1.Tagging

Sleeping parrotfish were captured on SCUBA at night in a small purse seine net and then slowly brought to the surface to reduce the likelihood of greatly enlarged swim bladders. Once divers reached the surface, the fish was anaesthetised in a large container and an ultrasonic tag was surgically implanted into the gut cavity. Fish where marked with a t-bar tag for visual identification, given a shot of tetracycline, and then placed in a sea pen where they were kept for 3-10 days in order to recover. Once it was determined that the fish were well, they were released from the sea pen and tracked.

The largest challenge in the tracking work was capturing B. muricatum. We could only capture this fish in the new moon period (when it slept in predicable passage areas and was easily approached due to the absence of the moon), and even when diving at this time, we frequently failed to see any B. muricatum. Sharks eating the wounded B. muricatum also hampered the ultrasonic work and fish held in captivity often developed fin rot that made them unfit to be released. Nevertheless, some fascinating data has emerged from this work and we have developed a unique methodology for tracking this fish, which should be more successful if applied in a less heavily fished area.

Sewing an ultrasonic tag into the gut cavity of an anaesthetised topa (bumphead parrotfish) that was captured while sleeping at night

2. Spearfishing surveys

The fishing pressure placed on B. muricatum and C. undulatus was estimated by recording nighttime spear fishing catches (this species is only taken by nighttime spearfishing). Analysis of 82 nighttimes catches in Roviana lagoon (representing 239 B. muricatum) reveals that this resource is being heavily over fished, with 56% of the catch being juveniles. Comparisons of catch data from Roviana with catch data from the only recently fished areas of the uninhabited island of Tetapare provide a stark and disturbing insight into the impact of night time spearfishing on this species.

Weighing in a habili (Humphead Maori wrasse) that was speared during the day in the Roviana Lagoon

3. Relative abundance surveys

A dive survey of six sites in Roviana Lagoon (two inner, two passage, and two outer reef sites) was conducted from October 2000 to July 2001. This survey consisted of carrying out 500 metre transects twice a month at GPS marked sites. Dives were done around the new moon and full moon of each month. The length and distance along the marked transect was recorded for all B. muricatum and C. undulatus seen 10 meters in either side of the transect. Short-term variation and spatial variation was also estimated throughout this survey.

This survey has revealed some previously unknown aspects of B. muricatum and C. undulatus life history. Most interestingly of all was the discovery of shallow water spatially restricted inner lagoon nursery areas containing high abundances of very small juveniles of both these species. These nursery areas support a high degree of algae cover, which is where very small cryptic species are found.

Richard and Armi diving in an outer-reef in the Vonavona Lagoon

4. Reproduction and Growth

A total of 115 B. muricatum gonad samples were collected throughout this study and preserved in FACC for histology purposes. Although these gonad samples are yet to be analysed, it is clear from macro morphology that this species has Initial Phase (IP) and Terminal Phase (TP) males, with females reaching up to 92cm before changing into TP males. Gonad Weight Indices (GWI) data collected throughout fieldwork shows that females in this species matures at 62cm, spawns throughout the year, and spawning does not appear to be influenced by lunar stages. Further, 22 gonad samples were also collected from C. undulatus specimens. The histology of all these gonad samples will be carried out at Townsville, Australia latter this year.

Also, otoliths from B. muricatum and C. undulatus caught by local fishers were collected throughout fieldwork. Sets of 221 otoliths were collected for B. muricatum specimens ranging between a 35g/110mm juvenile to a 26500/1110mm TP male. Also, 40 sets of otoliths were collected for C. undulatus specimens ranging from a 35g/120mm juvenile to a 23800g/1130mm male. Length-weight curves have been generated from this data and growth curves will be generated once all otoliths are cut and aged.

Extracting otoliths from a habili

5. Interview work

Roviana and Vonavona fishers have a deep awareness of the biological rhythms of their lagoon and the creatures that inhabit its numerous habitats. Fishers can predict the behavior of marine organisms by an inherited body of ecological knowledge and by their own experience with the ecosystems that they exploit. The history of B. muricatum fisheries and past anecdotal abundances of this fish was investigated by interviewing spearfishing experts and elders across the region. Divers were predominantly men in there 40-50's who had extensive diving experience. The result of this work shows a bleak future for B. muricatum in Roviana. Nighttime spearfishing began in the region in the mid 1970's (with the introduction of the underwater flashlights into this area) and it has had a drastic effect on B. muricatum populations. Catch rates are markedly down, many predicable nigh time aggregations no longer occur, and the mean size of caught B. muricatum has decreased significantly. Most disturbing is that some spear fishermen have begun targeting juveniles in new inner lagoon areas in response to greatly reduced catches at traditional outer reef and passage sites.

We are working with local fishers and authorities to ban nighttime spearfishing in selected "no-take""areas and to curtail this activity during the first quarter of the lunar cycle. We are also asssisting local communities to ban all bumphead parrotfish and Maori wrasse fishing during the months of June through October when they are reputed to spawn.

Shankar conducting indigenous knowledge interviews with Roviana informants