Time filter

Source Type

Rojas P.M.,Institute Fomento Pesquero IFOP | Landaeta M.F.,University of Valparaiso | Ulloa R.,Autonomous University of Nayarit
Revista de Biologia Marina y Oceanografia | Year: 2011

The impact of the El Niño event (1997-1998) on the spatial dynamics as well as on the changes in the aggregation patterns of anchoveta eggs and larvae due to the alteration in the thermal anomalies were analyzed. Six bio-oceanographic surveys were carried out in northern Chile from Arica (18°29′S, 70°19′W) to Antofagasta (23°38'S, 70°24′W) over different periods (before and during) of the 1997-1998 El Niño event. Changes in the vertical distribution and aggregation patterns of anchoveta in early life stages were registered as well as an increase in zooplankton biomass with the arrival of El Niño; moreover, the spatial distribution of anchoveta was altered due to the gradually poleward displacement of spawning areas as a result of the arrival of subtropical warm waters from the north. The increase in zooplankton biomass linked to a change in the species composition suggests a negative impact on the anchoveta larval feeding. Our results suggest that abrupt changes in the environment would have immediate consequences on the spatial distribution of anchoveta in early life stages, causing a potential impact on the recruitment of this small pelagic fish in the Humboldt Current System off northern Chile.

Cerna F.,Institute Fomento Pesquero IFOP | Plaza G.,Pontifical Catholic University of Valparaiso
Bulletin of Marine Science | Year: 2014

Age, growth, maturity, and natural mortality estimates were made for chub mackerel (Scomber japonicus Houttuyn, 1782) captured off the Chilean Pacific coast. The von Bertalanffy growth parameters for combined sexes from north and central-south areas were L∞ = 36.9 cm, k = 0.22 yr -1, and t0 = -1.35 yrs, and L∞ = 40.0 cm, k = 0.23 yr-1, and t0 = -1.34 yrs, respectively. The spawning period in the northern area ranged from November to February of each year; it was restricted to January and February in the central-south area. The size at maturity (Lm50%) estimated for the north and central south areas, respectively, were 25.1 and 29.6 cm fork length (FL) in males, and 25.9 and 28.1 cm FL in females. Natural mortality was similar in the two areas: 0.45 yr-1 in the north and 0.46 yr-1 in the central-south region. Results support the existence of two stocks off Chile's southeastern coast. © 2011 Rosenstiel School of Marine and Atmospheric Science of the University of Miami.

The role of daily vertical migration (DVM) of ichthyoplanktonic associations off Punta Angamos, in northern Chile, was examined. In September 1998 and January 1999, two oceanographic surveys were conducted during coastal upwelling events. Fish larvae were collected during the day/night in three depth strata (0-20, 20-80 and 80-200 m) and inside/outside of upwelling filaments. The study area was dominated by a southward flow along 200 m depth; meanwhile, the Ekman layer did not exceed 20 m depth. The greatest accumulation of larvae was found in the middle layer (20-80 m), where the current velocity was low and did not interact with the circulation associated with upwelling the filament formation. Most fish larvae were found in non-upwelling waters in the middle stratum. Independent of the origin of water (upwelling/non-upwelling), larvae of Dioge-nichthys laternatus (Myctophidae), Engraulis ringens (Engraulidae) and Bathylagus nigrigenys (Bathylagidae) showed a deeper vertical distribution during the day, suggesting a daily vertical migration. This behavior can potentially increase retention of larvae near the coast in productive areas through vertical evasion of the Ekman layer during upwelling events.

Salgado P.,Institute Fomento Pesquero IFOP | Salgado P.,FARO | Riobo P.,CSIC - Institute of Marine Research | Rodriguez F.,FARO | And 2 more authors.
Toxicon | Year: 2015

Among toxin-producing dinoflagellates of the genus Alexandrium, Alexandrium ostenfeldii is the only species able to produce paralytic shellfish poisoning (PSP) toxins, spirolides (SPXs) and gymnodimines (GYMs). In this study we characterized and compared three A. ostenfeldii strains isolated from the Baltic, Mediterranean, and southern Chile Seas with respect to their toxin profiles, morphology, and phylogeny. Toxin analyses by HPLC-FD and LC-HRMS revealed differences in the toxin profiles of the three strains. The PSP toxin profiles of the southern Chile and Baltic strains were largely the same and included gonyautoxin (GTX)-3, GTX-2, and saxitoxin (STX), although the total PSP toxin content of the Chilean strain (105.83 ± 72.15 pg cell-1) was much higher than that of the Baltic strain (4.04 ± 1.93 pg cell-1). However, the Baltic strain was the only strain that expressed detectable amounts of analogues of GYM-A and GYM-B/-C (48.27 ± 26.12 pg GYM-A equivalents cell-1). The only toxin expressed by the Mediterranean strain was 13-desmethyl SPX-C (13dMeC; 2.85 ± 4.76 pg cell-1). Phylogenetic analysis based on the LSU rRNA showed that the studied strains belonged to distinct molecular clades. The toxin profiles determined in this study provide further evidence of the taxonomic complexity of this species. © 2015 Elsevier Ltd. All rights reserved.

Jewell R.,SMRU Ltd | Jewell R.,University of St. Andrews | Thomas L.,University of St. Andrews | Harris C.M.,University of St. Andrews | And 5 more authors.
Marine Ecology Progress Series | Year: 2012

Measuring the effect of anthropogenic change on cetacean populations is hampered by our lack of understanding about population status and a lack of power in the available data to detect trends in abundance. Often long-term data from repeated surveys are lacking, and alternative approaches to trend detection must be considered. We utilised an existing database of linetransect survey records to determine whether temporal trends could be detected when survey effort from around the world was combined. We extracted density estimates for 25 species and fitted generalised additive models (GAMs) to investigate whether taxonomic, spatial or methodological differences among systematic line-transect surveys affect estimates of density and whether we can identify temporal trends in the data once these factors are accounted for. The selected GAM consisted of 2 parts: an intercept term that was a complex interaction of taxonomic, spatial and methodological factors and a smooth temporal term with trends varying by family and ocean basin. We discuss the trends found and assess the suitability of published density estimates for detecting temporal trends using retrospective power analysis. In conclusion, increasing sample size through combining survey effort across a global scale does not necessarily result in sufficient power to detect trends because of the extent of variability across surveys, species and oceans. Instead, results from repeated dedicated surveys designed specifically for the species and geographical region of interest should be used to inform conservation and management. © 2012 Inter-Research.

Discover hidden collaborations