July 9, 2012 July 9, 2012 Brian J. Zgliczynski, Alan Friedlander, Scott Hamilton, Stuart A. Sandin Brian J. Zgliczynski, Alan Friedlander, Scott Hamilton, Stuart A. Sandin The indirect effects of predators on coral reef fish assemblages Scripps Institution of Oceanography Scripps Institution of Oceanography

Gradient of predatory fish biomass North  South Inhabited islands Reduction of large predatory species Reduction of large predatory species Alteration of species composition Alteration of species composition Reduced standing stock Reduced standing stock Shift in the size-structure of fish community Shift in the size-structure of fish community Reduction of large predatory species Reduction of large predatory species Alteration of species composition Alteration of species composition Reduced standing stock Reduced standing stock Shift in the size-structure of fish community Shift in the size-structure of fish community

Examine the indirect effects of predators by comparing body condition factors and life-history characteristics of important coral reef fishes across a gradient of predatory biomass. Research Goal

Examine the indirect effects of predators by comparing body condition factors and life-history characteristics of important coral reef fishes across a gradient of predatory biomass. Positive behavioral responsesPositive behavioral responses Negative behavioral responsesNegative behavioral responses Trophically mediated responses, + or –Trophically mediated responses, + or – Key responses are mass at length and length at age Positive behavioral responsesPositive behavioral responses Negative behavioral responsesNegative behavioral responses Trophically mediated responses, + or –Trophically mediated responses, + or – Key responses are mass at length and length at age Reductions in predatory fish biomass will elicit:

50 individuals across range of body size 50 individuals across range of body size Line Islands 2010 Targeted Collections Apex predator Carnivores Herbivore Acanthurus nigricans Acanthurus nigricans Cephalopholis urodeta Paracirhites arcatus Cephalopholis urodeta Paracirhites arcatus Lutjanus bohar Planktivore Chromis margaritifer Uninhabited Inhabited

Acanthurus nigricans L inf k Log 10 SL (mm) Log 10 Weight (g) SL (mm) Annuli Uninhabited Inhabited Herbivore Greater mass at length at inhabited islands Greater mass at length at inhabited islands Individuals grow faster at inhabited islands Individuals grow faster at inhabited islands Max age greater at inhabited islands Max age greater at inhabited islands At inhabited islands food resources are not limited At inhabited islands food resources are not limited Trophically mediated response Greater mass at length at inhabited islands Greater mass at length at inhabited islands Individuals grow faster at inhabited islands Individuals grow faster at inhabited islands Max age greater at inhabited islands Max age greater at inhabited islands At inhabited islands food resources are not limited At inhabited islands food resources are not limited Trophically mediated response p= 0.04

Chromis margaritifer L inf k Log 10 SL (mm) Log 10 Weight (g) SL (mm) Annuli Uninhabited Inhabited Planktivore No difference in mass at length and growth between islands Oceanography likely plays an important role at the island scale Oceanography likely plays an important role at the island scale No difference in mass at length and growth between islands Oceanography likely plays an important role at the island scale Oceanography likely plays an important role at the island scale

Paracirhites arcatus Carnivore Log 10 SL (mm) Log 10 Weight (g) SL (mm) Annuli L inf k Uninhabited Inhabited Greater mass at length at inhabited islands Greater mass at length at inhabited islands Individuals grow faster at uninhabited islands Individuals grow faster at uninhabited islands Reallocation of energy to length rather than condition in the presence of predators(?) Reallocation of energy to length rather than condition in the presence of predators(?) Positive behavioral response Greater mass at length at inhabited islands Greater mass at length at inhabited islands Individuals grow faster at uninhabited islands Individuals grow faster at uninhabited islands Reallocation of energy to length rather than condition in the presence of predators(?) Reallocation of energy to length rather than condition in the presence of predators(?) Positive behavioral response P= 0.04

Lutjanus bohar Cephalopholis urodeta L inf k k Log 10 SL (mm) Annuli Log 10 SL (mm) Log 10 Weight (g) SL (mm) Annuli p= 0.004p= Apex Predator Carnivore Greater mass at length at uninhabited islands Greater mass at length at uninhabited islands Individuals grow faster at uninhabited islands Individuals grow faster at uninhabited islands Growth affected by direct exploitation Growth affected by direct exploitation Positive behavioral response Uninhabited Inhabited

Summary Predators indirectly affect the life history of fish species from lower trophic levels

Summary Reductions in predatory fish biomass result in species-specific: Positive behavioral responsesPositive behavioral responses Negative behavioral responsesNegative behavioral responses Trophically mediated responsesTrophically mediated responses Reductions in predatory fish biomass result in species-specific: Positive behavioral responsesPositive behavioral responses Negative behavioral responsesNegative behavioral responses Trophically mediated responsesTrophically mediated responses

Scripps Institution of Oceanography Center for Marine Biodiversity and Conservation Scripps Institution of Oceanography Center for Marine Biodiversity and Conservation AcknowledgementsAcknowledgements Integrative Graduate Education and Research Traineeship Program (IGERT) Ed DeMartini, NOAA Pacific Islands Fisheries Science Center Sandin Lab, Scripps Institution of Oceanography