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Proceedings 9th International Symposium, Bali, 23-27 October 2000, Vol. 2.

Coral reef monitoring in Tubbataha Reef National , ,

M.C. Ledesma1 and M. Mejia2 ABSTRACT Tubbataha Reef National Marine Park in the Philippines has been a prime research site for scientists and conservationists. Seven permanent transect sites were set to be monitored annually from 1997 to 2000 using video and visual census techniques, although only three of the sites were considered for change through time analysis for benthic cover. From 1997 to 1999, mean live coral cover decreased by 24.9%; this was attributed to the coral bleaching of 1998. However, a 3.3% increase in live coral cover was found from 1999 to 2000 which could indicate recovery. Algal cover significantly increased from 1998 to 1999. Despite the decrease in live coral cover, there was a 530% increase in mean total fish biomass from 1998 to 2000 in the three sites. Although this was not statistically significant when the analysis was extended to include all seven sites, there was a significant increase in mean total fish biomass. The increases in fish biomass and density could be due to the strict enforcement of the Marine Park as a “no take” zone.

Keywords Tubbataha reef, monitoring, Marine Given the critical levels of over-exploitation of many reserves, Fish biomass coral reefs, marine reserves may be the only viable option available to maintain levels of spawning stock biomass Introduction necessary to sustain reef fisheries (Russ et al. 1992). Hence, the goals of our monitoring efforts are to expand Tubbataha Reef lies in the middle of the Sulu Sea and knowledge of the unique ecosystem of Tubbataha and to is one of the last marine frontiers of the region. Because provide technical information that will improve and faci- of its globally significant biodiversity, UNESCO declared litate the management of this Marine Park. it a natural World Heritage Site in December 11, 1993.

The total area of the Park covers 33, 200 hectares Methods including surrounding waters. Tubbataha Reef consists of two coral atolls, separated by an eight-kilometer channel Survey of Benthic Communities (Fig. 1). Seven (100 meter) permanent transects were set The coral reefs of Tubbataha Reef National Marine parallel to the reef crest at an average depth of 10 meters Park have been surveyed since 1982 (White and Arquiza around the two atolls of Tubbataha in 1997 (Fig. 1). 1999). Many different organizations and academic agen- These sites were to be monitored annually from 1997 to cies have visited and collected data in these two remote 2000. However, due to technical difficulties that pre- atolls in the Sulu Sea. Hypothesized to populate neigh- vented the collection of data in some sites (Table 1), only boring reefs with fish and coral larvae due to the three of the sites were considered in the change through prevailing currents in the Sulu Sea (Alcala 1993), Tubba- time analysis. Change in percentage cover of benthic taha Reef is a valuable resource to the country. communities through time was recorded using the video Tubbataha is one of the last few reefs in the Philippines technique, modified from English et al. (1997) except for that is relatively intact and harbors an abundant and 1999 when the benthos point-intercept transect method diverse association of organisms. In one survey alone, was used. A separate benthos point-intercept transect more than 300 coral species and at least 379 species of survey was done in 2000 to compare the results obtained fish were recorded (White and Arquiza 1999). by the two methods. A paired T-test showed that there The Park, despite its remoteness, was still affected by was no significant difference between the two methods illegal fishing practices commonly found all over (T=0.012, P =0.990), therefore data obtained from 1999 Southeast Asia. Tubbataha experienced the highest levels was included in the change through time analysis. Coral of destruction in the 1980’s and by 1989 the reefs were no mortality indices were calculated based on Gomez et al. longer in pristine condition (White and Arquiza 1999). (1994). A one-way ANOVA was used to test for changes The stresses on the reef eased when it was designated as a through time. Data sampling for benthic cover was National Marine Park in 1988 and was closed off to conducted within the summer months of March to May. fishing. However, due to lack of surveillance equipment, illegal fishers still continued to exploit the Park. Fish Visual Census A Tubbataha Management Board Fish populations were surveyed from 1998 to 2000 (TPAMB) was established in July 1999 and as a result, the rules of the Park are now fully and strongly enforced using the visual fish census modified from English et al. by a composite team of Park rangers, using a new radar (1997) in all seven (100 m) permanent transect sites. For system and more chase boats. This has led to many each variety of fish encountered, the numbers and sizes improvements in the Park and has kept illegal fishers out. were estimated. Biomass of fish assemblages were

1 WWF-Philippines, Research Officer, WWF-Philippines, #3 WESCOM Road, City 5300 Philippines, Tel. No. (63 48) 434-2100, 2 WWF-Philippines, 23 Maalindog St., U.P. Village, Diliman, Quezon City 1101 Philippines, [email protected]

calculated based on Kulbicki et al. (1993) and ICLARM Philippines was relatively fair. The bleaching in the Fishbase and was standardized to metric tons per square country was described by Wilkinson et al. (1998) as kilometer. Data on fish density were standardized to moderate and patchy on some reefs in large areas, with a density per square meter. A one-way ANOVA was used mix of coral recovery and approximately 20-50% morta- to test for changes between years. Biomass data was log lity. Other countries recorded as high as a 95% mortality transformed prior to analysis to ensure normality. Data rate (Wilkinson et al. 1998). The bleaching all over the sampling for the fish census was conducted also within world was most pronounced in shallow water (less than the summer months of March to May. 15 m) and particularly affected staghorn and plate Acropora and other fast growing species (Wilkinson et al. Results 1998). Dead but intact Acropora forests were observed in Sites 1 and 5. It was observed that these were Mean live coral cover in the three sites (sites N1, N3 colonized by turf algae upon close inspection. This obser- and S5) decreased by 24.9% from 1997 to 1999. vation could be the after effect of the bleaching event However, there was a recorded 3.3% increase in live coral when algae colonizes over corals unable to recover after cover from 1999 to 2000 (Fig.2). Results from the one- being bleached and an explanation for the significant way ANOVA, however, show that both hard coral and increase in algal assemblage (AA) between 1998 and soft coral did not differ significantly over time. There 1999. There was no significant change in live coral cover were no significant differences in the abiotic component from year to year, nevertheless, there was a recorded and other live benthic components (OT). Algal cover, 24.9% decline from 1997 to 1999. The recorded 3.3% however, significantly increased (F=15.585, P= 0.001) increase in live coral cover from 1999 to 2000 could between 1998 and 1999, and dead coral with algae (DCA) indicate the absence of both natural and anthropogenic (F=23.010, P=0.0001) between 1999 and 2000, thus stresses within the year and could indicate signs of showing an increase in coral mortality from 1998-2000 recovery. (Fig. 2, Table 2). There was a significant increase (F= The coral mortality index was highest in year 2000 4.307, P= 0.030) in the mean total fish biomass in all (Table 2). However, the low coral mortality index in seven sites over the latter three years. Estimated mean 1999 could be an underestimated value; the significant total fish biomass was 63.73, 446.92 and 647.33 metric increase in algae in 1999 could have covered areas of tons per square kilometer (MT/km2) for 1998, 1999 and dead coral which the observer was unable to distinguish, 2000 (Fig.3), respectively. This dramatic increase in fish thus some accounted for algae and not dead coral with stocks represents more than 900% rise since 1998. It was algae (DCA). the presence of large schools of pelagic fish species that accounted significant increase (F= 4.246, P= 0.031) while Fish Visual Census demersal fish species showed no significant changes over Fish Density and Biomass time (Fig. 3). Although mean density of total fish species decreased by 10% from 1999 to 2000, the value for 2000 The mean total density of fish in the seven sites was 36% higher than that recorded for 1998. Pelagic decreased from 1999 to 2000, mainly due to the decrease species, Caesionids, significantly increased in mean in damselfish density. In 1999, 58% of the average fish density from 1998 to 2000 (F=5.091, P=0.018) while density was made up of damselfishes, this lessened to Carangids displayed increasing trends. Some comercially 49% in year 2000. It was noted in 2000 that fish density important demersal fish families such as Lethrinids and was not comprised mainly of the smaller reef such Serranids showed an increase in both mean density and as anthiases and damselfishes compared to the past years. biomass over the study period, however, these were not It was observed that there were greater aggregations of statistically significant (Fig.4). larger fish species, such as more encounters with pelagic For the purpose of comparing the relationship of species. Total fish density in 2000 was still higher than in benthic cover and fish biomass, the mean total fish 1998. In support of this data, according to the Tubbataha biomass for three transect sites used in the survey of report of Sulu Fund and CRMP, average fish density has benthic communities were calculated. The estimated increased by 26% since 1996 (White et al. 2000). mean total fish biomass was 56.98, 128.92 and 302.09 Compared to the past years, there were more larger metric tons per square kilometer (MT/ km2) for 1998, commercially valuable fishes in 2000. This explains the 1999 and 2000 (Fig.3), respectively. This increase was large increase in fish biomass. Important food fish and not statistically significant (F=4.470, P = 0.065), never- pelagic species which accounted for the significant theless, this still represented a 530% increase in total fish increase were present in greater numbers this year biomass. compared to 1999. In 2000 pelagic species made up 77% of the total biomass (501.57 MT/ km2). In 1998 and 1999, Discussion pelagic species made up 16% (12.55 MT/ km2) and 58% (275.01 MT/km2) of the total biomass respectively. Coral Reef Benthic Communities Unlike demersal species, pelagics are not permanent The decline in coral cover was attributed to the residents of a reef, instead, they only visit seaward reef bleaching event caused by the El Nino phenomenon in dropoffs or enter deep lagoons and are adapted to life in 1998. Compared to other countries, the bleaching in the the open ocean (Lieske and Myers 1996). However, the

presence of pelagics in great numbers, being carnivorous constraints. Therefore, more transect surveys at different fish, could indicate the abundance of food resources in the depths, to show different habitats, should be done to give area. Demersal fishes (biomass) on the other hand a fuller view of the status of Tubbataha Reef. The outer decreased by only 5% from 1999 to 2000. However, there reef slope and reef walls could display some resiliency was an increase from 1998 to 1999 by 45%. This could being relatively free from environmental stresses and be explained by the 123% increase in Acanthurid density, minimally affected by bleaching, therefore would display which are herbivorous fishes. Though not statistically a different status than that of the reef crest. significant, this increase could be explained by the significant increase in algae between 1998 to 1999. Des- Conclusion pite of the decrease in total live coral cover from 1997 to The monitoring of Tubbataha’s complex marine 1999, the mean total fish biomass in the three permanent ecosystem found increases in fish populations and transect sites (N1, N3 and S5) from 1998 to 2000 was decrease in live coral cover due to the bleaching event. also increasing but this was not statistically significant. This outcome is promising for the ecosystem’s conser- The significant increase in total fish biomass and vation and is rewarding for conservation organizations increasing trends in density of some commercially impor- that have worked to save this natural World Heritage Site. tant fishes in the seven sites are promising in terms of Tubbataha’s remoteness and relative resiliency to stresses Tubbataha’s recovery. These increases could suggest the compared to other reefs in the country sets its reputation decline in fishing due to the increased enfor- for being the last marine frontier of the Philippines. Other cement in the protection of the Park. It is believed that studies that explore this reef’s importance and con- the increased patrols in Tubbataha have curtailed fishing nectivity to other reefs should be done to further expand inside the park. According to Salm et al. (2000), predatory knowledge to implement the appropriate management of fishes such as groupers, emperors, jacks and snappers are the Park. the first fishes to disappear from heavily fished areas.

Conversely, their presence in increasing numbers supports References the grounds that the decrease in fishing pressure could be one of the main reasons why fish biomass has increased greatly. Alcala AC (1993) Ecological Importance of the Coral Reefs in the Cagayan Ridge, Sulu Sea, Philippines. The resulting increase in biomass that could indicate Siliman Journal, 36 (2): 1-3. the decrease in fishing pressure over the years is starting to pay conservation dividends. Anecdotal evidence from Castro P, Huber ME (1997) . 2nd ed. Wm. C. Brown Publishers. (nearest municipality to Tubbataha) fisher- men seems to bear out that there has been some kind of Dolar LL, Alcala AC (1993) Notes on the Ichthyo- spillover effect. The spillover effect is the adult (post- plankton and Marine Mammals of the Sulu Sea, settlement) movements from reserve to fished areas (Russ Philippines. Siliman Journal, 35 (2): 43-57. and Alcala 1996). The fishermen have observed large fish Kulbicki M, Mou Tham G, Thollot P, Wantiez L (1993) Length- relationships of fish from the lagoon of species coming back into their fishing grounds and a number of them attributed this to the protection of New Caledonia. NAGA, ICLARM Q. 16 (2-3): 26-30. Tubbataha. Lieske E, Myers R (1996) Coral Reef Fishes: Indo-Pacific and Caribbean. Harper Collins Publishers. Due to the prevailing currents in the Sulu Sea, fish larvae may not be retained in Tubbataha reefs until Russ GR, Alcala AC (1996) Do marine reserves export recruitment size, but may be carried away by water adult fish biomass? Evidence from , Cen- tral Philippines. Marine Ecology Progress Series. currents to other reefs (Dolar and Alcala 1993). There- fore Tubbataha could also serve as a source of fish larvae 32:1-9. and other larval recruits (Alcala 1993). Russ GR, Alcala AC, Cabanban AS (1992) Marine Reserves and Fisheries Management on Coral Reefs

Recommendations with Preliminary Modelling of the Effects on Yield per Recruit. Proc 7th Int Coral Reef Symp, 2:978-985. The surveys were conducted on the reef crest and Salm RV, Clark J, Sirila E (2000) Marine and coastal some on the upper reef wall, which only gives a fraction areas. A guide for planners and managers. 3rd ed. overview of the reef. To serve as baseline data to monitor IUCN, Washington DC. change over time, the comprehensiveness of the data White AT, Courtney CA, Meyer MC, Alvarado A, White collected is essential for understanding the reef eco- E, Apurado J, Christie P (2000) Summary Field system. The data collected so far do not give the full Report: Coral Reef Monitoring Expedition to Tubba- view of Tubbataha Reef. The reef crest of an atoll is taha Reef National Marine Park, Sulu Sea, Philip- strongly influenced by wind and waves (Castro and Huber pines, May 21-30, 2000. Coastal Resource Mana- 1997), therefore more exposed to more stresses compared gement Project and the Sulu Fund for Marine Con- to the reef slopes and walls. Bleaching and mortality servation Foundation, Inc., Cebu City. were also more pronounced in waters less than 15 m in White AT, Arquiza YD (1999) Tales from Tubbataha. depth (Wilkinson et al. 1998). Tubbataha is known for its 2nd ed. The Bookmark, Inc. steep slopes and walls that were not surveyed due to time