Skipjack Tuna Katsuwonus Pelamis Research Articles

Anisakid larvae in the skipjack tuna Katsuwonus pelamis captured in Japanese waters: Two-year monitoring of infection levels after the outbreak of human anisakiasis in 2018

In 2018, human anisakiasis caused by the ingestion of the skipjack tuna Katsuwonus pelamis occurred frequently in Japan. This may be attributable to a heavy infection of A. simplex (s.s.) in the host's muscle tissue. In this study, we investigate infection levels of anisakid L3 larvae in skipjack tuna captured in Japanese waters afterward (2019–2020) to contribute to predict and prevent the outbreak of human anisakiasis. A total of 476 larvae were detected from 78 out of 85 skipjack tuna captured at 14 stations of the Pacific and East China Sea. The present parasitological survey suggests that infection levels in 2019–2020 were low, comparing that in 2018; in total only seven larvae were found from the host's muscle tissue. The collected larvae were identified by molecular methods to Anisakis berlandi, A. pegreffii, A. simplex (s.s.), A. typica and Skrjabinisakis physeteris (s.l.). Not only larvae of A. simplex (s.s.) but also those of A. berlandi were found from the muscle tissue and thus the latter species may also be a causative agent of human anisakiasis. In addition, this study confirmed the geographic distribution pattern that A. simplex (s.s.) is abundant in the Pacific, while A. pegreffii is dominant in the East China Sea. Our results contribute to understanding the risk of food poisoning and stock delimitation of host animals.

Total mercury in three small tunas from southeastern Brazil: Stable isotope relations and human risk assessment

Mercury (Hg) bioaccumulation can be highly variable in marine species. Its concentration is influenced by several physico-chemical and biotic processes, including size, age, diet composition and foraging habitats. Herein, we addressed total mercury (THg) concentrations in three small tuna species in Brazil: the frigate tuna Auxis thazard, the little tunny Euthynnus alletteratus and the skipjack tuna Katsuwonus pelamis. Samples were collected from commercial landings in the SE Brazilian coast from 2017 to 2019. The influence of trophic ecology and habitat preference on Hg accumulation was assessed through stable isotope [carbon (δ13C) and nitrogen (δ15N)] measurements. Additionally, the human health risk regarding the species consumption was assessed by the estimated weekly intake (EWI) and the provisional tolerable weekly intake (PTWI) for total consumers, adult men and adult women. Variables such as size and age were positively correlated to Hg, due to the bioaccumulation process. Trophic position appears to positively influence the mercury concentrations for A. thazard and K. pelamis, since relationship between δ15N and THg was significant. For E. alletteratus, the lack of relationship suggests that δ15N values do not vary much among adult fish (> 300 mm). Muscle THg concentrations in the three species did not exceed the established tolerable limit for mercury by Brazilian and international organs, as indicated by the %PTWI. This finding suggests that the consumption of those species caught off southeast Brazil at the considered amounts does not present a risk for healthy adults.

Using geostatistical analysis for simultaneous estimation of isoscapes and ontogenetic shifts in isotope ratios of highly migratory marine fish

Tracking migration of highly migratory marine fish using isotope analysis (iso-logging) has become a promising tool in recent years. However, application of this method is often hampered by the lack of essential information such as spatial variations in isotope ratios across habitats (isoscapes) and ontogenetic shifts of isotope ratios of target animals. Here, we test the utility of geostatistical analysis to generate isoscapes of δ13C and δ15N in the western Pacific and estimate the ontogenetic shifts in δ13C and δ15N values of a target species. We first measured δ13C and δ15N in the white muscle of juvenile (n = 210) and adult (n = 884) skipjack tuna Katsuwonus pelamis sampled across the northwest Pacific. Next we fitted a geostatistical model to account for the observed spatial variations in δ13C and δ15N of skipjack by fork length and other environmental variables with spatial random effects. We then used the best-fit models to predict the isoscapes of δ13C and δ15N in 2021. Furthermore, we measured δ15N of amino acids (δ15NAAs) of skipjack (n = 5) to determine whether the observed spatial variation of isotope ratios resulted from baseline shifts or differences in trophic position. The geostatistical model reasonably estimated both isoscapes and ontogenetic shifts from isotope ratios of skipjack, and the isoscapes showed that δ13C and δ15N can clearly distinguish the latitudinal migration of skipjack in the western Pacific. The δ15NAAs supported the results of the geostatistical model, that is, observed variations in skipjack δ15N were largely derived from a baseline shift rather than regional differences in trophic position. Thus, we showed that geostatistical analysis can provide essential basic information required for iso-logging without compound-specific isotope analysis.

First record of skipjack tuna (Katsuwonus pelamis) from Dahab in the Gulf of Aqaba, Red Sea, Egypt

First record of skipjack tuna (Katsuwonus pelamis) from Dahab in the Gulf of Aqaba, Red Sea, Egypt

Multi-proxy approach for studying the foraging habitat and trophic position of a migratory marine consumer in the southwestern Atlantic Ocean

Skipjack tuna Katsuwonus pelamis sustains the largest catches among tuna species. Despite its relevance for global food security and the tuna canning industry, information about its foraging ecology in the southwestern Atlantic Ocean (SWAO) is limited. We combined amino acid (AA) and bulk tissue nitrogen isotope (δ15N) analysis with stomach content analysis (SCA) to study skipjack foraging habitat and trophic position (TP) in the SWAO. Mean (±SD) δ15N values of source AAs lysine (Lys: 6.5 ± 1.3‰) and phenylalanine (Phe: 10.6 ± 1.3‰) were higher at higher latitudes (30-34°S) of the southern area relative to the northern area between 20-26° S (Lys: 3.4 ± 1.1‰, Phe: 8.2 ± 1.2‰). Correlations between bulk tissue δ15N (δ15Nbulk) and source AA δ15N showed that Lys is a more robust indicator of δ15N baseline variation in this region than Phe. Regional mixing models based on AA δ15N indicated spatial structure in foraging habitat: smaller individuals use the southern area and larger individuals forage at lower latitudes or in offshore areas. TP estimates using the Glx-Lys trophic-source AA pair were in much better agreement with TP estimates based on SCA (TPSCA) and on bulk tissue analysis (TPbulk) than those using Glx-Phe. Skipjack forages across multiple food webs throughout its lifecycle in the SWAO and increases its TP with ontogeny (TPGlx-Lys: 3.5-4.0). Stock management strategies should consider that the southern region supports dense aggregations of juvenile skipjack, which may be more vulnerable to non-selective fisheries.

A Bayesian Multilevel Ordinal Regression Model for Fish Maturity Data: Difference in Maturity Ogives of Skipjack Tuna (Katsuwonus pelamis) Between Schools in the Western and Central Pacific Ocean

The maturity ogive is vital to defining the fraction of a population capable of reproduction. In this study, we proposed a novel approach, a Bayesian multilevel ordinal regression (i.e., Bayesian continuation ratio model), to model the maturity ogive. The model assumes that the observed maturity stage originates from the categorization of latent continuous variables. We demonstrated this approach by testing whether there are differences in the maturity ogive of skipjack tuna (Katsuonus pelamis) in the western and central Pacific Ocean between two school types, i.e., free-swimming and floating-object-associated schools. The model results show that K. pelamis, given the same fork length, are more likely to have a higher maturity stage in a free-swimming school than those associated with floating objects. The gonadosomatic index revealed the same conclusion. Our results indicate that fish aggregation devices (FADs) could negatively affect the maturity of K. pelamis and consequently reduce the population reproductive potential. This study provides (1) an alternative approach to analyze fisheries ordinal data; (2) important quantitative evidence to evaluate the existing ecological hypotheses; and (3) implications for tuna fisheries management.

Impacts of fisheries-dependent spatial sampling patterns on catch-per-unit-effort standardization: A simulation study and fishery application

Abundance indices derived from fisheries-dependent data (catch-per-unit-effort or CPUE) are known to have potential for bias, in part because of the usual non-random nature of fisheries spatial distributions. However, given the cost and lack of availability of fisheries-independent surveys, fisheries-dependent CPUE remains a common and informative input to fisheries stock assessments. Recent research efforts have focused on the development of spatiotemporal delta-generalized linear mixed models (GLMMs) which simultaneously standardize the CPUE and predict abundance in unfished areas when estimating the abundance index. These models can include local seasonal environmental covariates (e.g. sea surface temperature) and a spatially varying response to regional annual indices (e.g. the El Niño Southern Oscillation) to interpolate into unfished areas. Spatiotemporal delta-GLMMs have been demonstrated in simulation studies to perform better than conventional, non-spatial delta-generalized linear models (GLMs). However, spatiotemporal delta-GLMMs have rarely been evaluated in situations where fisheries spatial sampling patterns change over time (e.g. fisheries expansion or spatial closures). This study develops a simulation framework to evaluate 1) how the nature of fisheries-dependent spatial sampling patterns may bias estimated abundance indices, 2) how shifts in spatial sampling over time impact our ability to estimate temporal changes in catchability, and 3) how including seasonal environmental covariates and/or regional annual indices in spatiotemporal delta-GLMMs can improve the estimation of abundance indices given shifts in spatial sampling. Spatiotemporal delta-GLMMs are then applied to a case study example where the spatial sampling pattern changed dramatically over time (contraction of the Japanese pole-and-line fishery for skipjack tuna Katsuwonus pelamis in the western and central Pacific Ocean). Results from simulations indicate that spatial sampling in proportion to the underlying biomass can produce similar abundance indices to those produced under random sampling. Though estimated abundance indices were not perfect, spatiotemporal GLMMs were generally able to disentangle shifts in spatial sampling from temporal changes in catchability when shifts in spatial sampling were not too extreme. Lastly, the inclusion of seasonal environmental covariates and/or regional oceanographic indices in spatiotemporal GLMMs did not improve abundance index estimation and in some cases resulted in degraded model performance.

Research of parasites with zoonotic potential for humans in skipjack tuna (Katsuwonus pelamis)

The skipjack tuna (Katsuwonus pelamis) is commonly found in the tropical waters of the oceans. It is a fishing resource of high economic value and available for national and international markets. Therefore, it is important to know the fish parasites for a correct sanitary inspection, as the pathogenesis in humans can occur through spoliative, toxic or mechanical action. This study aimed to identify the zoonotic parasitic fauna that infects the beautiful-striped using morphological methods. A total of 06 samples were analyzed. The fish were necropsied for parasitological evaluation of the musculature and internal organs. The samples were visually inspected and the structures with morphology combining with parasitic shapes were analyzed both in stereoscopic and microscope. The parasites found were fixed in 70% alcohol for later identification. All samples showed the presence of zoonotic parasites for humans. Two genera of zoonotic parasites have been found for humans that have beautiful tuna as their hosts, namely Anisakis sp. (Nematoda) and Trypanorhyncha (Eucestoda). A 100% of the infections occurred in the muscles and 66.6% in the liver. The results reinforced the importance of inspection by responsible organisms on the importance of evisceration as quickly as possible to avoid migration of larvae to the muscle.

Species-specific heavy metal concentrations of tuna species: the case of Thunnus alalunga and Katsuwonus pelamis in the Western Mediterranean.

Albacore Thunnus alalunga and skipjack tuna Katsuwonus pelamis are highly migratory species that are usually caught together in the Western Mediterranean. These species are top predators that are highly affected by the biomagnification process through the trophic chain. Bioaccumulation pattern of the main metal pollutants (mercury, Hg; lead, Pb; and cadmium, Cd) were analyzed in muscle tissues of 52 individuals (26 T. alalunga and 26 K. pelamis) of these highly consumed species in order to address two objectives: (1) compare the species-specific bioaccumulation between these large-pelagic species, and (2) assess the healthy properties of such valuable resources based on the trace metal limits established by the European Commission Regulation (ECR). Both generalized linear mixed models and redundancy analysis indicated a differential bioaccumulation between these two tuna species. While T. alalunga accumulates higher concentrations of Hg (0.1996 ± 0.0602 mg·kg-1 weight wet-ww), K. pelamis accumulates higher concentrations of Cd (0.0076 ± 0.0049 mg·kg-1 ww) and Pb (0.0031 ± 0.0017 mg·kg-1 ww). Size and trophic ecology support the differences detected in the bioaccumulation pattern. Heavy metal concentrations were below the tolerable limits considered by ECR (1, 0.1, and 0.3 mg·kg-1 ww for Hg, Cd, and Pb, respectively).

Species composition and infection levels of Anisakis (Nematoda: Anisakidae) in the skipjack tuna Katsuwonus pelamis (Linnaeus) in the Northwest Pacific.

Parasites can be used as biological tags to assess stock structures in various marine fish species. In the present study, the species composition and infection levels of parasitic nematodes of the genus Anisakis in the skipjack tuna Katsuwonus pelamis were examined in the Northwest Pacific and adjacent seas. A total of 867 third-stage larvae of Anisakis were collected from 112 skipjack tunas captured around Japan and in other subtropical localities. All larvae were identified as A. berlandi, A. pegreffii, A. simplex (s.s.), A. typica, and A. physeteris (s.l.) by the direct sequencing of the mitochondrial cox2 gene and real-time PCR assays targeting the nuclear ITS region. Anisakis species composition differed among northeastern Japan, the Sea of Japan, and other areas (central Japan, the Nansei Islands, and subtropical region), which is largely concordant with previous stock discrimination of skipjack tuna. Molecular phylogenetic analysis resulted in two intraspecific genetic groups in A. simplex (s.s.), one of which occurred almost exclusively in northeastern Japan. This could be a useful indicator for stock discrimination. Skipjack tunas from northeastern Japan were also characterized by a remarkable variety in the intensity of A. simplex (s.s.), suggesting the commingling of individuals with different migrationpatterns. This idea might be further justified by the geographic distribution of two genetically distinct groups of A. physeteris (s.l.).

Tunas off northwest Africa: The epipelagic diet of The Bigeye and Skipjack tunas

Tunas are among the most exploited top predators worldwide, with negative impacts on some of their stocks. Changes in their population abundance can impact marine food-webs and have the potential to alter entire ecosystems. To better understand the impacts of the exploitation of tuna stocks in the most critical habitats, basic knowledge on the diet of these species in each region is required. Here, we describe the diet of the two most fished tuna species in the archipelago of Madeira, the Bigeye tuna Thunnus obesus and the Skipjack tuna Katsuwonus pelamis, based on stomach contents analysis. To gain further insights into the diet, and also better assess the possible bias caused by the occurrence of live bait in stomachs, we compared tuna mercury values with those of two other predators with similar diets that are not directly targeted by fisheries, and with Bigeye and Skipjack tunas from other ocean basins. Bigeye tunas fed mostly on Atlantic chub mackerel Scomber colias and mackerel Trachurus sp., which together contributed with 85% of total prey weight. Only 7.5% of prey weight was constituted by mesopelagic prey, including myctophids and cephalopods. Skipjack tunas had an epipelagic diet (NF = 97%), with the Atlantic chub mackerel representing half of the total prey weight, despite Longspine snipefish Macroramphosus scolopax and Sand smelt Atherina sp. accounting for 62.9% of the total number of prey. There were interannual variations in diet likely linked to interannual pelagic community shifts. Bait did not bias the results of the stomach analysis of these tunas and bait species were observed to be part of the natural diet of both tuna species. Baseline data provided by this study should allow for more informed decisions for an efficient ecosystem-based fisheries management.

Identification of Selected Tuna Species in Commercial Products.

This study was conducted to develop systems for the identification of four tuna species (skipjack tuna Katsuwonus pelamis, yellowfin tuna Thunnus albacares, bullet tuna Auxis sp. and Atlantic bonito Sarda sp). At first, raw samples of these species and a mix intended as internal control were prepared for the authentication of fish muscle tissue of the genus Thunnus sp., Auxis sp. and Sarda sp. DNA from raw muscle tissue, the mix and samples was extracted with the DNeasy mericon Food Kit (Qiagen GmbH, Hilden, Germany). The concentration and purity of DNA in raw samples were evaluated using a spectrophotometer. Primers and probe sequences were specifically designed to identify the selected species. In addition, primers and a probe for the endogenous 12S rRNA gene were designed to determine the presence of amplifiable fish (especially tuna) DNA in samples. Furthermore, the species specificity of the designed primers and probes was verified in DNA samples of various tuna and bonito species. Limit of detection for the selected species was calculated as well as the coefficient of determination R2 and efficiency of real-time PCR testing was determined. To evaluate the developed real-time PCR methods, 70 commercial tuna products were analysed. The results show that mislabelling of fish products can still be encountered and, moreover, the presence of an additional species can be identified.

Effects of preservation on chemical composition and sensory analysis of skipjack tuna (Katsuwonus pelamis) in Tema, Ghana

Although fish is an integral part of Ghanaian diets and play important nutritional role, much research has not been conducted with respect to the nutritional composition and sensory analysis of marine fishes in Ghana. This study evaluated chemical composition and sensory analysis of Skipjack tuna (Katsuwonus pelamis) sampled from Tema in the Greater Accra region of Ghana. Four different samples; very dry smoked (Sample A), dry smoked (sample B), moist smoked (sample C) and fresh (sample D) skipjack tuna were used for this study. Chemical composition (moisture, ash and protein) was analysed using standard laboratory methods whilst sensory parameters (colour, odour, flavour, texture and overall acceptance) were assessed using 20 trained panelists. There were significant differences in moisture and crude protein contents (P < 0.05). Ash content was however non-significantly different. Moisture content for very dry smoked skipjack tuna, dry smoked skipjack tuna, moist smoked skipjack tuna and fresh skipjack tuna were 49.79 ± 1.73 %, 60.22 ± 1.80 %, 59.32 ± 0.01 % and 68.65 ± 0.16 %, respectively whilst crude protein content were 90.83 ± 1.09 %, 73.32 ± 1.09 %, 88.15 ± 1.19 % and 91.72 ± 0.19 %, respectively for very dry smoked skipjack tuna, dry smoked skipjack tuna, moist smoked skipjack tuna and fresh skipjack tuna. It can be concluded that different methods of preservation (smoking) have significant influence on proximate composition as well as sensory analysis. It is suggested that further studies be conducted on sensory analysis and proximate composition of fish sold on Ghanaian markets. In addition, we recommend that the Food and Drugs Authority (FDA) conduct regular studies on fish to ascertain the quality.

Comparison of handline tuna catches in Indian Ocean and Banda Sea waters

There are two essential landing sites for handline tuna in Indonesia: Palabuhanratu (in the Indian Ocean) and Kendari (in the Banda Sea). This paper analyzes handline catches from the Indian Ocean and Banda Sea waters as the main fishing ground. The catch composition of the handline tuna landed in Kendari is more varied than Palabuhanratu. Several species commonly caught are yellowfin tuna (Thunnus albacares), skipjack tuna (Katsuwonus pelamis), bigeye tuna (Thunnus obesus) as a target species, and some billfish species as bycatch. Mean CPUE for handline tuna landed in Palabuhanratu is lower than Kendari. A significant difference is based on the monthly mean CPUE variation between Palabuhanratu and Kendari landing sites (p < 0.001). Handline catches in Palabuhanratu had a more comprehensive range of length sizes than Kendari, using a two-sample K-S test showed significant differences (p < 0.001). The fish size landed in Kendari is relatively smaller than Palabuhanratu. The average length of fish caught by handline is smaller than the length at first maturity (Lm) value in both landing sites. The use of large size hook for hand lines is recommended for catching tunas in this area.

Region Proposal and Regression Network for Fishing Spots Detection From Sea Environment

In this paper, a two-stage method is proposed for predicting the catch of skipjack tuna ( Katsuwonus pelamis ) from a 2D sea environmental pattern. Following the assumption that sea water temperature and sea surface height (SSH) which fishermen often use for finding fishing spots has a correlation with the skipjack tuna catch, a new approach of using Faster R-CNN in object detection is proposed. The proposed method consists of two part. In the first part, taking a sea temperature map as input, Faster R-CNN extracts the candidates of where skipjack tuna would be on the map in order to imitate the behaviors of fishers. In the second part, Support Vector Regression (SVR) estimates the catch amount in each candidate. Fater R-CNN is applied to several sea environmental patterns with three different loss functions and compares each performance. The proposed model is evaluated by comparing the result with average fishers’ ability on the skipjack tuna catches and several criteria for evaluating the proposed model. The results show that the proposed method is able to outperform the average fishers’ ability by an average of 3%.

A review of the fisheries, life history and stock structure of tropical tuna (skipjack Katsuwonus pelamis, yellowfin Thunnus albacares and bigeye Thunnus obesus) in the Indian Ocean.

Skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tuna are the target species of tropical tuna fisheries in the Indian Ocean, with high commercial value in the international market. High fishing pressure over the past three decades has raised concerns about their sustainability. Understanding life history strategies and stock structure is essential to determine species resilience and how they might respond to exploitation. Here we provide a comprehensive review of available knowledge on the biology, ecology, and stock structure of tropical tuna species in the Indian Ocean. We describe the characteristics of Indian Ocean tropical tuna fisheries and synthesize skipjack, yellowfin, and bigeye tuna key life history attributes such as biogeography, trophic ecology, growth, and reproductive biology. In addition, we evaluate the available literature about their stock structure using different approaches such as analysis of fisheries data, genetic markers, otolith microchemistry and tagging, among others. Based on this review, we conclude that there is a clear lack of ocean basin-scale studies on skipjack, yellowfin and bigeye tuna life history, and that regional stock structure studies indicate that the panmictic population assumption of these stocks should be investigated further. Finally, we identify specific knowledge gaps that should be addressed with priority to ensure a sustainable and effective management of these species.

Hydroacoustic studies on Katsuwonus pelamis and juvenile Thunnus albacares associated with light fish-aggregating devices in the South China Sea

Using scientific echosounders, we investigate the distribution and in situ target strength (TS, dB) of skipjack tuna Katsuwonus pelamis and juvenile yellowfin tuna Thunnus albacares associated with light fish-aggregating devices in the South China Sea. We analyze the volume backscattering strength (SV, dB), TS, and density (the number of fish in the effective reverberation volume, fish/sampling volume) of fish. In natural conditions (without light), tuna occur at depths exceeding 50 m. After luring lamps are turned on, SV and TS increase, especially from 21 to 50 m, with SV manifesting time and depth-related differences. Skipjack and yellowfin tunas occur mainly from 31 to 50 m between 24.0 °C and 28.0 °C, and 21–30 m between 28.2 °C and 28.7 °C, respectively. From 18:30 to 21:30, mean TS tends to increase with density when density exceeds a cut-off value, indicating that overlapping echoes contribute to increased TS. From 21:30 to 22:00, there was no significant relationship between increased mean TS and density. Mean TS values for skipjack tuna of mean fork length 36.1 cm are −50.77 dB at 70 kHz and −52.29 dB at 120 kHz. Mean TS values of yellowfin tuna of mean fork length 41.2 cm are −38.01 dB at 70 kHz and −38.30 dB at 120 kHz. These results can be used to estimate tuna abundance, and monitor and identify their behavior.

Ingestion of plastic debris by commercially important marine fish in southeast-south Brazil

Rising concentrations of plastics in the oceans are leading to increasing negative interactions with marine biota, including ingestion by endangered and/or economically important seafood species such as fish. In this paper, we visually evaluated plastic debris ingestion by 965 specimens of eight commercially exploited fish species from different marine habitats off the southeast-south coast of Brazil. All species ingested plastics, with pelagic animals having higher amounts, frequency of occurrence, diversity and sizes of ingested items than demersal-pelagic and demersal animals. Highest frequency of occurrence (FO%) of plastic ingestion (25.8%) was observed for the pelagic skipjack tuna Katsuwonus pelamis (Scombridae), and lowest (5%) for the demersal bluewing searobin Prionotus punctatus (Triglidae). Microplastics predominated in all species, and fibers/lines and fragments were the main items found, possibly derived from fishing materials. The most abundant plastic colors were transparent, black and blue, and the most common polymers were polyamide and polyurethane. With the available data, no relationship between the size of the individuals and amount of ingested plastics was observed. Considering the negative impacts of plastic ingestion on marine fish, and potentially on human health due to their consumption, understanding ingestion patterns is critical for better evaluating their origin and possible causes, and consequently for helping define prevention strategies for this problem.

Source-dependent compositional changes in coconut flavoured liquid smoke and its application in traditional Indian smoked fishery products

ABSTRACT Smoking is an age-old food preservation method. Intense smoking results in deposition of carcinogenic polycyclic aromatic hydrocarbons (PAH) in food. Replacing traditional smoking practices with application of liquid smoke or smoke flavouring is proven to reduce the PAH content without adversely affecting flavour of the products. This study explores source-dependant variations in composition of a coconut-flavoured liquid smoke. Liquid smoke produced from coconut husk (CH), coconut fibre (CF) and coconut fibre powder (CP) was analysed for total phenolic content, total carbonyls, titratable acidity, pH and PAH content. Resultant liquid smokes were also compared a commercial liquid smoke (CL) for composition. Total phenolic content in the liquid smokes ranged from 1518 ± 184 (CH), 1037 ± 110 (CF), 834 ± 48.23(CP) and 20047 ± 193 mg L−1 (CL). Commercial liquid smoke showed highest total PAH content 215 ± 15.45 ng ml−1 followed by 8.23 ± 1.47 (CP), 7.22 ± 1.44 (CF) and 0.64 ± 0.13 ng m−1 (CH). Further, process parameters for producing ‘masmin’ – a popular traditional smoked and dried ready-to-eat product – by replacing traditional smoking practices with liquid smoking were standardised using Response Surface Methodology. Spraying cooked skipjack tuna (Katsuwonus pelamis) loins with coconut husk liquid smoke containing 4% salt for 155 min at flow rate of 3 L hr−1 and chamber temperature of 60°C was found to give the product a matching flavour with traditional masmin.

Potential predictability of skipjack tuna (Katsuwonus pelamis) catches in the Western Central Pacific

The Pacific Island countries have a substantial socio-economic dependency on fisheries. Skipjack tuna is one of the most important species in the Western Central Pacific (WCP) and its catches in this region exhibit a spatio-temporal variability influenced by ocean conditions, mainly the El Niño-Southern Oscillation (ENSO). This study investigates the relationship between skipjack tuna catch amounts and environmental variables in the equatorial Pacific during 1990–2014, and evaluates the potential predictability of the catches based on their statistical relationship. A series of regressed and reconstructed spatial patterns of upper-ocean temperature, salinity, currents and precipitation represent ENSO-like variability, and their principal component time series are used to estimate the predictability of skipjack tuna catches in the Federated States of Micronesia (FSM). ENSO-like variability depicted from 100 m temperature and 5 m salinity in the equatorial Pacific exhibit a significant predictability for the annual catch amount in the FSM for several years with a training period of > 20 years. This suggests that the subsurface temperature or near surface salinity can be a better predictor of ecosystem variability than widely used sea surface temperature. Applications of this result to other species could have broad implications for the fishery industry in the WCP.