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Effects of different phenolic compounds on the redox state of myoglobin and their potential for preserving the color and chemical quality of refrigerated longtail tuna (Thunnus tonggol) slices were studied. Purified myoglobin from dark muscle (15.83 kDa) was prepared. Catechin, EGCG, quercetin, and hyperoside affected the absorption spectra and redox state of metmyoglobin (metMb) at 4 °C for up to 72 h differently. Reduction of metMb to oxymyoglobin (oxyMb) was notably observed for two flavonols (EGCG and quercetin) at 50 and 100 ppm. Based on the reducing ability of metMb, EGCG and quercetin were selected for further study. Longtail tuna slices were treated with EGCG and quercetin at 200 and 400 mg/kg. Color (a* and a*/b*), proportion of myoglobin content, and quality changes were monitored over 72 h at 4 °C. Tuna slices treated with 200 mg/kg EGCG showed better maintenance of oxyMb and color as well as lower lipid oxidation (PV and TBARS) and protein oxidation (carbonyl content) than the remaining samples. Nevertheless, EGCG at 400 mg/kg exhibited lower efficacy in retaining the quality of tuna slices. Thus, EGCG at 200 mg/kg could be used to maintain the color and prolong the shelf life of refrigerated longtail tuna slices. [ABSTRACT FROM AUTHOR]

A study was carried out to determine the effects of the steaming process on the proximate composition of the dark and white muscle tissue of Thunnus tonggol sampled from Terengganu waters. The mean percentage of moisture, ash, lipid, and protein of the raw dark muscle was 59.1%, 3.8%, 12.1% and 33.9%, while in the raw white muscle were 66.7%, 2.9%, 2.7% and 33.9%, respectively. Both types of muscle showed a significantly different value in the lipid content. There was significant increase recorded in the protein content in both types of muscle after the steaming process (79.1% and 93.0% in dark and white muscles, respectively). Likewise, the percentage of ash showed some increment with 4.8% in the dark muscle and 7.9% in the white muscle. However, the cooking process decreased the percentage of moisture and lipid in both dark and white muscles. The percentage of moisture in dark muscle was reduced to 7.7%, and 9.7% in white muscle. On the other hand, percentage of lipid content in both types of muscles after the steaming process was 0.43% in dark muscle and 0.03% in white muscle. This study reveals that the cooking process had considerable effects on the proximate composition of both dark and white muscles. [ABSTRACT FROM AUTHOR]

The population genetic diversity and demographic history of the longtail tuna Thunnus tonggol in Malaysian waters was investigated using mitochondrial DNA D-loop and NADH dehydrogenase subunit 5 (ND5). A total of 203 (D-loop) and 208 (ND5) individuals of T. tonggol were sampled from 11 localities around the Malaysian coastal waters. Low genetic differentiation between populations was found, possibly due to the past demographic history, dispersal potential during egg and larval stages, seasonal migration in adults, and lack of geographical barriers. The gene trees, constructed based on the maximum likelihood method, revealed a single panmictic population with unsupported internal clades, indicating an absence of structure among the populations studied. Analysis on population pairwise comparison ФST suggested the absence of limited gene flow among study sites. Taken all together, high haplotype diversity (D-loop = 0.989-1.000; ND5 = 0.848-0.965), coupled with a low level of nucleotide diversity (D-loop = 0.019-0.025; ND5 = 0.0017-0.003), "star-like" haplotype network, and unimodal mismatch distribution, suggests a recent population expansion for populations of T. tonggol in Malaysia. Furthermore, neutrality and goodness of fit tests supported the signature of a relatively recent population expansion during the Pleistocene epoch. To provide additional insight into the phylogeographic pattern of the species within the Indo-Pacific Ocean, we included haplotypes from GenBank and a few samples from Taiwan. Preliminary analyses suggest a more complex genetic demarcation of the species than an explicit Indian Ocean versus Pacific Ocean delineation. [ABSTRACT FROM AUTHOR]

Longtail tuna ( Thunnus tonggol) is one of the most economically important tuna species in Iranian waters of Persian Gulf and Oman Sea. Some population dynamics parameters of this species were investigated in coastal waters of the northern Persian Gulf and Oman Sea from January to December 2014. The fork length (FL) of all specimens ranged from 27 to 107 cm, and total weight (TW) was between 200 and 12,000 g. Among the length frequencies examined, specimens with fork length in the range of 62-65 cm were the dominant group. The equation of length-weight relationship was estimated as TW = 0.00003 × FL ( R = 0.84) and isometric growth model was determined for longtail tuna in study area. The parameters of Von Bertalanffy growth function were obtained as: L = 111.23 cm, k = 0.3 year and t = −0.38 years and ϕ′ = 3.6. The annual instantaneous rate of total mortality ( Z), natural mortality ( M) and fishing mortality ( F) was estimated to be 1.15, 0.43 and 0.72 year, respectively. The exploitation rate ( E) was calculated as 0.63 indicating that longtail tuna was fully exploited in the study region. [ABSTRACT FROM AUTHOR]

The study was conducted to detect histidine decarboxylase-producing bacteria and determine histamine content for evaluation of potential histamine poisoning in 30 frozen specimens of longtail tuna harvested from the Oman Sea. Bacteriological isolates and the amount of histamine were obtained from 500 g of gill muscles. Trypticase soy agar was used for examination of mesophilic and psychrophilic counts. Enterobacteriaceae and histamine producing bacteria were enumerated in violet red bile dextrose agar and Niven's media, respectively. The results indicated that the average of total count and psychrophilic count were 4.81±0.26 and 4.66±0.25 Log10 CFU/g, respectively. Several bacteria were identified as histidine decarboxylase-producing bacteria. Among them, Clostridium perfringens had the highest contribution (24.4%) followed by Proteus spp. (23.0%), Klebsiella spp. (13.9%) and Enterobacter spp. (11.1%). Histamine contents in 20.0, 15.0 and 65.0% of samples were <20, 20-50, and >50 ppm, respectively. The high percentage of samples (65%) with histamine content higher than the standard (<50 ppm) suggests potential histamine poisoning due to longtail tuna fish consumption in humans. [ABSTRACT FROM AUTHOR]

Longtail tunaThunnus tonggolis a neritic species of the family Scombridae, having a confined coastal distribution to tropical and temperate waters of the Indo-Pacific region. In the present study, the population structure of longtail tuna was examined using sequence analysis of the mtDNA control region from two geographically distinct locations along the northwest coast of India. A 500 bp segment of the D-loop region was sequenced and analysed for 98 longtail tuna individuals. Analysis of population differentiation showed no significant genetic differentiation between the two sampling localities (ΦST= 0.005,P= 0.200). Results were further corroborated by a non-significant nearest-neighbour statistic (Snn= 0.489,P= 0.549). Phylogeographic analysis revealed two haplogroups, but there was no obvious phylogeographic pattern separating the samples of the two localities. The present study suggests a single panmictic population of longtail tuna in the northwest coastal waters of India. [ABSTRACT FROM PUBLISHER]

Advances in fishing technologies have increased the efficiency and diversification of recreational fisheries. This poses challenges for surveying specialised or 'hard-to-reach' recreational fishers (e.g. sport fishers) that may take the majority of the recreational catch for some species, but are too rare within the general population to be sampled cost-effectively using existing methods. We trialled two new methods-time-location sampling (TLS) and online diaries-for surveying specialised recreational longtail tuna ( Thunnus tonggol) fishers. Results were compared with a concurrent traditional access point survey (APS). Online diaries were inexpensive but unsuitable for collecting representative data due to avidity, volunteerism, and differential recruitment bias. APS yielded high resolution data on catch, effort and size composition but was expensive and ineffective for sampling all components of the fishery. In contrast, TLS conducted at fishing tackle stores was cost-effective for accessing the breadth of fisher types due to the need for all fishers to purchase or to inspect fishing-related products at some point. Given the frequent absence of complete list frames for recreational fisheries, we suggest undertaking multiple TLS surveys to collect catch rate data and to simultaneously estimate population size using capture-recapture approaches in order to estimate the total recreational catch of species of interest. [ABSTRACT FROM AUTHOR]

Effectiveness of ethanolic galangal extract as an antioxidant in fish mince and fillet was investigated. The extract (5.8 μ gallic acid equivalent; GAE) reduced deoxygenation of sea bass haemoglobin ( Lates calcarifer) at pH 6.5. The lag time for TBARs development in washed sea bass mince mediated by the haemoglobin at pH 6.5 was extended from 2 to 8 days by added galangal extract (0.02% w/w GAE). Washing the sea bass fillet with low preformed lipid hydroperoxide (LHP) content by galangal extract solution (0.2% w/v GAE) effectively inhibited the TBARs formation throughout the storage. However, in the longtail tuna fillet ( Thunnus tonggol) having a significant content of preformed LHP, there was nonsignificant difference in the reaction lag time of the samples washed with the solution and with water. Thus, galangal extract can be used as an antioxidant in fish if its application is performed before initiation of lipid oxidation. [ABSTRACT FROM AUTHOR]

Deals with the study that attempted to process small tuna into ara-bushi. Number of longtail tuna used in the study; Determination of moisture content; Comparison of the chemical compositions of the raw meats and the product.