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Reef Fish Monitoring - General Description
Visual
censuses of the fish assemblages associated with benthic habitat transects
is conducted using a standard 25m x 5m underwater visual belt transect
survey method (Brock, 1954; Brock, 1982). Four 25m fish transects are run
at each location along the 100m length of the CRAMP fixed
benthic transect site. A SCUBA diver swims each transect at a constant speed
(~ 15 min/transect), identifying all fishes visible within 2.5m to either
side of the centerline (125m2 transect area). Standard length
(SL) of fish is estimated to the nearest centimeter. Care is taken to avoid
disturbing the fishes prior to the census. The fish census team is the first
to enter the area before any transect lines are set. The first diver attaches a 25m
transect line to the first pin of the transect and swims slowly down the
transect corridor while reeling out the transect line and counting fish. At
the end of the 25m transect the diver advances 5m to the next pin and
continues with the second 25m transect. The process is repeated for the 3rd
and 4th transects.
Eric Brown runs fish transect at Hakioawa during August 2000. Photo by Paul Jokiel.
Live wet weight (W) of all fishes recorded in all censuses is subsequently calculated from the visually estimated standard length (SL) using the relation W = a(SL)b. Values of the fitting parameters a and b were derived from previous work of the Hawai‘i Cooperative Fishery Research Unit.
References:
Brock VE (1954) A preliminary report on a method of estimating reef fish populations. Journal of Wildlife Management 18: 297-308.
Brock RE (1982) A critique of the visual census method for assessing coral reef fish populations. Bulletin of Marine Science 32: 269-276.
Last Update: 04/21/2008
By: Lea Hollingsworth
Hawai‘i Coral Reef Assessment & Monitoring Program
Hawai‘i Institute of Marine Biology
P.O. Box 1346
Kāne‘ohe, HI 96744
808-236-7440 phone
808-236-7443 fax
email: jokiel@hawaii.edu