Biophysical Survey of Mafia Island Marine Reserves

transects. Commercial fish species were looked for during surveys in 33 categories
including specific species and family groups, of these categories, 23 were recorded at
SIMR. High abundances were recorded for Snappers, Trevallys, Parrotfish, and
Sweetlips, although the highest levels were observed for fish such as Goatfish,
Surgeonfish, and Fusiliers. Large numbers of Blue Spot String Rays were seen during
survey dives, and this is in part recorded on the commercial fish data. However, rays are
generally found on the sandy substrate around the edge of the reef and are likely to be
under-recorded as swims were conducted primarily above coral rock substrates. The
diverse benthic community found on the reef at SIMR clearly provides suitable habitat
for a wide range of fish species, and is therefore of high ecological importance.
The seagrass flats at SIMR are extensive, and are similar in composition to those
found at MBIMR, although seem to support slightly lower invertebrate and fish numbers.
Analysis of the data collected on fish abundance on seagrass beds around SIMR
demonstrates the importance of these habitats for commercially important food fish
species, particularly juvenile emperor species.
Sites found to be of particularly conservation importance are:
• The reserve area as a whole provides key habitat for highly threatened and
ecologically important species of shark and turtle. It is therefore recommended that
the entire site should be considered as of high importance. As previously stated,
the island cannot provide a site as a fishermen’s base, and is unsuitable for any
form of tourism other than for day trips. The site is likely to be highly susceptible
to disturbance; damage to one type of habitat or ecosystem or over-fishing of a key
species could have serious repercussions for the reserve as a whole. It is therefore
recommended that the island, its shallow and deep seagrass beds, and surrounding
coral reef should be considered as a single core zone. Complete protection of this
site would provide the necessary refugia for endangered species and provide an
intact source reef which is able to supply recruits to surrounding reefs.