Development and Field Application of a Model Predicting Effects of Episodic Hypoxia on Short-Term Growth of Spot

Abstract

AbstractIn North Carolina and elsewhere, there is concern that excessive nutrient loading and resulting hypoxic conditions in coastal ecosystems are adversely affecting the native fauna, but quantifying the effects on fish can be difficult. Hypoxia may reduce fish growth via direct exposure or indirectly (e.g., cost of low-oxygen avoidance, reduced food availability, and density-dependent effects in oxygenated refuges). Given the fine spatial and temporal scale of oxygen dynamics in estuarine habitats, evaluating the impacts of hypoxia on fish growth requires short-term growth indicators that integrate the effects of rapidly changing environmental conditions. To address this need, we experimentally determined the sensitivity and response time of a suite of bioindicators of recent growth (RNA:DNA ratio and RNA concentration in muscle tissue; insulin-like growth factor-I messenger RNA expression in the liver; hepatosomatic index; and Fulton’s condition factor K) to changes in the specific growth rate of juv...