| Summary: | We review recent work on the effect of hypoxia and turbidity (two factors that often co-occur in coastal areas) on escape performance, including swimming and timing variables. We hypothesize that hypoxia and turbidity may affect escape responses as a result of a decrease in sensory performance (e.g. in responsiveness and timing) and in stimulus strength, respectively. Fish were startled using mechanical and visual stimuli. The effect of hypoxia was studied in three species of fish from Mediterranean lagoons (Mugil cephalus, Liza aurata and Dicentrarcus labrax). Hypoxia affected the responsiveness of all three species. When performing aquatic surface respiration (ASR) in hypoxia, M. cephalus showed improved responsiveness. However, previous work has shown that ASR may be inhibited by the presence of aerial predators. Locomotor performance was affected only in severe hypoxia when the surface was obstructed in L. aurata. The effect of turbidity on visually-mediated escape responses was investigated in juvenile cod (Gadus morhua) by using a predator model. Putative escape success (PES) was used to assess escape performance, and took into account escape timing, direction and swimming performance. Cod had low PES in high turbidity because of decreased responsiveness and poorly timed escapes. The effect of turbidity on PES also depended on predator attack velocity. Overall, the results show that both hypoxia and turbidity may alter the escape ability of fish, by affecting a combination of swimming and timing variables.
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