Larval growth, condition and fluctuating asymmetry in the otoliths of a mesopelagic fish in an area influenced by a large Patagonian glacier

摘要

The interaction of melting glaciers and oceanic stormy weather produce a large variability in the water column structure of the coastal sea from the south Pacific coast of Patagonia. This area is largely utilized as spawning and nursery ground for the mesopelagic fish Maurolicus parvipinnis (Sternoptichyidae) during the austral spring. Using microstructure analysis of sagittal otoliths and fluctuating asymmetry of M. parvipinnis larvae from 4.0 to 11.4 mm standard length (SL), we studied the spatial distribution, the variation of larval condition and recent growth during October-November 2009 between 50°06' and 52°45'S. Hydrographic conditions varied between 1.4 and 9.5℃, 14.6-33.5 units of salinity, 11.5-26.5 units of sigma-t and the stability ranged from 3.6 to 594 cycles h~(-1). Larval abundance ranged between 3.1 and 293.7 ind. 10 m~(-2), with the highest abundance associated with channels connecting fjords and the adjacent ocean. Larvae grew at a rate of 0.174 mm day~(-1), and those individuals collected in areas with intermediate water column stability (216-270 cycles h~(-1)) showed greater body condition, measured as recent otolith growth index (ROGI). However, these larvae had a similar departure from ideal symmetry (FA1 residual model) as larvae collected in more stratified or well-mixed areas. Overall, larvae showed size-dependent asymmetry, sagittal otoliths of smaller larvae (< 7 mm SL) being more asymmetrical than those of large larvae (P<0.05). This suggests that M. parvipinnis larvae may be experiencing the impacts of water column variability differently, as well as other ecological interactions at different larval stages. Thus, water column structure at hatching would be important for the survival of this fish inhabiting the Patagonian fjords of southern Chile.