TANZANIA MARINE RESEARCH PROGRAMME. Utende, Mafia Island, Tanzania

Transcription

1 TANZANIA MARINE RESEARCH PROGRAMME Utende, Mafia Island, Tanzania TZM Phase 151 Science Report 15 th December th March 2015 (Research Officer) 1

2 Acknowledgements I would like to extend my gratitude to Alison Shafer, Amanda Dennis, Daniel Gill, Lasse Oersted,Jensen and all the volunteers for their assistance in carrying out surveys, data collation and data entry. I am extremely grateful to Lasse Oersted Jensen for the statistical analysis carried out in this report. I would also like to thank Jenna Griffiths for all her guidance and constructive criticism with reviewing this report. I would also like to thank Musa, Rama, and Rozi for all their local knowledge and for welcoming everybody at Frontier Tanzania to their island and making us all feel like locals. A special thanks to Amanda Dennis for all her help with everything logistical, without her tireless efforts this project would be unable to run. 2

3 Abstract Mafia Island Marine Park encompasses an area of extremely high biodiversity and is host to multiple important habitats. However, it also lies of the coast of Tanzania s capital city, resulting in increasing pressures of fishing and tourism. Frontier Tanzania carries out underwater line intercept transects called Baseline Survey Protocols (BSPs) to monitor the habitats in the area, the species they encompass (with particular emphasis on species targeted by fisheries), and the effect the Marine Protected Area (MPA) is having on these ecosystems. Overall, the hypothesised effect of increased biodiversity in areas of increasing protection can be seen in both the invertebrates and the fish when looked at on the macro level. This trend could also be demonstrative of the spill over effect caused by areas of stricter protection. However, due to the increased amount of variables and differing life-history strategies trends become less obvious when not looked at in these macro groupings. Analyses of Millepora and Scleractinia reveals that there is a strong correlation between the two (P=0.0336), suggesting competition for an ecological niche. There was also a strong correlation between invertebrate diversity and percentage cover of Scleractinia (P=0.0004), possibly supporting the hypothesis that benthic heterogeneity will support a higher diversity of species. However, it was not possible to draw definitive conclusions when comparing this to homogenous Millepora habitats as there is a <10% cover of Millepora across all sites in the MIMP. Analyses of invertebrates targeted by fisheries reveals very low numbers of octopus and lobster, however, sea cucumbers numbers (11.6 per hectare) fall within averages found in similar locations. These results may hold management implications for the MIMP. 3

4 Staff Members Name (RH) Daniel Gill (DG) Lasse Oersted Jensen (LO) Allison Shafer (AS) Amanda Dennis (AD) Catie Gutmann Roberts (CGR) Louise Howell (LH) Position Research Officer (RO) Assistant Marine Research Officer (AMRO) Assistant Marine Research Officer (AMRO) Assistant Marine Research Officer (AMRO) Dive Officer (DO) Principal Investigator Outgoing (PI) Dive Officer Outgoing (DO) Volunteers Name Katja van Rennes Oliver Harper Harry Pearce Gould George Hackshall Jordan McGinty Sam Jones Madeline Brach Maryanne Szymanski Jenny King Warren Price Inge Schrijver Suzie Fordce Mike Taylor Harriet Stephenson Basia Hutniczak Programme Marine conservation and diving Adventurer Marine conservation and diving Marine conservation and diving Marine conservation and diving Whale shark and turtle volunteer Whale shark and turtle volunteer Marine conservation and diving Marine conservation and diving Marine conservation and diving Marine conservation and diving Marine conservation and diving Divemaster Internship Marine conservation and diving Marine conservation and diving 4

5 Contents 1. Introduction Training Briefing Sessions Science Lectures Field Work Training Tropical Habitat Management BTEC Research Work Program Survey Areas Survey Methodology Physical Parameters Benthic Composition Invertebrate Assemblages Fish Assemblages Statistical Analysis Method Results Benthic Analyses Invertebrate Analyses Fish Analyses Discussion Benthic Composition Invertebrate Distribution Distribution and Size of Commercially Targeted Fish Limitations Conclusions Proposed work programme for next phase References Appendices

6 1. Introduction Tropical regions contain some of the most highly productive coastal ecosystems on the planet. Coral reefs, seagrass meadows and mangrove forests combine to form areas of abundant biodiversity that form the basis of the marine food webs throughout these regions (Souter & Linden, 2005). Within the Indian Ocean Region, much of the coastal human population depend upon these ecosystems for their livelihoods in some way (Souter & Linden, 2005). The waters around Tanzania contain abundant marine resources of which large portions of the population are reliant upon. The majority of the fisheries use traditional vessels and techniques with majority of fish products going to subsistence use (Öhman, 1999). In Tanzania and East Africa as a whole, fishing is considered to be the largest local threat to coral reefs (McClanahan et al, 2000; Souter & Linden, 2005), resulting from a variety of related impacts e.g. destructive fishing gear, migrant fisherman, dynamite fishing, and excess harvesting (Obura, 2004; Souter & Linden, 2005). Other Anthropogenic threats to these reefs include pollution, coral mining, tourism, shipping, sedimentation from construction and coastal development (Obura et al 2004, Souter & Linden 2005). In addition, between East Africa coral reefs were severely impacted by the El Nino Southern Oscillation with some reefs in Northern Tanzania bleaching to 80% or greater (Obura et al 2004, Riegl, 2002). With these threats in mind, Mafia Island Marine Park (MIMP) was established in 1995 and declared as Tanzania s first marine protected area (MPA). The MIMP falls within the Mafia Island administrative district, 20 km offshore of the Rufiji Delta, one of Africa s largest delta systems and 120 km from the capital of Tanzania, Dar es Salaam (Mwaipopo, 2008; MPRU, 2011). The district comprises of an archipelago, Mafia Island the largest and most populous and several smaller islands, some of which are uninhabited and used by fishermen as temporary camps (Mwaipopo, 2008). Whilst less developed than the neighbouring Zanzibar and Pemba Islands, Mafia Island is showing a steady increase in tourism with a 665% increase between 2000 and 2006 (Holberg, 2008). Marine protected areas (MPAs) are increasingly considered to be effective an instrument to preserve habitat and vagile fauna from the damaging effects of overfishing particularly in coastal regions (Claudet et al, 2006; Sanchirico, 2002). MPAs have been shown to increase biomass of exploited species that in turn leads to spill over into surrounding nonprotected areas (Goni et al, 2008). In Tanzania studies have shown that density of fish in MPAs is significantly higher than the surrounding unprotected areas (Souter & Linden, 2005). One of the main limiting factors to the success of these MPAs in developing countries is the level of local acceptance and involvement, especially when fishing areas are closed and there is difficulty in demonstrating the spill over effect (Obura et al 2004). In Tanzania there is a larger component of local implementation and co-management of MPAs, with successes on the local level of enforcing laws against dynamite fishing and boosting ecotourism (Obura et al 2004). There is also an increasing number of coral reef research and management organisations in East Africa as a whole, with increasing numbers of studies on the socio-economics of coral reefs, and programs to improve the management of MPAs in the region (Obura et al, 2004; Sanchirico, 2002). The Mafia Island Marine Park covers approximately 822 km 2 and contains a diverse range of tropic habitats including coral reefs, seagrass beds, mangroves, and a threatened remnant lowland coastal forest (MPRU, 2011). The Marine Park is host to a very high marine biodiversity, with 273 coral species from 63 genera and 15 families, and 394 fish species from 56 families (Garpe & Ohman, 2003; Obura, 2004). The area is also host to an abundance of marine invertebrates, although due to the specialist knowledge needed to study many of these organisms, little or no research has been done (MPRU, 2011; Richmond, 2001). The Marine Park also contains small but significant breeding grounds for Hawksbill Eretmochelys imbricata and Green Chelonia mydas turtles and provides feeding grounds for several more turtle species and dugongs, which were once thought to be extinct in the area (MPRU, 2011; Muir 2005). The marine park is divided into three types of use-zones; Core, Specified-use and General-use (see Figure 1)(MPRU, 2011). As approximately people live within the Marine Park boundaries, the zonation was created to spatially separate local resource use areas from conservation significant habitats (MPRU, 2011). The three types of zones 6

7 provide different levels of protection; the Core zone gives the highest level of protection with extractive use prohibited, however, some controlled tourism and scientific research are permitted; the Specified-use zone has an intermediate level of protection with residents of the marine park able to utilize some of the marine resources (fishing, seaweed harvesting etc); the General-use zone is able to be used by residents and non-residents for sustainable extractive use, however, non-residents must have permission from MIMP and where relevant from village councils. The General-use zone is intended to relieve pressure from the areas of higher protection (Holberg, 2008; MPRU, 2011). Figure 1: Management zonation of the MIMP (figure courtesy of MPRU, 2011). Only a limited number of studies have quantified reef fish assemblages, and the structure of coral reefs in Tanzania (Bergman & Ohman, 2001; Garpe & Ohman, 2003; Obura, 2004) or the relationship between macro invertebrates and reef structure in an MPA (Alexander et al, 2009). In addition, seagrass monitoring has by and large been neglected in coral reef monitoring programs (Obura et al, 2004). Most marine research undertaken in Tanzania and the Mafia Island region has focused on fisheries and how they can be developed further, with very few focusing on other aspects (Narriman et al, 2001). However, within Tanzania efforts are expanding to develop coral reef and fisheries monitoring programs that contribute to assessments of coral reef condition (Obura et al, 2004). The Mafia Island Marine Parks Authority has highlighted the need to carry out regular monitoring of indicators of biodiversity and critical habitat condition, as there are significant gaps in the technical knowledge of biodiversity of the area (MPRU, 2011). However, no monitoring is currently being done by the Marine Park Authority, resulting in management actions that 7

8 are not science-driven but solely based on guesswork alone (Machumu, 2015). Due to the limited resources of the MIMP, a collaboration was established between Frontier and the Marine Parks and Reserves Unit to conduct a five year research programme within Chole Bay. The objectives of this collaboration are, but not limited to: 1. Collection of baseline biodiversity data on coral reefs 2. Collection of baseline mangrove survey data and mapping of habitats 3. Collection of baseline seagrass bed data and mapping of habitats 4. Comparison of biodiversity in different use zones 5. Collection of socio-economic survey data on fisheries areas and fishing methods 6. Collection of socio-economic survey data on mangrove harvesting, forest logging and coral mining 7. Collection of socio-economic level data, including poverty, access to health care, education and impact of tourism 8. Collection of socio-economic data on community relations 9. Feasibility studies of potential aquaculture projects 10. Development of a management plan and risk assessment report for the MIMP, based on evaluation of datasets. Frontier has been conducting Baseline Surveys of the local marine environment within Chole Bay for the last five years. The data collected has been instrumental in monitoring the health of the coral reef, mangrove, and seagrass ecosystems within Chole Bay and the assemblages they encompass. This data is further utilised to monitor fisheries in the area with the hypothesis that long-term data sets will demonstrate the spill over effects found in MPAs around the world with similar artisanal fisheries (Claudet et al, 2006; Goni et al, 2008; Lester et al, 2009). It is also hypothesised that protected areas in Chole Bay will exhibit higher levels of biodiversity, particularly in areas with maximum protection. It is further hypothesised that areas of increased habitat heterogeneity will exhibit higher levels of biodiversity than homogenous ones. Whilst MPA benefits are often difficult to demonstrate empirically due to site specificity and lack of management and baseline data replication (Goni et al, 2008), the Frontier project on Mafia Island has the distinct advantage of ongoing data collection using consistent methodology over long periods of time. 2. Training 2.1 Briefing sessions All Research Assistants (RAs) received several introductory lectures upon arrival and were tested on their knowledge of these lectures. Introductory lectures encompassed topics such as health and safety, hazards of the local environment, medical briefing, TZM project aims and objectives, camp life and duties. Table 1. Introductory lectures conducted during phase 151. Introductory Lectures Presenters Health and safety Medical Introduction to TZM Hazards of the Reef 8 RH, AD RH, AD RH, AD RH, AD

9 2.2 Science lectures The Research Assistants (RAs) were trained in the identification of marine invertebrates and fish to the family and species levels (identification level is largely dependent upon the degree to which the species is targeted by local fisheries or whether the species is a useful indicator of reef health). RAs are also trained in identification of benthic composition, however, knowledge of morphology rather than taxonomy is imparted to ensure high data accuracy due to the difficulty of taxonomic identification for non-specialist surveyors. All lectures are given by staff members who have knowledge of the local marine ecology and who are also experienced in species identification in the field. In addition to the core lectures, supplementary lectures are given to increase the RA s knowledge of marine ecology, threats, and conservation, with a focus on the Mafia Island region. Table 2. Science lectures conducted during phase 151. Core Science Lectures Commercial Territorial Fish Commercial Schooling Fish Surveying and Monitoring Methods Benthic composition Invertebrate Identification Angelfish Identification Surgeonfish Identification Butterflyfish Identification Extra Science Lectures Fish morphology and ecology Mangroves Seagrass Marine Protected Areas Fisheries of Mafia Island Turtle Conservation Whaleshark Biology Importance of Coral Reefs Presenters RH, AD, AS, DG RH, AD, AS RH, AD, AS RH, AD, AS, DG RH, AD, AS RH, AS RH, AS RH, AS RH, AS RH, AS RH, AS RH, AS RH, AS RH, AS RH, AS RH, AS 2.3 Field Work Training All training for fieldwork was provided by PowerPoint presentations and practical sessions directly in the field. The current phase (151) continued to use the list of species and families from the previous phase (144), this list has been adapted from the Commercial Fish Species List used by the MIMP s long-term monitoring program. This monitoring program looks at the commercial fish species that are caught by the islands local fishing communities and therefore serve as indicators for reef health and overfishing. In the lectures given to the RAs, all the species and families of fish required for the surveys are split into either territorial or schooling to assist memorisation and recognition in the field. After relevant core lectures are completed, tests are given using a PowerPoint presentation. Before an RA can take part in surveying they must pass the test with 95% or above and all staff members require a 100% pass mark. If the pass mark isn t achieved the RA is given time for more private study and attends practical underwater identification sessions, they are then re-tested until a score of 95% or higher is attained. RAs must also pass a fish size estimation 9

10 test with a 95% pass mark for 15 sizes of fish. This was carried out by accurately estimating (to within 5cm) the size of suspended plastic fish whilst snorkelling. After passing identification and size estimation tests the RAs are closely monitored during underwater sessions to ensure consistency in surveying skills and accuracy of their data. 2.4 Tropical Habitat Management BTEC BTEC s completed this phase: George Hackshall Goatfish distribution (4 weeks) Katja van Rennes Seagrass and fish species (10 weeks) Jenny King Invertebrates and Fire coral (4 weeks) 3. Research Work Programme 3.1 Survey Areas All marine surveys currently undertaken by Frontier are situated at a number of sites (see Table 3) within the Core, Specified, and General Use Zones of Chole Bay (see Table 4). The Bay itself contains several important marine habitats such as coral reefs, seagrass beds, and mangrove forests and is bathymetrically complex with an average depth of 20 metres below mean tide levels. The bay is connected to the ocean through Kinasi Pass and Chole Pass and has strong currents (up to 4.5 knots) and a high tidal range (up to 4 metres). Figure 2. Satellite image of Chole Bay showing locations of survey sites. Core zone is shown in yellow and Specified Use Zones in red, General Use Zone is any area found outside these polygons (Google Earth, 2015). 10

11 Table 3. Surveys sites. Site Location Depth (metres) Description Milimani North GPS: S E Milimani South GPS: S E Chole Reef GPS: S E Utumbei Deep GPS: S E Usumbiji GPS: S 075 E 039 Small Rock GPS: S E m Located several hundred metres west of Kinasi Pass and facing inwards from the mouth of the bay, this area of fringing reef is surrounded by sand and seagrass beds m A fringing reef that lies to the west of Kinasi Pass and borders the channel running from the mouth of the bay inwards. Runs perpendicular to Chole Reef m Steep shelving wall falling away to a deep-water channel filled with sandy rubble that is exposed to fast currents m Continuation of Kinasi Pass leading into Milimani South. Steep sloping channels. Straddles border of Core and Specified zones. TZM currently using as a Core Zone survey site due to inaccessibility of other sites m Located next to the marker buoy for edge of Specified Use zone. Patchy reef with some large rock pinnacles m Small limestone island surrounded by reef that creates a wall dive. Westerly side shallow, Easterly side deep. Table 4. Number of surveys at each site and their designations Site Designation Deep Shallow Milimani North Specified 5 4 Milimani South Specified 7 3 Chole Reef Specified 6 5 Utumbe Deep Core/ Specified 4 2 Usumbiji General Use 6 6 Small Rock Core Survey methodology The Baseline Survey Protocol (BSP) method of surveying was used for all surveys. This method allows surveyors to gather concurrent data on physical parameters, benthic composition, invertebrate and fish assemblages. The BSPs are conducted by a team of three to five surveyors using Self-Contained Underwater Breathing Apparatus (SCUBA). Each survey is 80 metres long consisting of three 20m transects with a 10m break between each (i.e. 0-20, and 60-80m). As reef community assemblages have been shown to vary in association to reef depth, zones, and the biotic and 11

12 physical structure of their habitat, often with predictable spatial distribution (Garpe & Ohman, 2003), BSP s were classified as either deep or shallow dependant upon the depth of the survey site (Table 2). BSPs are categorised as Deep (deeper than 8 metres) or Shallow (shallower than 8 metres). During the survey, transects were kept as close as possible to a constant depth dependent upon the contours of the reef. All surveys were completed with five surveyors unless volunteer numbers were low. Surveys were able to be completed with a minimum of three surveyors. These were carried out by surveying Physical, Schooling fish, and Territorial fish parameters on the outward transects and Invertebrate, Benthic, and Physical parameters on the return transects. Surveys were aborted if there was an increase in the sea state, strength of current or if the tank pressure of a surveyor reached 70 BAR Physical parameters The Physical surveyor notes the date, survey site, number of fishing vessels in the area, Beaufort sea state (0-8), cloud cover (0-8), and ambient air temperature ( C). After descending to the survey site the start time, the maximum depth (metres), the visibility (estimated in metres), and the water temperature ( C) are recorded. The measuring tape is then secured and reeled out by the Physical surveyor, who follows closely behind the Schooling fish surveyor Benthic composition The Benthic surveyor moves along the tape measure recording all benthic structure (see Appendix 2) changes below the line which are recorded to the nearest cm. Due to the non-specialist nature of the volunteer surveyors, morphology rather than taxonomy is focused upon. This allows investigation into the structure of the reef system without the need for specialist knowledge below the morphological level Invertebrate assemblages The Invertebrate surveyor follows closely behind the Benthic surveyor, moving along the transect line in a zigzag motion surveying 2.5 metres either side (see Figure 3) and thoroughly investigates all crevices for cryptic species. Figure 3. Invertebrate surveying technique. 12

13 3.2.4 Fish assemblages The fish surveying is divided into two parts, Schooling and Territorial. The Schooling surveyor is the first to survey to minimise disturbance to fish by other surveyors. They are followed closely by the Physical surveyor who reels out the transect line. The Schooling surveyor records all predetermined species (see Appendix 1) that are Generally found within groups in the area. The Territorial fish surveyor waits approximately five minutes to begin surveying to allow disturbed Territorial species (see Appendix 1) to return to the area. Both fish surveyors surveyed 2.5 metres either side of and five metres above the transect to create a 25 metre squared box (see Image 4). Fish surveyors recorded both numbers of fish seen and also an estimation of the size of fish seen, using predetermined size categories (0 10 cm, cm, cm cm and 71cm +). Figure 4. BSP procedure for a 20m transect. Fish seen in the 25m 2 box are recorded by the surveyor. 3.3 Statistical Analysis Method All fish species surveyed were analysed in this report, however, commercially targeted fish species and families that were abundant were focused upon. Fish families were analysed by looking at the number of individuals surveyed vs. location. Only the most abundant fish species of each family were analysed by looking at the size of fish vs. location. Fire coral cover was analysed using mean percentage cover vs. location, zone, and percentage of hard coral cover. Shannon-weaver index vs. location was to analyse benthic diversity, invertebrate diversity, and fish diversity (families and species combined). Invertebrate diversity was also compared to hard coral and fire coral cover. All statistical analysis was performed in R, an open-source language for statistical computing (R Core Team, 2014). All ANOVAs are considered significant on a 5% level. In all graphs, the sites surveyed that are found in: the Core zone are coloured in red; the Specified zone are coloured in green; and the General zone are coloured in blue. 13

14 3.4 Results Benthic Analysis Figure 5. Benthic diversity across the; a) Core, Specified, and General zones, b) Survey sites. The highest Benthic diversity was found in the General zone and the lowest diversity was found in the Specified zone (fig. 5), but there was no significant difference between the zones (ANOVA; F = 0.337, P = 0.716).The highest benthic diversity was found at Milimani North and the lowest benthic diversity was found at Chole Reef, however, the difference between the sites was not found to be statistically significant (ANOVA; F = 1.338, P = 0.263). Figure 6a and 6b: Fire coral cover across; a) Core, Specified, and General zones; b) survey sites. The highest Fire coral cover was found to be in the Specified zone whilst the lowest was found to be in the General zone. Fire coral cover was found to be significantly different between survey sites (ANOVA; F = 9.782, P < 0.001) with the most surveyed at Utembe Deep and the least at Small Rock (fig. 6b). 14

15 Figure 7. Percentage cover of hard coral compared to percentage cover of fire coral. When data was analysed combining all survey sites, the density of fire coral cover was found to be negatively correlated with hard coral cover and this correlation was found to be statistically significant (R 2 = , P= )(Fig. 7) Invertebrate Analysis Figure 8a and 8b: Invertebrate Shannon diversity across; a) Core, Specified, and General zones; b) survey sites. Invertebrate diversity was found to be highest in the Core zone and lowest in the General zone (fig. 8a), however, was not found to be significantly different (ANOVA; F = 1.007, P = 0.372). Utembe Deep had the highest invertebrate diversity and Milimani South had the lowest (fig 8b). 15

16 Figure 9: Invertebrate Shannon diversity compared to percentage of hard coral cover. When data was analysed combining all survey sites, the percentage cover of hard corals was found to be strongly positively correlated with the diversity of invertebrates and this correlation was found to be statistically significant (R 2 =0.1924, P=0.0004)(Fig. 9). Figure 10: Invertebrate Shannon diversity and percentage cover of fire coral. When data was analysed combining all survey sites, the percentage cover of fire coral was found to be weakly negatively correlated with the Shannon diversity of invertebrates, this correlation was not found to be statistically significant (R 2 =0.007, P=0.441)(Fig. 10). 16

17 Table 5. Numbers of heavily targeted macro invertebrates surveyed during Phases Species Abundance Abundance Mean number of Approximate between Phase between Phase 144 individuals per number of 141 and 143 and 151 (23/9/14 survey for Phase individuals per (6/1/14 and and 16/4/14) 141 to 151 hectare 22/9/14) Octopus Lobster Sea Cucumber Tiger Cowrie N/A Table 5 shows the abundance of the main macro invertebrates targeted by local fishers across phases 141 to 143 (9 months) and phases 144 to 151 (6 months). It also presents the mean number of individuals surveyed per survey and the approximate numbers of individuals per hectare Fish Analysis Figure 11a and 11b: Fish diversity of species and families combined across; a) Core, Specified, and General zones; b) survey sites. The Shannon diversity of fish surveyed with species and families combined was found to be highest in the Core zone and lowest in the General zone (fig. 11a), however, this was not found to be statistically significant (ANOVA; F = 1.042, P = 0.36). Of the sites surveyed, Small Rock was found to have the highest fish diversity and Usumbiji the lowest (fig. 11b), however, when all survey sites were analysed this was not found to be statistically significant (ANOVA; F = 0.772, P = 0.574). 17

18 Figure 12a, b, c, and d: Variations in distribution and size of selected commercially targeted territorial fish in the Core, Specified, and General zones. a) and c) numbers of fish surveyed in each zone at the family level. b) and d) size distributions across the zones of the most abundant territorial species surveyed. Figures 12a and 12c show numbers of territorial fish surveyed that are highly targeted by fisheries, at the family level. Groupers were found to be more abundant in the Core zone and showed the lowest abundance in the General, however the difference between the zones was not found to be significant (ANOVA; F = 0.047, P = 0.954). The Peacock grouper was the most often surveyed of the grouper family. The largest Peacock groupers surveyed were found in the Core and Specified zones with the smallest fish being surveyed in the General zone (fig. 12b), however this was not found to be significant (ANOVA; F = 0.837, P = 0.438). The highest number of Sweetlips surveyed were found in the Core zone with the lowest number surveyed in the Specified zone (fig. 12c); the difference between the number of fish surveyed in the different zones was not found to be significant (ANOVA; F = 1.105, P = 0.339). Blackspot Sweetlips were the most often surveyed of the Sweetlips family. The largest Blackspot Sweetlips were found in the General zone with the smallest found in the Specified zone (fig. 12d), however the difference between the zones was not found to be significant (ANOVA; F = 1.078, P = 0.347). Figure 13a, b, c, d, and e: Variations in distribution and size of selected commercially targeted schooling fish in the Core, Specified, and General zones. a) and d) numbers of fish surveyed in each zone at the family level. b), c), and d) size distributions across the zones of the most abundant schooling species surveyed. 18

19 Figures 13a and 13d show numbers of schooling fish surveyed that are highly targeted by fisheries, at the family level. Emperors were found to be more abundant in the Core zone and showed the lowest abundance in the General, however the difference between the zones was not found to be significant (ANOVA; F = 1.004, P = 0.373). The most often surveyed Emperor species surveyed were the Big Eye Emperor and the Yellowspot Emperor (fig. 13b and 13c). The Big Eye Emperors were found to be largest in the Specified zone and smallest in the Core zone (fig 13b), however the difference between the zones was not found to be significant (ANOVA; F = 1.452, P = 0.243). The Yellowspot Emperors were found to be largest in the Specified zone and smallest in the General zone (fig 13c), however the difference between the zones was not found to be significant. The highest number of Snappers surveyed were found within the General zone with the lowest number surveyed in the Specified zone (fig. 13d); however the difference between the zones was not found to be significant (ANOVA; F = 0.994, P = 0.377). Blackspot Snapper were the most often surveyed of the Snapper family. The largest Blackspot Snapper were found in the Core zone with the smallest found in the General zone (fig. 13e), however the difference between the zones was not found to be significant (ANOVA; F = 1.133, P = 0.33). Figure 14a, b, c, and d: Variations in distribution and size of selected commercially targeted schooling fish in the Core, Specified, and General zones. a) and c) numbers of fish surveyed in each zone at the family level. b) and d) size distributions across the zones of selected commonly surveyed schooling families. Figures 14a and 14c show numbers of schooling fish surveyed that are highly targeted by fisheries, at the family level. The numbers of Trevally surveyed were highest in the Core zone and lowest in the Specified zone (fig. 14a); however the difference between the zones was not found to be significant (ANOVA; F = 0.57, P = 0.569). The size of the Trevally surveyed were found to be largest in the Specified zone and smallest in the Core zone (fig. 14b), however the difference between the zones was not found to be significant (ANOVA; F= 1.274, P= 0.299). The numbers of Fusiliers surveyed were highest in the Specified zone and lowest in the General zone (fig. 14c), however the difference between the zones was not found to be significant (ANOVA; F = 1.061, P = 0.353). The size of the fusiliers surveyed was found to be highest in the Core zone and lowest in the General zone (fig. 14d), this was found to be highly significant (ANOVA; F = 20.49, P < 0.001). 19

20 Figure 15a and 15b: Variations in fish diversity across the Core, Specified, and General zones a) schooling fish b) territorial fish. Figure 15a and 15b show variations in the Shannon diversity of fish across the Core, Specified, and General zones a) schooling fish b) territorial fish. Schooling fish Shannon diversity was found to be highest in the Core zone and lowest in the General zone (fig. 15a), however the difference between the zones was not found to be significant (ANOVA; F = 0.651, P = 0.526). Territorial fish Shannon diversity was found to be highest in the Core zone and lowest in the General zone (fig. 15b), however the difference between the zones was not found to be significant (ANOVA; F = 1.703, P = 0.192). 3.5 Discussion Benthic composition Diversity of benthic substratum and topographical complexity is widely recognised as supporting higher fish abundance and species richness (Pittman & Brown, 2011; Garpe & Ohman, 2003). Within the MIMP Benthic diversity was found to be highest in the General zone and lowest in the Specified zone, however, caution should be used when using diversity of benthic substratum as an indictor of reef health as the benthic data encompasses a variety of substrates such as dead coral, sand, bleached coral, and firecoral Millepora.. Millepora cover was found to be highest in the Specified and lowest in the General zone. The low rate of Millepora in the General zone may be a result of the single site surveyed, this site may not be a representative sample of the whole zone and additional survey sites should be explored to determine this. It was also found that there was a significant statistical difference across the sites surveyed with the lowest abundance of Millepora found at Small Rock and the highest seen at Utembe Deep. This was seen to be unusual as both sites are found in the Core zone, however, Utembe Deep has a high amount of anchor damage at the top of the wall where dive operators anchor. The amount of Millepora found at Utembe Deep may be due to the ability of Millepores to recover faster then Scleractinia from severe disturbances, due to a short colony life and the ready regeneration of corolla fragments (Lewis, 2006). Figure 7 may also be representative of Millepores ability to recover faster then Scleractinia with the percentage cover of Millepores increasing as the percentage cover of Scleractinia decreases. This figure may also demonstrate the 20

21 competition between Scleractinia and Millepores for suitable substratum to settle and grow. This competition has been noted by several authors (Chornesky, 1991; Lewis, 2006; Wahle, 1980) with cases of Millepores effectively destroying Scleractinia and vice versa. Although there are many ecological and morphological similarities between the Millepora and Scleractinia, Millepores are also generally able to escape predation to a greater degree than Scleractinia, due to their small polyp size and powerful nematocysts (Lewis, 2006). Globally the whole reef cover of Millepora is usually <10% of the substratum, however, exceptions include upto 36% in parts of the Red Sea and upto 48% in Florida (Lewis, 2006). Within the MIMP the mean percentage cover of Millepora is <10% in all zones and at all sites surveyed Invertebrate distribution Very little is known about invertebrate species and their distribution within the Western Indian Ocean (Richmond, 2001). Nevertheless, there is a growing body of literature demonstrating the effects of MPAs on invertebrate populations (Alexander et al, 2009; Lester et al, 2009; Mayfield et al, 2005; Shears & Babcock, 2003). Within the MIMP invertebrate distribution was found to be highest in the Core zone and lowest in the General zone although statistically this was not seen to be significant, this distribution pattern is primarily due to the distribution of invertebrates not targeted by local fishers. Macro invertebrates commonly targeted by local fishers such as lobster and octopus (MPRU, 2011; Mwaipopo, 2008), were surveyed in very low numbers (lobster, n=2; octopus, n=3), therefore it was not possible to draw and decisive conclusions about their distribution. These low numbers may be a result of habitat preference outside the sites surveyed, for example, near intertidal areas for octopus, however, it is highly likely that these numbers are a result of overexploitation of these organisms. Overexploitation and illegal fishing of commercially important macro invertebrates in Tanzanian waters has been reported by numerous authors (Marshall et al, 1999; Mohammed et al 1999; Muhando & Mohammed, 2002; Obura et al, 2000) with notable declines in landings throughout the region, neighbouring Zanzibar saw landings of lobster drop from 450 mt in the early 1990s to 55 mt in 1996 (Marshall et al, 1999). It is also unlikely that these low numbers are a result of seasonal fluctuation as traders claim that fishing continues all year (Marshall et al, 1999). Results from surveys conducted by Frontier over the previous nine months confirm this with numbers low year round (lobster, n=9; octopus, n=1). Historically, Mafia Island was home to three octopus and lobster processing facilities but since the collapse of these fisheries two have closed down completely and the third now only processes prawns (Jiddawi & Öhman, 2002; MPRU, 2011). Lester et al (2009) notes that reserves with little to no enforcement and high levels of poaching will show little responses to protection. However, despite the low numbers of surveyed, with increased protection these numbers should rebound with studies showing that lobster in particular make ideal candidates for reserve protection with high growth rates and dispersal (Lester et al, 2009). Sea cucumber fishing is banned in MIMP, although some fishers still harvest it illegally and export its products through Zanzibar and Dar es Salaam (MPRU, 2011). However, no sea cucumber products are eaten locally with all animals caught being exported to the Asian market (Marshall et al, 1999). The average density of sea cucumbers surveyed within Chole Bay was found to be 11.6 individuals per hectare (Table 5), which falls between the range of individuals per hectare found in the Torres Strait, Papua New Guinea, New Caledonia and Tonga (Bruckner et al, 2003). Due to the lack of knowledge of invertebrate densities in the Western Indian Ocean (Richmond, 2001) it may prove difficult to determine if the current densities fall within the range of the virgin biomass of the area, however, analysis of any available historical data needs to be carried out. This, coupled with further monitoring of these populations is needed to determine if there is a localised recovery due to the ban on harvesting. However, studies have shown that sea cucumber populations may take up to 50 years without exploitation to recover to previous virgin biomass (Bruckner et al, 2003). Tiger cowries Cypraea tigris are targeted for the marine curios trade due to their desirable shell (Lovell, 1999), despite a ban on collection of this species within the Marine Park, 250 kg of illegally collected cowries were seized in 2006 (Mwaipopo, 2008). However, the collapse of the marine curio trade in Tanzania has largely protected these organisms 21

22 from unsustainable demands (Jiddawi and Öhman, 2002). Prior to Phase 144 C. tigris were not surveyed but continued monitoring will be carried out in further Phases to ascertain whether populations within Chole Bay remain stable. Invertebrate diversity within the MIMP was found to be strongly correlated with the percentage cover of hard corals (fig. 9). Alexander et al (2009) and Garcia et al (2008) have noted that it is not necessarily the coral that causes this correlation but the reef structure itself, with a heterogeneous habitat able to support a more diverse range of lifehistory strategies than a homogenous one. Invertebrate diversity was not found to be significantly influenced by fire coral cover (fig. 10), this may be related to the relatively low cover (<10%) of fire coral at most sites. Whilst Millepora and Scleractinia share many ecological and morphological similarities, it appears that Millepores are less susceptible (than hermatypic corals) to predation and grazing from both invertebrates and vertebrates, with even the Crown of Thorns starfish Acanthaster planci avoiding it (Lewis, 2006). Studies to date have found that spatial distribution of coral reef associated invertebrates are highly species specific (Dumas et al, 2006). These species/habitat distributions are influenced by biological and behavioural processes, e.g. mobile or sedentary, as well as diverse environmental factors e.g. water flow rate, substrate etc. (Dumas et al, 2006) This diverse range of influencing factors make analyses of distribution difficult when looking at such a high taxonomic level and more significant results may be found when looking at the genus or species level, however, due to time constraints this analysis were unable to be carried out in this report Distribution and size of commercially targeted fish Fish distribution was looked at in a number of ways; firstly fish distribution as a whole was looked at across the Core, Specified, and General zones, Secondly the fish surveyed were divided into Territorial and Schooling and analysed using the various zones, thirdly the most frequently surveyed families within Territorial and Schooling were analysed using the various zones, fourthly the most frequently surveyed species within these families were then further analysed using zone and the size of the fish within these zones. As catches of fish in the area are dominated by catches of reef-associated species such as emperors, snappers, and a smaller number of trevallys and jacks (MPRU, 2011), these were the fish families that were focused upon in this report. When looking at the fish surveyed as a whole, the highest abundance was found in the Core zone and the lowest in the General zone. High Territorial fish abundance was also found in the Core zone and the lowest occurred in the General, and at the family level, Groupers and Sweetlips were found in highest abundance in the Core zone. This trend may be the result of the site specificity of Territorial species when looked at as a whole and the vulnerability to over exploitation of species with small home ranges (Taylor et al, 2012). Therefore these territorial species residing within the Core zone would remain relatively unexploited. However, the two most commonly surveyed Territorial species did not fit this trend. Schooling fish abundances were found to be similar in the Core and Specified zones and lowest in the General, however, this only occurs when the group is analysed as a whole with high variation in size and abundance of fish at the family or species level. The overall trend of a higher abundance of fish in the Core zone and lower in the General zone when analysed on the macro level may be explained by the increased areas of protection resulting in increased abundance which may inturn result in the spill over effect of the MPA, however, once analysed on the species level no trend occurs. Lester et al (2009) observes that responses to MPAs will vary greatly depending upon which taxonomic level is focused upon. In all the fish data analysed in this report only the size of Fusiliers was found to be significant with all other data showing a lack of statistical significance, this lack of significance maybe explained by the high vagility many of teleosts. One other possible explanation for these results may come from the way the fish surveyed were grouped, with the groupings of Schooling and Territorial not specific enough to encompass the variety of life history strategies. In a study on the fish assemblages of MIMP, Garpe & Ohman 2003 found that up to 93% of variation in species numbers, total abundance and taxon-specific abundance could be explained with measurable habitat variables alone. It therefore may not be appropriate to statistically analyse the fish assemblages surveyed by grouping them into Schooling and Territorial. Whilst these categories are useful for 22

23 memorisation by volunteer surveyors, they are not appropriate for statistical analyses because they encompass a variety of species with significant variation in life-history strategies. A more appropriate method for analyses would be to group surveyed species according to family i.e. Lutjanidae, Haemulidae or according to life-history strategy i.e. piscivore, coralivore etc. It can be seen from the results that, although there is a trend from higher overall diversity in the Core zone to lower in the General zone, on the species level no trend is apparent. The species level decrease in trend is possibly the result of variation in life-history strategies and benthic topographical site specificity. For example, whilst Haemulidae were surveyed and analysed as a Territorial species, they in fact exhibit ontogenetic habitat shift (Jorden et al, 2012), which may result in habitat use across all zones. Studies have also shown that reserves will not result in substantial increases in all species (Lester, 2009). These life history strategies must therefore be taken into account when analysing these species in all encompassing groups. The existence of geographical and topological specificity may also be related to life-history strategies, such as a habitat generalist that is capable of utilising multiple habitat types and geomorphological zones or a habitat specialist that is dependent on a single habitat type (Pittman & Brown, 2011). Pittman and Brown (2011) found that different species showed individualistic responses to different predictors such as topological complexity with this pattern indicative of ecological zonation. Such predictors included distance to reef shelves and beaches, habitat structure, substrate composition, and structural complexity (Pittman & Brown, 2011; Garpe & Ohman 2003). Whilst analyses for this report focused on difference among the marine park zones and survey sites, it would be of great value to analyse the fish diversity and abundance and relate it to the topography (not just benthic composition) of each site as this may result in management implications for the marine park. However, due to time constraints, analyses of the site specificity of individual species were not able to be carried out in this phase but will be carried out next phase Limitations Due to logistical issues only 14 surveys were able to be carried out in Phase 151, therefore data for this report was compiled with data from Phase 144 to give a larger data set (59 surveys in total). This not only gave a larger data set but also gave the advantage of a longer time period over which the data was collected which may encompass seasonal changes not usually seen in the Phase cycle (3 monthly) used by Frontier. This may have further implications for future studies by Frontier in the region and the way data is compiled for future reports Conclusion Overall, the hypothesised effect of increased biodiversity in areas of increasing protection can be seen in both the invertebrates and the fish when looked at on the macro level. This trend could also be demonstrative of the spill over effect caused by areas of stricter protection. However, due to the increased amount of variables and differing lifehistory strategies trends become less obvious when not looked at in these macro groupings, therefore genus or species specific investigation is required. Analyses of Millepora and Scleractinia reveals that there is a strong correlation between the two, suggesting competition for an ecological niche. There was also a strong correlation between invertebrate diversity and percentage cover of Scleractinia, possibly supporting the hypothesis that benthic heterogeneity will support a higher diversity of species. However, it was not possible to draw definitive conclusions when comparing this to homogenous Millepora habitats as there is a relatively low percentage cover of Millepora in MIMP. Analyses of invertebrates targeted by fisheries reveals very low numbers of octopus and lobster, however, sea cucumbers fall within averages found in similar locations. Continued monitoring should be carried out within the Mafia Island Marine Park to continue to gather data on this little studied environment. Particular emphasis should be placed upon continued monitoring of taxons targeted by fisheries due to the high levels of poaching and the low levels of enforcement. Mafia Island continues to show high levels of biodiversity and relatively healthy habitats, however, caution should be observed particularly with unregulated fisheries and increasing tourism. 23

24 4.0 Proposed work programme for next phase The proposed work programme for TZM during phase 152 includes: Analyses of topographical complexities of survey sites and related life history strategies of organisms found across those sites. Analyses of long term data sets to look for any assemblage changes in species with slow growth rates and low fecundity. Look into establishing permanent transects in Chole Bay. Look at anchor damage within Chole Bay at popular dive sites and survey sites. Create a fauna inventory for the local environment encompassing habitats such as mangrove forests, seagrass beds, and coral reefs. Continued collection of long-term commercial fish and coral reef health data within the MIMP. Seagrass mapping and continued surveys to assess the health of the habitat and the biotic assemblages it encompasses. Continued collection of Acanthaster planci sightings. 5.0 References Alexander TJ, Barrett N, Haddon M, Graham Edgar. (2009) Relationships between mobile macro invertebrates and reef structure in a temperate marine reserve. Marine Ecology Progress Series Vol. 389: Bergman KC, Öhman MC. (2001) Coral reef structure at Zanzibar Island. Marine Science Development in Tanzania and Eastern Africa Proc 20th Ann Conf Adv Mar Sci Tanzania, pp Bruckner, A W, K A Johnson, and J D Field Conservation Strategies for Sea Cucumbers : Can a CITES Appendix II Listing Promote Sustainable International Trade? Chornesky, E. A. (1991). The ties that bind: Inter-clonal cooperation may help a fragile coral dominate shallow highenergy reefs. Marine Biology 109: Claudeta J, Pelletier D, Jouvenel JY, Bachet F, Galzina R. (2006) Assessing the effects of marine protected area (MPA) on a reef fish assemblage in a northwestern Mediterranean marine reserve: Identifying community-based indicators. Biological Conservation 130(3): Darwall WRT, Dulvy NK. (1996) An evaluation of the suitability of non-specialist volunteer researchers for coral reef fish surveys. Mafia Island, Tanzania - A case study. Biological Conservation, 78: Dumas, P, M Kulbicki, S Chifflet, R Fichez, and J Ferraris. (2007). Environmental Factors Influencing Urchin Spatial Distributions on Disturbed Coral Reefs (New Caledonia, South Pacific ) 344: Garcia, Tatiane Martins. (2008). Macrofauna Associated With Branching Fire Coral Millepora Alcicornis (Cnidaria : Hydrozoa) 24 (1): Garpe KC, Öhman MC. (2003) Coral and fish distribution patterns in Mafia Island Marine Park, Tanzania: fish habitat interactions. Hydrobiologia 498: