Marudu Bay Research Articles

Reproductive Biology and Condition Index of Meretrix meretrix in Marudu Bay, Malaysia: Implications for Conservation and Management

Reproductive Biology and Condition Index of Meretrix meretrix in Marudu Bay, Malaysia: Implications for Conservation and Management

Reproductive cycle and size at maturity of wild mud crab, Scylla tranquebarica(Fabricus, 1798) in Marudu Bay, Sabah

This study was conducted to investigate the reproductive cycle and size at maturity of wild mud crab, Scylla tranquebarica, in the mangrove forest of Marudu Bay. The sampling was conducted for 12-month consecutively with the assistance of local fishermen. Each sampling was carried out for 2 days, and baited crab traps were deployed in the river. During the sampling period, a total of 1459 crab specimens were caught. The different maturation stages of crab can be found throughout the year. The percentage of mature female crabs (Stage III to V) was relatively higher in February (38.5%) and May (50.5%), and lower in March (17.6%) and June (17.4%). A similar trend was observed in the male crab. Recruitment of crabs into the mangrove forest was observed after the breeding season. It was observed through histological observations that when 50% of the crabs were sexually mature, the size at maturity was in the range of 94.0 to 96.1 mm and 97.0 to 99.5 mm carapace width for female and male, respectively. This study suggests that S. tranquebarica breeds throughout the year and shows two peak breeding seasons and recruitment in Marudu Bay. This information can be used as baseline for mud crab fisheries management in Sabah.

Distribution and Accumulation of Heavy Metals in Marine Sediment from Marudu Bay, Sabah

This study aims to analyse the distribution and factors that control the accumulation of heavy metals in marine sediment from Marudu Bay, Sabah. The sediment samples originated from the various types of rocks, namely ultrabasic rock, basic rock, and chert of ophiolite sequence, and sedimentary rock of the Kudat Formation. A total of 20 sediment core samples were systematically sliced for physico-chemical analysis such as pH value, organic matter (OM), and particle size distribution (PSD). Seven heavy metals are analysed in this research, namely cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), vanadium (V), and zinc (Zn) which is measured using the ICP-OES instrument. Descriptive statistics were used to study the distribution and accumulation of heavy metals from two main stations, namely Sg Karang Station (ST) and Kg Tampakan Station (SK). The results from both stations showed various levels of heavy metal concentration. The average concentration of Mn is between 2.19 mg/kg - 94.77 mg/kg and followed by Cr (0.87 mg/kg - 21.11 mg/kg). For Ni, Zn, Cu, V, and Co, the concentration range were between 0.28 mg/kg - 11.48 mg/kg, 0.94 mg/kg - 6.95 mg/kg, 0.55 mg/kg - 6.01 mg/kg, 0.64 mg/kg - 3.77 mg/kg, and 0.02 mg/kg - 0.85 mg/kg respectively. The result of correlation analysis showed the significant negative relationship between pH with Co, Cr, Ni, Mn, and Zn indicated the increasing concentration in acidic condition. A strong negative correlation between percentage of sand and Co, Cr, Mn, and Ni indicated the decreasing concentration in coarse sediment particle size. However, there was a strong positive correlation between percentage of sand and V due to the association in the carbonate minerals. The Kruskal-Wallis tests showed there were no significant means difference of the percentage of heavy metals based on sample depth and the distance from the shoreline except for V and Mn.

Combined climate impacts and vulnerability index on coastal ecosystems in prediction of future scenarios: extended sustainable indicator tool for adaptive strategy

This study presents the coastal vulnerability due to the forecasted climate change impact on the marine environment, including the sea level rise physical trait of risk impact. A combined methodology using Representative Concentration Pathways (RCPs), which corresponds to the greenhouse gas emissions scenarios, is used in this research; combined with Climate Change Vulnerability Index (CCVI) to rank the relative risk for each of the marine ecosystem zones in relation to the potential hazard exacerbated by climate change and sea-level rise. This method presents vulnerability in numerical data, which cannot be calculated directly based on their physical properties. From the results, it shows that the coastal areas of the study area of Marudu Bay would experience a warmer atmosphere both under RCP 4.5 and RCP 8.5 with an increment of 1.0 °C and 1.7 °C; meanwhile, the climate projection for total exhibits of increase in total precipitation by 2.6 mm/day and 1.6. mm/day under RCP 4.5 and RCP 8.5 at the regional measure. At the same time, the projection simulates an increase of sea level by 0.21 m and 0.27 m over the northern region of Marudu Bay under RCP 4.5 and RCP 8.5, respectively. In addition, 43.84 ha and 57.02 ha of land estimated would be potentially inundated by the mid-century year 2050 under RCP 4.5 and RCP 8.5. By the end of the century 2100, the sea level is projected to increase locally at about 0.32 m under RCP 4.5 and 0.38 m under RCP 8.5, consequently resulting in a total of 66.84 ha and 79.78 ha of additional inundation coverage. Therefore, the result from this study can be used when making effective adaptive strategies and conservation planning despite its inherent uncertainties.

Sustainable Livelihood Strategies of Fishing Communities in Marine Protected Area (MPA), Sabah, Malaysia

Marine Protected Areas (MPA) are an important management tool adopted by most the nations for conservation of marine and fisheries to save marine ecosystems that are in danger of being overexploited. Malaysia is no exception as coastal regions of Malaysia is prospective for fisheries and many others development activities. The MPAs have an immense impact on people’s livelihood. This study aims to understand the livelihoods of the fishing community in MPAs, Marudu Bay, Sabah, Malaysia. It is guided by the Sustainable Livelihoods Framework (SLF) to analyze the indicators of sustainable livelihood capitals and strategies of the MPAs fishing communities. This study uses a qualitative approach. In-depth interviews with five informants were chosen for the data collection using the purposive sampling technique. According to the findings, the informant’s human capital, such as education, health, leadership, skills, and training, has not yet reached a level that could offer a reasonable standard of living and livelihood for the research site's population. Residents of the study sites do not have many options for increasing their household income level. In many locations, fishing is a less appealing occupation. The study provided recommendations and strategies on how to further develop and sustain the livelihood of the fisheries community in MPAs, Sabah.

Sex ratio, gonadal and condition indexes of the Asiatic hard clam, Meretrix meretrix in Marudu Bay, Malaysia

Abstract. Duisan L, Salim G, Ransangan J. 2021. Sex ratio, Gonadal and Condition indexes of the Asiatic Hard Clam, Meretrix meretrix in Marudu Bay, Malaysia. Biodiversitas 22: 4895-4904. Asiatic hard clam, Meretrix meretrix is one of the important shellfishery resources in Marudu Bay, Sabah, Malaysia. It is among the most popular clam species being widely traded in the local wet markets around Sabah, Malaysia. Unfortunately, the shellfishery management for this species has not been well established. In addition to overexploitation, habitat destruction is also one of the significant threats to this species due to the extensive land use of the coastal areas in Sabah. Hence, conservation and breeding efforts for this species are greatly required. Therefore, the current study was conducted to examine the sexual maturity of the clam with respect to shell length classes for artificial seed production purposes. For this study, a total of 86 clam specimens were randomly collected from mudflats in Marudu Bay. The specimens were utilized for gonad histological and condition analyses. The clams were grouped into three shell length classes; (3.00-4.99) cm, (5.00-6.99) cm, and (7.00-8.99) cm prior to the analyses. Results showed the natural stock of the Asiatic hard clams in Marudu Bay was dominated by females (1.39:1) over males with no hermaphroditism observed. The gonadal index was recorded higher among clams with shell lengths between 5.00 and 6.99 cm. The condition index analysis also recorded high (>4.0) for clams in all the shell length classes. The findings of this study suggest that the clams with shell lengths between 5.00 cm and 7.00 cm are already fully matured and can be utilized as a broodstock candidate for an artificial breeding program in the hatchery.

Population dynamics and condition index of natural stock of blood cockle, Tegillarca granosa (Mollusca, Bivalvia, Arcidae) in the Marudu Bay, Malaysia

Population dynamics and condition index of natural stock of blood cockle, Tegillarca granosa (Mollusca, Bivalvia, Arcidae) in the Marudu Bay, Malaysia

Growth and Mortality of Green Mussel Perna viridis Farmed at Ambong Bay and Marudu Bay, Sabah, Malaysia

Abstract Asian green mussel is commercially farmed in tidal waters in several enclosed bays in Sabah, Malaysia. In this study, two areas on the west coast of Sabah – Ambong Bay and Marudu Bay – were selected for the monitoring of the growth and mortality rates of green mussels farmed in suspension raft. Both growth and survival rates were then correlated with physicochemical parameters (dissolved oxygen, pH, salinity, temperature, water transparency, chlorophyll-a), nutrients (phosphate (PO4 3-), ammonia (NH3-N), nitrate (NO3-N) and nitrite (NO2-N) and condition index of mussel from each study site, as well as between the study sites. The twelve-month growth study (September 2017 to August 2018) was started with a total of 180 mussel specimens (90 at each site). The initial size (mean) of the mussel seed used was 47.7 ± 3.5 mm and 51.1 ± 3.9 mm for Marudu Bay and Ambong Bay, respectively. Mussels in Marudu Bay attained mean size of 73.47 ± 11.05 mm (SGR 0.17% ± 0.22) compared to 64.05 ± 7.44 mm (SGR 0.11% ± 0.22) for Ambong Bay at the end of the experiment. The cumulative mortality rates were 9.2% ± 4.9 and 55.5% ± 30.0 for Marudu Bay and Ambong Bay, respectively. The Pearson correlation indicated a significant positive relationship between mortality and water transparency (r = 0.684, p<0.01). There was a significant negative relationship between ammonia in seawater and mussel mortality (r = -0.561, p<0.01), as well as significant negative relationships between nitrate and growth (r = -0.480, p<0.05) and mortality (r = -0.460, p<0.05), as indicated by Spearman’s Rank-order Correlation analysis. Overall, the growth performance of green mussels farmed in Marudu Bay was better than in Ambong Bay, however, the mortality of mussels in Ambong Bay was higher.

Coastal Communities' Willingness to Pay for Mangrove Ecotourism at Marudu Bay, Sabah, Malaysia

The revenue contribution of mangrove forests to Malaysia’s economic growth is usually associated with fishing. Generally, fishing is one of the main sources of income for coastal communities, and mangroves are found in abundance in coastal areas. Nowadays, mangrove forests have become a very significant product in the tourism sector. It enhances Malaysia’s economy through increasing the earnings of local communities and creating more job opportunities. The potential of mangrove forests as a dynamic ecotourism industry is being rapidly capitalized in many parts of Malaysia. However, the economic benefits of mangrove forests in the tourism sector have not been used to its fullest because of the non-existent market for this resource. This study aims to determine the willingness to pay (WTP) of the coastal communities in Marudu Bay, Sabah, to develop their mangrove areas as an ecotourism destination. To achieve this, the study engages in the contingent valuation method (CVM). Questionnaires were distributed to 400 respondents from five selected coastal villages, asking them whether they are willing to pay for five bid prices, RM5, RM10, RM15, RM20 or RM30, for mangrove ecotourism conservation. Logistic regression was applied to estimate the mean WTP by using three different types of logit models. Results indicate that the estimated mean for each WTP model is as follows: Model 1 (the full model) at RM12.96/person/year, Model 2 (the restricted model) at RM16.08/ person/year and Model 3 at RM25.68/person/year, respectively. The coastal communities’ responses of their WTP were based on the bidding prices and their socio-demographic variables. The majority of them had the WTP because they were confident that the conservation of mangroves promotes sustainable ecotourism and can improve community income, hence would better their livelihoods for generations to come.

Avian diversity in Marudu Bay mangrove forest, Sabah, Malaysia

Avian diversity in Marudu Bay mangrove forest, Sabah, Malaysia

Species diversity and distribution of mud crab in Marudu Bay mangrove forest reserve, Sabah, Malaysia

Sabah has extensive mangrove forests surrounded by oceanic waters which provide suitable habitat for many species of animals including mud crabs (Scylla spp.). This study was conducted to obtain information on the species composition, distribution and catch per unit effort in Marudu Bay, Sabah. Samplings were done monthly in five mangrove areas along the river channels in Marudu Bay (06°33’N; 114°44’E) from October 2012 to September 2013 using collapsible baited crab traps. From a total of 1859 mud crab specimens caught in Marudu Bay, three species were identified. Scylla tranquebarica was the dominant species forming 78% of the total followed by S. paramamosain 13% and S. olivacea 8%. The number of males (n=1224) was higher compared to females (n=635) with an average sex ratio male : female of 1.0:0.5. The catch per unit effort (CPUE) showed an average value of 0.55 trap-1 day-1 and revealed a declining trend throughout the sampling. S. tranquebarica was widely distributed in all the rivers surveyed, however, it mostly occurred in near the lower reaches of the river near the areas open to the sea where average water salinity ranged from 12.98 to 14.28 ppt and the environment favoured the growth of Rhizophora sp. Other species, S. paramamosain and S. olivacea, were mostly found in upstream areas covered generally by Nypa sp. and where average water salinity varied from 6.93 to 7.50 ppt. The information on the species composition, distribution and CPUE of the mud crabs in Marudu Bay can be useful for mud crab fisheries resources management in Sabah.

Dredging-induced shell damages to hard clam (Meretrix meretrix): a Malaysian case study

The hard clam (Meretrix meretrix) is a popular edible shellfish in South and Southeast Asia, being heavily exploited by hand dredging in Marudu Bay, Malaysia. The current study was performed to evaluate the shell damages caused by this artisanal dredging gear. Samplings were conducted in triplicates at two sites using both hand dredging and hand collecting (control) sampling methods. The shell length and total weight, damage areas and breakage patterns of each clam were recorded. A questionnaire survey was conducted with local bivalve harvesters to gather information on the fishing pressure in Marudu Bay. Results revealed that the efficiency (fishing yield) of hand dredging gear was three times higher than hand collecting. However, hand dredging gear causes lethal shell damages to small hard clams (<3cm in shell length). Hard clam harvesting is the main occupation of most fishermen in Kg. Popok, but most of them do not comply with the minimum harvesting size established by the fishery department. Moreover, most of the stakeholders are not aware of the negative impacts of hand dredging to the sustainability of the hard clam fishery in Marudu Bay. Therefore, organizing more awareness programs combined with introducing community-based fishery management are highly recommended to promote the sustainability of this artisanal fishery.

Predicting the sacculinid Sacculina beauforti infection status of the orange mud crab Scylla olivacea by discriminant analysis

Parasitic sacculinids Sacculina beauforti infection is prevalent in the orange mud crab Scylla olivacea population in Marudu Bay, Sabah. Being a commercially important species and of high-value to the aquaculture and fisheries sector, this infestation on S. olivacea is alarming. Discriminant ratios were calculated based on the measurements of carapace width, abdomen width, gonopod length and pleopod length. A stepwise discriminant analysis was conducted and two discriminant functions were proposed for identifying infected males and females from the normal S. olivacea population. Only applicable in male, Function 1 incorporates five ratios and correctly classified 93.7% of individuals. Function 2 uses two ratios to identify infected females and has a success rate of 100%. When tested with the ratios of normal S. olivacea from other populations, Function 1 achieved 89–98% whereas Function 2 achieved 100% of re-classification success. These functions may serve as a fast, simple, inexpensive and non-invasive tool for identifying infected crabs rapidly when other methods such as molecular approach and direct identification based on the presence of externa are not applicable. The availability of this tool will aid in the control of S. beauforti infection by preventing them from being spread to other S. olivacea populations and/or aquaculture farms.

Occurrence and Distribution of Marsh Clam, <em>Polymesoda</em> spp. in Marudu Bay, Sabah, Malaysia

Marudu Bay is part of the Tun Mustapha Marine Park, the largest marine protected area within the Malaysian region of the Coral Triangle Initiative. The bay is known for its diversed fisheries resources including bivalves. Although some of these bivalve species are commercially important, their occurrence, distribution and stock status in the bay are not well documented. Hence, the current study was conducted to determine the occurrence, distribution and the stock status of marsh clam, Polymerasoda spp. in the mangrove swamp situated at the southernmost of the Marudu Bay. Samplings were carried out at the mangrove swamps which covered an area of 500 sequare meter per sampling site. Two marsh clams species, Polymesoda erosa and P. expansa were found to inhabit the sampling sites. In general, juvenile marsh clams were noticed to dominate the seaward mangrove swamp, whereas the high tidal regions were dominated by adults. The current study also suggested a link in the distribution and the morphometric measurements of the marsh clams with the sediment grain size.

Heavy metals in marsh clam (Polymesoda expansa) and green mussel (Perna viridis) along the northwest coast of Sabah, Malaysia

Bivalves are known for their ability to accumulate contaminants such as heavy metals. This allows them to be widely used as bioindicator in monitoring of heavy metals in the marine environment. This study was conducted to determine the levels of heavy metals, namely Copper (Cu), Chromium (Cr), Nickel (Ni), Lead (Pb), Arsenic (As), Zinc (Zn) and Manganese (Mn) in marsh clams (Polymesoda expansa) and green mussels (Perna viridis) along the northwest coast of Sabah (Marudu Bay, Ambong Bay, and Mengkabong). The results showed that As (5.1 to 12.8 μg/g) and Mn (33.5 to 116.0 μg/g) concentrations in both marsh clams and green mussels collected from all the sampling stations along the northwest coast of Sabah were much higher than the permissible limit set by the Ministry of Health Malaysia and FAO/ WHO. Similarly, concentration of Zn (265.8 to 535.9 μg/g) in marsh clams from all the sampling areas and that of Cr (53.9 μg/g) in green mussel collected from Marudu Bay were also much higher than the permissible limits. The data also suggested that marsh clams accumulated higher Pb and Zn, whereas green mussels tend to contain higher concentrations of Cr, Cu and Ni. Since bivalves are an important protein source for the local population, a regular monitoring of all edible bivalve species should be conducted so that consumers can be advised about the toxicological and health risks due to consumption of bivalves.

Infestation of parasitic rhizocephalan barnacles Sacculina beauforti (Cirripedia, Rhizocephala) in edible mud crab, Scylla olivacea.

Screening of mud crab genus Scylla was conducted in four locations (Marudu Bay, Lundu, Taiping, Setiu) representing Malaysia. Scylla olivacea with abnormal primary and secondary sexual characters were prevalent (approximately 42.27% of the local screened S. olivacea population) in Marudu Bay, Sabah. A total of six different types of abnormalities were described. Crabs with type 1 and type 3 were immature males, type 2 and type 4 were mature males, type 5 were immature females and type 6 were mature females. The abdomen of all crabs with abnormalities were dented on both sides along the abdomen’s middle line. Abnormal crabs showed significant variation in their size, weight, abdomen width and/or gonopod or pleopod length compared to normal individuals. The mean body weight of abnormal crabs (type 1–5) were higher than normal crabs with smaller body size, while females with type 6 abnormality were always heavier than the normal counterparts at any given size. Sacculinid’s externa were observed in the abdomen of crabs with type 4 and type 6 abnormalities. The presence of embryos within the externa and subsequent molecular analysis of partial mitochondrial COI region confirmed the rhizocephalan parasite as Sacculina beauforti. Future in-depth descriptions of the life cycle and characteristics of S. beauforti are recommended as it involves a commercially important edible crab species and the effect on human health from the consumption of crabs is of crucial concern.

Effects of nutrients and zooplankton on the phytoplankton community structure in Marudu Bay

Current study was carried out to provide a better understanding on spatial and temporal variations in the phytoplankton community structure in Marudu Bay, an important nursery ground for fishery resources within the Tun Mustapha Marine Park and Coral Triangle Initiative, and their relationship with environmental variables. Samplings were conducted monthly from April 2014 to April 2015 in Marudu Bay, Malaysia. Water samples were collected for nutrients analysis, zooplankton and phytoplankton counting. Moreover, the in situ environmental parameters were also examined. The field study showed a total of forty seven phytoplankton genera, representative of 33 families were identified. The nutrient concentrations in Marudu Bay was low (mesotrophic) throughout the year, where the phytoplankton community was often dominated by Chaetoceros spp. and Bacteriastrum spp. In general, increase in nitrate concentration triggered the bloom of centric diatom, Chaetoceros spp. and Bacteriastrum spp. in Marudu Bay. However, the bloom of these phytoplankton taxa did not occur in the presence of high ammonia concentration. In addition, high abundance of zooplankton also a limiting factor of the phytoplankton blooms particularly at end of southwest monsoon. High silica concentration promoted the growth of pennate diatoms, Proboscia spp. and Thallassionema spp., but the depletion of silica quickly terminated the bloom. Interestingly, our study showed that Chaetoceros spp., tolerated silica depletion condition, but the average cell size of this taxon reduced significantly. In summary, the phytoplankton community structure in mesotrophic environment is more sensitive to the changes in zooplankton abundance, nutrient concentration and its ratio than that in nutrient rich environments. This study also recommends that bivalve farming at industrial scale is not recommended in Marudu Bay because it potentially depletes the primary productivity hence jeopardizing the availability of live food for larvae of many natural fishery resources in the bay.

Population Dynamics of Yellowtail Scad, Atule mate (Cuvier 1833) in Marudu Bay, Sabah, Malaysia

The yellowtail scad, Atule mate, forms important fisheries throughout the Indo-Pacific region. To know about the stock status of A. mate in Malaysia, various population parameters were measured, by utilizing length-frequency data, that included asymptotic length (L∞), growth coefficient (K), mortality rates (Z, F and M), exploitation level (E) and recruitment pattern of this species from Marudu Bay, Sabah, Malaysia. Total length and body weight relationship was estimated as W = 0.007TL3.148 (R2 = 0.937). The asymptotic length (L∞) and growth coefficient (K) were estimated 27.80 cm and 1.50 yr−1, respectively. Total mortality (Z), natural mortality (M) and fishing mortality (F) were found to be 4.53, 2.46 and 2.07 yr−1, respectively. The exploitation level (E) was estimated 0.46. It was showed that the recruitment pattern was continuous with two major peaks per year. Relative yield per recruit predicted a maximum exploitation rate (Emax) which was 0.55. The current E value (0.46) is lower than the optimum exploitation (E = 0.50) as well predicted Emax. Therefore, it could be concluded that stock of A. mate in the investigated area of Marudu Bay, Sabah is under exploited.

Health Risk Assessment Due to Heavy Metals Exposure via Consumption of Bivalves Harvested from Marudu Bay, Malaysia

Concern over health risk from consumption of bivalves originating from Marudu Bay is escalating due to the rapid agricultural development surrounding the bay. This has motivated us to estimate the health risk index (HRI) of heavy metals from four commercially important and highly exploited bivalve species which are abundant in the bay. Samples (n = 30) of green mussel (Perna viridis), Asiatic hard clam (Meretrix meretrix), Pacific oyster (Crassosstrea gigas) and marsh clam (Polymesoda expans) were acquired from fishermen in Kg. Teritipan, Marudu Bay. These bivalves were analyzed for heavy metals content using the Inductively Couples Plasma-Optical Emission Spectroscopy (ICP-OES). The study found that the mean contents of Arsenic (As) and Manganese (Mn) in all analyzed bivalves exceeded the permissible limits as well as copper (Cu), lead (Pb) and zinc (Zn) in Pacific oyster, and Zn in marsh clam. It was also noticed that consumption of different bivalve species may bring about health risk from different metals as indicated by varied Total Hazard Index (THI) values. Consumption of the four bivalves was noticed to promote high health risk from As intoxication. Although metal pollution index (MPI) analysis revealed that the bivalves from the bay are currently not seriously impacted by heavy metal pollution, vigorous efforts should be taken to preserve the natural condition of the bay for years to come. There are several ways to minimize health issues from bivalve consumption which include keeping the bivalve natural habitat away from heavy metals pollution by strictly enforcing environmental laws and policies, establishing zones for bivalve fisheries, monitoring heavy metals concentration in bivalve on a regular basis and making depuration process a compulsory requirement in every seafood restaurant throughout the country.

Feasibility of green mussel, Perna viridis farming in Marudu Bay, Malaysia

Bivalve aquaculture is an important source of affordable animal protein for coastal community. The success and sustainability of this industry is highly influenced by the suitability of the environment in which it is carried out. Present study was carried out to evaluate the feasibility of green mussel (Perna viridis) farming in Marudu Bay. The site suitability for green mussel farming was evaluated based on biophysical parameters and food availability. The in situ environmental parameters, phytoplankton abundance and composition were collected from 10 sampling stations on monthly interval from May 2014 to April 2015. The results showed that the environmental parameters and food availability in most of the sampling stations were suitable for green mussel. However, the presence of phytoplankton taxa (Chaetoceraceae) which are unfavorable by green mussel in most of the stations located at the bay pocket make those areas less recommended for green mussel farming. In contrast, stations located on the mouth of the bay exhibited high site suitability rating points and hence are highly recommended for cultivation of green mussel.