphonophores) or semigelatinous (chaetognaths) organisms (Palma and Rosales, 1997; Palma et al, 1999; Palma and Aravena, 2001, 2002). Hydromedusae are common to all the oceans, no information is available regarding these conspicuous gelatinous organisms in this extensive southern channel region except for the work of Pagès and Orejas (1999), which describes the presence of 17 species around the Strait of Magellan. Recent studies show a steady increase in the populations of gelatinous organisms in diverse marine areas (Mills, 2001; Brodeur et al, 2002). These organisms play a preponderant role in zooplankton structure and dynamics due to the heavy impact of their predatory activity (Matsakis and Conover, 1991). Some medusae species have proliferated in the interior waters of Chile’s southern region. From February to June 2002, proliferations of Aequorea coerulescens, Chrysaora plocamia, and Phacellophora camtschatica affected salmon farming installations in the interior waters off Chiloé Island, with high mortality rates for the farmed fish (unpublished data)
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