Open Collections

Lang Abarzúa, Carolina

University of British Columbia

Jack mackerel (Trachurus murphyi) is a migratory species broadly distributed in the Pacific Ocean. Its main spawning grounds are located in the high seas zone off the Chilean coast. Several ichthyoplankton surveys have been conducted in this region, showing shifts in egg distribution, which have become more noticeable in the last decade. It is widely known that environmental conditions play an important role in determining the optimal conditions for development and survival for early life stages. However, the environmental drivers underlying changes in the egg distribution have been little studied. Yet, this knowledge is critical for understanding the effects of environmental forcing on spawning grounds and trends in this fish’s population. The aim of this research was to elucidate how eggs distribution is mediated by the environment and determine the impacts of climate variability on spawning grounds. Egg presence data from 14 ichthyoplankton surveys (1999-2018), as well as remote sensing data, were used to model egg-environment relationships using the Maxent species distribution model. Specifically, I analyzed the optimum temperature parameter, tolerance range and maps of habitat suitability index. The results suggest that temperature is the main driver of egg distribution, and its interannual variability has an impact on eggs by reducing the occurrence probability due to abnormally warmer or cooler conditions. Further, the tolerance range defined a thermal strip that varied spatially in the N-S and E-W directions as a function of the sea surface temperature variability. The latitudinal shift of the egg distribution and the thermal strip were in sync. Thus, the northerly and southerly egg displacements may indicate the species' adaptive response to environmental fluctuations. Other factors, such as wind and temperature anomalies, also shaped suitable conditions for spawning. Changes in these parameters due to climate variability, resulted in unsuitable conditions and restricted egg distribution. Based on these findings, adaptive boundaries in the sampling design are recommended in future ichthyoplankton surveys to prevent sampling bias.

Text

2021-06-28

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/78832

Oceans and Fisheries

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/