Competition-driven growth of Atka mackerel in the Aleutian Islands ecosystem revealed by an otolith biochronology

Abstract

Fish otolith increment biochronologies can reveal factors contributing to growth. These annually resolved, multi-decadal biochronologies have been used to identify temporal and spatial patterns in growth variability. Here, we used a linear mixed modeling approach to determine the relative importance of intrinsic factors (e.g., sex, age) and extrinsic factors (e.g., temperature, abundance of con-specifics and competitors) to growth of Atka mackerel (Pleurogrammus monopterygius), a commercially important groundfish dominant in the Aleutian Islands ecosystem. A yearly alternating pattern of wide and narrow increments was observed, and was negatively correlated with abundance of pink salmon (Oncorhynchus gorbuscha), suggesting possible competition over shared food resources such as large copepods (which were positively correlated with the otolith biochronology). There was no detectable effect of temperature on otolith growth, which could be a result of relative stability in water temperatures at the study site. We also contrast the otolith biochronology with a body condition index to examine the relationship between otolith and somatic growth. This represents the first otolith biochronology developed in the Aleutian Islands and provides insight into potential species interactions and their impacts on growth within this highly dynamic and productive ecosystem.