Western Indian Ocean Journal of Marine Science 2021-04-02T11:29:06+00:00 Professor J Paula Open Journal Systems <p>The <em>Western Indian Ocean Journal of Marine Science (WIOJMS) </em>provides an avenue for the wide dissemination of high quality research generated in the Western Indian Ocean <em>(</em>WIO) region, in particular on the sustainable use of coastal and marine resources. The journal publishes original research articles dealing with all aspects of marine science and coastal management. Topics include, but are not limited to: theoretical studies, oceanography, marine biology and ecology, fisheries, recovery and restoration processes, legal and institutional frameworks, and interactions/relationships between humans and the coastal and marine environment. In addition, <em>Western Indian Ocean Journal of Marine Science </em>features state-of-the-art review articles and short communications. The journal will, from time to time, consist of special issues on major events or important thematic issues. Submitted articles are subjected to standard peer-review prior to publication.</p> <p>Other websites associated with this journal: <a href=""></a></p> The influence of habitat preference on longitudinal population composition and distribution of Groupers (Serranidae) in Chumbe Island Coral Park, Zanzibar, Tanzania 2021-04-02T11:28:35+00:00 Caroline Daley <p>A survey of six common grouper (Serranidae) species was conducted on both the western protected and eastern unprotected reefs around Chumbe Island, Zanzibar. Species, estimated maturity, and habitat were recorded using standardized categories. Fundamental niche and general habitat preference were extrapolated based on observed realized niche and qualified based on substrate, depth, slope position, and general reef region. Taking habitat preference into account, abundance and biomass density of serranid populations were compared between locations on the reef in order to best account for how habitat influences distribution and population health. The results of this study provide depth to previous research on the protected reef and indicate noteworthy shifts in population composition between 2014 and 2018 that favour species with less specified habitat preference, such as Aethaloperca rogaa and Cephalopholis argus. Surveys of Chumbe’s nearby unprotected eastern reef indicate low levels of species abundance, which this study hypothesizes is the result of inappropriate habitat structure, increased fishing pressure, and decreased population health within the MPA. Ultimately, this study suggests that MPAs do not protect all species equally, and habitat preference must be taken into account when assessing MPA effectiveness at protecting different species. Indeed, especially as serranid habitat faces continued degradation, serranid conservation will depend even more on protection of each species’ preferred habitat in coral systems. As such, assessing serranid populations as a whole fails to capture the changes in population distribution and composition that is occurring between species, which may be more indicative of shifts and disturbances in the ecosystem.</p> 2021-04-02T11:17:03+00:00 Copyright (c) 2020 Western Indian Ocean Journal of Marine Science The trophic structure of fish in seaweed farms, and adjacent seagrass and coral habitats in Zanzibar, Tanzania 2021-04-02T11:28:39+00:00 Batuli M. Yahya Saleh A. Yahya Aviti J. Mmochi Narriman S. Jiddawi <p>Coral reefs, seagrasses and seaweed farms (<em>Eucheuma denticulatum</em>) are characteristic habitats in many parts of the coast of Zanzibar, Tanzania. However, information on trophic interactions, movements of fish, and variation in fish diet specialization between these habitats are scarce. The present study determined the trophic structure and the variation in diet composition of fish caught in (floating) seaweed farms, and in adjacent seagrass and coral reef habitats in Pongwe, Zanzibar. Fish were caught using traditional basket traps (<em>dema</em>) and gut contents of 392 fish were analyzed. A one-way Analysis of Similarities (ANOSIM) showed that there was a significant difference in the composition of prey items eaten by invertivores in different habitats (Global R = 0.109, p = 0.002.). There was no significant difference in the composition of prey items eaten by herbivores, invertivore-piscivores and omnivores (p &gt; 0.05), likely due to movement of fish between these habitats for foraging. There was no significant difference in the relative proportion of trophic groups between the habitats (p &gt; 0.05) except for herbivores (p &lt; 0.05). Floating seaweed farms attract invertebrates and smaller fish, thus providing feeding grounds for predatory fish, and should be considered as ecologically important habitats as are coral reefs and seagrass beds.</p> 2021-04-02T11:18:14+00:00 Copyright (c) 2020 Western Indian Ocean Journal of Marine Science A socio-ecological system perspective on trade interactions within artisanal fisheries in coastal Kenya 2021-04-02T11:28:42+00:00 John Ndarathi Cosmas Munga Jean Hugé Farid Dahdouh-Guebas <p>Assessments of coastal artisanal fisheries are progressively adopting a social-ecological system (SES) approach as an effective means to accumulate knowledge and integrate findings on different aspects of the fisheries. Ostrom’s SES framework was used to guide assessment of interactions between and within the harvesting and supply-chain processes and the effect of external drivers, seasonal monsoons and tourism, on both processes in a coastal artisanal fishery system in Gazi Bay, Kenya. Specific analyses focused on seasonal catch composition, key resource user groups involved in the fish trade and the resource units traded by each user group. The snowball method was used to identify key resource user groups within the fishery sector, who were then interviewed using semi-structured questionnaires (n = 60). Additionally, existing annual shore-based catch assessment and monthly fish landings data for the years 2014 and 2015 were incorporated for analysis of artisanal catch properties (species composition and weight). Comparison of seasonal catch composition was carried out using sample-based rarefaction curves. Higher fish landings and higher species diversity were recorded during the North-East Monsoon season. Further, a simple fish harvesting-supply network comprising of six key resource user groups (i.e. hotels, fish processing companies, dealers, small-scale fish processors (mama karanga), fish mongers and fishers) was outlined. The tourism industry, through hotels, creates a high demand for fish coinciding with a higher catchability and supply during the calm North-East Monsoon season and consequently, dealers hire migrant fishermen to target pelagic fish. Evidence of interactions within and between different fishery sub-systems, as well as the effect of monsoon seasons and tourism on the exploitation and market dynamics of the multispecies fishery, highlight the need for comprehensive management plans to strengthen self-organization among resource users and to increase adaptive capacity within the fishery system.</p> 2021-04-02T11:18:54+00:00 Copyright (c) 2020 Western Indian Ocean Journal of Marine Science Movement patterns and growth rate of cavebass Dinoperca petersi (Pisces: Dinopercidae) in the iSimangaliso Marine Protected Area, South Africa 2021-04-02T11:28:46+00:00 Bruce Q. Mann Gareth L. Jordaan Ryan Daly <p><em>Dinoperca petersi</em> is a relatively common fish species caught in the line-fishery in KwaZulu-Natal (KZN), South Africa. Yet, little is known about the biology and ecology of this species. Movement patterns and growth rate of this species were studied based on data obtained from a long-term tag-recapture study conducted in the iSimangaliso Marine Protected Area in northern KZN between 2001-2019. Results showed that <em>D. petersi</em> is a highly resident species with a linear home-range size of 290-405 m. While most fish showed high site fidelity, 8.8 % of the tagged fish showed wider ranging movements of 2.4-90 km. However, only 5 fish showed movements out of no-take zones into adjacent exploited areas, suggesting limited adult spillover. Growth rate of tagged fish was found to be reasonably slow compared to other sympatric predatory reef fish with an average growth rate of 61.76 mm y<sup>–1</sup> for smaller fish (g<sub>α</sub> = 300) and 9.58 mm y<sup>–1</sup> for larger fish (g<sub>β</sub> = 550). Based on these life history characteristics, options for the future conservation and management of this species are discussed.</p> 2021-04-02T11:19:57+00:00 Copyright (c) 2020 Western Indian Ocean Journal of Marine Science Conservation of cultural heritage for community socio-economic prosperity: The case of Lamu East and West Sub-Counties, Lamu County, Kenya 2021-04-02T11:28:48+00:00 Salim M. Bunu Annie H. Ong'ayo Halimu S. Shauri <p>Worldwide, cultural heritage has become both an element and a tool for achieving socio-economic prosperity.<br>This study assessed the contribution of conservation of cultural heritage as a resource for the development of Lamu County. A descriptive survey design was used to conduct the study. Proportionate and systematic random sampling procedures were used to sample key informants and households selected from a sampling frame obtained from Lamu West and East Sub-Counties. An interview schedule and a semi-structured questionnaire were used to collect data from key informants and households respectively. Data were analysed using descriptive statistics and narratives. The results revealed that cultural heritage conservation contributes to job creation both directly and indirectly. However, cultural barriers contributed to observed exclusivity in benefitting from income generated from tangible and non-tangible activities. Revenue gains from the cultural heritage are also limited by the poor state of sites such as Pate and Ishakani ruins. The study recommends development and implementation of training programmes in cultural heritage conservation activities to ensure the community is educated and empowered to utilize cultural heritage for socio-economic development. The Government should also institute proper revenue sharing mechanisms to enhance socio-economic development of the Lamu County community.</p> 2021-04-02T11:20:46+00:00 Copyright (c) 2020 Western Indian Ocean Journal of Marine Science Microplastic pollution in the surface waters of creeks along the Kenyan coast, Western Indian Ocean (WIO) 2021-04-02T11:28:51+00:00 Joyce O. Kerubo Agnes W. Muthumbi John M. Onyari Edward N. Kimani Deborah Robertson-Andersson <p>Microplastic pollution has been recognized as a global threat in marine environments and a danger to prey, predators and humans. Yet there have been limited studies in the Western Indian Ocean (WIO) and along the Kenyan coast making it difficult to estimate the extent of such pollution. This is the first study on microplastics (MPs) in the surface waters within creeks (Tudor, Port-Reitz and Mida creeks) in Kenya. Sampling was done in January/ February and September 2018 to collect microplastics from surface water. Neuston nets of 500 μm (large) and 250 μm (medium) size were towed for ten minutes and 50 litres of seawater sieved through a 20 μm net (small) in three replicates. The samples were digested in 10 % Potassium Hydroxide, sieved, and then filtered with cellulose nitrate membrane microfilters. Concentrations of total microplastics, different shapes and colours were established under a microscope. High concentrations of small size (20-250 μm) MPs were encountered and Tudor and Port Reitz had higher concentrations compared to Mida Creek. The study provides data on microplastic concentrations within the creeks and recommends focussing on small size microplastics for monitoring purposes, which due to their high concentrations can be hazardous to organisms.</p> 2021-04-02T11:21:22+00:00 Copyright (c) 2020 Western Indian Ocean Journal of Marine Science Morphological and meristic characters of six rabbitfish species (Family: Siganidae) in Kenya 2021-04-02T11:28:54+00:00 Rashid O. Anam Chrisestom M. Mwatete Nina Wambiji <p><em>Siganus</em> species (rabbitfishes) are caught by artisanal fishers in Kenyan marine waters. The identification of recently captured rabbitfish species is based on colour patterns, but colours fade after death or during preservation, making species identification more difficult. Morphometric measurements and meristics are then useful in differentiating between species. Twenty-four morphological and twelve meristic characteristics of rabbitfish were obtained from samples collected at six landing sites along the Kenyan coast. Principal Component Analysis (PCA) and Mann-Whitney U-tests were used to evaluate variability among the species. Four of six rabbitfish species showed similar body morphometry and could not be distinguished using PCA analysis, but <em>Siganus stellatus</em> and <em>S. luridus</em> differed from the other species and each other. No clear morphological evidence of separate stocks of individual rabbitfish species was found, apart from <em>S. rivulatus</em> for which the sample size was small. It is recommended that existing taxonomic descriptions are updated to include additional distinctive characters documented in this study.</p> 2021-04-02T11:21:54+00:00 Copyright (c) 2020 Western Indian Ocean Journal of Marine Science Valuation of harvested goods in Mida Creek with application of the TESSA approach 2021-04-02T11:28:56+00:00 Cecilia O. Olima Paul K. Muoria Margaret A. Owuor <p>Mangroves are considered a highly productive blue forests resource providing services that are important to the community both locally and globally. In recent times there has been an increase in studies on valuation of ecosystem services provided by mangroves. However, there is need to provide a simplified approach to identify, assess and quantify ecosystem services. In this study the Toolkit for Ecosystem Services Site-based Assessment (TESSA) was used to assess the value of harvested goods provided by the mangroves of Mida Creek in the current state and under plausible alternative scenarios. Spatial methods (GIS) were used to collect data for the period 1985-2019, and household interviews were used to collect data on harvested goods. Descriptive statistics were used to summarize quantitative data. Results show that the estimated current annual value of harvested goods in Mida Creek is US$ 11.2 million. This value increased to US$ 14.3 million under the conservation scenario and reduced to US$ 10.9 million under the business as usual scenario (BAU). These findings add to the growing literature on ecosystem service valuation and the need to use site-specific non-modelling tools like TESSA.</p> 2021-04-02T11:22:24+00:00 Copyright (c) 2020 Western Indian Ocean Journal of Marine Science Nematodes as bio-indicators of physical disturbance of marine sediments following polychaete bait harvesting 2021-04-02T11:28:58+00:00 Matthews Wafula Agnes W. Muthumbi Virginia Wangondu Charles Kihia Julius Okondo <p>Sediment disturbance in marine environments is caused by activities including polychaete bait harvesting, trawling, dredging, sediment erosion and treading. These activities affect the benthic communities by changing the densities, community assemblage and diversity. The aim of this study was to evaluate the potential of nematodes as indicators of sediments disturbance following polychaete bait harvesting. The study was conducted in three sites experiencing different bait harvesting intensities in Mida Creek, Kenya. Sediment samples were collected from the mudflats during low tide, preserved in 5% formalin and transported to the laboratory for processing and identification of nematodes. The highly disturbed site recorded the lowest nematode genus richness while the less disturbed sites had the highest. Overall, the most abundant nematode genera in the non-disturbed (Dabaso) and less disturbed sites (Kirepwe) were selective deposit feeders (<em>Spirinia</em> and <em>Terschellingia</em>), while most disturbed sites (e.g. Mayonda) had predators/omnivores (<em>Pheronus</em>, <em>Aporcelaimellus</em>) and selected members of the genus Spirinia. The disturbed site was characterised by low nematode diversity (H’) and low dominance (D) while the non-disturbed and less disturbed sites had higher diversity and dominance. Clearly, nematode community assemblage, diversity and feeding guilds changed following disturbance to a low diversity that favoured higher proportions of predator/omnivore taxa.</p> 2021-04-02T11:22:54+00:00 Copyright (c) 2020 Western Indian Ocean Journal of Marine Science Fine-scale habitat use by humpback whales (Megaptera novaeangliae) in Zavora Bay, Mozambique 2021-04-02T11:29:00+00:00 Charlotte D. Van Driessche Nakia Cullain Yara Tibiriçá Ian O'Connor <p>Little is known about the humpback whales (Megaptera novaeangliae) of the East-African Coast genetic sub-unit (C1). With an estimated population size of 7000 whales, they demonstrate the resilience of the species after commercial whaling caused population numbers to decline drastically. Zavora Bay, Mozambique offers an ideal observation point of the passage of the whales during their annual migration towards the breeding ground of southern Africa and serves as an operating base to monitor this population. This study aimed at identifying the importance of Zavora Bay as part of this breeding ground and the core regions for humpback whale use within the study area. Results showed the waters off the coast of Zavora are actively used for breeding and do not merely serve as passage towards the wintering habitats. A mother-calf pair separation with a preference for shallower waters closer to shore was observed. Besides depth and distance to shore, slope also proved to have a significant influence on the distribution of adult humpback whales. Increased survey effort and more detailed investigation of the threats to humpback whales within the waters of Zavora are recommended.</p> 2021-04-02T11:23:27+00:00 Copyright (c) 2020 Western Indian Ocean Journal of Marine Science Stock assessment of the Tigertooth croaker, Otolithes ruber (Bloch & Schneider, 1801) from the commercial prawn trawl fishery by-catch in coastal Kenya 2021-04-02T11:29:02+00:00 Fatuma A. Mzingirwa Jane M. Nyamora Johnstone O. Omukoto Paul Tuda <p>Commercial bottom prawn trawling has been reported to generate a higher proportion of by-catch of up to 70% in Kenya. The Tigertooth croaker, <em>Otolithes ruber</em> is one of the species caught in large quantities as commercial by-catch and also by artisanal fishers. This has led to growing concern that the species could be at risk of over-exploitation. The purpose of this study was to carry out a stock assessment of <em>O. ruber</em>. Stock assessment parameters were estimated using ELEFAN with the generic algorithm as included in the R package TropFishR. The length-converted catch curve and the length-based yield per recruit model were employed. The exploitation rate (F/Z = 0.71) indicates that the stock is overfished based on the length-converted catch curve. The current fishing mortality (F = 2.3) based on the catch curve is larger than the reference level ( = 1.1) based on the yield per recruit analysis and also indicates that the stock is overfished (= 2.09). To reverse the current trend of exploitation, improved management of the stock is required, which should include further studies on other by-catch species and the generation of data to capture the whole fishery for a better estimation of stock status.</p> 2021-04-02T11:24:00+00:00 Copyright (c) 2020 Western Indian Ocean Journal of Marine Science New strandings of True’s beaked whale, Mesoplodon mirus, in Mozambique and their destiny as marine bushmeat 2021-04-02T11:29:04+00:00 Katie E. Reeve-Arnold Jennifer A. Keeping Vic G. Cockcroft Almeida Guissamulo <p>True’s beaked whales have a uniquely fragmented distribution of sightings recorded, mostly from stranding reports. The species is assumed to be associated with deep oceanic waters, occurring in both the northern and southern hemispheres. A hotspot for strandings in the southern hemisphere is South Africa. The third and fourth reported stranding of True’s beaked whales for Mozambique is presented, and the first for Tofo Beach, Inhambane Province. This stranding event resulted in the carcasses being butchered and the bushmeat taken for human consumption. This report develops and discusses strategies for mitigation of future risk to public health from aquatic bushmeat consumption in Mozambique.</p> 2021-04-02T11:24:46+00:00 Copyright (c) 2020 Western Indian Ocean Journal of Marine Science