Trachurus Trachurus Research Articles

Fourier-transform near-infrared spectroscopy first application to age determination in European fish species: the case of the Atlantic horse mackerel from the central Mediterranean Sea

Fourier-transform near-infrared spectroscopy (FT-NIRS) has recently been used to reduce the processing time for estimates of annual age in several fish species. The present study represents the first application of this technique to marine organisms from the European waters. Atlantic horse mackerel (Trachurus trachurus) from the central Mediterranean Sea was selected for its ecological role, its socioeconomic value, and because its age is regularly estimated by otolith reading under a stereomicroscope for stock assessment purposes. Absorption spectra of the whole otoliths were acquired by FT-NIRS across a multiyear dataset, obtained during acoustic surveys carried out in different regions of the central Mediterranean Sea. The acquired spectra were processed to optimize calibration models to predict age. The best linear models obtained by the optimizing procedure predicted age successfully with a coefficient of determination of 0.95–0.96, mean squared error of 0.5 years, and bias <0.03 years. Although regional calibration models were also obtained separately, the models with all regions combined appeared much more robust and encompassing the whole age range, suggesting its usefulness for the entire spatial distribution range considered in the preset study. The use of FT-NIRS allowed to successfully predict age for horse mackerel between the ages 1 and 14, with similar or better precision (and bias) of the traditional methods, also increasing the standardization by repeatability of age assignments. The preliminary results obtained by this study encourage further effort to fine-tune the calibration model for new species, in order to apply a precise, rapid, cost-effective method for stock assessment purposes of Mediterranean fish resources.

Ecology, Anatomy, Reproduction, and Diet of the Atlantic Horse Mackerel, Trachurus trachurus: A Comprehensive Review

Ecology, Anatomy, Reproduction, and Diet of the Atlantic Horse Mackerel, Trachurus trachurus: A Comprehensive Review

The aggregation effect of offshore mussel farming on pelagic fishes

AbstractThe increase in hard artificial structures in the marine environment is contributing to ocean sprawl. As well as adding hard structure to the seabed, mussel aquaculture adds rope droppers and anchor lines to the water column, where such structure would otherwise be absent. This paper aims to monitor the effects of mussel headlines on the pelagic fish community over time, as well as to investigate whether there is an interaction between the age of cultivated mussels with the number of epibiota species and the abundance of pelagic fishes. Two surveys were carried out: a time series monitoring survey to assess whether the mussel headlines change the surrounding fish species relative to control areas over time, and a fish aggregation device effect survey to investigate whether older and larger mussels support greater abundances of pelagic fishes and epibiota. The most abundant fish species was Atlantic horse mackerel, Trachurus trachurus, with significantly greater numbers recorded around ropes growing older mussels. Results from the surveys show that the physical farm infrastructure has provided a substrate for colonisation by a variety of epibiota: A total of 21 species were recorded growing on the mussel ropes. Furthermore, the older and larger the mussels become, the greater the numbers of epibiota taxa that can colonise, coupled with a greater abundance of pelagic fish recorded around the ropes. The sustainable development of offshore Blue Industries is essential to produce renewable resources. This study brings essential evidence for marine managers and regulators that offshore mussel farming can provide benefits for pelagic and benthic species of both conservation and commercial importance while producing sustainable protein to feed a growing population.

Morphometrical characters of Atlantic horse mackerel Trachurus trachurus (Linnaeus, 1758), in the North Atlantic zone of Morocco

The Atlantic Horse mackerel Trachurus trachurus (Linnaeus, 1758) is subject to considerable fishing pressure. under strong fishing pressure, the objective of the research is to establish the species morphological characterization: the growth model, sex-ratio and the body condition factor, using standard morphometric methods and truss network analysis. 1494 samples were collected from the North Moroccan Atlantic coast, sampling was carried out from July 2021 to July 2022 at the port of Tangier and Larache (35°47, 33°89), indeed individuals total length measured between10 and 41 cm and the body weight presented between 35 and 500 g, All morphometrical analyses showed similar results, The values for males, females and the total sample showed that the growth of T. trachurus was minor, which that mean the weight grows less quick than the length, The condition factor was calculated indicating the smallest values were observed in the range of Total length between 10 and 19 cm.

Trophic Interactions of European Hake Merluccius merluccius (Linnaeus, 1758) in Benthic Communities off the Moroccan Mediterranean Coastline: Seasonal and Ontogenetic Shifts.

The European hake, Merluccius merluccius (Linnaeus, 1758), is one of the most important resources for Mediterranean fisheries. Due to its pivotal role in energy transfer from lower to higher trophic levels, this species is a crucial component of the ecosystem's functioning. The ecological role of Merluccius merluccius, off the Moroccan Mediterranean Sea (southern Alboran Sea), was investigated, exploring seasonal and ontogenetic shifts, geographical variations in prey composition, and feeding strategy. Between November 2020 and July 2022, a total of 402 hake specimens were collected by oceanographic bottom trawl surveys (MEDITS) that were carried out during warm and cold seasons to assess their diet and feeding habits. The sample was analyzed according to fish sizes and seasons, and qualitative/quantitative feeding indices were calculated. The trophic spectrum of Merluccius merluccius included 24 prey items in total, mainly belonging to Osteichthyes (12), Crustacea (10), Cephalopoda (1), and Polychaeta (1), suggesting a generalist behavior of this predator as in numerous regions of the Mediterranean Sea, with several species that occasionally occurs in its diet. In the Moroccan Mediterranean Sea, Osteichthyes proved to be the most important prey item (%IRI = 78.56) among the different zoological groups, followed by Crustacea (%IRI = 16.22). The other food items were occasionally and randomly consumed, and cannibalism was low (0.8%). Hierarchical cluster analysis and nonmetric multidimensional scaling (nMDS) showed different feeding habits of two main groups separated at 60% similarity: small specimens <10 cm TL, primarily feed on zooplanktonic prey, while medium and large specimens hold a diet based on Osteichthyes with crustaceans. Furthermore, a significant positive relationship between hake and fish prey size was confirmed. Seasonally, mesopelagic Osteichthyes were the main food prey in the summer season, while pelagic species were predominant during the autumn. SIMPER analysis revealed that the prey items contributing the most to the differences between seasons and length classes were Engraulis encrasicolus, Micromesistius poutassou, Boops boops, Macroramphosus scolopax, gobids, Gadiculus argenteus, and most of Crustacea. The diet does not appear to be influenced by sex (>0.05). A trophic level (TROPH) of 4.1 was calculated, indicating that the species is a top predator (quaternary consumers). The TROPH values ranged between 2.58 and 4.38 from juveniles to adults, increasing asymptotically with the size of specimens. In contrast to what has previously been found in other Mediterranean regions, where ichthyophagous hake feed mostly on pelagic Osteichthyes, such as Engraulis encrasicolus, Sardina pilchardus, and Micromesistius poutassou, the study points up the vital role played by Atlantic horse mackerel Trachurus trachurus for hake diet in the Moroccan Mediterranean Sea. Information on the feeding ecology of fish species as provided in this study is essential to improve ecosystem conservation in accordance with multispecies approach to fishery management, leading to a better understanding of the role of hake in the Moroccan Mediterranean Sea demersal communities.

Abundance and operating area by benthic trawl of Atlantic horse mackerel in the central Mediterranean

Abundance and operating area by benthic trawl of Atlantic horse mackerel in the central Mediterranean

Influence of Different Previous Frozen Holding Periods on the Canned Fish Quality.

The combined effects of thermal processing (i.e., sterilisation treatment) and the prior frozen storage time (3 or 6 months at -18 °C) on the quality loss in canned Atlantic horse mackerel (Trachurus trachurus) were determined. Thus, the sterilisation step led to a remarkable (p < 0.05) formation in the canned fish muscle of fluorescent compounds, free fatty acids (FFAs), and trimethylamine and an increase in the L* and b* colour parameters; meanwhile, a decrease (p < 0.05) in the total ω3 FA/total ω6 FA ratio and the a* colour value were detected. The prior frozen storage period led to an increased (p < 0.05) lipid oxidation (peroxide, thiobarbituric acid reactive substance, and fluorescent compound formation) and hydrolysis (FFA formation) development and to increased L* and b* colour values in the corresponding canned samples; additionally, a lower (p < 0.05) polyene index and phospholipid content were observed in canned fish previously subjected to frozen storage. In most indices, physico-chemical changes related to quality loss were found to be higher if the previous storage period was increased. According to the marked effects of the sterilisation step and the prior frozen storage period, the optimisation of such processing conditions is recommended to maximise the quality of canned horse mackerel.

Population Dynamics and Stock Assessment of Atlantic Horse Mackerel (Trachurus trachurus) Stocks in the Western Egyptian Mediterranean Waters

Population Dynamics and Stock Assessment of Atlantic Horse Mackerel (Trachurus trachurus) Stocks in the Western Egyptian Mediterranean Waters

Occurrence of Anisakis larvae in Atlantic horse mackerel (Trachurus trachurus) sold in the city of Marrakesh, Morocco

Human anisakidosis is a parasitic infection caused by the ingestion of nematode larvae of the Anisakidae family contained in various organs of fish and cephalopods consumed raw or undercooked. The aim of this work was to detect and identify morphologically and genetically (PCR and sequencing) the nematode larvae present in both flesh and abdominal cavity of horse mackerel (Trachurus trachurus) which are widely consumed by the population of Marrakesh. For this purpose, 299 fish were purchased at the wholesale market in refrigerated conditions. They were originated from seven different landing ports along the Atlantic coast (Agadir, Dakhla, El Jadida, Essaouira, Mohammedia, Safi and Sidi Ifni). The fishes were analyzed from November 2017 to December 2019, and 4815 larvae were detected out of 294 positive horse mackerel. This resulted in a prevalence of 98.33% and a mean intensity of 16.38 larvae per fish. Horse mackerel from Mohammedia, El Jadida, Safi, Essaouira, Agadir and Sidi Ifni were more infested than those from Dakhla with a mean intensity of 25.29, 21.33, 18.88, 16.15, 15.90 and 13.86 larvae per fish, respectively, while that from Dakhla was the least infested with a mean intensity of 11.83. These results could be explained by the availability of primary intermediate hosts of Anisakis spp., such as crustaceans (shrimps), which are more abundant in the northern Moroccan Atlantic coast. Furthermore, we have recorded a higher infection in fish during warm seasons (spring and summer) than during cold ones. We also have noticed that as the distance from the fishing area increased, the larvae had more time to migrate from the abdominal cavity to the muscles. All detected larvae were identified morphologically as Anisakis type I and genetically as Anisakis simplex sensu stricto. Statistical analysis showed that the intensity of infection by Anisakis L3 larvae was positively correlated with the weight of horse mackerel and that origin had no impact on fish parasitism.

Bioactive angiotensin converting enzyme inhibitory activity and antihypertensive activity derived from fish protein hydrolysate: a systematic review

In the fish processing sector, fish have been processed in large quantities, are generated and discarded into the sea or dumped into the oceans. However, by employing effective strategies, this fishery waste can be utilized and converted into fish protein hydrolysate (FPH). FPH is a rich source of amino acids and peptides that have biological properties such as angiotensin-converting enzyme (ACE) inhibition, antimicrobial, antioxidant, and anticancer activity. The FPH has been used as a functional food perspective related to improving human health, primarily by maintaining blood pressure and normal heart function as measured by antihypertensive activity. FPH can be produced by various fish species, parts, and hydrolysis methods. Several studies have been published on the acceptability of FPH in obtaining bioactive properties from various fish, each using a different method to obtain bioactive properties. FPH is commonly produced by fish species such as Atlantic Cod, Lizard Fish, Atlantic Chub Mackerel, Atlantic Horse Mackerel, and Kawakawa (Mackerel Tuna). Furthermore, we summarized the various methodologies used by various researchers based on raw material data collection, method of production, ACE-inhibitory assay, ACE-inhibitory activity, degree of hydrolysis, molecular weight, purification method, and ACE-I peptide structure in this review.

Proximate and Mineral Composition of Atlantic Mackerel (Scomber scombrus) and Atlantic Horse Mackerel (Trachurus trachurus)

Atlantic mackerel (Scomber scombrus) and Atlantic horse mackerel (Trachurus trachurus), locally known as kote, are fishery species consumed in Nigeria due to their high nutritional values. This research determined the nutritional composition of the local dried fish, Scomber scombrus and Trachurus trachurus. Results for Scomber scombrus shows the mean value of the moisture, ash, crude fat, crude fiber, and crude protein contents in percent (%) as: 5.260.00, 5.200.10, 35.600.00, 2.900.10 and 46.300.01 respectively. For Trachurus trachurus, the moisture, ash, crude fat, crude fiber, and crude protein contents in percent (%) were 9.520.00, 32.260.01, 24.140.00, 11.910.85 and 40.950.00 respectively. The mineral composition of Scomber scombrus was as follows: Sodium (Na) had the highest mineral composition with 78.90 mg/100g, followed by magnesium (Mg) with 15.90 mg/100g, manganese (Mn) with 0.86 mg/100g, zinc (Zn) with 0.282 mg/100g, and iron (Fe) with 0.10 mg/100g. Trachurus trachurus has magnesium (Mg) at 27.00 mg/100g as its highest mineral composition, followed by sodium (Na) at 22.50 mg/100g, zinc (Zn), iron (Fe) at 0.17 mg/100g, and manganese (Mn) at 0.09 mg/100g. It is concluded from the study, that Scomber scombrus and Trachurus trachurus are good sources of essential nitrates, fat, proteins containing essential amino acids, and other micronutrients that are beneficial to human health.

Enhancement of Lipid Stability of Frozen Fish by Octopus-Waste Glazing.

The antioxidant properties of the liquor resulting from commercial octopus cooking were analysed for this study. Two different concentrations of octopus-cooking liquor (OCL) were tested as glazing systems during the frozen storage period (-18 °C for up to 6 months) of whole Atlantic horse mackerel (Trachurus trachurus). Compared to water-control glazing samples, an inhibitory effect (p < 0.05) on lipid oxidation development (the formation of thiobarbituric acid reactive substances and fluorescent compounds) was detected in frozen fish treated with the most concentrated OCL-glazing system. Additionally, a preservative effect (p < 0.05) on polyunsaturated fatty acids (measurement of polyene index) was also proved. However, no effect (p > 0.05) on the free fatty acid content and on the ω3/ω6 ratio was detected with the presence of the OCL in the glazing system. An increased lipid quality in frozen horse mackerel was established by including the OCL solution in the glazing system. According to previous research, the observed preserving properties were explained on the basis of the presence of antioxidant compounds in the cooking liquor. A novel and valuable combination of glazing processing and the employment of a marine waste substrate is proposed to enhance the lipid stability of frozen fish.

Fish length, diet, and depth drive Anisakis levels in a zooplankton-feeding fish

Parasites play a key but overlooked role in the functioning of marine systems. Understanding the drivers of parasite infection in fish is thus crucial. Anisakis levels in the Atlantic horse mackerel Trachurus trachurus resulted from both biotic and environmental drivers. Ontogenic variation of the diet was the first driver of Anisakis level. The nonlinear pattern confirmed that the variation in parasitism was related to ontogenetic dietary shifts. The impact of depth on diet also explained the effect of depth on parasites. In deeper areas, fish only access pelagic prey, where Anisakis presence is high, consistent with the pelagic nature of the parasite. Finally, relative proportions of parasitic burden by tissue appeared to be driven by lipid content. In lipid-rich species like T. trachurus, Anisakis can find favorable conditions in the body cavity and in muscle and avoid the liver. Parasitism levels in fish are thus the result of patterns at play at different levels, and these factors should be better considered before being able to include parasites in an integrated vision of marine ecosystem functioning.

The genomic basis and environmental correlates of local adaptation in the Atlantic horse mackerel (Trachurus trachurus).

Understanding how populations adapt to their environment is increasingly important to prevent biodiversity loss due to overexploitation and climate change. Here we studied the population structure and genetic basis of local adaptation of Atlantic horse mackerel, a commercially and ecologically important marine fish that has one of the widest distributions in the eastern Atlantic. We analyzed whole-genome sequencing and environmental data of samples collected from the North Sea to North Africa and the western Mediterranean Sea. Our genomic approach indicated low population structure with a major split between the Mediterranean Sea and the Atlantic Ocean and between locations north and south of mid-Portugal. Populations from the North Sea are the most genetically distinct in the Atlantic. We discovered that most population structure patterns are driven by a few highly differentiated putatively adaptive loci. Seven loci discriminate the North Sea, two the Mediterranean Sea, and a large putative inversion (9.9 Mb) on chromosome 21 underlines the north-south divide and distinguishes North Africa. A genome-environment association analysis indicates that mean seawater temperature and temperature range, or factors correlated to them, are likely the main environmental drivers of local adaptation. Our genomic data broadly support the current stock divisions, but highlight areas of potential mixing, which require further investigation. Moreover, we demonstrate that as few as 17 highly informative SNPs can genetically discriminate the North Sea and North African samples from neighboring populations. Our study highlights the importance of both, life history and climate-related selective pressures in shaping population structure patterns in marine fish. It also supports that chromosomal rearrangements play a key role in local adaptation with gene flow. This study provides the basis for more accurate delineation of the horse mackerel stocks and paves the way for improving stock assessments.

FoodSmarTag: An innovative dynamic labeling system based on pyranoflavylium-based colorimetric films for real-time monitoring of food freshness

A colorimetric pyranoflavylium-based pH-indicator with an improved formulation was obtained and studied as an intelligent label for food freshness monitoring. Pyranoflavylium pigment at 0.2% (w/w) and glycerol at 30% (w/w) were immobilized in a cellulose acetate matrix, and a thin film was obtained by the solvent casting method. The pH-responsive properties of the film were evaluated in solutions at different pH values (pH 4 to 8) and compared with a previous formulation. Film photostability and pigment migration over time were assessed. The label's performance was evaluated using real samples (fish and meat) at controlled conditions (3 °C and modified atmosphere packaging). The results showed that increased pigment concentration visually favored its colorimetric efficacy. Regarding pigment migration and photostability, the label showed to be suitable for application in fresh meat and fish packaging. The best performance was observed for the freshness monitoring of fish samples. The indicator demonstrated high efficacy in detecting spoilage of Atlantic horse mackerel (Trachurus trachurus). After 5 days of storage, freshness parameters exceeded the limit defined by EU regulations, indicating that the fish was unfit for consumption. Simultaneously, the yellow label started to turn purple, effectively indicating the beginning of the spoilage process.

Growth variability in Atlantic horse mackerel Trachurus trachurus (Linneus, 1758) across the central Mediterranean Sea: contrasting latitudinal gradient and different ecosystems

Data on Atlantic horse mackerel Trachurus trachurus (Linneus, 1758) were collected along 8-year acoustic surveys (2011-2018). Age and growth variability of horse mackerel from the Central Mediterranean Sea were investigated within different, contrasting habitats, from the south of Sicily to the north Tyrrhenian (Ligurian Sea). Data from satellite provided the habitat features along the study period over the whole surveyed area. For comparison purposes, according to the ecosystems difference the study area has been split into four subareas: Strait of Sicily (SoS), North of Sicily (NS), south Tyrrhenian Sea (ST) and north Tyrrhenian Sea (NT). In terms of the FAO Geographical Sub-Area definition the SoS corresponding to GSA15 and 16, NS to GSA 10 south, ST to GSA10 north and NT to GSA 9. Results showed a growth homogeneity in the study area, suggesting a unique stock inhabiting these waters. The only exception was recorded for juveniles (Age 0 class) in the SoS, where a lower size at age was detected compared to other areas. A multiple linear modelling analyses suggested that variability in length at age 0 was mainly linked to the oceanographic differences between an upwelling driven system (Strait of Sicily) and the other ecosystems, where enrichment processes are mainly due to river runoff (relevant in ST and NT). Namely, Absolute Dynamic Topography (ADT) and body condition factor (Kn) were significantly related to differences in length at age 0. Results revealed that currents (and gyres) are among the principal abiotic factors controlling Atlantic horse mackerel growth in its first year of life, suggesting that circulation and food-related processes (i.e., zooplankton concentration) are of major importance for this species. Finally preliminary observations suggest the Strait of Sicily may be the main spawning area among those analyzed.

Assessment of Heavy Metals in the Atlantic Horse Mackerel (Trachurus Trachurus) from Cold Storage in Benin Metropolis, Nigeria

Heavy metals can contaminate fish and water which in turn present a risk to humans. The dearth of eco-toxicological data on the heavy metal content in Trachurus trachurus particularly from cold storage in Benin Metropolis, Nigeria, warranted this research, which was achieved via Atomic Absorption Spectrometric technique. The mean concentrations (mg/kg, wet weight) of heavy metals in T. trachurus by cold storage point ranged from 0.242 for Cd at Uselu to 52.98 for Zn also at Uselu with significant differences (p&lt;0.05) in the mean concentrations of heavy metals in T. trachurus between cold storage points. The total toxicity of mixtures (TTM) value for heavy metals was 0.845 while the estimated annual intake (EAI) and estimated daily intake (EDI) of heavy metals peaked for Zn with values of 1.345 mg/person/year and 0.00368 mg/person/day respectively. The target hazard quotient (THQ) values ranged from 0.0000276 (Cd) to 0.0000135 (Zn) with a total target hazard quotient (TTHQ) value of 0.0000267 while the quota for heavy metals in T. trachurus ranged from 0.36% for Cd to 87.80% for Zn. The total heavy metal burden in T. trachurus by cold storage point ranged from 46.95 mg/kg at Oliha to 54.37 mg/kg at Uselu. T. trachurus from cold storage were safe for human consumption with regard to heavy metal levels as International thresholds for heavy metals in fish were not surpassed. It was proffered that continuous monitoring of the heavy metal status of this fish species is maintained in order to protect the health of potential consumers.

Pathological lesions associated with Vibrio infection in Atlantic horse mackerel (Trachurus trachurus L., 1758) from the western coast of Tripoli, Libya.

Vibrios are aquatic bacteria causing Vibriosis in humans and aquatic animals. Vibriosis is a significant disease of cultured and wild fish. The present study aimed to address the impact of Vibrios on the health status of Trachurus trachurus inhabiting the coastal area of Tripoli. A total of 100 samples of (T. trachurus) were collected randomly from the Western Coast of Tripoli and Bab Al-Baher market, throughout the period from spring 2019 to summer 2019. All the sampled fish were examined externally and internally and lesions were recorded. Bacterial isolation from the liver and kidney was carried out using the appropriate culture media. Tissue samples were taken from the liver, kidney, and spleen in 10% neutral buffered formalin for a histopathology examination. The tissue sections were stained with hematoxylin and eosin to assess morphologically and Perl's Prussian blue for the demonstration of ferric iron. On average 69% of the infected fish exhibited at least one pathological lesion. Vibrios were recovered from 90% of the examined fish. The histopathological changes of the liver showed severe congestion of blood vessels (BVs), mononuclear cell infiltration surrounding a bile duct, granular degeneration and coagulative necrosis of hepatocytes in the centrilobular area, marked vacuolar degeneration of hepatocytes, activation of melano-macrophage centers (MMCs), multiple cysts of nematode in hepatic tissue (incidental finding). The histopathological alterations of the kidney showed severe congestion of BVs, vacuolar degeneration of the renal tubular epithelium, severe interstitial mononuclear cell infiltration, and marked activation of MMCs in the kidney. Moreover, congestion of BVs and marked activation of melano-macrophages (MMCs) were found in the spleen. The MMCs of most of the sampled tissues showed a strong positive reaction for ferric iron. The polluted aquatic environment by sewage at Tripoli Coast is an essential factor for triggering the pathogenicity and invasion of Vibrios to vulnerable Atlantic horse mackerel. Also, this study is a preliminary step to give a baseline for further future studies on epidemiology and control of Vibrio infection in Libyan fish.

Trophic ecology of northern gannets Morus bassanus highlights the extent of isotopic niche overlap with other apex predators within the Bay of Biscay

Understanding the linkages within complex and evolving marine food webs is essential to comprehend marine ecosystem structure and dynamics. Carbon (δ13C) and nitrogen (δ15N) stable isotope signatures are recognized to be powerful descriptors of the trophic ecology and trophic relationships within marine communities. Apex predators such as seabirds can influence the structure of communities by predating in lower trophic levels. They also convey information both over a range of spatial and temporal scales due to their high mobility and longevity, respectively. For this reason, here, we studied the trophic ecology of northern gannets and the extent of niche overlap with other apex predators within the Bay of Biscay (North-East Atlantic), a key feeding area for numerous predatory species. Mixing models indicated that northern gannets fed primarily on European anchovy Engraulis encrasicolus and on a mixed group composed of European sardine Sardina pilchardus, European sprat Sprattus sprattus, juvenile hake Merluccius merluccius, Atlantic mackerel Scomber scombrus and Atlantic horse mackerel Trachurus trachurus. Within the apex predator community, the northern gannets trophic niche overlapped the most with common guillemots Uria aalge (15.58%, based on Stable Isotope Bayesian Ellipses (SIBER)) and overlapped to a lesser extent with cetacean species occupying shelf habitats (i.e., the harbour porpoise Phocoena phocoena (9.99%) and the short-beaked common dolphin Delphinus delphis (10.37%)). Overall, the overlap found was moderate indicating trophic similarities and dissimilarities between these species. Information on trophic interactions between co-existing species is necessary for holistic environmental management, particularly in areas where several megafauna species share their foraging grounds with fisheries activity.

Fatty Acid Profile of Atlantic Horse Mackerel (Trachurus trachurus) oil Obtained using Different Extraction Methods

The effect of three extraction methods which include soxhlet, gas and charcoal powered smoking kiln on extraction of oil from Trachurus trachurus were investigated. Chemical analyses of the oil was carried out to determine its quantity and quality in terms of fatty acid composition by using standard laboratory methods. The results obtained indicated that the highest oil yield (14.0%) was recorded in oil extracted with soxhlet method, while the lowest (0.93%) in oil extracted with charcoal powered kiln extraction method. Based on the fatty acid profile of the oils, there are sixteen fatty acids in all the extraction methods with stearic acid (53.62%) as the highest saturated fatty acid (SFA); oleic acid (7.05%) as the foremost monounsaturated (MUFA) and linolenic acid (23.31%) as the major polyunsaturated fatty acid (PUFA). The Soxhlet methods consistently recorded the highest oil yield, and can be used to extract oil for industrial use. While, the gas powered kiln can be used to extract oil for consumption purpose.