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Heredity Or Traditional Knowledge: Fishing Tactics And Dynamics Of Artisanal Mangrove Crab (Scylla Serrata) Fishery.
Abstract
Globally, artisanal fisheries are challenged by the combined impacts of overfishing, ecosystem degradation,
climate change and lack of management intervention. Little is known of how traditional
knowledge/skills held by fishers influence ability to exploit marine resources and whether such information
could be incorporated into management practices. Failure to understand fishers’ traditional
knowledge/skills and behaviour may undermine the success of fisheries management measures. Use of
traditional knowledge in exploitation of mangrove crabs (Scylla serrata) on local fishing grounds is
assessed. The study used complementary approaches (field experiments and fisher-based surveys) to
investigate fishing tactics employed by artisanal crab fishers. Also time series data from the ministry of
fisheries was used to assess annual trends in production and value of the fishery. Fishers with calibrated
GPS fished in different areas and catch per unit effort (CPUE), fishing time, distance and efficiency were
assessed. Key informant and semi-structured interviews and direct observation were conducted among
mud crab fishers to establish knowledge/skill requirement, fishing tactics and entry into the fishery. The
results indicate that mud crab fishing is a male dominated activity. Fishing is done at spring low tide by
foot fishers in burrows mainly with rare use of baited traps and lift nets at ankle height water along the
intertidal mangrove front boundaries or channels. Fisher’s follow specific tracks that are strongly guarded
by individual fishers. Fishing for adult crabs showed deeper and further movement in the mangrove
forest unlike juvenile crab collection. Fisher’s in new areas collected few crabs due to low efficiency
compared to well known areas. Entry into the fishery is minimal and skills are inherited from parents or
grand parents with limited transfer being obtained from colleagues. The average size of marketable crabs
has declined over the years while season and tide have remained major challenges for production and
market determination in the fishery. Fisher-based surveys overestimated CPUE and sizes of smallest
crabs caught while it underestimated fishing time and distance moved. A weak management system was
observed with most fishers operating without a license and lacking a synchronized landing system.
Inability of fishers to shift to new areas, “natural closures” and limited distance covered by foot fisher’s
support site-specific management for the fishery.
... The results indicate that mismanagement or misuse of power is a common phenomenon for the mud crab fishery in Bangladesh, which is indeed a similar case in developing countries (Mirera 2011). Corruption and poor administrative control are a man-made threat for fisherfolks (Mirera et al. 2013;Mirera 2011). This study indicates that the mismanagement and misuse of power are pathetic for fisherfolks considering their social position and status of living conditions. ...
... This study found crab harvesting is an important option for earning small-scale fishers' livelihood in the Sundarbans areas also common in South-East Asia and Africa (Mirera et al. 2013;Apine et al. 2019). Livelihood diversity is essential to alleviate poverty and promote the sustainable development of coastal communities (WRI 2008). ...
... The mud crab fishery industry is growing faster due to increasing international market demand (Mirera et al. 2013). Our study indicates the expansion of the market and globalization of this fisheries product has both positive (e.g., higher income during peak season) and negative impacts (e.g., seasonal demand and price fluctuations) on small-scale mud crab fishers ( Figure 5). ...
Small-scale fisheries are affected by both local and external pressures,
despite the contribution to poverty alleviation, employment, and
food and nutritional security. Diverse social and ecological pressures
make small-scale fishing communities trapped in persistent cycles of
a particular fisheries resource dependence. Consequently, the overall
sustainability of that particular species, especially biological, economic and social aspects, becomes vulnerable. This study investigates the biological, economic, and social aspects of a commercially important fish species, i.e., mud crab (Scylla sp.) and explores its link to social-ecological traps. The findings show how the social-ecological traps are forming based on mud crab resource utilization, poverty, overcapitalization and seasonality of crab availability, coupled with weak institutions and governance. Apart from ongoing environmental risks (e.g., extreme climate events), negative feedback comes from poor enforcement of rules and regulations, illegal and destructive fishing, inadequate income, social conflicts, and declining stock. In response to crises, fishers are increasingly dependent on middlemen, leading to the unfair price of their products compared to the market. To escape from the social-ecological traps, strong local institutions, alternative income opportunities, compliance of fishing laws (e.g., gear selectivity, harvest, and trade prohibition of undersize crabs), strong collaboration between management authority and local stakeholders are important toward ensuring the sustainability of the mud crab fishery in the Bangladesh Sundarbans.
... Crabs of less than 500 g are sold at US $8 kg -1 and those more than 1 000 g at US $15 kg 1 . Crab for local consumption are sold from USD 0.2-0.5 kg -1 ; those sold to private homes and tourist hotels go for USD 2-5 kg -1 and US $8-15 kg -1 for export markets (Mirera et al., 2013). However, the revenue accrued from the fishery is poorly represented in national production statistics, because the market is not well defined and poorly monitored. ...
... Lamu County is ranked the highest producer of Mud Crabs at 49.7% followed by Kwale 26.9%, Mombasa 11.2%, Kilifi 11.9% and Tana River 0.3%. The Mud Crab catch per unit effort has been estimated at 0.25-1.7 kg hr -1 and with a fisher spending between 2.5-5.0 hours fishing in a day (Mirera et al., 2013). In recent years, increased interest has been demonstrated in Mud Crab farming in Kenya. ...
... In most of the crab farming ventures, crabs are collected from the wild for fattening (Mirera and Mtile, 2009). Studies have shown that juvenile crabs are collected in intertidal zones that are accessible to a wide range of crab collectors who cannot enter the mangrove forests to get bigger crabs (Mirera et al., 2013). The increasing demand for crabmeat creates a need to develop the aquaculture, targeting all stages. ...
Lakes, rivers and oceans provide unique resources and support fisheries and aquaculture worldwide. The fisheries and aquaculture sector of Kenya contributes approximately 0.8% to the country’s GDP. Marine production is about 9 000 tonnes per year. Marine finfish form the bulk of the marine production, while shellfish (e.g. prawns, lobsters and crabs), molluscs (e.g. octopi and squids) are underexploited. The Fishery sector has the potential of about USD 5 billion for the Blue Economy in Kenya. Crab fishery in Kenya is active in some areas of the south and north coast. The crab resources along the Kenyan waters are diverse and a variety of species are edible. The most commonly fished crab by artisanal fishers is the Mangrove Mud Crab Scylla serrata. Semi-commercial and industrial fishers usually have portunid and other deep sea crabs as by-catch in trawl and longline fisheries, which in many cases are unutilized. Exports of live crabs have increased over the years, with exports mainly to Asian countries. Export of frozen crabs started recently. The need to sustainably utilize lake, river and ocean resources is recognized and important in promoting Blue Economy. Sustainable development of crab fishery provides a potential area for the Blue Economy development in Kenya. Research is essential to crab fishery development.
... The future of capture fisheries production in tropical countries is challenged by increasing demand for resources combined with the effects of global climate change thus on the declining trend (Francis and Bryceson 2001;Cheung et al. 2010;Worm and Branch 2012;Mirera et al. 2013). Indeed, most of the tropical countries are socio-economically vulnerable and thus need to develop adaptive strategies to cope with climate change and declining fisheries. ...
... In addition, they exist in data poor conditions which makes it difficult to capture both socio-economic contributions leading to their under valuation and un-appreciation by policy makers in many countries (Gillett and Lightfoot 2002;Andrew et al. 2007). In Kenya and other countries of East Africa, the situation is more worrying along the coastline due to the social and cultural constraints that have slowed the pace of mariculture development as opposed to other areas where freshwater aquaculture has progressed (Brummett and Williams 2000;Mirera and Ngugi 2009;Mirera 2011a, b;Mirera et al. 2013;Ndanga et al. 2013). Indeed, African mariculture development is small and only reached 24,000 metric tons in 2007, which is 3 % of overall aquaculture production (FAO 2010). ...
... Out of the four communities along the coast of Kenya, only two have an active mud crab farming activity. However, the communities consider mariculture as a viable alternative livelihood option to fishing households due to declining catch and sizes caught from their traditional fishing grounds (Primavera 2006;Primavera et al. 2010;Mirera 2011b;Worm and Branch 2012;Mirera et al. 2013). Thus, crab farming acts as a new way of maximising the value of crabs in the domestic and export markets, and it is integrated easily because it complements or adds value to the artisanal mud crab fishery (Mirera 2011b;Bondad-Reantaso et al. 2012;Moksnes et al. 2012). ...
Small-scale mud crab aquaculture was introduced in East Africa in late 1990s as a mangrove friendly aquaculture to improve the livelihood of coastal communities through organised community groups (OCGs). The OCGs approach was a strategy aimed at ensuring benefits to the village and regulating access to the open access resource (land in mangrove forests). A social and economic assessment was conducted at Majaoni, Ma-kongeni, Ihaleni and Dabaso along the Kenyan coast. The paper looks at the social and economic characteristics of the groups, their management systems, contribution of mud crab aquaculture to the livelihoods of local communities and policy issues related to the interventions. There is wider involvement of the mijikenda community in mud crab farming; however, the level of women participation is low. A strong market link exists between the groups and the different market outlets, where hotels and exporters offer the highest prices. Regional price variations existed and may need networking between the groups. The paper concludes that national policies may need to be redirected to support small-scale aquaculture development and ensuring capacity building for women, operation and management of groups, provision of extension services, data management and pro-vision of user rights for communities working in the mangrove environment.
... According to Mirera et al. (2013), fishing that is carried out in the mangrove forest with simple local gear is regulated by tides and seasons. The limited migrant fishing and the average catch of the sizes of the fishery is limited. ...
... In fact, the fisher people follow specific tracks that are strongly guarded by individual fishers. Mirera et al. (2013) go on to explain that adult fish movement goes deeper and further in the mangrove forest, unlike juvenile fish. They conclude that many fisher folks were operating without license permit. ...
Cameroon’s forest is one of the richest ecosystems in the Congo Basin and in Africa as a whole in terms of its biodiversity. These forest types are currently subjected to multiple categories of threats. By enacting a new forestry law in 1994, the government of Cameroon intended to intensify efforts toward the protection and conservation of this rich biodiversity. This study aimed to compare two forest management systems, a state management system (the case of Takamanda National Park) and a community-based management system (the case of Bimbia- Bonadikombo Community Forest), to determine which management system better conserves and protects the forest against biodiversity loss. The study applied a methodological framework that made use of selected indicators and criteria to evaluate the extent of sustainability of the two forest management systems and challenges faced in implementing them. Both quantitative and qualitative results were realized through the administration of questionnaires, semi-structure interview and in-depth contents analysis of Law No.94-1 of 20th January 1994 that lays down forestry, wildlife and fisheries regulations and the 1996 Environmental Management Law that directs Cameroon’s compliance to the international standard of protecting the environment.Results indicated that community-based system of forest management is a much more sustainable approach of forest management than a state management system. Based on the criterion of cultural values attributed to natural resources in the community-based management zone (Bimbia- Bonadikombo Community Forest), 78.2% of the local communities were more willing to protect biodiversity as opposed to 48.3% from state management zone (Takamanda National Park). This study found that the level of participation in the community-based management system was much more inclusive and transparent. On the other hand, in the state management system, a high level of corruption, lack of transparency, delayed and irregular salaries of forest guards and minimal participation of local communities in forest management decision-making was noted and likely responsible for the ineffectiveness and unsustainable management efforts in this system. The study recommends the adoption and implementation of a more inclusive, transparent and accountable management in the state managed system (Takamada national park), particularly the full involvement of respected Elites, Chiefs and Traditional Councils.
... El conocimiento de las áreas de pesca puede ser la diferencia entre obtener buenas capturas o bajas capturas, es por ello, que la mayoría de los pescadores optan por visitar áreas ya conocidas en lugar de nuevas áreas de pesca, éste conocimiento de sobre dónde pescar y cómo pescar en la mayoría de los casos es transmitido a los nuevos pescadores por los padres o abuelos (Bastos & Petrere 2010;Mirera et al. 2013). Durrenberger & Palsson (1986) describen en pesquerías de Islandia que los pescadores seguían a las embarcaciones de aquellos capitanes que por lo general tenían éxito en sus viajes de pesca, Guenther et al. (2015) encontraron un comportamiento similar en pescadores de langosta de las costas de California. ...
... El conocimiento de saber dónde, cuándo y cómo pescar aunado a las habilidades innatas y adquiridas por el pescador, son variables que influyen en el éxito o en el fracaso en la actividad de la pesca así como en el riesgo de sufrir o no un accidente de buceo (Durrenberger & Palsson 1986;Holland & Sutinen 1999;Bastos & Petrere 2010;Mirera et al 2013;Guenther et al. 2015). ...
... crassum Smith, 1870, from eastern Pacific (see Vega et al., 2018;Zambrano and Meiners, 2018;Zambrano and Solano, 2018) and C. guanhumi (Latreille, 1828) from western Atlantic (see Rodríguez-Fourquet and Sabat, 2009;Carmona-Suárez and Guerra-Castro, 2011;Santos et al., 2022); and four Scylla species -S. serrata (Forsskål, 1775), S. olivacea (Herbst, 1796), S. tranquebarica (Fabricius, 1798), and S. paramamosain Estampador, 1949, from different areas of the world (Fondo et al., 2010;Mirera et al., 2013;Rahman et al., 2020;Leoville et al., 2021). ...
Ucides cordatus is one of the main fishery resources of the "Todos os Santos" Bay (BTS), State of Bahia, Brazil. Population parameters (structure, density, and fishery potential) of this crab species were analyzed in the dry and rainy seasons in nine mangrove areas of BTS. Five sample quadrats (5 × 5 m) were used to record the number and diameter of active open burrows (with biogenic activity) and closed burrows of U. cordatus, tree variables (composition, density, and diameter), and flood level. Crab density (ind.m − 2) was indirectly estimated by counting galleries. The diameter of open galleries was converted into carapace width (CW) using a regression model to later characterize the U. cordatus population structure. There were more galleries in the dry season than in the rainy season. Crab density ranged from 0.32 to 2.63 ind.m − 2 (1.32 ± 0.90 ind.m − 2), and the mean density was higher during the dry period (t = 0.02; p < 0.05). Crab density differed among sampling areas regardless of seasonal period. Crab size (CW) in BTS was 52.4 ± 16.7 mm, with specimens significantly larger during the dry period (t = 0.01; p < 0.05), and there was a significant difference (F = 4.57; p = 000.1) among mangrove areas. Non-commercial size animals (CW < 60.0 mm) were more abundant (65.2%) than those with commercial size (34.8%) in BTS. Crab density and flood level showed significant negative correlation (p = − 0.51; p < 0.05), while there was a positive correlation between CW and flooding level (p = 0.40; p < 0.05). U. cordatus population parameters differed significantly among BTS sampling sites due to their heterogeneity. This study is the first assessment of "uçá"-crab populations in BTS mangroves and reveals a need for a sustainable management in the area. Furthermore, this study could be a model for monitoring other large brachyuran species inhabiting estuarine systems, which are economically and biologically relevant.
... Hasil Pengamatan Wisata Mangrove Kawasan CMCsangat sesuai dilakukan di Pantai Clungup yang memiliki tingkat kerapatan mangrove yang cukup tinggi dengan substrat pasir berlumpur. MenurutMirera et al, (2013), substrat jenis lempung berpasir atau berlumpur merupakan substrat yang sangat cocok untuk tempat tumbuhnya jenis Rhizophora Sp dan Sonneratia alba. Pasang surut di kawasan pantai juga tidak lebih dari 1 meter, dan terdapat beragam biota khas ekosistem mangrove seperti ikan, udang, kepiting, moluska, reptile, dan burung. ...
This study aims to determine the suitability and carrying capacity of coastal areas in the Clungup Mangrove Conservation (CMC) Malang Regency, East Java for coastal tourism activities such as beach recreation, mangrove tourism, snorkeling, and fishing. This research was conducted from August to October 2020 through a survey with an observative approach to obtain primary data, while secondary data was obtained from area managers as supporting data. The carrying capacity of the area for beach tourism activities is 3,234 people/day, mangrove tourism is 6,675 people/day, diving tours are 684 people/day, and snorkeling is 59 people/day. As for fishing activities, this area can accommodate 553 people/day, Canoeing 20,025 people/day, and camping 120 people/day. The number of tourists in the CMC area is still below its carrying capacity. The management of the number of tourists that are currently controlled is considered appropriate and follows the carrying capacity of the environment. However, the potential for the area to be developed closer to its carrying capacity is still possible. Increased tourist visits will provide economic benefits for the community and business actors who support tourism around the CMC area, causing an economic multiplier effect.
... Hasil Pengamatan Wisata Mangrove Kawasan CMCsangat sesuai dilakukan di Pantai Clungup yang memiliki tingkat kerapatan mangrove yang cukup tinggi dengan substrat pasir berlumpur. MenurutMirera et al, (2013), substrat jenis lempung berpasir atau berlumpur merupakan substrat yang sangat cocok untuk tempat tumbuhnya jenis Rhizophora Sp dan Sonneratia alba. Pasang surut di kawasan pantai juga tidak lebih dari 1 meter, dan terdapat beragam biota khas ekosistem mangrove seperti ikan, udang, kepiting, moluska, reptile, dan burung. ...
This study aims to determine the suitability and carrying capacity of coastal areas in the Clungup Mangrove Conservation (CMC) Malang Regency, East Java for coastal tourism activities such as beach recreation, mangrove tourism, snorkeling, and fishing. This research was conducted from August to October 2020 through a survey with an observative approach to obtain primary data, while secondary data was obtained from area managers as supporting data. The carrying capacity of the area for beach tourism activities is 3,234 people/day, mangrove tourism is 6,675 people/day, diving tours are 684 people/day, and snorkeling is 59 people/day. As for fishing activities, this area can accommodate 553 people/day, Canoeing 20,025 people/day, and camping 120 people/day. The number of tourists in the CMC area is still below its carrying capacity. The management of the number of tourists that are currently controlled is considered appropriate and follows the carrying capacity of the environment. However, the potential for the area to be developed closer to its carrying capacity is still possible. Increased tourist visits will provide economic benefits for the community and business actors who support tourism around the CMC area, causing an economic multiplier effect.
... In addition, crabs play a key role in the food chain (Wolff et al., 2000), the plant cycle (Schories et al., 2003), and in the bioturbation of sediment (Smith et al., 1991;Kristensen, 2008). However, the combined effect of overfishing and expanding degradation of mangrove ecosystem can affect the sustainability of local crab populations (Le Vay et al., 2008;Cheung et al., 2010;Mirera et al., 2013). Recently, the environmental authorities of the West-Indian Ocean have developed conservation programs focused on the restoration of mangrove ecosystems and regulation of crabs' fisheries to ensure the resource sustainability (e.g. ...
Mud crab, Scylla serrata, is a common mangrove species in the Indian Ocean. Over the last decades, fishing pressure has greatly increased especially in Madagascar. Therefore, improving the knowledge of mud crab biology and ecology is crucial to guide conservation and restoration plans. This study aimed at describing the distribution of burrows of the mud crab in a mangrove in southwestern Madagascar. Burrows fulfill an essential functional role by limiting the exposure of crab to environmental stress, such as desiccation during low tide, and predation. A total of 140 burrows were observed and available conditions were described at 168 random sampling points at low tide in three different mangrove zones, during the dry season (July 2014). Twelve environmental factors were recorded to reflect the position within the mangrove, the substrate composition and the surrounding floristic structure. A multivariate ordination analysis highlighted an overall association between burrows and specific habitat conditions. Boosted regression trees then indicated that the burrows distribution was predominantly explained by the avoidance of hard substrates. The occurrence of burrows was positively related to the upper intertidal zone of the mangrove where the water level was below 100 cm. Although the tree density had a positive effect, the occurrence of burrows was higher for low percentage of shade (<40%). These results provide insight for identifying mangrove areas that have an essential functional role for the conservation of mud crab populations.
... Despite being an introduced organism with a largely undocumented ecological impact in Hawai'i, S. serrata has high market value locally in the islands and throughout the Indo-Pacific where it is also cultivated through aquaculture in many locations (Quinitio et al. 2001;Triño and Rodriguez 2002;Mirera et al. 2013). In 1999, the total global catch of S. serrata was 13 431 tonnes, with Indonesia and Thailand reporting the Moveable sluice gates can be used to partially control flow of water through channels into and out of fishpond. ...
Hawaiian fishponds, or loko i‘a, are ancient aquaculture systems and models of sustainable aquatic resource management from traditional Native Hawaiian harvest practices. Of the 488 fishponds documented in ancient Hawai‘i, only 38 are currently actively managed. Building on Indigenous and local knowledge, fishponds are being adapted to current community needs. Functional fishponds perpetuate culture, improve food security, enhance ecosystem services and transform conservation biology through Indigenous perspectives. Here we examine how Indigenous practices effectively maintain sustainable harvest of an introduced, but economically important, crab species, the mud crab, Scylla serrata (Forskål 1775). The State of Hawai‘i has only a size limit, and no bag limits, for this species. With Indigenous management in a Hawaiian fishpond, limits are set and enforced in response to fluctuations in catch. We used a mark–recapture experiment to parameterise a size-structured population model, which we used to investigate the impact of changing harvest rates. Throughout the study period of 2017–20, the mean number of crabs per harvest was 28 individuals (s.d. = 7) and average catch per unit effort was 0.20 crabs per trap-hour (s.d. = 0.054). During winter, catch per unit effort was lower but mean crab size was larger than during summer. Model simulations indicated that current Indigenous practices are less likely to cause a decline in population growth rate than a strict size limit. Using information from Indigenous harvest practices and the mark–recapture study, we codeveloped a versatile crab population model that can be tailored to changing management objectives.
... Similarly, on the global scale seaweed farming is ranked as a major source of livelihood to many coastal communities in low-income countries where dependency ratio is high (Hurtado-Ponce et al., 2001;Ask et al., 2003;Msuya et al., 2007). Comparatively, seaweed farming has a high lump some earning compared to other fisheries where earnings are on a daily basis and unable to support meaningful investment other than food (Smith and Renard, 2010;Mirera et al., 2013). In Tanzania and Philippines, a higher income from seaweed farming was found to contribute significantly to an increased standard of living for the families (Mshigeni, 1994;Hurtado-Ponce et al., 2001). ...
... Over the years, communities have developed significant traditional knowledge concerning their environment. However, with increasing population and the increasing number of widows and orphans, intertidal resource harvesting in Kenya has in recent years experienced entry of children and women to meet the emerging and expanding family needs (Mirera 2011b;Mirera et al., 2013). This increase in pressure on resources is likely to lead to serious problems of over-exploitation in the future. ...
A number of donor-funded projects by NGOs, government departments and faith-based organizations have piloted milkfish farming along the coast of Kenya at different scales with the aim of addressing poverty and food security at the community level. This paper provides an overview of the history of milkfish farming, organisation of operations, funding, farmers trends, and production dynamics, using both secondary and primary data. Primary data were obtained from quantitative and qualitative assessments covering 26 community milkfish farming groups, while secondary data were obtained from the grey literature and donor-funded project reports. Additional primary data were obtained through 9 key informant interviews covering three coastal Counties, and focus group discussions (8-10 members) at all the community milkfish farms. The study established that milkfish farming could be traced back to the early 1980’s as a by-product of the prawn farming intervention by FAO, and later in other private farms that practised prawn farming. Community/village based small-scale milkfish farming was initiated about two decades ago using organised community groups (OCGs) as the entry point. The number of OCGs undertaking milkfish farming fluctuated with availability of donor funds and increased significantly between 2007 and 2015 with an increase in earthen pond farming area from 0.9ha to 6.8ha over this period. However, the scale of production remained low. Annual milkfish production increased from less than 50kg in 2005 to a maximum of 3.2 tons in 2015. Milkfish farming has not attained production levels that can address poverty and food security issues; a fact that was associated with the lack of reliable milkfish seed for stocking culture facilities. Harvests from existing farms are sold at the farm gate and in nearby market centres with a few communities venturing into opening fish shop outlets to sell their produce.
... The giant mud crab, Scylla serrata (Forsskål), and the blue-swimmer crab, Portunus pelagicus (L.), are two examples of economic and socially important estuarine species in many tropical and subtropical regions across the Indo-West-Pacific (Mgaya & Chande, 2004;Le Vay et al., 2008;Mirera, Ochiewo, Munyi & Muriuki, 2013;Alberts-Hubatsch et al., 2015). Due to rapid increases in market demand, fishing effort for these crabs (using baited traps) across their range has drastically increased over the last few decades (Mirera, 2011;Alberts-Hubatsch et al., 2015). ...
The issues surrounding illegal, unregulated and unreported fishing, and that of abandoned, lost and discarded fishing gears, leading to ghost fishing, are intensifying. Estuarine crab trapping is likely subject to high levels of illegal and potential ghost fishing, because it also has good economic incentives regarding potential catch, low gear acquisition costs and accessible fishing grounds. To improve the efficiency and effectiveness of fisheries monitoring, control and surveillance operations, the efficacy of small consumer‐grade drones for sighting traps in an estuary in NSW, Australia, was tested. Twelve sets of two flights were undertaken at 20 and 30 m altitude over a 600‐m stretch of estuary for 5 days to quantify the detectability of submerged mesh traps of three different mesh colours. The drone was able to detect the majority of traps efficiently, with depth in relation to water clarity being the main factor affecting detection. In shallow water, detection rates were high for all mesh colours, but in the slightly deeper placements, orange traps were more readily detected. This study demonstrates that drones could be an efficient and reliable tool for rapidly assessing areas for illegal and derelict traps and can be supplemented into land or vessel‐based fisheries operations.
... Sampling was done by purposive sampling method. This method is carried out by walking down the coast at the intertidal area in order to find crabs [8]. Each crab samples obtained were sorted and preserved with Alcohol 70 % for wet preservation and 10 % solution of formaldehyde for dry preservation. ...
Crabs are members of the subphylum Crustacea that can be found in various habitats, such as in the intertidal zone at Sundak Beach. However, Sundak Beach is a popular tourist attraction with tremendous activities in the intertidal zone. This can cause habitat loss of crabs. Information on the diversity of crabs at Sundak Beach is still limited. Therefore, this study aims to conduct crabs inventory at Sundak Beach. Samples were collected at night in Aug 2016 and Jan 2017 using purposive sampling method. The results showed that 16 species from six families were found at Sundak Beach, including Calappa gallus (Calappidae); Eriphia scabricula (Eriphiidae); Grapsus albolineatus and Percnon planissimum (Grapsidae); Tiarinia cornigera (Majidae); Charybdis annulata, Portunus granulatus, Portunus pubescens, Thalamita coeruleipes, Thalamita intermedia, Thalamita prymna, and Thalamita sima (Portunidae); Actaeodes tomentosus, Atergatis floridus, Ozius rugulosus, and Zosimus aeneus (Xanthidae).
... Lokasi yang memiliki indeks kategori sedang akibat rusaknya atau terdegrada- Dari aspek ekologi, ekosistem mangrove Teluk Bintan secara umum kodisi lingkungannya mendukung untuk kelangsungan hidup kepiting bakau atau dengan kata lain secara ekologis kawasan mangrove tersebut layak sebagai habitat dan memiliki potensi untuk tumbuh kembangnya kepiting bakau (Scylla serrata). Menurut Mirera et al. (2013) permasalahan perikanan kepiting bakau tidak hanya masalah terdegradasinya ekosistem mangrove, namun secara global juga dihadapkan oleh permasalahan gabungan yaitu dampak penangkapan berlebihan dari alam, perubahan iklim dan kurangnya intervensi pengelolaan serta kurangnya pengetahuan atau keterampilan yang dimiliki oleh nelayan dalam mengeksploitasi sumberdaya kepiting bakau. Sehingga untuk menjaga agar kegiatan penangkapan kepiting bakau di Teluk Bintan dapat berlanjut dan tidak terancam berkurang secara drastis, maka perlu upaya pengelolaaan ekosistem mangrove secara baik agar kualitas lingkunganya tidak menurun. ...
p> Mud crab ( Scylla serrata ) is one of small scale fisheries commodity that have high economic value and typically associated with good mangrove ecosystem . A habitat degradation will cause a serious impact on the existence of mud crab population. The puropse of this study was to assess the ecological quality of mud crab habitat condition on B intan B ay’s mangrove ecosystem . Ecological data collection was conducted by using plots line transect for mangrove and the mud carb data collection by using fishermen catch ( fisher based survey ) . The results showed the value of habitat quality index (HQI) of mud crab ( Scylla serrata ) ranged from 52-82 w hich mean in the “m oderate ” category (index value 43-66) and "good" (index value 67-90). It show ed that Bintan Bay’s mangrove e cosystems was good enough to support the viability of mud crab. Habitat quality had a linier impact on body weight gain ( R2 = 99 . 7 8%) and carapace width ( R2= 99 . 21% ) . This showed that higher the index value of habitat quality, the size of the body weight and carapace width will increases.
Keywords : Scylla serrata, habitat quality, ecology, mangroves, and Bintan Bay </p
... Due to rapid population growth in coastal areas in East Africa, exploitation of mud crabs and other sea food has increased drastically. The rapidly expanding tourism industry and export trade has also led to increased demand and exploitation of mud crabs in the region [10]. As a result, the preferred market size has decreased consistently from more than 1 kg two decades ago to the current size of 0.5 kg [2]. ...
The giant mud crab Scylla serrata provides an important source of income and food to coastal communities in East Africa. However, increasing demand and exploitation due to the growing coastal population, export trade, and tourism industry are threatening the sustainability of the wild stock of this species. Because effective management requires a clear understanding of the connectivity among populations, this study was conducted to assess the genetic diversity and connectivity in the East African mangrove crab S. serrata. A section of 535 base pairs of the cytochrome oxidase subunit I (COI) gene and eight microsatellite loci were analysed from 230 tissue samples of giant mud crabs collected from Kenya, Tanzania, Mozambique, Madagascar, and South Africa. Microsatellite genetic diversity (He) ranged between 0.56 and 0.6. The COI sequences showed 57 different haplotypes associated with low nucleotide diversity (current nucleotide diversity = 0.29%). In addition, the current nucleotide diversity was lower than the historical nucleotide diversity, indicating overexploitation or historical bottlenecks in the recent history of the studied population. Considering that the coastal population is growing rapidly, East African countries should promote sustainable fishing practices and sustainable use of mangrove resources to protect mud crabs and other marine fauna from the increasing pressure of exploitation. While microsatellite loci did not show significant genetic differentiation (p > 0.05), COI sequences revealed significant genetic divergence between sites on the East coast of Madagascar (ECM) and sites on the West coast of Madagascar, mainland East Africa, as well as the Seychelles. Since East African countries agreed to achieve the Convention on Biological Diversity (CBD) target to protect over 10% of their marine areas by 2020, the observed pattern of connectivity and the measured genetic diversity can serve to provide useful information for designing networks of marine protected areas.
... Lokasi yang memiliki indeks kategori sedang akibat rusaknya atau terdegrada- Dari aspek ekologi, ekosistem mangrove Teluk Bintan secara umum kodisi lingkungannya mendukung untuk kelangsungan hidup kepiting bakau atau dengan kata lain secara ekologis kawasan mangrove tersebut layak sebagai habitat dan memiliki potensi untuk tumbuh kembangnya kepiting bakau (Scylla serrata). Menurut Mirera et al. (2013) permasalahan perikanan kepiting bakau tidak hanya masalah terdegradasinya ekosistem mangrove, namun secara global juga dihadapkan oleh permasalahan gabungan yaitu dampak penangkapan berlebihan dari alam, perubahan iklim dan kurangnya intervensi pengelolaan serta kurangnya pengetahuan atau keterampilan yang dimiliki oleh nelayan dalam mengeksploitasi sumberdaya kepiting bakau. Sehingga untuk menjaga agar kegiatan penangkapan kepiting bakau di Teluk Bintan dapat berlanjut dan tidak terancam berkurang secara drastis, maka perlu upaya pengelolaaan ekosistem mangrove secara baik agar kualitas lingkunganya tidak menurun. ...
p> Mud crab ( Scylla serrata ) is one of small scale fisheries commodity that have high economic value and typically associated with good mangrove ecosystem . A habitat degradation will cause a serious impact on the existence of mud crab population. The puropse of this study was to assess the ecological quality of mud crab habitat condition on B intan B ay’s mangrove ecosystem . Ecological data collection was conducted by using plots line transect for mangrove and the mud carb data collection by using fishermen catch ( fisher based survey ) . The results showed the value of habitat quality index (HQI) of mud crab ( Scylla serrata ) ranged from 52-82 w hich mean in the “m oderate ” category (index value 43-66) and "good" (index value 67-90). It show ed that Bintan Bay’s mangrove e cosystems was good enough to support the viability of mud crab. Habitat quality had a linier impact on body weight gain ( R2 = 99 . 7 8%) and carapace width ( R2= 99 . 21% ) . This showed that higher the index value of habitat quality, the size of the body weight and carapace width will increases.
Keywords : Scylla serrata, habitat quality, ecology, mangroves, and Bintan Bay </p
... Another study was performed in the Huave Lagoon System of Mexico, where the integration of fishermen's perspectives and opinions with the consensus-building process allowed the construction of a holistic management policy to conservation of the lagoon and maintenance of traditional fishery activity (Tenorio et al., 2013). Considering the traditional communities of fishers who inhabit coastal regions, little is known about how their traditional knowledge influences their ability to exploit natural resources or how this knowledge could be applied to management practices (Mirera et al., 2013). Brachyuran crustaceans, including Ucides cordatus Linnaeus, 1763 (mangrove crab), Cardisoma guanhumi Latreille, 1825 ('guaiamum' ), and Goniopsis cruentata Latreille, 1803 ('aratu'), are among the main resources exploited in Brazilian mangrove forests by surrounding communities ( Nishida, 2002, 2003; Firmo et al., 2011 ). ...
... Another study was performed in the Huave Lagoon System of Mexico, where the integration of fishermen's perspectives and opinions with the consensus-building process allowed the construction of a holistic management policy to conservation of the lagoon and maintenance of traditional fishery activity (Espinoza-Tenorio et al., 2013). Considering the traditional communities of fishers who inhabit coastal regions, little is known about how their traditional knowledge influences their ability to exploit natural resources or how this knowledge could be applied to management practices (Mirera et al., 2013). ...
Buku ini berisi tentang bagaimana implementasi Kampus Merdeka dan target pencapaian IKU Perguruan Tinggi dapat dioptimalkan dalam rangka mengatasi persoalan bangsa, khususnya stunting. Selain itu, buku ini juga berisi tentang hasil pemikiran kontributor dari berbagai latar belakang profesi dan keilmuan. Hasil pemikiran tersebut ada yang berupa hasil penelitian dan kajian literatur. Pembahasan dibagi menjadi empat bagian. Bagian satu menjelaskan tentang bagaimana Universitas Teuku Umar melaksanakan Program Kompetisi Kampus Merdeka (PKKM) tahun 2021 yang fokus pada penanganan stunting di enam kabupaten di Provinsi Aceh. Bagian dua berkaitan dengan kajian sosial dan ekonomi dalam ruang lingkup isu stunting. Bagian tiga berisi kajian hukum dan politik tentang penanganan stunting. Bagian empat pembahasan tentang industri pertanian dan marina sebagai alternatif solusi penanganan stunting.
The Kenya Coast is endowed with some of the world’s most valuable coastal and marine resources that not only support economic activities but also the livelihoods of the people. The resources include mangrove forests, estuaries and deltas, sand dunes, beaches, coral reefs, seagrass beds as well as pelagic habitats among others. These resources are environmentally sensitive and easily degrade if poorly managed and used. This report presents the numerous issues and challenges facing the coastal and marine environment in Kenya. Notable drivers of environmental degradation in coast region are: high rates of population growth, urbanization, expansion of industrial developments, overexploitation of natural resources and climate change among others. This report, commissioned by National Environment Management Authority (NEMA), reviews the first edition of the State of the Coast (SOC) Report for Kenya prepared in 2009 and provides an update with additional data and information on the status of the coastal and marine environment. The findings provides evidence on the need to foster integrated approach to management of the coastal zone.
Peranan ekosistem mangrove dalam menunjang kehidupan masyarakat khususnya masyarakat pesisir sangatlah penting, seperti mencegah abrasi, sebagai tempat berlindung dan berkembang biak beberapa jenis ikan, penyerap karbon dari kegiatan sehari hari bahkan dalam jumlah yang banyak dapat menyerap karbon skala industri dan dapat diperjual belikan dalam bentuk kredit karbon (jasa lingkungan) dan mangrove juga mempunyai nilai estetika dalam wujud wisata mangrove.
ABSTRAKKepiting bakau (Scylla serrata) merupakan salah satu potensi komoditas perikanan skala kecilyang memiliki nilai ekonomi tinggi. Kelimpahan populasi dipengaruhi oleh upaya penangkapan dankondisi ekosistem mangrove sebagai habitat utamanya. Produksi kepiting bakau di Teluk Bintanmenurun dan penyebabnya belum diketahui dengan pasti. Oleh karena itu, perlu dilakukan kajiantentang biologi kepiting bakau di Teluk Bintan. Penelitian ini bertujuan untuk mengkaji statuspopulasi kepiting bakau yang meliputi struktur ukuran, parameter pertumbuhan dan laju mortalitasdan eksploitasi. Pengambilan data kepiting bakau dilakukan dengan pendekatan yaitu fisher-basedsurvey. Hasil penelitian menunjukkan ukuran kepiting bakau yang tertangkap mulai dari lebar karapas(CW) 64-172 mm, ukuran fase muda kepiting jantan yang tertangkap mencapai 46,62% dan betinamencapai 48,06%, keduanya hampir setengah dari tangkapan total, ini menunjukkan bahwa alattangkap yang digunakan belum selektif. CW∞ jantan mencapai 176,93 mm lebih tinggi dari kepitingbetina sebesar 169,58 mm, namun sebaliknya nilai koefesien K jantan (0,360) lebih kecil dari betina(0,390), sehingga pertumbuhan kepiting bakau betina lebih cepat dari jantan. Perkiraan angkakematian alami (M) jantan = 0,5566 dan kematian akibat penangkapan (F) jantan = 0,6434 sedangkanM betina = 0,59 dan F betina = 0,41. Laju eksploitasi (E) kepiting jantan mencapai 53,62%, ini dapatdikatakan telah terjadi lebih tangkap atau over eksploitasi.Kata kunci: Scylla serrata, parameter pertumbuhan, struktur ukuran, mangrove and Teluk BintanABSTRACTMud crab (Scylla serrata) is one of the potential of small-scale fishery commodities that havehigh economic value. The abundance of the population is affected by the fishing effort and conditionsmangrove ecosystem as its main habitat. Mud crab production in the Gulf of Bintan declined and thecause is not known with certainty. Therefore, it is necessary to study on the biology of mud crab in theGulf of Bintan. This study aims to assess the status of mangrove crab population that includes the sizestructure, parameters of growth and the rate of mortality and exploitation. Data retrieval is done witha mangrove crab fisher-based survey. The results showed that the size of mud crab caught fromcarapace width (CW) 64-172 mm, the size of the young phase male crabs caught females reached46.62% and reached 48.06%, both are almost half of the total catch, it indicates that fishing gearused is not selective. CW∞ males reach 176.93 mm higher than the female crabs of 169.58 mm, butinstead value koefesien K males (0.360) is smaller than females (0.390), so that the growth of femalemud crabs faster than males. Estimated natural mortality rates (M) male = 0.5566 and deaths fromarrest (F) male = 0.6434 while M females female F = 0.59 and = 0.41. The rate of exploitation (E)male crabs reached 53.62%, can be said to have occurred over fishing or over-exploitation.Keywords: Scylla serrata, growth parameters, structure size, mangrove and bay Bintan
ABSTRAKKepiting bakau (Scylla serrata) merupakan salah satu potensi komoditas perikanan skala kecil yang memiliki nilai ekonomi tinggi. Kelimpahan populasi dipengaruhi oleh upaya penangkapan dan kondisi ekosistem mangrove sebagai habitat utamanya. Produksi kepiting bakau di Teluk Bintan menurun dan penyebabnya belum diketahui dengan pasti. Oleh karena itu, perlu dilakukan kajian tentang biologi kepiting bakau di Teluk Bintan. Penelitian ini bertujuan untuk mengkaji status populasi kepiting bakau yang meliputi struktur ukuran, parameter pertumbuhan dan laju mortalitas dan eksploitasi. Pengambilan data kepiting bakau dilakukan dengan pendekatan yaitu fisher-based survey. Hasil penelitian menunjukkan ukuran kepiting bakau yang tertangkap mulai dari lebar karapas (CW) 64-172 mm, ukuran fase muda kepiting jantan yang tertangkap mencapai 46,62% dan betina mencapai 48,06%, keduanya hampir setengah dari tangkapan total, ini menunjukkan bahwa alat tangkap yang digunakan belum selektif. CW∞ jantan mencapai 176,93 mm lebih tinggi dari kepiting betina sebesar 169,58 mm, namun sebaliknya nilai koefesien K jantan (0,360) lebih kecil dari betina (0,390), sehingga pertumbuhan kepiting bakau betina lebih cepat dari jantan. Perkiraan angka kematian alami (M) jantan = 0,5566 dan kematian akibat penangkapan (F) jantan = 0,6434 sedangkan M betina = 0,59 dan F betina = 0,41. Laju eksploitasi (E) kepiting jantan mencapai 53,62%, ini dapat dikatakan telah terjadi lebih tangkap atau over eksploitasi. Kata kunci: Scylla serrata, parameter pertumbuhan, struktur ukuran, mangrove and Teluk Bintan ABSTRACTMud crab (Scylla serrata) is one of the potential of small-scale fishery commodities that have high economic value. The abundance of the population is affected by the fishing effort and conditions mangrove ecosystem as its main habitat. Mud crab production in the Gulf of Bintan declined and the cause is not known with certainty. Therefore, it is necessary to study on the biology of mud crab in the Gulf of Bintan. This study aims to assess the status of mangrove crab population that includes the size structure, parameters of growth and the rate of mortality and exploitation. Data retrieval is done with a mangrove crab fisher-based survey. The results showed that the size of mud crab caught from carapace width (CW) 64-172 mm, the size of the young phase male crabs caught females reached 46.62% and reached 48.06%, both are almost half of the total catch, it indicates that fishing gear used is not selective. CW∞ males reach 176.93 mm higher than the female crabs of 169.58 mm, but instead value koefesien K males (0.360) is smaller than females (0.390), so that the growth of female mud crabs faster than males. Estimated natural mortality rates (M) male = 0.5566 and deaths from arrest (F) male = 0.6434 while M females female F = 0.59 and = 0.41. The rate of exploitation (E) male crabs reached 53.62%, can be said to have occurred over fishing or over-exploitation. Keywords: Scylla serrata, growth parameters, structure size, mangrove and bay Bintan
The recent revision of the genus Scylla into four species provides a basis for the development of a better understanding of their ecology, population biology and the sustainable management of fisheries, as well as the selection of species for aquaculture. In many cases, previous studies of mud crab fisheries and ecology have reported the occurrence of more than one " type " of mud crab, but data for any one currently known species have rarely been recorded. Consequently, much of the biological and ecological data in the literature must be reviewed. This paper summarizes the current state of knowledge on mud crab ecology in relation to population biology and management, and discusses priorities for future research to support the development of sustainable mud crab aquaculture and fisheries.
Research is devoted to solving complex aims: educational (the development of ecological competence of managers), and socioeconomic (optimization of access to recreational resources) through the improvement of innovative algorithms, theory and practice of wildlife management. We also tried to identify the problems of integration of Natural and Human sciences as the problems of environmental education. This article contains a description of the elements of how to organize environmental management training in real situations. On the example of integrated assessment of the socio-natural potential (of the Caucasian Mineral Waters region) shows the role of competence in making optimal decisions that affect human values. The article emphasized that the possibility of society full of ecosystem services is directly linked to the idea of the uniqueness and intrinsic value of the natural world, whose safety should be regarded as a guarantee of human health. (C) 2012 Published by Elsevier Ltd. Selection and/or peer review under responsibility of Prof. Dr. Huseyin Uzunboylu
The present study explores the local knowledge held by fishers of Ratnagiri coast about the ecology and biology of mud crab Scylla serrata, an important food species to the local people. It attempts to address the differences and similarities between the information provided by fishers with published biological data about mud crab. A total of about 30 fishers resorting to traditional crab fishery were interviewed using semi structure interview schedule incorporating all the items on which the information was needed. Similarities were noted in respect with habitat, migratory movement for feeding, burrowing habit, size at first maturity and peak spawning season suggesting general pattern. The information provided by the fishers also included differences with published data with respect to breeding migration and feeding preferences of mud crab. Abundance of Scylla serrata along with edible oysters was noted by most fishers. Apart from this, the effect of various ecological phenomenon such as rainfall, light, temperature, tides and lunar cycle on the behavior, condition and availability of mud crab was studied. Local ecological knowledge held by fishers agrees with available Scientific literature about Scylla serrata providing hypotheses to be investigated through biological research. The present study highlights some contributions the fishers' local knowledge may give to local management of Scylla serrata, such as to improve the Scientific knowledge and sensitize the Scientists to local conditions as well as promote the interaction between fishers and Scientists.
The riverside communities devised a community-based program to negotiate with the local government so that they are not evicted. As an intervention package, -which aims to upgrade the living environment and increase the residents’ pro-environmental behaviour-, this program consists of organization and information, combined with social interaction, commitment and feedback performance. Intensive observations were used to examine the effectiveness of the program to environmental behaviour change and upgrading settlement. The finding reveals that having common objective of renovation is the most influential variable in motivating individuals to increase environmentally friendly behaviour on the upgrading environment.
This paper addresses the situation and issues regarding indigenous knowledge among the Malay community at the Eastern Coast of the Peninsular Malaysia. The tacit knowledge of this community and knowledge sharing potentials the indigenous population is explored. The paper examines the opportunities of the members of the community to ascend into the economic mainstream and improve their quality of lives through participation in the industry based on their indigenous knowledge. Some suggestions are incorporated in the paper to yield a conceptual framework of tools for the agencies as support system to build a sustainable livelihood and heritage preservation of the rural community.
ABSTRACT. - There has been considerable confusion regarding the taxonomy of
species in the genus Scylla, commonly known as mud or mangrove crabs. To resolve
this confusion we collected material from the Red Sea (the original type locality of
Scylla serrata), and from many other locations throughout the Indo-Pacific. Two
independent genetic methods, allozyme electrophoresis and sequencing of two
mitochondrial DNA genes, cytochrome oxidase I and I 6s RNA, were employed in an
attempt to discriminate species. The genetic data show that there are at least four distinct
Scylla species. Using this knowledge their morphology was critically examined, and
morphometric data analysed, to determine useful characters for field separation.
Nomenclatural problems have been addressed with appropriate neotype and lectotype
designations. The species recognised are: S. serrata (Forskal, I 775), S. olivacea (Herbst,
1796), S. tranquebarica (Fabricius, 1798), and S. paramamosain Estampador, 1949.
Apparent declines in abundance of mangrove crabs Scylla serrata (Forsskal, 1755) in Kosrae, Federated States of Micronesia, have prompted con- cern regarding long-term persistence of this important cultural and economic resource. To support development of effective management strategies, we gath- ered basic biological information about mangrove crabs on this island, where S. serrata is the only mangrove crab species present. In particular, we were inter- ested in understanding movement patterns and evaluating spatial variation in population structure. Many population characteristics, including estimated life span, ontogenetic shifts in habitat use, sex-specific allometric relationships, male-biased sex ratios, and evidence for limited (
Little is known about the effects of mud crabs population patterns on
their exploitation. We used complementary approaches (experimental,
fisher-based) to investigate how small-scale variations in density, size
and sex-ratio related to the ecology of S. serrata may impact fishing
practices in New Caledonia. Crabs were measured/sexed across 9 stations
in contrasted mangrove systems between 2007 and 2009. Stations were
described and classified in different kinds of mangrove forests
(coastal, riverine, and estuarine); vegetation cover was qualitatively
described at station scale. Annual catch was used as an indicator of
fishing pressure. Middle-scale environmental factors (oceanic influence,
vegetation cover) had significant contributions to crab density (GLM,
84.8% of variance), crab size and sex-ratio (< 30%). While
small-scale natural factors contributed significantly to population
structure, current fishing levels had no impacts on mud crabs. The
observed, ecologically-driven heterogeneity of crab resource has strong
social implications in the Pacific area, where land tenure system and
traditional access rights prevent most fishers from freely selecting
their harvest zones. This offers a great opportunity to encourage
site-specific management of mud crab fisheries.
A pen culture system of the mud crab, Scylla serrata was introduced in Mtwapa mangrove creek with the aim of finding an alternative source of income and food for the local communities, who practice artisanal fishery in the creek. Other objectives were to motivate the interaction between scientists and the community through technology transfer, and to collect scientific data necessary for maintenance and management of the culture system. Pen construction took place from October 2000 - January 2001. The pen was located in the intertidal area and measured 800 m2. It was constructed and fenced using uzio (fish trap) material made of mangrove poles and wood. Stocking of the pen with seed crabs occurred from February- May 2001. Local sources was used to obtain a total of 1697 crab seeds which were measured (carapace length and width), weighed and sexed before stocking. The crabs were fed with trash fish obtained from a local fish processing plant. Feeding was conducted once daily, preferably at high tide. Salinity of the pond ranged from 12.8 to 35 ‰; temperature between 25 and 36 ºC, pH from 7.95-8.25 and dissolved oxygen (DO) from 2.65-4.00 mg/l. Harvesting of the crabs started after 4 months from date of stocking. Additional activities that occurred in the pen were planting of suitable mangrove seeds (Rhizophora mucronata and Avicennia marina) in the bare areas of the pen. These provided canopies for the crab as well as reforesting the area.
The mud crab Scylla serrata is lightly exploited along the East African seaboard. This study reports on fishing practices and gives preliminary estimates of abundance and size structures of the mud crab populations in Utende, Chole Island and Juani Island, Tanzania, and west of Quirimba and Ibo Island, Moçambique. Estimates for three mangrove habitats (in Tanzania); open channel (<1 per 25 m2), mangrove fringe (3 per 25 m2) and inner forest (1 per 25 m2) were obtained using burrow density and from burrow occupancy from fisheries data. Mud crabs from Tanzania were significantly smaller (carapace width) and less abundant (in terms of mass) than those from Moçambique. This newly exploited resource provides a potential alternative source of income, but local management and monitoring plans need to be implemented early.
Artisanal fisheries for mud crabs are an important source of income in coastal communities of the Mekong Delta. However, populations are subject to pressure from increasing fishing effort to provide seed crabs for pond culture, as well as diminishing mangrove habitats. In the present study, Scylla paramamosain was found to be the dominant mud crab species within an estuarine mangal system, representing over 96.8% of mud crab fishery landings between February 1998 and March 1999. S. olivacea was also present in relatively low abundance (3.2% of landings). Analysis of catch-per-unit-effort (CPUE) data collected throughout 1997 and 1998, for an intertidal hand-fishery, shows that mud crabs were present in a fairly narrow range of mean abundance throughout the year, despite protracted periods of freshwater conditions during the rainy season. Recruitment of juvenile S. paramamosain (3–4 cm carapace width) was continuous through 1998, with a significant peak at the beginning of the dry season. No juvenile S. olivacea (< 5="" cm="" carapace="" width)="" were="" found="" during="" the="" study.="" the="" mangal="" appears="" to="" provide="" a="" nursery="" habitat="" for="">S. paramamosain, with predominantly juveniles and sub-adults present, while a higher proportion of adults were recorded in the sub-tidal component of the population. Mature females were present throughout the year, with a peak in September–October 1997. The CPUE analysis provides a baseline of seasonal variation in crab abundance that can be used to monitor the effectiveness of resource management and potential impacts of future changes in habitat.
Fisheries managers frequently try to protect juveniles in order to preserve stocks. Juveniles can be protected by either implementing changes designed to avoid catching immature animals (e.g. increasing mesh size or altering fishing techniques) or protecting nursery grounds. To prevent the capture of immature animals, an estimate of size at maturity is required as well as a knowledge of both fishing methods and the exact location of the nursery grounds. Strong demand for juvenile mud crabs to stock aquaculture ponds has resulted in development of fisheries targeting crabs of all sizes from instar 1 to mature individuals. Using five different fishing methods, different stages in the life cycle of Scylla paramamosain were followed for a period of 16months in an estuarine population in the Mekong Delta, Vietnam. Mangrove habitat utilisation begins when crabs settle out from the plankton at instar 1 [modal internal carapace width (ICW), 0.5cm] amongst the pneumatophores at the mangrove fringe. Increasingly larger crabs were found deeper into the mangrove but they were still living on the surface (modal ICW size class, 1.5cm). As their size increases, the crabs either dig burrows (modal ICW size class, 4.5cm) or they live in the sub-tidal zone, migrating into the mangrove with each tide to feed (modal ICW size class, 4.5cm). Larger crabs were caught offshore (modal ICW size class, 12.5cm) where females accounted for 60% of the catch although of these, only 63% were mature. Recruitment of early instars was continuous but peaked in December to February. Subsequent peaks in the catch rates of larger size classes indicated the development of a single cohort with an estimated growth rate of 2.0cm ICW per month. On the basis of abdominal width, females were estimated to mature at 10.2cm ICW although at 9.7cm ICW, 50% of females had disengaged abdomens. Abdominal disengagement occurred in males at the slightly smaller size of 9.1cm ICW. Allometric relationships between chela height and carapace width suggested 50% of males acquire mature chelae at 10.2cm ICW. These results demonstrate the close linkage between early life stages of S. paramamosain and certain specific niches within mangrove habitats, with the main adult population found to be living sub-tidally at some distance from the mouth of the estuary. The study also highlights the special importance of the mangrove fringe, the border between the mangrove forest and the sea, an area which is particularly vulnerable to physical and anthropogenic impacts.
A socio-economic assessment was conducted at Vanga, Shimoni, Majoreni and Gazi villages in the Kenyan south coast with focus on the sea cucumber fishing patterns, the social and economic characteristics of the fisher communities, the contribution of sea cucumbers to the local livelihoods, and analysis of the management systems. The results indicate that sea cucumber fishers are mainly men. Fishing is done in sub-tidal areas (3–10 m deep) and inter-tidal areas depending on the species being targeted. Those who fish in the sub-tidal areas do skin diving without using SCUBA diving gear. Sea cucumber fishing is heavily done during the northeast monsoon season when the sea is calm and water is clear. About 32% of the sea cucumber fishers also collect other marine products such as octopus. The sea cucumbers are sold fresh from the sea to local first level middlemen who process and sell them to the second level middlemen and exporters in Mombasa. The fishers occasionally borrow money from first level middlemen especially when they fail to catch sea cucumbers but this in turn creates conditions of dependence and possible exploitation. Almost all sea cucumber fishers have stated that they are not willing to make sea cucumbers part of their daily diet. The economic value of the product was substantial; the average monthly revenue for dry sea cucumbers in the area was estimated to US$ 8000. The relative highest profits are derived from juvenile species, thus there is an economic incentive hindering local stocks to reach sexual maturity, which in turn may create a situation in which recruitment success is highly dependent on faraway populations. The present management system falls into general fisheries regulations and was found weak. No specific management plan for sea cucumbers was found.
The current study was carried out over a period of one year to characterise the coastal migrant fishery of Kenya. The study looked at gears and vessels used, and ownership, demographic factors including ages of the fishers and family sizes, migrant activity and resource conservation at two main fishing villages in Kenya; Vanga and Mayungu in the south and north coasts, straddling at 4.663°S and 39.215°E and 3.214°S and 40.135°E respectively. Further, the fishers were categorised with regard to fishing, gear and vessel operation and trade, and evolution upon entry into the fishery was also assessed in order to define fisher-stake in the fishery for resource management and conservation planning. Structured questionnaires were used to interview the fishers, and data and information recorded from 1018 fishers during the survey. Migrants accounted for over 63% of the fishers in the two study sites, with majority of the fishers lying in the 15–45 year age bracket. Dependence level averages at 4–6 person families per fisher. Entry to the fishery was mainly at seamen level, progressing to fishermen and finally to fish dealers (tajiris), with the latter holding >62% capital in the fishery. Resource management in the fishery was low and only ∼10% of the fishers were active participants in marine conservation and community beach management issues. Fisher migrations were mainly monsoon season-linked (>58%) although social factors such as family location determined to a great extent the expanse of the migrations. The revival of fisheries cooperatives and active participation in community resource management and conservation groups is envisaged as the key to the sustainability of both the marine resources and the economies associated with this high mobility, cross-border fishery.
Mangrove crabs (Scylla serrata) were trapped in summer and fall 2004 at four sites, each in a separate municipality on the Pacific island of Kosrae, Federated States of Micronesia. Carapace width (CW) of the 219 crabs averaged 15.1 ± 0.13 cm (SE), slightly larger than the mean size of 221 crabs trapped from the same sites 4 y earlier. Mean CW of the 56 crabs in the upper quartile was 17.5 ± 0.17 cm (SE). In the current study, both sizes of crabs as well as degree and direction of change in size from summer to winter varied among the municipalities. The average CW of crabs from one municipality was significantly larger than from any of the other municipalities. Average CW of crabs from another municipality decreased from summer to fall. These results suggest that although the island-wide crab population appears to be stable, some municipalities may wish to enact site-specific management policies to obtain a harvest regimen that will meet local needs.
amount of fishing effort. The consequence has been the elimination of some substocks, such as herring, cod, ocean perch, salmon, and lake trout. He concluded that an MSY based upon the analysis of the historic statistics of a fishery is not attainable on a sustained basis. Support for Larkin's view is provided by a number of reviews of the history of fisheries (2). Few fisheries exhibit steady abundance (3). It is more appropriate to think of re- sources as managing humans than the con- verse: the larger and the more immediate are prospects for gain, the greater the polit- ical power that is used to facilitate unlim- ited exploitation. The classic illustrations are gold rushes. Where large and immediate gains are in prospect, politicians and gov- ernments tend to ally themselves with spe- cial interest groups in order to facilitate the exploitation. Forests throughout the world have been destroyed by wasteful and short- sighted forestry practices. In many cases, governments eventually subsidize the ex- port of forest products in order to delay the unemployment that results when local tim- ber supplies run out or become uneconomic to harvest and process (4). These practices lead to rapid mining of old-growth forests; they imply that timber supplies must inev- itably decrease in the future. Harvesting of irregular or fluctuating re- sources is subject to a ratchet effect (3):
We analyzed the small-scale fishery in the port of Vilanova i la Geltru (NW Mediterranean) to assess the fishing practices in this fishery and produce economic indicators of its status. We defined the fishing tactics (or metiers) of this fishery with a multivariate analysis approach for evaluating the main fishery resources and fishing gears employed. Our results show that netters in this fishery practice 7 types of fishing tactics. Five of these fishing tactics, in terms of target species, gear and seasonality, are also used in other small-scale Mediterranean fisheries. The main types of fishing gear (trammel nets, gillnets) and target species (Sepia officinalis, Solea vulgaris, Mullus surmuletus and Merluccius merluccius), and a well defined seasonality, are also observed in other studies of Mediterranean small-scale fisheries. We show that the seasonal rotation of fishing tactics is determined by the availability of different fish species rather than market price. Identifying the fishing tactics, which in the Mediterranean are relatively limited in number, of small-scale fisheries provides information for developing monitoring and management strategies for these fisheries. We also assessed the economic performance of the small-scale fishery in Vilanova i la Geltru and its conflicts with other uses of the coastal zone. We conclude that small-scale fisheries are an economically viable activity although seriously threatened by concurrent uses of the coastal zone (conflict with other extractive activities; competition for space with tourism and leisure activities; pollution). The integrated management of the uses of the coastal zone is necessary in order to sustain small-scale fisheries, which have become less important in economic terms, but which are an important social component of local coastal communities and are a source of high quality seafood with a low ecological impact.
The mud crab Scylla serrata was collected from Ramisi river estuaryfor a period of 14 months (January 1990–February 1991) using madema traps. For each crab, the carapace width (mm), sex and weightwere noted, and the number of ovigerous female crabs was recorded. Both ovigerous and non-ovigerous females were dissected in order to observeof the maturity stages of ovaries. The ovarian maturity stages weredescribed as stage zero – virgin/resting, stage one – developing, stage two– well developed and stage thre e– ripe. The most abundant was stage twothroughout the study period. The smallest ovigerous crab had a carapacewidth of 139 mm. A test of homogeneity of the binomial distributionof the sex ratio showed homoscedasticity (?2 = 14.615; d.f. = 13; p> 0.05) and the overall sex ratio did not differ from 1:1 (?2 = 0.776; d.f. = 1; p> 0.05). The variance test ofhomogeneity of the binomial distribution of sex in relation to size showeda very significant heterogeneity (?2 = 32.83; d.f. = 9; pp< 0.001). The relatively high numbers of females with stage two ovariesindicated that spawning took place throughout the year with a possible peakin the second half of the year.
Because everyday citizens and nonexpert stakeholders are either directly or indirectly involved in ocean health restoration plans and engage in activities that may place fisheries at risk, it is important to understand the scope and depth of their policy-relevant knowledge. Using a mail survey of more than 3000 Pacific Northwest U.S. citizens, we investigated levels of coastal and ocean policy-relevant knowledge, information sources associated with higher levels of policy-relevant knowledge, and relationships between knowledge and support for Pacific fisheries restoration. We found that citizens knowledgeable about ocean conditions were most supportive of ocean and coastal protection; that somewhat malleable situational factors are important predictors of knowledge; and that some sources of information are more directly connected to knowledge than others. This study concludes that public knowledge is a critical component of support for ocean and coastal management and that there are effective means for enhancing public knowledge.
Summary This paper reveals how the socioeconomic and management objectives of a three-year sea cucumber pro- ject in the western Indian Ocean (WIO) (cf. Conand et al. 2006) will be addressed. A conceptual model of sea cucumber resource dynamics is presented. This model encompasses multiple levels and considers the main structures of the sea cucumber fishery such as fishing and collection grounds, resource users and other stakeholders involved in the fishery (e.g. fishers, middlemen and importers), the links between stake- holders, villages and countries, and the associated management initiatives at different levels. This frame- work is promising when analyzing the sea cucumber fishery from a holistic perspective, considering both social and ecological interactions. The results of the study will provide knowledge and management advice for the sustainability of the sea cucumber fishery in the WIO; however, the framework is not restricted to the WIO, and may be adapted to other fisheries.
Mud crab (Scylla serrata) is a delicacy for subsistence consumption in fisher communities and tourist hotels in the coast of Kenya while export demand to markets in China and Japan is expanding and provides competitively higher prices. Crab exploitation and degradation of the mangrove forests have increased over the last decades therefore threatening the capture fishery. The preferred market size crab has consistently decreased from more than 1 kg two decades ago to the current size of 0.5 kg therefore posing both management and livelihood threat to the critical ecosystem (mangrove) and coastal populations. To meet the increased tourist and export demand and provide surplus for the local community while conserving the critical crab ecosystem, small-scale aquaculture has been initiated in the concept of silvofisheries. Initial culture methods have targeted sub-adult crabs of 150–350 g for culture to market size (>0.5 kg) in drive-in cages and pens (mud crab fattening). These technology attained survival of between 50 and 70% and a market price of 5 dollars per kilogram. However, research is ongoing to assess viability of stocking juvenile seed crabs directly in ponds as practised in South East Asia (SEA) as opposed to stocking of sub-adults in drive-in cages. In comparison with other areas, crab capture fisheries in East Africa have limited management and enforcement frameworks/capabilities within the wider regional fisheries policies. Also there is limited understanding of wild mud crab resources and suitable management options to avoid over-exploitation as observed in SEA. The double-edged demand (wild market size capture and juvenile capture for aquaculture) for mud crabs in addition to mangrove degradation are likely to cause great challenges to stock exploitation and livelihoods of the coastal people dependent on the resource. This review paper provides an inside onto the tradition, trends and options for development of mud crab capture and culture in Kenya.
The populations in coastal areas in east Africa have increased dramatically in the last decades, resulting in increased pressure on coastal resources. The examples are declining fish catches, deteriorating conditions of coral reefs and reduction of mangroves forests. The objective of the study was to asses the potential of grow-out Aquaculture of mud crabs Scylla serrata, as an alternative livelihood for resource-poor coastal communities. Growth rate and survival of mud crabs (S. serrata) cultured in individual drive-in cages (30 x 30 x 30 cm) located in the mangrove forests dominated by Rhizophora mucronata were evaluated. The effect of feed (Terebralia pallustris -gastropod meat, fish offal and mixture of the 2) was determined in a completely randomised design. Feeding was done at 10% body weight at incoming tide throughout the experimental period of 120 days. Monthly sampling was employed and total weight (g), cheliped length (cm), carapace length (cm) and width (cm) were measured. The study aimed at establishing the growth rate, moulting and mortality of crabs fed using locally available feeds. A total of 180 drive-in cages were used for the experiment giving 60 replicates for each treatment. Drive-in cages were built with "fitos" and grouped in sets of 10 for easy management. Crab seed stock of 50 -380 g for the experiment were bought from artisanal fishermen. Application of ANOVA and post-hoc test revealed that crabs fed with mixed feed had significantly higher % growth (47.9%) compared to fish offal (33.4%) but were similar to gastropod meat (43.2%) p < 0.05. Growth rate was significantly affected by feed type, where higher values were recorded in mixed feed diets (gastropod meat and fish offal, 1.29 g/day) compared to the individual feeds (0.96 and 0.97 g/day for fish offal and gastropods meat respectively. There was no significant difference in growth of monosex crabs female (0.996 -1.55 g/day) and males (0.893 -1.01 g/day) p = 0.373.
Summary 1. Many aspects of human behaviour impact on ecological systems. Ecologists therefore need information on changes in these behaviours and are increasingly using methods more familiar to social scientists. 2. Understanding patterns of wildlife harvesting is important for assessing the sustainability of harvests. Interviews are commonly used in which informants are asked to summarize their activities over a period of time. However, few studies have investigated the reliability of such data, the usefulness of interviews for monitoring trends, and how their information content can be maximized. 3. We carried out rapid assessment interviews with villagers in Madagascar about the quantity, timing and spatial patterns of crayfish Astacoides granulimanus and firewood collection. We compared the results with information from daily interviews with the same informants. We used mixed models to investigate how accurately people reported their activities in the rapid assessment interviews, and estimated the probability of detecting a change in harvesting from two such interviews using a Bayesian approach. 4. The interviews provided reliable information on quantities, effort, and the spatial pattern of harvesting. Simulations suggested the interviews would detect changes in catches and harvesting effort with reasonable power; for example, a 20% change in the amount of time spent crayfish harvesting could be detected with 90% power. Power is higher when the same informants are questioned in repeat interviews. 5. Synthesis and applications . Ecologists are increasingly using social techniques and it is vital that they are subject to rigorous testing to ensure robustness in trend detection. This study suggests that interviews can be used to monitor changes in harvesting patterns by resource users, but whether the power is adequate will depend on the needs of the study. To maximize the power of interviews, informants should be interviewed independently and the same informants interviewed in subsequent years.
The abundance, recruitment and mortality of the mud crab S. olivacea were studied in mangrove forests associated with the Kra Buri River in Ranong, southern Thailand. Data were obtained for mud crabs from two catch series. From March 1998 to March 2000, mud crabs were collected at monthly intervals from four to six fishermen who trapped the crabs at three different locations in the Kra Buri River estuary (commercial catch series). In addition, mud crabs were trapped experimentally in a 2000 ha mangrove area from March 1999 to May 2000 (experimental catch series). The external carapace width (ECW) and sex of each crab caught in this area were recorded and the population estimated from the average number of fishermen operating there. The size distribution in the mud crab catch was mono-modal with a size range of 5.0–13.5 cm ECW. Fewer female crabs were caught than male crabs and berried females were observed only in offshore catches (ECW: 8.2–11.6 cm). The size distributions from the two catch series were analysed using catch-at-length analysis with natural mortality rates set to 0.05, 0.1, 0.2. Mortality rates were lower for females (0.49 and 0.53 per month) than for males (0.90 and 1.00 per month). Estimated abundance increased with the size of the selected natural mortality rate, but irrespective of the rate set, the estimate of mud crab abundance remained within a narrow range with no significant upward or downward trend. In the experimental fishing area, average abundance was estimated to be 21–28 crabs/ha (min: 14 ha−1, max: 38 ha−1) including both males and females. Recruitment into the fishery was continuous throughout the year without any strong seasonal fluctuation, but the trends for male and female mud crabs were slightly different. Females also recruited into the fishery at a smaller average size compared to males.
A study conducted in South Coast, Kenya to determine the factors that influence the harvesting of fish in the area, assess the changes that have occurred in local fishing practices and their socioeconomic impacts; establish stakeholder characteristics in relation to changing fishing practices; and identify the winners and losers in the changing fisheries management regimes. Information and data were collected from four sites, namely Vanga, Shimoni, Msambweni and Gazi. It was established that changing fishing practices in the area have led to over-exploitation of the fish stocks from the coral reefs.Regression analysis of the data indicated a significant inverse relationship between fish harvesting rate and price. This is inconsistent with the theory of production, which predicts output to increase with increase in price. In the study area, when the price of fish is low, fishermen tend to spend more hours per day fishing in order to compensate for the lost income due to price decrease. This results in over-fishing within the coral reef. Similarly, the output has a significant inverse relationship with distance to the fishing ground. There is a significant positive relationship between effort and output; when fishing effort increases by one unit, output increases by 0.43 units in weight. The other explanatory variables, particularly income, education and age, have a positive but insignificant relationship with output; the adjusted R2 is 0.714, which means that these variables explain 71% of the variation in output. From the estimation of a transformed log–log model, the results obtained are consistent with the estimates of the original model.
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