Wish you had a reason to travel to Hawaii during Seattle’s chilly and wet winters? Then you might envy the Seattle Aquarium biologists who travel to the west coast of Hawaii’s Big Island every winter to conduct annual reef surveys, a research project that launched in 2009.
Survey sites are located in both marine-protected and non-protected areas, and the surveys themselves are conducted with underwater video shot by Aquarium divers. After returning to dry land, Aquarium staff members count the fish in the videos, and the resulting data is used to determine significant changes in species diversity or abundance over time, and between protected and non-protected areas.
Coral reefs and their associated fish assemblages are threatened and disappearing worldwide. Monitoring reef fish and coral health stability, growth or decline is important for the management of these fragile ecosystems.
Although there is variability in the counts from year to year, overall most fish species have increased slightly over time the monitoring began in 2009.
A total of 27 transects were recorded at seven sites, resulting in almost five hours of video. From these, the following counts were made:
|Site||Total fish||Total species||Shannon diversity index (H’)*|
*Commonly used to characterize species diversity in a community.
** Surveyed during high seas, resulting in very low visibility.
Results over time
Both number of species observed and Shannon diversity index from 2009 through 2017:
Figure 1: Average number of species observed in transects moving forward, across eight sites from 2009 to 2017 on the Big Island, HI. *Site 5 in 2017 was surveyed during high seas, resulting in very low visibility.
Figure 2: Shannon diversity index (H’) over eight sites from 2009 to 2017. This index takes into account both the number of species present and evenness of species in relation to one another. High values indicate more diversity.
Up-close look at increases in kole tangs over all sites and years:
Figure 3: Kole tang numbers
What do the results mean?
The numbers of fish species observed on transects over time remained relatively stable with gradual increases over time, and with dramatic increases in some species such as kole tangs. Plus there has been stable diversity of fish at most sites—with increases in diversity noted at sites 3 and 4 particularly. In other words, this is very good news!