Surveys in the Marshall Islands

Transects

NRAS surveys include recording fish, coral, invertebrate and seaweed data on a series of 4 transects; 2 divers work on each of the four transects that are located at predetermined depths. The transect method was chosen to represent the characteristics of the whole site, over a range of depths (between 5 to 20 m) to give a wide enough coverage on different zones on the reef . Each diver would swim the transect four times, accomplishing different duties at a time.

A 50 m tape measure is used as a marker so the same transect would be covered on return swims from one end of the transect to the other. 20 meters is the maximum depth for the deep transect, allowing enough time for the pair of scuba divers to complete the work without going in to decompression time. On each transect two scuba divers collect the information. Each diver has two jobs, accomplished by two separate transect swims.

"Fish" Surveyor (Diver to pass over site first): ........"Coral" surveyor:
Records large fish ...............................................Lays the 50m tape
Records smaller fish ...........................................Records the corals or substrate every 50cm
Records 4 quadrates of seaweed target genera .....Records the number of target invertebrates
and percentage coverage (at the markers of
10, 20, 30, 40 m on the tape)
Helps buddy roll up the tape measure ...................Reels up the 50m measuring tape

FISH DATA (belt transects). Fish counts are undertaken by one scuba diver, swimming along the 50 m length measuring tape. The fish surveyor swims along the designated depth contour recording fish while the buddy lays the tape measure behind. Fish surveyors record all target fish, within an estimated box of 5 meters, 2.5 m to either side of the tape, 5 m above and 5 m forwards. The target fish are recorded at family and species level. The fish species recorded are estimated into three size classes: A 6-10cm, B 10-20cm, C >20cm. The meandering swimming pattern allows to record the smaller species and the sedentary species.

INVERTEBRATE DATA (belt transects). The invertebrate data are collected by one scuba diver meandering across the 50 m measuring tape looking to a distance of 2.5 m either side of the tape as for fish, counting the target species. The purpose of criss-crossing the transect is to record the smaller species and the sedentary species.

BENTHIC LINE INTERCEPT TRANSECT (LIT). LITs are carried out according to AIMS-ASEAN methodology with minor adjustments (English, 1997). Recorders note all features at two levels, AIMS-ASEAM life-forms and target coral genera or species. The coral data is collected by a diver, swimming along the length of the 50 m measuring tape and recording the substrate below the tape at every 50 cm.

SEAWEED DATA COLLECTION. A quadrat of 25 cm x 25 cm dimension is placed next to the transect at the 10 m, 20 m, 30 m, and 40 m marks. Density or percentage coverage is estimated inside the quadrats and averaged for each depth. Target genera and larger groups are identified. Samples of seaweeds are taken for preservation and cataloguing at the library of the College of the Marshall Islands.

Reference:

English, S. A., C. R. Wilkinson, and V. J. Baker (eds.) 1997. Survey manual for tropical marine resources. Australian Institute of Marine Science, Townsville.

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