Ichthyoplankton spatial distribution and its relation with water column stratification in fjords of southern Chile (46°48′–50°09′S) in austral spring 1996 and 2008 |
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| Authors: | Claudia A Bustos Mauricio F Landaeta Fernando Balbontín |
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| Institution: | 1. Instituto de Investigaciones Marinas y Costeras (IIMyC), Consejo Nacional de Investigaciones Científicas y Técnicas – Universidad Nacional de Mar del Plata (CONICET – UNMdP), Funes 3250, B7602AYJ Mar del Plata, Argentina;2. Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Paseo Victoria Ocampo 1, B7602HSA Mar del Plata, Argentina;3. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC), Calle 526 e/ 10-11, B1906 La Plata, Argentina;4. Instituto Argentino de Oceanografía (IADO), CC 804, Florida 8000 (Camino La Carrindanga km 7,5) Complejo CCT CONICET Bahía Blanca, Bahía Blanca, Argentina;5. Universidad Provincial del Sudoeste (UPSO-Coronel Pringles), Sáenz Peña 867, B7530ASQ Coronel Pringles, Argentina;6. Universidad Nacional de Mar del Plata, Funes 3350, B7602AYL Mar del Plata, Argentina |
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| Abstract: | The occidental shore of the southern tip of South America is one of the largest estuarine ecosystems around the world. Although demersal finfish fisheries are currently in full exploitation in the area, the fjords south of 47°S have been poorly investigated. Two bio-oceanographic cruises carried out in austral spring 1996 and 2008 between 47°S and 50°09′S were utilized to investigate the spatial distribution of fish eggs and larvae. Small differences in the environmental conditions were identified in the top 200 m of the water column between years (5.3–10.5 °C and 0.7–33.9 units of salinity in October 1996; 6.3–11.5 °C and 1.2–34.2 units of salinity in November 2008). The low salinity surface layer generated a highly stable water column within the fjords (Brunt–Väisälä frequency, N>0.1 rad/s; wave period <60 s), whereas a well-mixed water column occurred in the gulfs and open channels. For both years, the ichthyoplankton analysis showed that early life stages of lightfish Maurolicus parvipinnis were dominant (>75% total eggs and >70% total larvae) and they were collected throughout the area, irrespective of the water column stratification. However, other components of the ichthyoplankton such as Falkland sprat Sprattus fuegensis, rockfish Sebastes oculatus, and hoki Macruronus magellanicus were more abundant and found in a wider range of larval sizes in less stable waters (N<0.1 rad/s). Oceanic taxa such as myctophids (Lampanyctodes hectoris) and gonostomatids (Cyclothone sp.) were collected exclusively in open waters. The October 1996 observation of Engraulis ringens eggs in plankton samples corresponded to the southernmost record of early stages of this fish in the Pacific Ocean. We found a significant negative relationship between the number of larval species and N, and a significant positive relationship between the number of larval species and wave period. Therefore, only some marine fish species are capable to utilize fjords systems as spawning and nursery grounds in areas having high amounts of freshwater discharges and very high vertical stratification during austral spring season. |
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