Summary of Kisiwa Panza and Kukuu Biodiversity Monitoring

Summary of Kisiwa Panza and Kukuu Biodiversity Monitoring

Biodiversity Survey Methods

Fish Indicator Species

Belt Transect for Fish Identification

Belt Transect for Macro-Invertebrates

• As with the belt transect for fish, a 50x5m transect is placed parallel to the shore, with an individual swimming along the surface counting macro-invertebrates species within the 250m2 area.
• The numbers of each individual observed are noted, with no differentiation by size.
• 6 of these transects are conducted for each site.

• A 50m measuring tape is placed on the seabed parallel to the shore. Recorders leave water for 5 minutes so fish return to area.
• Individual swims along this tape at a slow and steady pace, counting indicator fish species 2.5m either side of the tape, from the seabed to the top of the water column.
• During these observations estimates of fish sizes are made (small <15cm; medium 16-30cm; large 31-61cm; and very large >62cm).
• 6 of these are carried out at each site.

Macro-Invertebrate Indicator Species

Three Examples of the Relationship between Indicator Species

Quadrats for Sea Urchin Surveys

Point Intercept Transect for Substrate Type

Harvesting of triton shell --> increase in crown of thorns --> destruction of hard corals.

• This is used to determine the percentage makeup of substrate types (benthic biota) as an indicator of coral reef health.
• 20 measurements are taken at 1 metre intervals from 0-20m of the belt transect.

• Monitoring and measurements of sea urchins are carried out using quadrats.
• These are 1m2 frames made of PVC plastic pipes, with holes to allow them to sink.
• Depending on time available, 4-8 quadrats are laid within the 50x5m transect
• Sea urchins are recorded as either large/long-spined or small/short-spined.
• This method is repeated until all the quadrats are complete.

Butterflyfish as an indicator of reef health

'Corallivorous [fish that feed on live coral tissue] butterflyfishes have coevolved with, and are intimately related to the corals on which they fed (Reese, 1977, 1981, 1991; Harmelin-Vivien and Bouchon-Navaro, 1983; and Roberts et al., 1988). The distribution and abundance of these fishes should be directly correlated with the distribution and abundance of the corals. If the corals are adversely affected by stressful environmental conditions, such as chronic low levels of pollution, their health will deteriorate. This deterioration should bedetected by the fishes which feed on them.'

Crosby et al., 1996

Sea Urchin Indicators

Overfishing of triggerfish --> increase in sea urchins --> erosion of coral reefs and decline in sea cucumber populations.

• High abundance of sea urchins in reef system indicates reef degradation - tend to thrive when corals are dead.
• Triggerfish, emperor, snapper and wrasse feed on sea urchins, so high population can be seen as a sign of overfishing.
• One smaller species, Echinometra mathaei burrows into coral causing bioerosion.
• Some species feed on algae, helping coral recruits to settle and grow, sometimes feed on sea cucumbers
• One species, Tripneustes gratilla feeds heavily on seagrass and can have significant negative impact in large numbers.

Substrate Type Indicators

Djuwariah, 2009

Kisiwa Panza and Kukuu Results

Ngazi

Kangale

• 29% algae, 27.5% dead coral, only 17% live coral.
• Low fish abundance 23.5 individuals/250m2, almost all were in the small category.
• Low abundance of macro-invertebrates
• Example - low coral cover resulted in an average of 5.8 Butterflyfish within 250m2 area.
• Low fish abundance and high percentage of algae suggests overfishing.

• Live coral higher here (31.7%), but also coral rubble (19.2%) and algae (17.5%).
• Higher fish density than Kangale, particularly fish dependent on live corals such as Butterflyfish (18.7) and Parrotfish (31.7).
• Grouper present in the highest numbers of all sites (important as a top predator).
• More Triggerfish than other sites (link to no sea urchins at site).
• Macro-invertebrates - low densities
• High number of unoccupied octopus dens - link to monitoring on second last day of bamvua.

East of Jombe

South of Jombe

• Only 0.8% live coral (scattered), and 10% dead coral. 32.5% sand, 25.8% algae.
• Low fish densities of all species.
• High number of long- and short-spined sea urchins - overfishing

• Live coral (15%) scattered around the place, 20% seagrass, 26% sand.
• Fishers said area is fish breeding ground - many juvenile fish were seen during observations.
• Low fish density (all were small <15cm)
• High density of sea urchins - indicative of overfishing - high density of seagrass-eating Tripneustes gratilla is a concern due to presence of seagrass and role as shelter for juveniles.

Kukuu

• Very low density of fish indicator species, all individuals were small <15cm
• Only 9% live coral coverage - damaged reef
• Some large healthy patches of coral with high density of juvenile fish.
• Relatively high density of crown of thorns is a slight concern.
• High sea urchin density and low fish density suggest overfishing
• Large patch of hard coral rubble - local fishermen told us coral extraction for limestone takes place.

• Data (sea urchins, algae, fish densities) suggests overfishing is an issue at all sites, Kukuu in particular.
• Low densities of important economic macro-invertebrate species - sea cucumbers, (tiger) cowries, shells and clams.