Outlasting the Heat: Collapse of Herbivorous Fish Control of Invasive Algae During Marine Heatwaves.

Marine heatwaves (MHWs), coral bleaching, and chronic local stressors such as eutrophication are accelerating regime shifts from coral- to algae-dominated reefs, increasingly favoring the proliferation of invasive, fast-growing, and often more grazing-resistant turf and macroalgae. A central tenet of global reef management strategies is that herbivorous fishes can sustain critical top-down control of algal proliferation as oceans warm. Here, we challenge this tenet by experimentally evaluating, under controlled laboratory conditions, whether herbivorous coral reef fishes across three key functional groups-browser (Naso lituratus), grazer (Acanthurus triostegus), and scraper (Chlorurus spilurus)-can maintain effective algal control across present-day (24.

Eat more, often: The capacity of piscivores to meet increased energy demands in warming oceans.

Marine heatwaves (MHWs) profoundly disturb tropical coral reefs, imperilling species fitness and survival. Ectothermic piscivorous reef fishes are particularly vulnerable to MHWs since all aspects of their survival are dictated by ambient temperature. Severe +4 °C MHWs are projected to escalate daily energy demands by ~32-55 %, compelling piscivores to pursue larger or more frequent prey to survive.

Fish swimming mode and body morphology affect the energetics of swimming in a wave-surge water flow.

Fish swimming modes and the shape of both the fins and body are expected to affect their swimming ability under different flow conditions. These swimming strategies and body morphologies often correspond to distributional patterns of distinct functional groups exposed to natural and variable water flows. In this study, we used a swimming-respirometer to measure energetic costs during prolonged, steady swimming and while station holding in a range of simulated oscillatory wave-surge water flows, within the natural range of flow speeds and wave frequencies on coral reefs.

Latency of mechanically stimulated escape responses in the Pacific spiny dogfish, .

Fast escape responses to a predator threat are fundamental to the survival of mobile marine organisms. However, elasmobranchs are often underrepresented in such studies. Here, we measured the escape latency (time interval between the stimulus and first visible reaction) of mechanically induced escape responses in the Pacific spiny dogfish, , and in two teleosts from the same region, the great sculpin, , and the pile perch, We found that the dogfish had a longer minimum latency (66.

Swimming in unsteady water flows: is turning in a changing flow an energetically expensive endeavor for fish?

Unsteady, dynamic flow regimes commonly found in shallow marine ecosystems such as coral reefs pose an energetic challenge for mobile organisms that typically depend on station-holding for fitness-related activities. The majority of experimental studies, however, have measured energetic costs of locomotion at steady speeds, with only a few studies measuring the effects of oscillatory flows. In this study, we used a bidirectional swimming respirometer to create six oscillatory water flow regimes consisting of three frequency and amplitude combinations for both unidirectional and bidirectional oscillatory flows.