Local Stressors, Resilience, and Shifting Baselines on Coral Reefs in Kosrae

coral reefs

A study from Kosrae was just published examining how reefs and fishes may have changed over a longer period of time that we typically can observe in our lifetimes. Historical baseline data from Kosrae was used to examine changes in fish and coral assemblages since 1986 to present day. This historical dataset was collected by the Army Corps of Engineers for all FSM states, however, many historical reports get lost over the years or data become unavailable as computers die out. In Kosrae, a copy of the report and all datasets were preserved with both Katrina Adams, from the Kosrae Village Resort, and the Kosrae Conservation and Safety Organization (KCSO), prompting the study.

Despite the small island size and limited human population growth over the years, substantial shifts in the way coral and fish species were distributed around the island were found. Resources that were once in the best condition (plentiful coral growth and high numbers of large-bodied fish) on the western, leeward side of the island have been hit the hardest by fishing pressure, as leeward reefs offer protection from the prevailing northeast waves and greater access for fishermen over the years In turn, the wave exposed east coast is slowly becoming a refuge for framework building corals (i.e, table corals such as Acropora), and larger herbivores and predators. This does not appear to be unique to Kosrae in Micronesia, but the rare look into a past window helps resolve how change may have occurred.
The results of the study suggest that unsustainable fishing has slowly reduced ecosystem resilience over the years, as fish composition shifted to smaller species in lower trophic levels, driven by losses of large predators and herbivores. Lower resilience means that corals take longer to recover from small stress events, such as extreme low tides, bleaching, or passing large-wave events. While prior literature and anecdotal reports indicate that major disturbance events have been rare in Kosrae, small localized disturbances coupled with reduced resilience may have slowly degraded reef conditions through time. Improving coral-reef resilience in the face of climate change will therefore require improved understanding and management of growing artisanal fishing pressure and a greater focus on watershed pollution in the few urban areas that exist.
This study was complimented with a second study that is nearly completed, where a more detailed look at catch records for key fish species behind the changing reefs was examined. Together, these studies hope to define tangible ecosystem-based management objectives for reef fisheries, and we plan to start translating the results with the KCSO partners in more detail this upcoming year.
The work in this study represented the Master’s thesis for Mr. Matt McLean, and included many project partners: KSCO, Kosrae Department of Resources and Economic Affairs Division of Marine Resources, Kosrae Island Resource Management Authority, and Dr. Peter Houk’s research lab at the University of Guam. This project was funded through the US National Fish and Wildlife Foundation, and the Micronesia Conservation Trust. A copy of the study can be obtained by emailing to houkp@ uguam.uog.edu