Beginning in the late 1980's, concern regarding
the status of the Hawaiian Bottomfish Fishery began to escalate over
a decrease in commercial landings. Fishermen were fishing more and yet
catching less fish. At the urging of the Western Pacific Fishery Management
Council (i.e., the Council responsible for managing federal fisheries
in Hawaii and the Western Pacific), the Hawaii Department of Land and
Natural Resources implemented Administrative Rule Chapter
13-94 in 1998 to set regulations to conserve remaining bottomfish
During the process of creating these rules, the realization
was made that although the Hawaiian Bottomfish Fishery had been in
existence for hundreds of years, there was relatively little known
about their habitat requirements. Among fishermen, there was general
consensus that there existed some connection between the bottom and
these fish because time and time again one could find them at the same
In an effort to better understand what was so special
about these fishing sites, a partnership was formed in 1998 between
the Hawaii Department of Land and Natural Resources and scientists
at the Hawaii Undersea Research Laboratory
(the NOAA Undersea Research Program (NURP) Center for Hawaii and
the Western Pacific), NOAA Fisheries, NOAA Oceans & Coasts,
and the University of Hawaii's Hawaii Institute of Marine Biology
to answer the following question:
What are the important physical and biological
features that define (or characterize) bottomfish habitat?
After six years, this study has just begun to close
in on the answer.
Hawaiian Bottomfish -- What are they?
Hapupu Grouper (Epinephelus quernus)
Ehu Snapper (Etelis carbunculus)
Onaga Snappers (Etelis coruscans)
Kalekale Snapper (Pristipomoides sieboldii)
Hawaiian bottomfish are not what you would expect. If
you were to look up the definition in a scientific textbook, you would
find the following definition:
bottomfish n. Fish
that live on the sea bottom, especially commercially important gadoid
fishes like cod and haddock or flatfish like flounder.
However, this definition does not describe a Hawaiian
bottomfish. The fishery is actually made up of an odd assortment of
12 species grouped together because they have some connection with
the seafloor (i.e., bottom). The membership includes seven deepwater
snappers (family Lutjanidae), two jacks (family Carangidae), one grouper
(family Serranidae), one scorpionfish (family scorpaenidae, and one
alfonsin (family Berycidae).
Pisces V, a submersible operated by the
Hawaii Undersea Research Laboratory, can dive up to 6,280 feet
These fish typically live in deep water (i.e., 250 to
1000 + feet) and cannot be studied "in situ" using
snorkel or SCUBA gear. Thus, to investigate these fish and their habitats,
we have used the Pisces' submersibles to visit twenty-two
different sites since 1998 and record the difference between bottom
characteristics of locations where bottom fish existed and did not
exist. The Pisces submersibles are operated and maintained by the Hawaii
Undersea Research Laboratory and are capable of diving to depths greater
than 6,000 feet.
Here is what we found...
Each fishing site was part of an ancient coral reef
that "drowned" between 10,000 to 100,000 years ago. By drowning,
I mean that the living part of the reefs sunk too deep, where it was
too cold and dark for reef-building corals to survive.
As you may know from snorkeling - a typical shallow
water coral reef consists of numerous holes, nooks, crannies, cracks,
crevices, and ledges for fish and invertebrates to hide from predators
or to ambush prey.
Like a shallow water reef, the dead reefs also contained
these types of cavities which brought up another question - Were
the bottomfish using them to hide from predators or to ambush
prey just like shallow coral reef fish and invertebrates do?
The answer was yes. During our submersible dives we
found that smaller snapper species, such as the ehu (Etelis carbunculus)
and the kalekale (Pristipomoides sieboldii) used the cavities
as places to hide. Both of these snappers are voracious predators,
but were clearly attacked themselves by another bottomfish species,
the amberjack (Seriola Dumerili) and to a lesser extent by
sharks. The cavities were also being used by larger snapper species,
such as the onaga (Etelis coruscans) in their juvenile and
post-juvenile (up to 1 ft long) stages, when that species is most susceptible
Symphysanodon maunaloae, a favorite
prey of some bottomfish, shown hiding in a crevice.
In addition to serving as shelter for bottomfish, we
found that the dead reef cavities also served as shelter for their
favored prey. For example, cracks and holes on these habitat sites
contained small fish such as Symphysanodon maunaloae and several
anthiid groupers, as well as small invertebrates such as squat lobsters
(family Galatheidae), glass shrimp, and octopi. This was verified by
looking at the stomach contents of several bottomfish species caught
during fishing surveys conducted by us and other researchers.
Interestingly, we found that the presence of these prey
species at rocky locations with cavities was key to the presence of
the bottomfish. If a rocky location was void of cavities, it was also
void of prey species and bottomfish. We also found that the presence
of other invertebrates such as, gorgonians, seastars, and urchins,
were not critical elements for bottomfish habitat, since we found them
at some habitats, but not at others.
The mystery begins to unfold...
After six years, we have just begun to answer the question:
What are the important physical and biological
features of bottomfish habitats?
Prior to this study, little was known about the habitat
preferences for the various species in this fishery other than the
fact that bottomfish could consistently be found in the same locations.
This study has established that these fish gravitate towards a seafloor
that has a lot of cavities such as an old drowned reef, which provide
bottomfish with food, as well as shelter from predators. It furthermore
has helped to define the fish and invertebrate communities found in
A more in-depth report of the findings is presently
being prepared for publication. This study, of course, has also identified
to both scientists and resource managers that we still have a lot to
learn about the Hawaiian bottomfish, if we are to conserve them for
generations to come.