Trophic Plasticity of Bombay Duck (Harpadon nehereus) in the South-Central East China Sea Based on Stable Isotope Evidence

High trophic plasticity is often invoked to explain the successful expansion of many aquatic species. Bombay duck (BD) outcompete other traditionally commercial fishes in the East China Sea (ECS) in recent years, displaying a continuous and sharp increase of catches, however, little is known whether the competition advantage of BD was related to its trophic plasticity. Using stable isotope analysis (SIA), we investigated the trophic ecology of BD in the south-central ECS in two periods. Significant differences in δ13C and δ15N values were found between sampling months and among body sizes. Modal (95% credibility limits) estimation showed that BD’s trophic position (TP) gradually increased from 3.56 (3.31–3.82) in G1 (120–150 mm for body size) to 4.09 (3.69–4.50) in G5 (241–270 mm) in November, and from 3.37 (2.92–3.88) in G2 (151–180 mm) to 3.66 (3.07–4.23) in G4 (211–240 mm) in April, respectively, suggesting obvious ontogenetic variation of δ15N and TP. More importantly, the TP of BD within the same body size showed wide amplitude, indicating BD possess high trophic plasticity, and can capture prey from low to high trophic levels. Further quantitative analysis based on the MixSIAR model showed that BD mainly fed on zooplankton and fish, but its feeding habit was characterized by the consumption of gradually reduced zooplankton and increased fish associated with increased body size. Interestingly, the fish’s contribution to BD showed obvious seasonal variation. It can be explained by varied food availability in ECS. Relatively low fish prey in April forced BD to adjust its diet, adding the ingestion of shrimps and cephalopods corresponding to temporal variations in food availability. The present study provides the evidence that high trophic plasticity exists in the feeding strategy of BD, which is reflected in the ability to adjust the feeding preference according to nutritional needs and food environmental changes; thus, it is competitively advantageous and may partly explain why BD is becoming the predominant species and displays an extensive distribution in the ECS.

Comparative assessment of dried fish quality collected from market and drying centre at Kuakata in Patuakhali, Bangladesh

The study identified the quality differences of dried Chinese pomfret (Stromateus chinensis), Bombay duck (Harpodon nehereus) and ribbon fish (Trichiurus haumela) from market and drying center at Kuakata, Patuakhali. The sensory, nutritional and microbial quality of collected dried samples were evaluated following organoleptic quality index, standard AOAC and aerobic plate count methods, respectively. Organoleptically no significant difference found between the samples from market and drying center. The highest moisture content value was obtained in Bombay duck (29.78%) from the market and lowest value in Chinese pomfret (20.06%) from drying center. The highest and lowest protein content was in Chinese pomfret (60.73%) and Bombay duck (47.9%) from drying center and market, respectively. The lipid and ash content varied from 2.85% to 7.20% and 13.98% to 19.57% for all the dried fish species collected from both sites. Microbiologically, higher aerobic plate count (APC), total E. coli count (TEC) and total Salmonella count (TSC) were found in Chinese pomfret at 1.96×106 CFU/g, 3.98×105 CFU/g and 1.62×105 CFU/g from market and lowest count found in Bombay duck at 5.05×105, 2.22×105 and 0.81×105 from drying center, respectively. In ribbon fish no Salmonella sp. was found. Based on the sensory and nutritional quality the study conclude that among three species and two sites studied, the dried Bombay duck from the fish drying center had better quality characteristics than the counter parts. However, higher microbial load especially pathogenic TSC and TEC suggests to improve hygiene and sanitary practices, better market distribution and storage facilities need to be followed by the producers for safe and quality dried fishery products.

Studies on the Quality and Safety Aspects of Giant Tiger Prawn (Macrobrachium rosenbergii) and Bombay Duck (Harpodon nehereus) of the Bay of Bengal along the Cox’s Bazar Coast of Bangladesh

The quality and safety aspects of two commercially important species Macrobrachium rosenbergii and Harpodon nehereus were evaluated on this study by examining organoleptic properties, proximate composition, total volatile base-nitrogen (TVB-N) and tri methyl amine-nitrogen (TMA-N) contents of the samples. Both the species showed excellent sensory quality with the defect point 1.57 and 1.4 for M. rosenbergii and H. nehereus, respectively. The moisture content of M. rosenbergii and H. nehereus were 80.89±0.23% and 78.56±0.39%; the protein content were 11.76±0.3% and 13.74±0.04%; the lipid content were 2.15±0.007% and 1.89±0.34% and the ash content were 1.24±0.35% and 1.97±0.31% respectively. The TVB-N and TMA-N was found 19.3±0.45 mg/100 g and 3.19±0 mg/100g for M. rosenbergii and 22.37±0.15 mg/100g and 2.09±0.04 mg/100 g for H. nehereus respectively. The result showed the nutritional composition and quality attributes of these two species.

Composition and Occurrence of Fish Fauna from Thanbyuzayat Township, Mon Coastal Area

A total of 48 species of fish fauna were identified during the present study period. The dominant species of fish were found under order Perciformes in all study areas. The most species composition (40) was recorded in Setse fish landing area. The commercially important fish species were mostly found in Kyaikkhami area. Moreover, 17 species of fish were exported to other regions and foreign countries. Among the fish species, species such as Threadfin (Polynemidae), Croaker (Sciaenidae), Hilsa (Clupeidae), Bombay duck (Harpadontidae), Anchovy (Engraulidae), and Pomfret fish (Stomateidae) were the most economically important species. Bombay duck and Anchovy (especially Coilia dussumieri) were more abundant (70%) at the present study sites. Harpodon nehereus and Coilia species were the leading food employed as fresh and dried for local people in the present study areas. Key words: Ichthyology, Taxonomy, Compositions, Occurrence, fish landing centers, Thanbyuzayat Township, Mon Coastal Areas.

Growth, mortality and length-weight relationship of the Bombay duck Harpadon nehereus (Ham. 1822) from North-eastern tip of the Bay of Bengal

The present study was conducted to investigate the growth parameters, length-weight relationshipand diverse mortality rates of Bombay duck Harpadon nehereus, from North-eastern tip of the Bay of Bengal.The length weight data were collected from January to December 2017 where a total number of 2054individuals of both sex were analyzed. The von Bertalanffy growth parameters, the asymptotic length L?(cm), the growth constant K (year-1) and t0 were estimated as 38.50, 0.88, and -0.0181 years respectively.The growth performance index (Ø?) was found to be 3.115. The total length and body weight (L-W)relationship was found as W=0.004 L3.021, indicating that the growth rate showed a positive allometricpattern (b=3.021>3). The annual fishing morality rate (F) was 1.89, whereas the natural mortality rate (M)was 1.51. The obtained value of the exploitation rate (E= 0.56) indicated that the said population was inover-exploited condition.

ELEFAN Based Population Dynamics of Bombay Duck, Harpadon nehereus Inhabiting the Marine Waters of the West Coast of India

We studied ELEFAN based population parameters from length-frequency data for Harpadon nehereus collected from different landing centres along the west coast of India. We analyzed the size structure and estimated growth parameters, recruitment, mortality and exploitation rate using FiSAT-II software. The asymptotic length (Lµ = 366 mm), growth coefficient (K = 0.98 year-1), total mortality (Z=3.32 year-1), natural mortality (M=1.6375 year-1), fishing mortality (F=1.6825 year-1), growth performance index (Ø = 3.12) and exploitation ratio (E = 0.51) were worked out for the species. The exploitation ratios were computed as Emax= 0.661, E10= 0.568, E50= 0.345. The length at first capture (Lc50) was estimated at 163.44 mm. The present value of E was found close to appropriate fishing pressure on the stock and a further increase of fishing pressure is not recommended.

Survival of Methicillin-Resistant Staphylococcus aureus in Fish and Shrimp under Different Storage Conditions

ABSTRACT Foods that are extensively handled during preparation and stored without refrigeration are often associated with staphylococcal food poisoning. This problem is more confounding when contaminating strains belong to the methicillin-resistant Staphylococcus aureus (MRSA) group. In this study, we investigated the survivability of MRSA in two seafood matrices under different storage conditions. MRSA was inoculated at 6 and 3 log CFU/g into all sample groups of peeled shrimp (Parapeneopsis stylifera) stored at −20°C, Bombay duck fish (Harpadon nehereus) stored in ice, and dried Bombay duck fish stored at 30 ± 2°C. The populations of MRSA in frozen peeled shrimp inoculated with MRSA at 6 log CFU/g were reduced by 1.52 log CFU/g, whereas in samples inoculated with 3 log CFU/g levels remained stable after 60 days of storage. In fresh Bombay duck fish inoculated with 6 log CFU/g and stored in ice for 18 days, MRSA levels decreased by 2.75 log CFU/g. In contrast, in fresh fish inoculated with 3 log CFU/g the total viable count increased by 3.02 log CFU/g over 16 days of ice storage. In dried fish stored at 30 ± 2°C, MRSA levels declined by 3.27 log CFU/g in samples inoculated with 6 log CFU/g and by 0.91 log CFU/g in samples inoculated with 3 log CFU/g. These results suggest that the survival of MRSA depends on the temperature of storage and the inoculum level. In our study, MRSA survival was higher when inoculated at 3 log CFU/g regardless of the seafood matrix and storage temperature. HIGHLIGHTS