Wildlife Health

close up view of coral during a spawning event
Critically endangered Hawaiian monk seal basking in the sun next to the protected waters of the Papahānaumokuākea Marine National Monument. Credit: NOAA

Why is it a concern?

For “key” species in marine sanctuaries (e.g., keystone species, foundation species, indicator species, and other focal species) measures of condition and health can be important in determining the likelihood that these species will persist and continue to provide vital ecosystem functions and services. Measures of health condition may include growth rates, fecundity, recruitment, age-specific survival, tissue contaminant levels, pathologies (disease incidence, tumors, deformities), injuries and the presence and abundance of critical symbionts or parasite loads.

The population and biomass status of apex predators, such as sharks and jacks, habitat-forming corals, and protected species such as turtles, monk seals and seabirds, varies considerably. Apex predators are in near pristine conditions and represent significant biomass. Habitat-forming coral and sea turtle populations appear to have stable populations and biomass. The endangered Hawaiian monk seal has experienced a 60 percent population decline since the 1950s and is currently found in critically low numbers. Pre-1950s declines were the result of human disturbance of habitats during island occupation and exploitation, expeditions, and hunting. Declines since the 1950s are most likely related to a combination of factors. Both adult and juvenile monk seals are preyed upon by sharks. Imbalances in male/female sex ratios in the population have increased levels of male aggression toward other males competing for access to fewer reproductively active females. Decadal shifts in patterns and availability of food has impacted adult reproductive capacity and juvenile survival. The overall shrinking population and altered sex ratios has resulted in inbreeding, reduced genetic variance, and relative poor fitness to tolerate environmental stress, such as lack of food. Other factors, such as marine debris entanglement and eating ciguatera tainted fish, have caused some deaths of adult and juvenile monk seals.

Increased sea surface temperatures have resulted in several coral bleaching events. The geographic distribution and extent of bleaching varies based on the specific site characteristics and latitude. Corals have not been affected, for the most part, by diseases and remain relatively pristine. The ecosystem’s pristine status provides the opportunity to evaluate the influence of anthropogenic activities on disease outbreaks.

Overview of Research

Project Name PI and contacts Links

Coral bleaching and disease

Dr. Courtney Couch, Hawaii Institute of Marine Biology


Top predator movements in the Northwestern Hawaiian Islands

Dr. Carl Meyer, Hawaii Institute of Marine Biology



Science Needs and Questions

  • What is causing the continued sex ratio imbalance and failure of females to survive to reproductive age?
  • Does the main Hawaiian Island population have diminished genetic fitness similar to the Northwestern Islands population?
  • What is the anticipated impact of sea-level change on coastal habitats and organism dependent on those habitats?
  • What factors contribute to the occurrence and spread of coral diseases?
galapagos sharks
A group of Galapagos sharks swimming in the apex-predator dominated reefs of the Papahānaumokuākea Marine National Monument. Credit: Jim Watt, PMNM


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