Spatio-temporal variability of ichthyoplankton and its relationship with oceanographic conditions at the shelf break off Chilean Patagonia (43°S–51°S)

ABSTRACT

Larval fish composition and abundance have been studied in fjords of south Patagonia. However, the ichthyoplankton of the adjacent shelf and slope waters of the Pacific Ocean, which is an important spawning and nursery ground for demersal fishery species (e.g. austral hake and Patagonian grenadier), remains largely unknown. To compare ichthyoplankton occurrence with environmental conditions in August 2013 and 2014 (austral winter), two bio-oceanographic cruises were carried out between 43° and 51°S. Conductivity, temperature and depth (CTD) data and ichthyoplankton samples were collected. The highest frequency of occurrence (FO) was observed for eggs of lightfish Maurolicus parvipinnis (84 and 91% FO in 2013 and 2014, respectively) and larvae of the myctophid Lampanyctodes hectoris (60 and 94% FO, respectively). Ichthyoplankton composition and abundance varied significantly between years, and richness varied from 10 (2013) to 18 taxa (2014). Only larval L. hectoris showed a significant increase in abundance during the winter of 2014. Water column temperature and salinity were significantly different between years; the water was warmer and saltier in 2013. Canonical Correspondence Analysis detected positive relationships between temperature and salinity with egg abundance and larval distribution of Merluccius australis. The highest abundance of eggs of M. australis was found at ∼6–10°C, mainly off south Guafo Island. Additionally, ichthyoplankton from the shelf-break area off south Patagonia showed a wider latitudinal distribution in the winter of 2014 than in 2013.

SUBJECT EDITOR:

• Audrey J. Geffen

KEYWORDS:

• Brunt-Väisäla frequency
• Gadiform larvae
• larval fish assemblages
• pycnocline
• spawning area

Acknowledgements

We appreciate the comments and suggestions made by two anonymous reviewers to an earlier version of the manuscript. The authors would like to thank the technical staff on the cruises aboard the R/V Cabo de Hornos for their help.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the FIP 2013-13 project as well as the project ‘Evaluación del stock desovante de merluza del sur, merluza de cola y merluza de tres aletas, en aguas exteriores de la X y XII Regiones, año 2014’, both adjudicated by the Instituto de Fomento Pesquero. The study was partially supported by the project ‘Determinación del índice gonadosomático, estadios de madurez macroscópicos, ojiva de madurez, talla y edad de primera madurez y fecundidad de merluza del sur y merluza de cola en la zona sur austral, 2015’ (1049-23-LE15) granted by Instituto de Fomento Pesquero to the Universidad de Valparaíso.