Distribution and abundance of Euphausia mucronata: development stages and its relationship with temperature and chlorophyll-a concentration

Abstract

Euphausia mucronata abundance and distribution of the developmental stages (calyptopis, furciliae, juveniles, and adults) was analyzed as a function of seawater temperature and chlorophyll-a concentration between Paposo (25°S) and Coquimbo (30°S), Chile. Zooplankton samples were obtained using bongo nets during February of three consecutive years (2014-2016). The Q coefficient was used to explore the relationship between the distribution and abundance of the development stages of E. mucronata with the temperature recorded throughout the water column. The adults were considerably more abundant than the rest of the ontogenetic development stages during the study period. The abundance of adults decreased from February 2014 to 2016, having a negative correlation with temperature. Relative abundance of juveniles and larvae increased positively related to the total euphausiid abundance. The Q coefficient showed a significant association of all development states concerning the low-temperature intervals recorded throughout the seawater column. Q coefficient showed no association with chlorophyll-a concentration through the recorded intervals throughout the water column and neither with the vertical abundance and distribution of E. mucronata specimens.

Disentangling species-specific krill responses to local oceanography and predator’s biomass: The case of the Humboldt krill and the Peruvian anchovy

“…In general, our results suggest that chlorophyll-a concentration remains sufficiently high to support large euphausiid populations off northern Chile and is not a controlling factor of krill species abundances and distribution, at least at the spatial and temporal scales covered in this study. Gonzaĺez et al (2021) found no relationship between chlorophyll-a concentration and Humboldt krill developmental stages. However, to properly determine whether there is food limitation, it is necessary to incorporate food ingestion rates (Antezana, 2010), growth rates (Riquelme-Bugueño et al, 2016), and biomass production (Riquelme-Bugueño et al, 2013) in future studies, to observe changes in these population parameters under different productivity scenarios.…”

“…However, those years did not exhibit proportional changes in productivity. In particular, the abundance of the upwelling-associated Humboldt krill species (Riquelme-Bugueño et al, 2012;Gonzaĺez et al, 2021) had significantly higher abundances during the years with the most negative temperature anomalies (late 2010, 2014, and 2017). These interannual abundance fluctuations were probably caused by distribution displacements driven by poleward water-mass advection and/or by coastal trapped waves linked to ENSO events, as it has been proved in the CCS (Lilly and Ohman, 2021).…”