Publication Date

Summer 2023

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Moss Landing Marine Laboratories

Advisor

Scott Hamilton; Amanda Kahn; Cheryl Logan

Abstract

Predator detection and successful escape behaviors are critical to the survival of juvenile fish. However, rising temperatures and increased nutrient pollution result in more frequent hypoxic events (i.e., low dissolved oxygen levels), which may impact fish health and survival. This research examined the effects of hypoxia on two flatfish species commonly found in the Elkhorn Slough, an important nursery habitat in central California. English sole and speckled sanddabs were exposed to five DO treatments ranging from 8.0 mg/L DO (normoxic) to 1.0 mg/L DO (severely hypoxic). A startle response trial was used to examine the impact of increasingly hypoxic conditions on reactions of juvenile flatfish to a simulated predator. To evaluate whether visual and olfactory senses used for predator detection are affected by increasing levels of hypoxia, flatfish underwent a two-part predator presence trial. To understand if exposure to hypoxia impacts the ability of juvenile flatfish to escape predators, flatfish were placed in a direct predation trial. English sole and speckled sanddabs exposed to low oxygen displayed altered behaviors including declines in responsiveness, slower movements, shifts in behaviors in the presence of predators, and failure to avoid predation. Changes in anti-predator behavior in response to hypoxia in these two species of juvenile flatfish are likely to have further negative impacts on nursery function and population replenishment in the offshore fishery. Quantifying organismal tolerance to environmental change can be used to develop effective management strategies.

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