are here: /main/research
2006/ Day 9
Fish Comparisons Between the Main Hawaiian Islands and the
Northwestern Hawaiian Islands
Ellyn Tong, Hawai`i Audubon Society
The Northwestern Hawaiian Islands provide an abundance of fish species
to count using REEF protocols. Photo: Claire Johnson/NOAA
REEF (Reef Environmental Education Foundation)
fish surveys are conducted throughout the world. They are not the kind of surveys that
governmental agencies usually use to create policy, however they are useful in that they
can give a general idea of the relative abundance both over time and between places, of
fish populations on coral reefs. Most governmental agencies simply do not have enough
funding to pay scientific divers to survey all areas under their management. REEF surveys
of the same area over time can alert governmental agencies of possible changes that may need
attention, and subsequently these agencies my decide to conduct more quantitative surveys.
REEF gives the participant training in fish identification for their area and then the volunteer
chooses a time, date and location to conduct the survey. The survey itself involves swimming
(diving or snorkeling) in a random pattern, without going over areas already surveyed, while
documenting fish species and their abundance.
A spotted knifejaw is a fish rarely seen in the Main Hawaiian Islands.
Photo Claire Johnson/NOAA
Numerous REEF surveys have been logged in the Main Hawaiian Islands.
One volunteer on Maui has logged over a hundred surveys alone. Few
completed in the Northwestern Hawaiian Islands. Not every reef in
the Northwestern Hawaiian Islands has been surveyed scientifically,
and getting some idea of fish numbers may be helpful for comparison
for example, a large storm event (like a hurricane) or a change in
average temperature (climate change). It may also be useful for those
doing surveys in the Main Hawaiian Islands to compare their findings
to surveys conducted in the Northwestern Hawaiian Islands.
In comparison to the Main Hawaiian Islands, it is known that rarely seen
fish and rare fish behaviors can be seen at Kure Atoll. On the mere four
surveys we have conducted thus far, we have to our
delight observed both fish rarely seen and experienced rare fish behaviors.
We saw both the barred knifejaws (Oplegnathus fasciatus) and spotted
According to Jack Randall’s book, Shore Fishes of Hawaii, these fish are rare
in the Main Hawaiian Islands, though not uncommon in the Northwestern Hawaiian
Islands. Knifejaws eat mollusks and
barnacles, crushing their prey with strong, fused teeth. Their food may be more
plentiful in the Northwestern Hawaiian Islands than the Main Hawaiian Islands.
Large species of barnacles are not
common in the Main Hawaiian Islands, but we observed several molted barnacle
exoskeletons floating in the water column in the same site we observed the knifejaws.
This barnacle’s molted exoskeleton
was at least one inch in diameter. According to Randal’s book, thicklipped jacks
are rare in the Main Hawaiian Islands, but we observed at least 50 schooling
with yellow fin goatfish
(Mulloidichthys vanicolensis) and yellowstripe goatfish (M. flavolineatus).
Large schools of these two fish are rarely seen in the Main Hawaiian Islands.
Schooling with these fish may be a defensive
strategy helpful to this species.
Surge wrasse exhibits territorial behavior, rarely seen in the Main Hawaiian Islands.
Photo: Claire Johnson/NOAA
Firsthand we experienced fish behavior rarely seen in the Main
Hawaiian Islands. On one of Thursday’s surveys a male surge
wrasse (Thalassoma purpureum) was exhibiting extremely
aggressive territorial behavior. No other male surge wrasses
were observed within a 50 yard radius of our
first encounter with him, and he stayed with us, often around
us or in our faces, until we exited his domain by getting
into the boat. Few other large fishes were seen within
this area. It could be guessed that any other intruders would be “har-wrassed” too.
Seven other smaller, less colorful surge wrasses were observed,
but they were all females,
assumed to be part of his harem. Surge wrasses are delicious
and this male’s in-your-face
behavior in the human populated Main Hawaiian Islands would
have made him, sadly enough, not long for this world.
The territorial surge wrasse follows a snorkeler busy counting fish. Photo: Paulo Maurin