MILESTONE REPORT
Q2 2000
Project
Title:
The effectiveness of refugia on restoring deepwater
snapper resources: Year 1 Evaluation.
Purpose:
To observe
and record the distribution, abundance, and behavior of deep-water snapper
species both within State of Hawaii bottomfish refugia and in adjacent open
fishing areas. In addition, habitat
and community associations are recorded to give a better understanding of what
features to look for when modifying or expanding refugia to gain maximum
benefit.
Effort:
Twelve Pisces V and thirty-five RCV-150 dives were
conducted in 1999 within bottomfish refugia and adjacent open fishing
areas. On the Pisces V operations
transects and bait stations were conducted to obtain abundance estimates of ehu
and onaga. RCV-150 operations were
conducted largely at night to assess benthic habitat and associated faunal
communities.
Customers:
The State of Hawaii and the Western Pacific Regional
Fishery Management Council benefit by an enhanced understanding of the effectiveness
of refugia in their fisheries management plans. The fishing industry receives long-term benefits by assuring that
a sustainable deepwater snapper resource is maintained. The scientific community receives valuable
data on deep slope habitat and faunal associations as well as an effective tool
for assessment of deep-water resources.
Significance:
The State of Hawaii established refugia for
bottomfish in July 1998 in response to critical declines in ehu and onaga
resources in the main Hawaiian Islands.
These two species of deep slope snapper were heavily fished for decades
resulting in reductions of their spawning stocks to less than 10% of original
levels and greatly reduced annual catches.
The established refugia are intended to allow rebuilding of ehu and
onaga stocks to healthy levels with spawning stocks of 40-50% of original
levels. At the same time, the refugia
complicate the evaluation of stock levels.
In the past, stock abundance was calculated from commercial catch and
effort data. With the refugia in place,
this data will give managers an estimate of stocks in the open fishing areas,
but give no clue as to their levels within the protected areas. Fishing within the refugia would provide the
necessary data, but would reduce the intended benefit of the refugia. The submersible and ROV observations
conducted during this project will be combined with similar data collected in
1998 to establish a baseline of relative abundance within two of the State’s
refugia.
Success:
Short “high light” tapes have been created from
submersible and ROV dive tapes and presentations made in several public forums
to educate the public on the problems of management of deepwater snapper
resources and generate support for the recently established management measures
including the establishment of refugia.
Data on deep slope habitats and associated
communities recorded on both submersible and ROV dives have been analyzed and
results will be presented at a special Deep Reef Symposium at the ASIH
conference in La Paz in June 2000.
Submersible transects are effective in gathering
data on ehu abundance and habitat associations. Ehu are observed associated with ancient, submerged coral reefs,
which have an abundance of crevices to hide in and of associated prey species
including Symphysanodon moanaloae.
Both ehu and onaga are attracted to bait stations
and relative abundance can be recorded as the maximum number observed at any
one time during the 30-minute observation period. The observing scientists used a 12-inch diameter plastic buoy,
fondly named "the pumpkin", to estimate the size of fish attracted to
the bait. Apparently the scientists
were not the ones who loved the pumpkin.
During one of the bait stations a large octopus came and gave the
pumpkin a big hug. The persistent
octopus remained close during the entire 30-minute bait station, occasionally
approaching the pumpkin, giving it a hug, trying to convince the pumpkin to
give up its career in science and form a lasting relationship.
Submersible and ROV observations continued to supply
valuable data on juvenile ehu and onaga habitats located in our Oahu study
sites. A detailed swath map of the area
shows where the hard bottom required for adult snappers is located. Small juveniles of both species ranging in
size from 6 to 10 inches in length were found associated with exposed rocks on
otherwise flat sandy habitat on top of the slopes where the adults were
found. More juveniles were seen in 1999
than in the same locations in 1998 indicating a good recruitment year. This pulse in recruitment will benefit
fishermen in the future when they grow to adult size and will supply the
refugia with needed breeding stock.
Future steps:
Work continues on analyzing and quantifying information from the dive
videotapes. Data collected on the
various types of habitat and their associated faunal communities can be used to
evaluate the appropriateness of current bottomfish refugia and provide
direction to future modifications. The
ehu and onaga abundance values obtained in 1999 will be combined with those
obtained in 1998 to establish baseline abundance for the two refugia visited
and their respective adjacent areas.
Another dive project will be proposed for 2002 (year 4 of the refugia)
to provide data on the benefit of refugia to snapper stocks prior to the
State’s planned five-year review of their management plan.
