Tanzanian Coast Research Articles

Population Expansion but Limited Gene Flow in Kuhl's Blue‐Spotted Maskray Along the Tanzanian Coast

Population Expansion but Limited Gene Flow in Kuhl's Blue‐Spotted Maskray Along the Tanzanian Coast

The vulnerability of fisheries-based livelihoods to climate variability and change in coastal small pelagic fishing communities in Tanzania

Fisheries-based livelihood activities constitute an essential means of income and well-being for the majority living in coastal areas. This paper examines vulnerability of fisheries-based livelihoods caused by climate variability and change. It focuses on three small pelagic fishers’ communities including Kipumbwi, Kilindoni, and Kilwa-Kivinje, along the Tanzanian coast, as a case study. Little research has been done on the effect of climate variability and change on the livelihoods of small-scale fishing communities in developing countries, particularly along the Tanzanian coast. In collecting data, questionnaire, focused group discussion and an interactive governance approach were used. Results showed that the natural vulnerability issues include, reduced catches, and strong winds. Economic vulnerability, mentioned lack of credit facilities. For social vulnerability, respondents mentioned an increased number of fishers and fishing vessels On the aspect of technology, respondents mentioned lack of modern fishing methods. As findings suggest, these vulnerability aspects, are possibly associated with anthropogenic factors such as illegal fishing, may not be related to climate change, but climate change may intensify them. The findings further showed that climate variability has negatively affected the fisheries on which fisher communities depend for income and for food security thus affecting their local economy. Climate change has negatively affected small pelagic fishers. The decline in fish catches and economic- un-matching changes in fish prices have negatively affected the fishing community's income, employment, and food security. The recommended means for reducing vulnerability include reducing taxes and levies, availability of facilities for reducing post-harvesting loss and availability of reliable markets.

Reviewing the interdecadal dynamics of micropollutants in the Tanzanian coastal zone from 2002 to 2022.

The Tanzanian coast is a vastly diversified ecosystem offering ecological, cultural, and economic services. However, anthropogenic and environmental stressors threaten its productivity and sustainability, prompting extensive research to understand the contamination extent, sources, and impacts. This review covers 77 original field research studies published between 2002 and 2022, focusing on the Tanzanian coastal area. A summary of information on the occurrences, levels, distributions, sources, and impacts of organic and inorganic micropollutants in environmental and biological compartments is provided. The studies were further discussed based on their research focus, where seven key areas were identified, which included the types of micropollutants analyzed, the parameters sampled, the locations investigated, and the crucial conclusions reached. The aim was to evaluate the research trends and identify gaps for future investigations. The studies reveal varying contamination levels, from low to severe, encompassing metals, persistent organic pollutants, pesticide residues, nutrients, and microbial contaminants. However, data gaps exist for micropollutant concentrations in ambient air, microplastics, pharmaceuticals, and emerging contaminants of concern. With increasing urbanization and socio-economic activities, the review emphasizes the necessity for solution-based research to remove and control micropollutants in the area. Addressing these challenges is crucial for sustaining the diverse ecological nature of this vital coastal system.

Seascape configuration influences big blue octopus (Octopus cyanea) catches: Implications for a sustainable fishery

Seascape configuration is known to influence fish distribution and abundance in coastal waters. However, there is little information regarding how the shape of the coastal seascape influences catches of landed fisheries species, particularly so in the understudied western Indian Ocean (WIO). With focus on big blue octopus (Octopus cyanea), which is a widely found cephalopod species in the WIO, we compared landed catches (biomass, catch rate, and density) in submerged and exposed reefs, and explored the influence of proximity to fishing villages and reef habitat size on octopus landings. We used fishery-dependent data collected between 2018 and 2020 from eight landing sites spread across the Tanzanian coast. We found a strong relationship between biomass of octopus catch and distance from fished reefs to fishing villages, with higher fished biomass on reefs farther away. Octopus densities were higher, while catch rates were lower, on reefs very close to (within one km distance from) fishing villages compared to more distant reefs. In general, submerged reefs provided higher catches than exposed reefs. The low octopus catches on the exposed reefs were attributed to high fishing pressure, while submerged reefs that are only accessible through diving provide optimal areas for octopuses to grow. Octopus catches were, however, not significantly affected by reef size. The findings suggest that management policies should proportionate fishing efforts to ensure sustainable exploitation of reefs and associated fishery resources.

Sociocultural and Economic Aspects of the Ancient Roman Reported Metropolis of Rhapta on the Coast of Tanzania: Some Archaeological and Historical Perspectives

Two thousand years ago, the Romans had knowledge of the western Indian Ocean seaboard. The East African seaboard was then known as Azania. The capital of Azania was recognized by the Romans as Rhapta. The unknown author of the Periplus of the Erythrean Sea seems to have visited the region himself and reported about the territory and its main settlements. However, Claudia Ptolemy, the geographer, got his information about the territory from skippers some who had been to Rhapta several times. After his third century report no more is heard about Rhapta. The search for the Azania settlements and particularly of Rhapta began from about 1950s in the colonial times. It is the research endeavor of the third author of this paper from the mid 1990s in the region of the Rufiji delta and the Mafia Island in south east Tanzanian coast that provided some clue to the location of Rhapta. With more recent research in Mafia archipelago, it is now apprehended that Rhapta got submerged on the northern side of the archipelago offshore of the Rufiji delta. With collected data from recent underwater and terrestrial archaeological surveys and available Roman historical reports, we can discuss socio cultural and economic aspects of Rhapta.

Prevalence and characterisation of microfibres along the Kenyan and Tanzanian coast

Microplastic pollution is ubiquitous, with textiles being a major source of one of the dominant microplastic types—microfibres. Microfibres have been discovered in the aquatic environment and marine biota, demonstrating direct infiltration in the environment. However, the impact of non-plastic microfibres has been overlooked until recently despite their prevalence and the ecotoxicological risk posed by chemical dyes and finishes used during processing. During an expedition from Lamu to Zanzibar (East Africa), a citizen science strategy was employed to innovate, educate and influence microfibre pollution reform through the Flipflopi project, a circular economy effort to stop the use of single-use plastic. Simple sampling methods were developed to replace costly equipment, which local citizens could use to partake in the collection and sampling of surface water samples from the previously understudied Kenyan and Tanzanian coast. To maintain the reliability of samples and to minimise contamination, a forensic science strategy was embedded throughout the methodology of the study, collection and analysis of the samples. A total of 2,403 microfibres from 37 sites were recovered and fully characterised with 55% found to be of natural origin, 8% regenerated cellulosic and 37% synthetic microfibres. Natural microfibres were in higher abundance in 33 of the 37 sampled sites. Congruent with recent studies, these findings further support the need for greater understanding of the anthropogenic impact of natural microfibres.

Impacts of Climate Change on Small Pelagic Fish Catches in the Coastal Artisanal Fishers Communities of Tanzania

Climate-related effects occur across all regions in Tanzania, affecting primary sectors such as agriculture and fishing. This study investigated the impacts of climatic change on small pelagic catches in fishers in Kilindoni, Kipumbwi and Kilwa Kivinje villages along the Tanzanian coast. We studied how changes in rainfall, sea surface temperature, wind speed and chlorophyll a affect small pelagic fisheries using primary and secondary data. Qualitative and quantitative methods were applied. Primary data collection involved questionnaires, focus group discussions and key informant interviews. Secondary data was obtained from Tanzania Meteorological Agency and remote sensing from Modi's sensor. Results showed an increase in sea surface temperature (tau = 0.0151, 0.0121, 0.0238 for Kilindoni, Kilwa Kivinje and Kipumbwi, respectively) and unpredictable changes in rainfall patterns which affected small pelagic fisheries. The average rainfall was 284.6, 97.5 and 56.4 mm in Kilindoni, Kilwa Kivinje and Kipumbwi, respectively. In recent years, rain has been unreliable compared to the past 20 years. Unpredictable rainfall, increased sea surface temperature, wind speed and chlorophyll a had negatively impacted the small pelagic fishery. There was a strong relationship between the decline of small pelagic catches and climatic variables. The findings of this study have implications for coastal fisher's livelihood, income and food security.
 Keywords: Coastal communities; small pelagic fishery; climate change; fisheries; livelihood

Low genetic diversity and lack of genetic structure among populations of the sandfish Holothuria (Metriatyla) scabra on the Tanzanian coast

ABSTRACT The tropical sandfish Holothuria (Metriatyla) scabra Jaeger, 1833 has been severely depleted in the Western Indian Ocean because it is easy to catch and in high demand. In response, Mainland Tanzania closed the fishery; however, the fishery remains open in the semi-autonomous islands of Zanzibar. Yet, it is unknown whether the aforementioned contrasting management measures are consistent with the genetic stock structure of the fishery. Therefore, this study analysed partial sequences (706 base pairs) of the cytochrome oxidase subunit I gene (COI) from four sandfish populations from Tanzania to assess the extent of genetic diversity and population structure. The populations showed low haplotype (0.17–0.44) and nucleotide diversities (0.025–0.084%), as well as small mutation-scaled effective size (9 × 10−4−17 × 10−4) compared to other marine macroinvertebrates from Tanzania, suggesting that the fishery has not recovered despite the ban that was imposed 16 years ago. Furthermore, Analysis of Molecular Variance (AMOVA) revealed a low and non-significant genetic differentiation index (F ST = 0.0047, p > 0.05), indicating a lack of population structure. The lack of population structure was further supported by phylogenetic analysis, which grouped together all COI haplotypes of sandfishes from both Zanzibar and Mainland Tanzania. This suggests that populations in Mainland Tanzania and Zanzibar are genetically homogeneous and that Zanzibari fishers may be targeting the same stock that is protected in Mainland Tanzania. Therefore, the fishery should be managed as a single unit and management measures between Mainland Tanzania and Zanzibar should be harmonized.

Genetic evidence for a single stock of giant tiger prawns Penaeus monodon in demarcated prawn fishing zones of Tanzania

AbstractTanzania demarcated three prawn fishing zones along its coast to spread fishing pressure and help the prawn fishery to recover. However, it is unknown whether the demarcated zones correspond to the genetic stock structure of the world's most commercially important prawn, the giant tiger prawn (Penaeus monodon). Thus, this study used partial mitochondrial control region sequences (534 base pairs) to test the hypotheses that (1) giant tiger prawns in Tanzania's demarcated prawn fishing zones are a single stock and (2) the giant tiger prawns on the Tanzanian coast experienced a recent demographic expansion. The sequences showed high haplotype diversity (h = 0.998–1.0) and low nucleotide diversity (θπ = 1.89%–2.24%). The neutrality test and mismatch analysis showed that the hypothesis of recent demographic expansion could not be rejected. The analysis of molecular variance revealed low and insignificant fixation indices between the zones (FST = 0.00025, p > 0.05; ΦST = −0.00027, p > 0.05), suggesting that the three demarcated fishing zones constitute a single stock and that fishers may be targeting the same stock. Furthermore, it was discovered that Zone 2 has the potential to replenish depleted areas; thus, it should be prioritised in future conservation planning.

Population Characteristics of Selected Small Pelagic Fish Species along the Tanzanian Coast

Although small pelagic fishing in Tanzania is rising, lack of information on population structure has been a significant concern in its management. This study aimed to determine the species composition, length-weight relationship and length at first maturity of Amblygaster sirm, Encrasicholina heteroloba, Encrasicholina punctifer, Stolephorus commersonii, and Spratelloides gracilis landed at Kilwa Kivinje, Kipumbwi and Shangani along the Tanzanian coast. These landing sites were chosen because of their locations and importance in the small pelagic fishery. Sampling was done monthly from October 2018 to June 2020. The catch composition was site specific such that E. heteroloba dominated at Kilwa Kivinje and Shangani, while E. punctifer dominated at the Kipumbwi site. Further analysis shows allometric coefficient to be greater than 3 for A. sirm and E. punctifer, indicating positive allometric growth, while for S. commersonii and S. gracilis, the allometric coefficient was less than 3, indicating negative allometric growth. Our findings showed that length at first maturity (L50) differed, implying that these species start spawning at different sizes, an essential biological reference for sustainable small pelagic fish exploitation. We recommend seasonal closure of the fishery to maintain reproductive seasons since many species are multiple spawners.
 Keywords: Population; Small pelagic; Maturity; Tanzania

Characterization of agar extracted from Gracilaria species collected along Tanzanian coast

The study was conducted to investigate the effect of spatial variation, alkali treatment and the volume of extractant on yield and gel strength of agar for three Gracilaria species (G. salicornia, G. edulis and G. corticata) collected from the Tanzanian coast (Dar es Salaam, Tanga and Zanzibar). Treated and untreated G. corticata showed the highest yield (27 ± 0.7 % and 26.2 ± 1.3 % for treated and untreated, respectively), followed by G. salicornia then G. edulis. G. salicornia collected from Zanzibar showed the highest mass yield (22.9 ± 4.3 % for treated) followed by those collected from Tanga. Varying the volume for extraction showed no significant difference in mass yield where the p-value was >0.05. The highest gel strength was recorded from treated G. salicornia collected from Tanga (495 ± 29.5 gcm−2). Gel strength varied significantly between species. Spatial variability showed a significant difference in gel strength; the sample collected from Tanga showed the highest gel strength, followed by Zanzibar then Dar es Salaam. The variation due to the volume of distilled water used for extraction showed no significant difference in gel strength at a p-value >0.05. The highest gel strength was recorded at the volume of 1500 mL (467.5 ± 98.4 gcm−2), and the smallest gel strength was recorded at 500 mL. In all cases, there was a significant difference in mass yield and gel strength between treated and untreated samples. G. salicornia showed promising results as a local source of agar as it showed the highest gel strength though it produced an intermediate amount of agar. Based on the finding of this study, the volume of extraction of agar should be maintained as 1000 mL because by increasing the volume of extraction from 1000 mL to 1500 mL, the agar yield and gel strength don't change significantly. Agar yield and gel strength of Gracilaria species (G. salicornia, G. edulis and G. corticata) can be improved by alkali treatment, but further study is needed to determine the optimum amount and concentration of alkali to be used that will produce maximum yield and gel strength.

Community Awareness and Understanding of the Origin of Swahili Archaeological Heritage and Ruins along Tanzania’s Swahili Coast: Conservation and Management Issues

The Tanzanian coast has many remains of medieval Swahili settlements dated between the twelfth and sixteenth centuries C.E. In the same region, Neolithic and Later Stone Age sites have also been reported, alongside evidence for Early Iron Working settlements. Swahili culture, and the ruins that can still be seen, have their origins in this rich cultural past. It appears, however, that the present communities along the Tanzanian Swahili coast, and the public, are unaware of this important heritage history. There is a popular belief among them that the origin and influence on the now ruined Swahili settlements came from the Middle East, and it is true that Arab and other travellers described Swahili civilization in their writings. In this article, we explore the communities and researchers’ different perspectives on the origin of the Swahili ruins, focusing on the conservation and management problems this raises. We also analyse the position and role of heritage management institutions in the country towards enhancing community awareness and proper conservation of the ruins. Finally, we propose ways of promoting community awareness of the origin of the Swahili ruins, influencing participation and actions towards their conservation and management.

Exploring Swahili urbanism through survey of Songo Mnara Island, Tanzania

This paper offers a mesoscale approach to the study of the urban landscape surrounding the fourteenth–sixteenth century Swahili site of Songo Mnara just off the southern Tanzanian coast. The study is based on a systematic, intensive survey of the town’s immediate island hinterland. Such an approach, we argue, exposes a set of activities that extend out from the urban core and situates the traditional objects of study (urban center, rural villages) in an integrated landscape. This scale of activity is particularly apparent in an island context where urban activities encompassed the island itself. This example demonstrates why urban societies in island contexts must be considered in their landscape setting, as a range of territorial relationships can be discerned in the past that were an integral part of the ways that urban lives were constructed.

Vegetation dynamics in response to human and climatic factors in the Tanzanian Coast

Vegetation dynamics in response to human and climatic factors in the Tanzanian Coast

Characterization of Agar Extracted from Gracilaria Species Collected Along Tanzanian Coast

Characterization of Agar Extracted from Gracilaria Species Collected Along Tanzanian Coast

Microplastics in beach sediments and cockles (Anadara antiquata) along the Tanzanian coastline.

Little is known about the prevalence of microplastics (MPs) in East Africa. In the present study, sediments were sampled at 18 sites along the Tanzanian coast that exhibit different levels of anthropogenic activity and were extracted using floatation methodology. Cockles (Anadara antiquata) were collected only from eight sites and MPs were extracted following NaOH digestion. MPs were most abundant at Mtoni Kijichi Creek (MKC, 2972 ± 238 particles kg-1 dry sediment), an industrial port in Dar es Salaam, and significantly higher than all other sites where the abundance range was 15-214 particles kg-1 dry sediment (p < 0.05, one-way ANOVA). Fragments and fibers were found at all sites. Polypropylene and polyethylene were identified polymers. MPs were found in cockles from all sampled sites with both frequencies of occurrence and MPs per individual subject to site-specific variation. This study provides a baseline of MP data in a previously uninvestigated area.

First Observation of Vervet Monkeys Chlorocebus pygerythrus Feeding on Seagrass Thalassodendron ciliatum along the Tanzanian Coast

The vervet monkey, Chlorocebus pygerythrus (F. Cuvier, 1821), is among the most abundant and widely distributed primates in eastern and southern Africa (Butynski et al., 2013). In Tanzania, it is found throughout most of the country, and in some places, forages in human settlement areas (Foley et al., 2014). Chlorocebus pygerythrus is an opportunistic omnivore, with flowers, leaves, seeds and invertebrates contributing a major part of its diet (Struhsaker, 1967; Wrangham & Waterman, 1981; Lee & Hauser, 1998; Butynski et al., 2013; Foley et al., 2014). Vervet monkeys are known to feed on terrestrial grasses e.g. Panicum spp, Sporobolus spp, Cynodon spp and Cenchrus mezianus (Leeke) Morrone (Struhsaker, 1967; Butynski et al., 2013), but there are no records of seagrasses as part of their diet. This note reports the first observation of C. pygerythrus feeding on the seagrass Thalassodendron ciliatum (Forssk.) Hartog (Cymodoceaceae) at Saadani National Park, on the shores of the Indian Ocean. Saadani National Park is one of 22 national parks in mainland Tanzania, and the only one bordering the Indian Ocean (TANAPA, 2020). It comprises the former Mkwaja ranch area, former Saadani game reserve and the Zaraninge forest (Treydte et al., 2005) and is located within the Zanzibar-Inhambane phytochorion (White, 1983). The mean annual temperature in the park is 25°C (Treydte et al., 2005) with the annual rainfall considerably variable between years (Tobler et al., 2003), generally averaging to 900 mm per annum (Treydte et al., 2005). Rainfall in the park is bimodal with a short rainy season from October to December and a long rainy season from March to early June (Treydte et al., 2005; Cochard & Edwards, 2011). Like most of the Western Indian Ocean, the hydrography of Saadani coast is shaped by northeast and southeast monsoon winds which occur between November to March and May to September respectively (Richmond, 2002; Lymo, 2011; Semba et al., 2019). The surface water temperature ranges from 20 to 30°C and is higher during northeast monsoon winds (Richmond, 2002; Lymo, 2011; Peter et al., 2018). At least 10 seagrass species are known along the Western Indian Ocean (Richmond, 2002; Gullstrom et al., 2002) with Thalassodendron ciliatum being among the most common (Gullstrom et al., 2002). A group of 22 vervet monkeys were observed on 31 August 2019 foraging along the shores of the Saadani National Park (6°01'42S, 38°46'44E ) for two hours from 10:00 h to 12:00 h during the low tide. The monkeys spent almost half of the time feeding on the terrestrial herbs Cynodon dactylon (L.) Pers., Sporobolus sp, Panicum sp and Anthericum sp on the supralittoral zone, before entering the littoral zone where they foraged on drift patches of the seagrass Thalassodendron ciliatum (figures 1 & 2). Identification of the seagrass followed Richmond (2002). The monkeys were observed eating rhizomes and shoots of T. ciliatum while avoiding the roots and leaves. Both direct mouth scrape and hand-to-mouth movements were used when the monkeys were feeding on the terrestrial grasses but only hand-to-mouth movements were used when feeding on T. ciliatum. A number of studies on non-human primates utilizing marine foods exist, in which marine animals dominate as food items (Son, 2003; Stewart et al., 2008; Lewis & O’Riain, 2017), especially invertebrates (Son, 2003).These reports indicate that marine resources contribute only small proportions of the primate’s food and that the animals invest little of their time on these feeding grounds (Lewis & O’Riain, 2017). However, detailed studies on feeding behaviour of vervet monkeys in Saadani National park will shed more light on feeding habits of primates along the Tanzanian coast. This observation supports the opportunistic nature of vervet monkeys as they are known to take advantage of available food resources (Struhsaker, 1967; Butynski et al., 2013). This is the first reported record of the seagrass T. ciliatum constituting a food item in the diet of vervet monkeys despite the occurrence of this seagrasses along parts of the distribution range of vervet monkeys.

Adaptive capacity and coping strategies of small-scale coastal fisheries to declining fish catches: Insights from Tanzanian communities

Small-scale fishing communities are expected to adapt to fish catch fluctuations linked to global environmental change. Notwithstanding, impacts from severe climate events and overexploitation of fisheries resources can compromise functions and resilience of ecosystems and associated species, and thereby jeopardize long-term population trend stability and fisheries productivity. To date, most assessments and vulnerability studies of fisheries-dependent populaces have focused on global, regional and national levels, while studies at village and community levels, where adaptive planning in the context of climate- and environmental changes is important, are less common. Based on data from official fishery records over a three-decadal period (1984–2016) and recent interviews with artisanal fishermen (319 fishers from eight communities) along the Tanzanian coast, we assessed small-scale fisheries with regard to (i) long-term trends in fishery landings, (ii) long-term alterations in fishing gear use, and (iii) fishers’ perceptions on how they have been coping and adapting to fluctuating fish landings. We further investigated (iv) the adaptive capacity of a wide range of coastal villages by assessing the fishers’ responses to an anticipated future scenario of a major (50 %) decline in landings from the current fisheries catch levels. The long-term trend records of fish landings showed a remarkable ∼50 % reduction in terms of both catch per vessel and catch per fisher from 1984 to 2016. According to the interviews, the majority of fishers (75 %) have changed fishing grounds from nearshore to offshore areas during the last decade, owing to a general perception that nearshore areas have suffered major reduction in fish stocks (due to overfishing and environmental changes related to extreme climate- or weather events), while offshore areas were considered still productive. The change in location of fishing grounds is probably a result of the clear switch in major gear type utilization from beach seine to ring net that occurred over the last decades. With a further progressive decline in fishery catches to a predictive level of 50 % of the current catch level, there is a general perception that artisanal fishers will continue fishing because alternative livelihoods (like crop farming, which employs more than 65 % of the population) have suffered similar negative impact. These findings highlight the need for building adaptive capacity in local coastal communities to develop alternative coping strategies for the impacts of climate- and environmental changes.

New Agraeciini species from the Eastern Arc Mountains, East Africa(Orthoptera: Tettigoniidae; Conocephalinae; Agraeciini).

Eleven new Agraeciini species are described. Six species of Afroanthracites are new to science from the North and South Pare, the West and East Usambara, the Udzungwa Mountains of Tanzania, and the Taita Hills of Kenya. The two Afroanthracites Hemp Ingrisch, 2013 species from the Pare Mountains, A. guttatus n. sp. and A. maculatus n. sp., and A. magamba n. sp., from Magamba Forest Reserve in the West Usambara Mountains are morphologically closely related to each other and form a morphological lineage with the already described species from the West Usambara Mountains (A. discolor Hemp, Ingrisch Ünal, 2013 and A. pseudodiscolor Hemp, 2015) and A. pommeri n. sp. from the Taita Hills of Kenya. A. lineatus n. sp. from Lutindi Forest Reserve in the East Usambara Mountains has its morphologically closest relative in A. jagoi Ünal Hemp, 2013 endemic to the Mazumbai Forest Reserve of the West Usambara Mountains while A. montium (Sjöstedt, 1910) from the Kilimanjaro/Meru area, A. inopinatus n. sp. from the South Pare Mountains and A. usambaricus (Sjöstedt, 1913) from the West Usambara Mountains form another morphological lineage. Morphological traits like the shape of the last abdominal tergite in males, the male cerci and the colour pattern suggest at least two lineages reflecting dispersal of the ancestors at a time when forest connected the mountain ranges in the past during climatic fluctuations. In the genus Afroagraecia Ingrisch Hemp, 2013 new species were collected on Zanzibar and in Kazimzumbwi Forest Reserve, the Udzungwa and Nguru Mountains. Distribution patterns and the morphology suggest recent speciation patterns of Afroagraecia in the Eastern Arc Mountains and along the Tanzanian coast. From the Nguru Mountains a third Dendrobia species of the genus, D. plagata n. sp., is described.

Effective co-management and long-term reef fish recovery from severe coral bleaching: Insights from Misali Island, PECCA, Tanzania

Misali, an uninhabited islet along the east coast of Pemba Island off the mainland Tanzanian coast, is a biodiversity hotspot and Marine Protected Area (MPA), consisting of a core non-extraction zone (NEZ) surrounded by a larger area where some artisanal fishing is allowed. Within a year of receiving official protection under a co-management agreement, the island underwent a catastrophic bleaching event in 1998, and funding and enforcement in the protected area have been inconsistent since a restructuring of management in 2006. In this study, we investigate current health of the island's fish community, and report 186 observed fish species. We estimate that, including unseen species and those outside the study area, the total species richness may be comparable to the historical baseline of 244 species; however, this represents a decline from the 270 species estimated in 2001 and the 350 species observed in 2004, after several years of successful protections. Patterns of species richness over time likely reflect changes in management effectiveness and engagement of Misali's fishing communities. Diversity of indicator (Chaetodontidae) and keystone (Scarinae) taxa were comparable to historical levels and greatest inside the NEZ, suggesting continued reef health and resilience. However, we found no other significant differences between fish communities inside and outside the NEZ, which observations indicate is poorly enforced, and the disproportionate loss of large predatory fish species may indicate overfishing. The case study of Misali suggests that a temporary reduction in fishing pressure while the island was recovering from a severe bleaching event may have had long-lasting benefits for reef health and resilience. For future management, we recommend consideration of species-specific protections, a possible re-designation of NEZ boundaries to include more unique habitat types, and reintegration of local fishing communities into MPA co-management.