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A joint spatio–temporal distribution model of mackerel (ages 3–10) was developed to investigate the age-based responses of mackerel to three environmental drivers: sea surface temperature (SST), mixed layer depth, and chlorophyll-a concentration during the summer months 2010–20 in the Nordic Seas. The study showed that SST was the most important variable amongst the ones tested and had the strongest impact on the distribution of the younger age classes (3–5), which had a narrower range of favourable SST and a stronger aversion to cold temperatures than older individuals. Consequently, the impact of SST differed regionally; in the polar front regions, SST explained up to 61% of the variability in the observed density of young individuals, where Arctic water masses likely acted as a barrier to these young individuals. That said, part of it could be confounded with the limited migration capability of young mackerels, which could not reach the furthest frontal regions. In warmer southern waters, the same environmental variables had less explanatory power for mackerel of all ages. Individuals in the south were likely not constrained by temperature and perhaps more influenced by other variables, such as food availability or ocean current (throughout their migration path), for which appropriate data are lacking. Moreover, the model showed that older mackerel were distributed more to the north and west, and their migration pattern changed when the 2013 year-class no longer migrated to the west compared to previous year-classes. Additionally, all-year classes started migrating more eastward from summer 2018. [ABSTRACT FROM AUTHOR]

We present a genome assembly from an individual Scomber scombrus (the Atlantic mackerel; Chordata; Actinopteri; Scombriformes; Scombridae). The genome sequence has a total length of 764.10 megabases. Most of the assembly is scaffolded into 24 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 16.56 kilobases in length.

The assessment of fish health has acknowledged the significance of helminthology and haematology characteristics as crucial instruments. The utilization of blood parameter measurement has been a longstanding practice in the field of fish health monitoring. The current study aimed to examine the impact of an indigenous infestation of parasites on various blood parameters, including activities of liver, kidney function tests, lipase, amylase, Creatine phosphokinase (CPK), and Lactate Dehydrogenase (LDH). The present study was undertaken to investigate the parasitic infection in a sample of 100 fish. The sample consisted of 50 of Euthynnus alletteratus, and 50 Scomber Scombrus. These fish were gathered from the waters of Misrata city, located in Libya. Results revealed the presence of statistically significant differences across various indices in both Euthynnus alletteratus and Scomber scombrus. A significant positive association was seen between urea values and many organs in Scomber scombrus, with the exception of the external body. Similarly, in Euthynnus alletteratus, a significant positive correlation was found between urea values and various organs, except for the external body and nostrils. The results of the study indicate that there is a positive link between creatinine levels and several internal organs in Euthynnus alletteratus, with the exception of external body tissues. A favorable correlation was seen between sodium levels and various organs in Scomber scombrus, with the exception of internal organs and the stomach. There was a positive correlation seen between potassium, Aspartate Aminotransferase (AST), Alanine Aminotransferase (ALT), Alkaline Phosphatase (ALP), lipase, amylase, CPK, and total protein levels in several organs of both Euthynnus alletteratus and Scomber scombrus. A significant correlation was observed between LDH levels and several organs in both Euthynnus alletteratus and Scomber scombrus, with the exception of the external body in Scomber scombrus. In Euthynnus alletteratus, LDH levels were favorably connected with the nose, internal organs, and anterior intestine. [ABSTRACT FROM AUTHOR]

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.

This research aimed at assessing the heavy metals concentration in imported Scomber scombrus fish samples purchased from cold rooms in Lagos, Nigeria. The samples were digested using the wet digestion method, and the concentration of Chromium (Cr), Arsenic (As), Lead (Pb), and Cobalt (Co) were determined using Atomic Absorption Spectrophotometer. Chromium (Cr) was present in twelve Scomber scombrus samples, and the level ranged from 0.004 to 0.046 mg/kg, while arsenic (As) was present in seven fish samples, with concentrations varying within 0.001 to 0.006 mg/kg. Lead (Pb) was present in eleven samples and not detected in SS5 and SS7. The concentration ranged from 0.004 to 0.062 mg/kg. Cobalt (Co) was present in seven Scomber scombrus samples, the level ranged from 0.004 to 0.046 mg/kg. However, SS3, SS10, and SS13 had lead concentrations above the maximum permissible limit (0.05 mg/kg) recommended by WHO/FAO. This study established the need for Nigerian agencies in charge of food to verify, check and ascertain the safety of imported fish before endorsing them as harmless for citizens' consumption.

Our histologial study, based on thin sections of undecalcified material, confirms the acellularity of bone in Scomber scombrus. The primary pseudolamellar bone shows some secondary vascular canals limited by relatively thin secondary bony layers. The teeth have a normal histological organization: a cone of orthodentine with an apical cap of enameloid. They also show dentine pleats in the pulp cavity that characterizes a simplexodont plicidentine organization as many other predatory teleosts. [ABSTRACT FROM AUTHOR]

The southern Gulf of St. Lawrence (sGSL) is considered to be the dominant spawning area of northern contingent West-Atlantic mackerel (Scomber scombrus). This premise underlies our basic understanding of the stock and its assessment. Because there are however indications of spawning outside the sGSL, we aimed to review the potential importance of various external regions for spawning, based on a weight of evidence approach. Fundamentally, important spawning areas can only exist where there is evidence of a considerable spawning stock biomass being present when environmental conditions are suitable for spawning. This should lead to direct observations of significant egg and larval densities. Based on an ensemble of evidence (migration patterns, environmental conditions, and ichthyoplankton observations), we investigated the dominance of the sGSL for northern contingent mackerel spawning. Elsewhere, such as on the Scotian Shelf, where mackerel starts its spring migration, there is evidence of minor but relatively consistent egg production. Spawning off Newfoundland, where mackerel can migrate to later in the year, appears sporadic and highly variable in intensity. This review should alleviate some of the uncertainty associated with the mackerel stock assessments and be a baseline to further our knowledge on mackerel spatial spawning dynamics. [ABSTRACT FROM AUTHOR]

A total of 46 chub mackerel and 23 Atlantic mackerel samples were taken from the commercial fishermen engaged in purse seine fishing from the Izmir Bay during the fishing period of 2020-2021. The samples were dissected in the laboratory, 15 ovaries from mature females were taken and fecundity was determined. The minimum, maximum and mean values of total length of Scomber scombrus respectively; It is 26.9-31 cm (mean: 28.89±1.44), 150 420-454 260 (mean: 259 300±97 369). A linear relationship was determined between total length fecundity in mackerel and this value was TL=25.396+0.000013×F (R2=0.83). Oocyte diameter; It is 1.1-.2 (mean: 1.16±0.10) mm. The minimum, maximum and mean values of total length of Scomber colias respectively; it is 25.1-25.9 cm (mean: 25.59±0.26), fecundity 134 853-417 500 (mean: 322 381±84 172). A linear relationship was found between total length fecundity in lichen and this value was TL=24.682+0.000003×F (R2=0.80). Oocyte diameter; It is 0.99-1 (mean:1.02±0.06) mm.

Here, we report the characterization (purification, autoxidation rate, pseudoperoxidase activity) and amino acid sequence determination of S. scombrus (Atlantic mackerel) and S. colias (Tinker mackerel) mioglobins (Mbs), considering the increasing consumption of fresh and canned mackerel meat and Mb implication in meat storage (e.g.: browning and lipid oxidation). We found that Atlantic mackerel Mb has major autoxidation rate (0.204 ± 0.013 h−1) compared to Tinker mackerel Mb (0.140 ± 0.009 h−1), while the pseudoperoxidase activity is major for Tinker mackerel (K m : 87.71 ± 7.19 μM; k cat : 0.32 s−1) Mb with respect to Atlantic mackerel (K m : 96.08 ± 6.91 μM; k cat : 0.50 s−1). These functional differences are confirmed by primary structure determination, in which six amino acid substitutions are found, with the first N -terminal amino acid residue acetylated. Furthermore, we predicted by AphaFold 3D model both fish Mbs and used them to investigate the possible structural differences. In addition, phylogenetic analysis using Mb sequences from Scombridae family confirms that Atlantic and Tinker mackerels are two distinct species. Finally, an analytic qualitative RP-HPLC method to distinguish S. scombrus and S. colias specimens was developed considering the different retention times of the two mackerel apoMbs. [Display omitted] • Purification of myoglobins (Mbs) from Atlantic and Tinker mackerels was carried out. • Atlantic mackerel Mb showed higher autoxidation rate than Tinker mackerel Mb. • Mackerel metMbs showed unaltered pseudoperoxidase activity in the presence of Ca2+. • The two haemoproteins consist of 146 amino acids and differ for 6 residues. • The possible use of apoMbs as a molecular marker was evaluated by RP-HPLC. [ABSTRACT FROM AUTHOR]

Abstract Background The research was carried out to assess the lipid characteristics of oil extracted from the head and gills of Claris macrocephalus and Scomber scombrus. Results The results confirmed the presence of C16:0, C18:0, C18:1, C18:2, C18:3, C22:6 as the major fatty acids. Titus fish head (TFHD) oil had a total saturated fatty acid (TSFA) of 40.804 ± 0.002% of which C16:0 and C18:0 were the most dominant fatty acids present while the total monounsaturated fatty (TMUFA) acids present in the oil was 33.853 ± 0.001%. The total polyunsaturated fatty acid (TPUFA) content of the TFHD oil sample was found to be 25.368 ± 0.002%. The results revealed that the total unsaturated fatty acid (TUFA) present in the TFHD was higher than the TSFA. The results obtained for Titus fish gills (TFGL) oil sample followed the same trend as observed in the head sample. The results showed that the four (4) oil samples contain high level of palmitic acid (C16:0) and stearic acid (C18:0) both of which are saturated fatty acids (SFA). The main MUFA identified was C18:1 (cis-6) and ranged from 14.120 ± 0.004 to 20.418 ± 0.002% for TFHD, TFGL, CFHD, CFGL and oleic acid (C18:1) ranged from 10.297 ± 0.001 to 11.570 ± 0.003% for TFHD, TFGL, CFHD and CFGL. Conclusions Oils of CFHD and TFHD showed higher peroxide values indicating suitability for human consumption.

Despite its commercial value, the shelflife of the Atlantic mackerel (Scomber scombrus) during refrigerated storage was poorly investigated. In this regard, the Quality Index Method (QIM) was proposed as a suitable scoring system for freshness and quality sensorial estimation of fishery products. This study aims to develop a deterministic mathematical model based on dynamic temperatures conditions and a successive statistical analysis of the results obtained. This model will be exploited to predict the shelf-life of the Atlantic mackerel based on specific storage temperatures. A total of 60 fresh fishes were subdivided into two groups and respectively stored in ice for 12 days at a constant temperature of 1±0.5°C (Group A) and a fluctuating temperature ranging between 1 and 7°C (Group B). Microbiological analysis and sensory evaluation through the QIM were performed on each fish at regular time intervals. A critical value of 6 Log cfu/g of spoilage bacteria (mainly psychotropic) associated with a significant decay of the sensorial characteristics was exceeded after 9 days of storage for Group A and 3 days for Group B. A reliable prediction of fish freshness was obtained by modelling the QIM as a function of the spoilage bacteria behaviour. A coefficient ß of correlation was determined to convert the spoilage bacteria load into a Quality Index score. The adoption of mathematical predictive models to assess microbial behaviour under different environmental conditions is an interesting tool for food industries to maximize production and reduce waste. [ABSTRACT FROM AUTHOR]

Despite its commercial value, the shelflife of the Atlantic mackerel (Scomber scombrus) during refrigerated storage was poorly investigated. In this regard, the Quality Index Method (QIM) was proposed as a suitable scoring system for freshness and quality sensorial estimation of fishery products. This study aims to develop a deterministic mathematical model based on dynamic temperatures conditions and a successive statistical analysis of the results obtained. This model will be exploited to predict the shelf-life of the Atlantic mackerel based on specific storage temperatures. A total of 60 fresh fishes were subdivided into two groups and respectively stored in ice for 12 days at a constant temperature of 1 0.5 C (Group A) and a fluctuating temperature ranging between 1 and 7 C (Group B). Microbiological analysis and sensory evaluation through the QIM were performed on each fish at regular time intervals. A critical value of 6 Log cfu/g of spoilage bacteria (mainly psychotropic) associated with a significant decay of the sensorial characteristics was exceeded after 9 days of storage for Group A and 3 days for Group B. A reliable prediction of fish freshness was obtained by modelling the QIM as a function of the spoilage bacteria behaviour. A coefficient β of correlation was determined to convert the spoilage bacteria load into a Quality Index score. The adoption of mathematical predictive models to assess microbial behaviour under different environmental conditions is an interesting tool for food industries to maximize production and reduce waste.

Inhibition of cholinesterases has been frequently used as a biomarker for contamination of aquatic environments, because these enzymes are frequent targets for toxic effects of contaminants, such as insecticides derived from phosphoric and carbamic acids. However, this enzyme is also responsive to other contaminants, including metals. The use of cholinesterase inhibition as effect criterion in ecotoxicology studies requires the previous characterization of the specific enzymatic forms that can be present in the different tissues and/or organs of species. This work characterized the soluble ChEs present in the brain and dorsal muscle of three marine fish species, namely Scomber scombrus, Sardina pilchardus and Chelidonichthys lucerna. Pesticides (chlorpyrifos) and metals (copper sulphate) in vitro assays were conducted to quantify the effects of these contaminants on cholinesterases activity. The results of this study showed that acetylcholinesterase (AChE) was the predominant form present in the brain tissues of the three species and in the muscle tissue of one species (Sardina pilchardus). For Scomber scombrus and Chelidonichthys lucerna, the cholinesterase form present in the muscle tissue evidenced properties between the classic acetylcholinesterase and those of pseudocholinesterase forms. The results for the metal (copper) and pesticide (chlorpyrifos) showed that this species may be suitable for monitoring contaminations for these types of contaminants. [ABSTRACT FROM AUTHOR]

Background: The research was carried out to assess the lipid characteristics of oil extracted from the head and gills of Claris macrocephalus and Scomber scombrus. Results: The results confirmed the presence of C16:0, C18:0, C18:1, C18:2, C18:3, C22:6 as the major fatty acids. Titus fish head (TFHD) oil had a total saturated fatty acid (TSFA) of 40.804 ± 0.002% of which C16:0 and C18:0 were the most dominant fatty acids present while the total monounsaturated fatty (TMUFA) acids present in the oil was 33.853 ± 0.001%. The total polyunsaturated fatty acid (TPUFA) content of the TFHD oil sample was found to be 25.368 ± 0.002%. The results revealed that the total unsaturated fatty acid (TUFA) present in the TFHD was higher than the TSFA. The results obtained for Titus fish gills (TFGL) oil sample followed the same trend as observed in the head sample. The results showed that the four (4) oil samples contain high level of palmitic acid (C16:0) and stearic acid (C18:0) both of which are saturated fatty acids (SFA). The main MUFA identified was C18:1 (cis-6) and ranged from 14.120 ± 0.004 to 20.418 ± 0.002% for TFHD, TFGL, CFHD, CFGL and oleic acid (C18:1) ranged from 10.297 ± 0.001 to 11.570 ± 0.003% for TFHD, TFGL, CFHD and CFGL. Conclusions: Oils of CFHD and TFHD showed higher peroxide values indicating suitability for human consumption. [ABSTRACT FROM AUTHOR]

Anisakis simplex sensu stricto is a parasite infecting several commercial fish species in the Northeast (NE) Atlantic, known to be the aetiological agent of the human zoonosis anisakiasis. The present study investigated the response of A. simplex (s. s.) third stage larvae (identified to species level by mtDNA cox 2 sequencing) to the storage time and temperature of Atlantic herring (Clupea harengus), Atlantic mackerel (Scomber scombrus) and blue whiting (Micromesistius poutassou) from NE Atlantic fishing areas. A total of 300 fish per species were divided in batches of 50 individuals straight after catch. Each batch was stored at different temperature conditions (2 °C, 5 °C, 15 °C) for different time intervals (24h and 48h). A batch of 50 fish of each species was frozen immediately after catch and used as control (time zero). All fish were inspected by the UV-press method. Blue whiting was the most infected fish species while mackerel harboured the highest proportion of intra-vitam A. simplex (s. s.) larvae in the musculature. In blue withing there was a significant increase in the proportion of larvae in the muscle with increasing storage temperatures (5 °C < 15 °C) and time (24h < 48h). Herring showed a weak trend of increasing parasite infection in the muscle with increasing temperature/time. In contrast, no significant differences of muscle/viscera larval distribution were observed between batches of mackerel stored at different temperatures for different time intervals. Storage temperature and time seem to play a role in the post-mortem motility of A. simplex (s. s.) larvae in herring and blue whiting. Keeping the temperature at ≤ 2 °C seems to prevent post-mortem larval migration into the flesh during fish storage, handling, and transport. Besides abiotic variables, the differences observed in larval post-mortem motility in the different fish species are biologically determined, and attributable to species-specific host-parasite interactions. • Response of A. simplex (s. s.) larvae to storage time/temperature in three fish species. • Intra-vitam and post-mortem migration were detected. • Intra-vitam migration rate depends on parasite and fish species. • Post-mortem migration rate can be controlled with proper storage temperature. • Storing fish at <2 °C can largely prevent post-mortem larval migration. [ABSTRACT FROM AUTHOR]

Maize has antioxidant properties and a high amount of carbohydrates, while fish has high-quality proteins and unsaturated fatty acids. The goal of this study was to prepare a functional food enriched with protein and n-3 fatty acids from Scomber scombrus. A sensory analysis was carried out, along with a texture profile, color and proximate analyses, content of EPA+DHA, and shelf life analyses on five formulations of the snack produced. The best-accepted formula turned out to be the one containing 15% fish, and in comparison with the control, it displayed similar fracturability, less hardness, a higher amount of protein and lipids, and EPA+DHA (p ≤ 0.05), providing 14.6% of the daily recommended intake of EPA+DHA (30 g of product). The development of new products, such as the one proposed in this study, can be a new and healthy alternative to substitute other similar, commercially sold products with a lower amount of nutrients.

The aim of this study was to investigate the presence of anisakids in three Scombridae fish species from Tunisian coasts (Mediterranean Sea): Scomber japonicus, Scomber scombrus and Auxis rochei. A total number of 188 chub mackerel (S. japonicus), 32 Atlantic mackerel (S. scombrus) and 31 bullet tuna (A. rochei), were collected from four Tunisian regions: Bizerte, Tunis, Nabeul and Mahdia. The parasite specimens were morphologically identified as Anisakis spp. type I larvae. 87.1% of bullet tuna were infected, followed by Atlantic mackerel (56.3%) and chub mackerel (20.7%). Prevalence, mean intensity and mean abundance values varied from one region to another. The majority of larvae were recovered in the visceral cavity. In 4% of examined fish, Anisakis spp. larvae were isolated from muscles. Moreover, the level of infection was associated with seasons, and the highest prevalence was registered during summer. The data suggest that studied fish species may present high-risk for anisakiasis zoonotic disease, and that parasitological control of seafood should be reinforced in order to protect consumers. [ABSTRACT FROM AUTHOR]

Study on the proximate a composition of flesh and other body parts of Clarias gariepinus and scomber scombrus was carried out in January, 2020 using standard procedures. For Clarias gariepinus the highest protein (25.69%) was observed in the head, followed by flesh (21.70%) and while the lowest protein (18.61%) was discovered in the bone. Highest fats (3.61%) was recorded in the flesh, followed by head (2.25) while (0.80%) recorded in the fins as the lowest fats. In fibre the highest (1.87%) was observed in head followed by (1.72) in the bone. The lowest fibre (0.60%) was reported in the flesh. The highest ash (22.03%) was recorded in fins, followed by bone (19.83%) while the lowest (1.30%) was discovered in the flesh. The highest moisture (75.76%) was recorded in the flesh, followed by fins (73.23) while the lowest (56.48%) was observed in the head. For scomber scombrus the highest protein (29.44%) was observed in the head, followed by bone (28.40%) and while the lowest protein (24.30%) was discovered in the flesh. Highest fats (6.42%) was recorded in the flesh, followed by head (1.48%) while (0.95%) recorded in the bone as the lowest fats. In fibre the highest (1.11%) was observed in fin followed by (0.69%) in the flesh. The lowest fibre (0.59%) was reported in the head. The highest ash (6.37%) was recorded in head, followed by bone (5.07%) while the lowest (0.33%) was discovered in the flesh .The highest moisture (68.68%) was recorded in the flesh, followed by head (66.56%) while the lowest (37.20%) was observed in the fin. .The highest carbohydrate (5.58%) was recorded in the bone, followed by fin (5.28%). The study showed that the best body parts in terms protein content of the two fish samples were the head. The Head has the highest crude protein content thus it can be recommended as a possible effective ways to solve protein malnutrition [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the presence of anisakids in three Scombridae fish species from Tunisian coasts (Mediterranean Sea): Scomber japonicus, Scomber scombrus and Auxis rochei. A total number of 188 chub mackerel (S. japonicus), 32 Atlantic mackerel (S. scombrus) and 31 bullet tuna (A. rochei), were collected from four Tunisian regions: Bizerte, Tunis, Nabeul and Mahdia. The parasite specimens were morphologically identified as Anisakis spp. type I larvae. 87.1% of bullet tuna were infected, followed by Atlantic mackerel (56.3%) and chub mackerel (20.7%). Prevalence, mean intensity and mean abundance values varied from one region to another. The majority of larvae were recovered in the visceral cavity. In 4% of examined fish, Anisakis spp. larvae were isolated from muscles. Moreover, the level of infection was associated with seasons, and the highest prevalence was registered during summer. The data suggest that studied fish species may present high-risk for anisakiasis zoonotic disease, and that parasitological control of seafood should be reinforced in order to protect consumers. [ABSTRACT FROM AUTHOR]

We investigated the effect of environmental conditions on Atlantic mackerel spawning habitat in the southern Gulf of St. Lawrence (sGSL). Based on generalized additive models, we (i) modelled the optimal spawning habitat of mackerel in the sGSL using daily egg production (DEP) in June, (ii) predicted known and new potential present spawning habitats in the GSL and the north‐west Atlantic, and (iii) assessed how they respond to future climate change. Our findings showed that both mackerel presence–absence and given‐presence DEP were associated with sea surface temperature (10–16.5°C), salinity above 31 and depth < 120 m. Adding zooplankton showed a marked effect on the DEP given‐presence compared to the presence–absence. Predictions of spawning habitats under present (1999–2012) and future scenario (2066–2085) conditions were estimated from the presence–absence model without zooplankton, using physical conditions of the BNAM. Under present conditions, our model predicted well the main spawning habitat in the sGSL and other known secondary spawning habitats in the northern GSL (nGSL), the western and southern Newfoundland, and the north‐west Atlantic coast. Under future conditions, our study suggests that spawning habitats in the sGSL and the nGSL would expand. Our results, therefore, suggest that mackerel could benefit from a warmer GSL, minimizing the potential for a northward migration of the stock due to decreasing suitability of the sGSL as its main spawning ground, and a new but spatially limited potential habitat in Newfoundland coasts. These results can be used to inform stock management and develop adaptive management plans in the context of climate change. [ABSTRACT FROM AUTHOR]

This study investigates the impact of season and sex variations on the total lipid contents and fatty acid composition of Scomber scombrus fillets from the Middle East Coast of Tunisia in order to dertermine the most favorable periods for consumption, and to see if the nutritional quality of the meat depends on the sex of the animal. The effect of fishing season induced significant changes in the lipid profile, and the highest values for total lipids were obtained in the spring for females with 13.2% and for males with 18.9%. The highest values for proteins were obtained in the summer for females with 22.0% and for males with 21.8%. Protein content variations were not significant (p > 0.05). The n-3/n-6 ratio showed a significant level, indicating a tendency toward n-3 fatty acid accumulation in mackerel fillets mainly represented by DHA, whose values were high during the study period for both sexes, except in autumun, which is the period of mackerel gonad maturation, when DHA decreased significantly (p < 0.05), reaching 23.2 and 34.0% for males and females, respectively. It was concluded that Scomber scombrus has high levels of proteins, lipids, and fatty acid contents mainly n-3 PUFA. DHA sex variations were not significant (p > 0.05). The Atherogenicity index (AI) and Thrombogenicity index (TI) were calculated. In our study the AI index was comprised between 0.3 and 0.6 for males and between 0.4 and 0.5 for females. The TI index values ranged from 0.6 to 0.8 for males, and was about 0.6 for females.

Maize has antioxidant properties and a high amount of carbohydrates, while fish has high-quality proteins and unsaturated fatty acids. The goal of this study was to prepare a functional food enriched with protein and n-3 fatty acids from Scomber scombrus. A sensory analysis was carried out, along with a texture profile, color and proximate analyses, content of EPA+DHA, and shelf life analyses on five formulations of the snack produced. The best-accepted formula turned out to be the one containing 15% fish, and in comparison with the control, it displayed similar fracturability, less hardness, a higher amount of protein and lipids, and EPA+DHA (p ≤ 0.05), providing 14.6% of the daily recommended intake of EPA+DHA (30 g of product). The development of new products, such as the one proposed in this study, can be a new and healthy alternative to substitute other similar, commercially sold products with a lower amount of nutrients. [ABSTRACT FROM AUTHOR]

This study investigates the impact of season and sex variations on the total lipid contents and fatty acid composition of Scomber scombrus fillets from the Middle East Coast of Tunisia in order to dertermine the most favorable periods for consumption, and to see if the nutritional quality of the meat depends on the sex of the animal. The effect of fishing season induced significant changes in the lipid profile, and the highest values for total lipids were obtained in the spring for females with 13.2% and for males with 18.9%. The highest values for proteins were obtained in the summer for females with 22.0% and for males with 21.8%. Protein content variations were not significant (p > 0.05). The n-3/n-6 ratio showed a significant level, indicating a tendency toward n-3 fatty acid accumulation in mackerel fillets mainly represented by DHA, whose values were high during the study period for both sexes, except in autumun, which is the period of mackerel gonad maturation, when DHA decreased significantly (p < 0.05), reaching 23.2 and 34.0% for males and females, respectively. It was concluded that Scomber scombrus has high levels of proteins, lipids, and fatty acid contents mainly n-3 PUFA. DHA sex variations were not significant (p > 0.05). The Atherogenicity index (AI) and Thrombogenicity index (TI) were calculated. In our study the AI index was comprised between 0.3 and 0.6 for males and between 0.4 and 0.5 for females. The TI index values ranged from 0.6 to 0.8 for males, and was about 0.6 for females. [ABSTRACT FROM AUTHOR]

Abstract In the mid-2000s, summer feeding distribution of Northeast Atlantic mackerel (Scomber scombrus) in Nordic Seas began expanding into new areas. The present study explores how spawning stock biomass (SSB) and environmental conditions influenced this expansion using data from scientific surveys conducted in Nordic Seas from 1997 to 2016. During that period mackerel distribution range increased three-fold and the centre-of-gravity shifted westward by 1650 km and northward by 400 km. Distribution range peaked in 2014 and was positively correlated to SSB. Mackerel was present in temperatures ranging from 5 °C to 15 °C, but preferred areas with temperatures between 9 °C and 13 °C according to univariate quotient analysis. Generalized additive models showed that both mackerel occurrence and density were positively related to location, ambient temperature, mesozooplankton density and SSB, explaining 47% and 32% of deviance, respectively. Mackerel relative mean weight-at-length was positively related to location, day-of-year, temperature and SSB, but not with mesozooplankton density, explaining 40% of the deviance. We conclude that geographical expansion of mackerel during the summer feeding season in Nordic Seas was driven by increasing mackerel stock size and constrained by availability of preferred temperature and abundance of mesozooplankton. Marine climate with multidecadal variability probably impacted the observed distributional changes but were not evaluated. Our results were limited to the direct effects of temperature, mesozooplankton abundance, and SSB on distribution range during the last two decades and should be viewed as such. [ABSTRACT FROM AUTHOR]

Atlantic mackerel ( Scomber scombrus ) ranks among the most valuable fish species in Europe. The NE Atlantic mackerel population is considered to comprise three main stocks (southern, western and North Sea), with variable proportions of these three intermixing at the northerly feeding grounds. The southern and western mackerel stocks have moved over the past 4–5 years further north- and westward. Consequently, large-scale mackerel fishing and processing have become thriving industries in Iceland and the Faroe Islands in just a few years. The mackerel population structure in the Mediterranean Sea is less well known but seems to comprise at least one, more or less isolated, spawning component. Although mackerel is an important food resource, systematic and concerted epidemiological surveys of Anisakis species in Atlantic mackerel from European fishing grounds have been lacking. As part of the EU FP7 PARASITE project (GA no. 312068), occurrence and specific identity of Anisakis spp. from 1801 mackerel from Northeast Atlantic and Mediterranean waters was investigated. In general, mackerel caught at the Atlantic fishing grounds exhibited markedly higher Anisakis spp. infection levels than fish from the Mediterranean localities. Mackerel caught off NW Spain and Portugal (ICES VIIIc, IXa) showed highest overall and muscular prevalence, reaching 87% and 52%, respectively, which differed significantly from all other Atlantic samples. Lowest overall Anisakis spp. prevalence and abundance was recorded in mackerel from Faroe Isles waters, while lowest muscular infection levels were found in the samples from the North Sea. Genetic nematode species identification showed that A. simplex ( sensu stricto ) is the dominating species in mackerel from the Atlantic areas, while A. pegreffii dominated in the samples from the Mediterranean Sea. The latter species showed generally low prevalence and intensity in the flesh, not exceeding 6% and one larva, respectively. While A. simplex (s. s.) and A. pegreffii seem to co-occur in mackerel from off NW Spain and Portugal, several A. pegreffii were also recorded in mackerel from the North- and Norwegian Seas. These findings imply that the actual mackerel started their feeding migration in waters south to the British Isles, which include parts of the sympatric area of the two sibling species. Thus, A. pegreffii could prove a useful supplementary marker to track migration routes of the different mackerel stock components in NE Atlantic waters. [ABSTRACT FROM AUTHOR]

Fresh fish remain the dominant seafood forms and preservation technologies have enabled them to access ever more distant markets. In this study, we used metabarcoding of the 16S rRNA gene to generate gill microbiomes from Scomber scombrus bought at fishmonger's stores as fresh products but whose labels showed they had been harvested in the Atlantic or Mediterranean FAO fishing areas. Microbial data were analysed with the aim of evaluating their ability to maintain signals from their different geographical origins and the presence of taxa which can potentially act as spoilers, foodborne pathogens, or histamine producers. Results revealed that microbiota, at the end of the wild fish supply chain, had differences related to the two FAO fishing areas (Atlantic vs Mediterranean). Despite the presence of microbial genera potentially associated with spoilage, histamine-production or foodborne pathogens, their patterns confirmed that low-temperature storage is a traditional but effective method of preservation. However, the ongoing spoilage processes were more evident in fresh non-local specimens, dominated by psychrophilic Gram-negative bacteria, whereas fresh local specimens contained Planctomycetes taxa. Therefore, despite the current limitations mainly related to time and cost of the method, our study highlighted that microbiome-based applications are an emergent tool for food system transformation. [Display omitted] • Microbiome-based applications are an emergent tool for food system innovation. • Post-mortem gill microbiomes distinguish geographic origins in fresh fish products. • Health status and post-harvest activities affect microbiomes in fish products. • Additional information on labels can enhance local economies and sustainability. • Microbiome data promote an innovative risk assessment in fish supply chains. [ABSTRACT FROM AUTHOR]

We determined high pressure processing (HPP) effects on the activities of cathepsins B and D in the muscles of mackerel (Scomber scombrus) and horse mackerel (Trachurus trachurus). In mackerel, the cathepsin B activity decrease reached 40% at 450 MPa while in horse mackerel, low and intermediate pressures (150 and 300 MPa) caused an activity increase (30%) but at 450 MPa a decrease of up to 60%. In both species, cathepsin D activity increased after a 300 MPa treatment (up to 2-fold for mackerel and 60% for horse mackerel) and decreased on a 450 MPa treatment. The activity increase is probably due to HPP damage of lysosome releasing enzymes into the fish muscle. Based on the HPP effects on the activities of cathepsins B and D, 450 MPa may be used to reduce the proteolytic activity of cathepsin B prior to chilled or frozen storage of these fish species.

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Mackerel is marketed at prices according to the species type,Scomber japonicusandScomber scombrus.Distinguishing these two species with the naked eye is difficult, and their differentiation becomes more difficult after they are processed by cooking, thereby leading to counterfeiting issues. Thus, in this study, we developed a method to differentiateS. japonicusfromS. scombrusby detecting polymorphisms in mitochondrial 16 s rRNA gene by using fluorescence melting curve analysis and locked nucleic acid probes. Our method could distinguishS. japonicusfromS. scombrusin a single experiment by using a single probe. The probes developed matched exactly withS. japonicusand had a melting temperature of 64 °C. However, the probes were mismatched withS. scombrus, resulting in a lower melting temperature of 46 °C. The high specificity of the locked nucleic acid probes resulted in this large difference in the melting temperatures. [ABSTRACT FROM PUBLISHER]

To ensure efficient and sustainable purse-seine fisheries, the catch process must be monitored to better understand the reactions of fish to the gear. In this study, we monitored the behaviours of herring (Clupea harengus) and mackerel (Scomber scombrus) schools during purseseine capture using a multibeam imaging sonar (Simrad MS70, 75-112 kHz) mounted on a research vessel. The fish behaviours differed between species and purse-seine sets. For both species, the acoustic volume backscattering coefficient increased as 0-80% of the seine was hauled aboard, indicating a corresponding increase in fish spatial density. This increase was significantly greater for herring than mackerel. As 0-40% of the seine was hauled aboard the fishing vessel, schools changed their spatial distribution and volume independent of seine hauling, while for some schools, depth and height decreased. The acoustic volume backscattering strength was up to 25 dB higher in the centre of the school than in the edges. The average lateral target strength was estimated for individual fish in the captured herring schools, and the effect of incident angle on the backscattering strength is considered. [ABSTRACT FROM AUTHOR]

During the industrial processing of jumbo squid ( Dosidicus gigas ), large amounts of by-products containing biological active compounds are generated. In this study, aqueous solutions including acetic acid-ethanol extracts of jumbo squid skin (JSS) were tested at three different concentrations as icing media. The effects of the JSS extracts on the quality evolution of chilled mackerel ( Scomber scombrus ) were monitored. A significant inhibition (p < 0.05) of microbial activity was determined in the fish batch corresponding to the icing condition including the highest JSS concentration. Additionally, fish specimens corresponding to batches including any of the JSS concentrations tested showed lower (p < 0.05) proteolytic counts and pH values than control mackerel. Sensory analysis revealed a marked shelf life extension in chilled mackerel stored in ice including the highest JSS concentration; specimens from such batch were found to be still acceptable after 13 days of storage, while all other mackerel batches were rejectable. The marked microbial activity inhibition observed could be explained on the basis of the presence in ice of lipophilic compounds obtained by acetic acid-ethanol extraction of JSS. [ABSTRACT FROM AUTHOR]

Herein, the potential risk of human anisakiasis through the consumption of mackerel, Scomber scombrus , sold at nationwide Spanish supermarket chains is assessed, by means of the identification of anisakid and other nematode species found, and the analysis of intrinsic and extrinsic factors that may influence the prevalence and abundance of nematode worms, as well as their presence in the viscera or in the flesh. 231 fresh mackerel specimens caught between 2008 and 2014 (140 from the Atlantic and 91 from the Mediterranean), captured in autumn and spring and acquired at nationwide Spanish supermarket chains, were examined dissecting their viscera and submitting their flesh to artificial digestion. Helminthological identification was based on the morphological criteria of L 3. Moreover, 62 larvae of different origins and seasons were molecularly characterized by RFLP-PCR. The target region, ITS1-5.8S rDNA-ITS2, was amplified and the restriction enzyme Hinf I was used for digestion. The potential influence of intrinsic (fish length and weight) and extrinsic (origin and season of capture, and days after catch) factors was statistically analysed. Total Anisakis type I prevalence was 58.4% (55.4% in viscera; 26.0% in the flesh) and 4.8% Hysterothylacium spp. 45 Anisakis simplex ( s.s. ), 12 hybrid genotype ( A. simplex s.s./ Anisakis pegreffi ) and only one larva of A. pegreffi were identified in the 58 L 3 molecularly characterized. The four Hysterothylacium larvae were identified as belonging to the species H. aduncum . There were statistically significant differences in the presence of Anisakis type I from the Atlantic and the Mediterranean (χ 2 = 47.341; p < 0.0001), in viscera as opposed to the flesh (χ 2 = 42.630; p < 0.0001), also in the longest specimens (χ 2 = 73.170; p < 0.0001) and in the highest weight (χ 2 = 27.469; p < 0.0001). A significant correlation (χ 2 = 22.458; p = 0.004) was found between the presence of larvae in the flesh and the number of days passed between the catch and the analysis. Hence, apart from the recommendation of freezing fish at −20 °C for at least 24 h in case the fish is consumed raw or poorly cooked, the aforementioned factors should be considered by the consumer when purchasing this fish species to avoid any potential anisakiasis risk. [ABSTRACT FROM AUTHOR]

Mackerel ( Scomber scombrus) is one of the ecologically and economically most important fish species in the Atlantic. Its recruitment has, for unknown reasons, been exceptional from 1998 to 2012. The majority (75%) of the survivors in the first winter were found north of an oceanographic division at approximately 52°N, despite the fact that mackerel spawns over a wide range of latitudes. Multivariate time series modelling of survivor abundance in the north revealed a significant correlation with the abundance of copepodites (stage I-IV) of Calanus sp. in the spawning season (April to June). The copepodites were a mix of C. helgolandicus (dominating) and C. finmarchicus. The growth of mackerel larvae is known to be positively related to the availability of nauplii and copopodites of preferred prey species, namely, large calanoid copepod species such as Calanus. The statistical relationship between mackerel survivors and abundance of Calanus, therefore, most likely, reflected a causal relationship: high availability of Calanus probably reduced starvation, stage-specific predation and cannibalism (owing to prey switching). The effects of other abundant, but less preferred zooplankton taxa, ( Acartia sp., Branchiopoda spp. and Echinodermata spp. larvae), as well as stock size, temperature and wind-induced turbulence were not found to be significant. However, stock size was retained in the final model because of a significant interaction with Calanus in oceanic areas west of the North European continental shelf. This was suggested to be a consequence of a density driven expansion of the spawning area that increased the overlap between early life stages of mackerel and food ( Calanus) in new areas. [ABSTRACT FROM AUTHOR]

Fisheries independent monitoring of widely distributed pelagic fish species which conduct large seasonal migrations is logistically complex and expensive. One of the commercially most important examples of such a species in the Northeast Atlantic Ocean is mackerel for which up to recently only an international triennial egg survey contributed to the stock assessment. In this study, we explore whether fisheries acoustic data, recorded opportunistically during the English component of the North Sea International Bottom Trawl Survey, can contribute to an improved understanding of mackerel distribution and provide supplementary data to existing dedicated monitoring surveys. Using a previously published multifrequency acoustic mackerel detection algorithm, we extracted the distribution and abundance of schooling mackerel for the whole of the North Sea during August and September between 2007 and 2013. The spatio-temporal coverage of this unique dataset is of particular interest because it includes part of the unsurveyed summer mackerel feeding grounds in the northern North Sea. Recent increases in landings in Icelandic waters during this season suggested that changes have occurred in the mackerel feeding distribution. Thus far it is poorly understood whether these changes are due to a shift, i.e. mackerel moving away from their traditional feeding grounds in the northern North Sea and southern Norwegian Sea, or whether the species' distribution has expanded. We therefore explored whether acoustically derived biomass of schooling mackerel declined in the northern North Sea during the study period, which would suggest a shift in mackerel distribution rather than an expansion. The results of this study show that in the North Sea, schooling mackerel abundance has increased and that its distribution in this area has not changed over this period. Both of these findings provide, to our knowledge, the first evidence in support of the hypothesis that mackerel have expanded their distribution rather than moved away. [ABSTRACT FROM AUTHOR]

Weight-at-length and length-/weight-at-age were analysed for mature 3- to 8-year-old Northeast Atlantic mackerel (Scomber scombrus; n = 26 084) collected annually in autumn (September and October) at the end of the annual feeding season during 1984 - 2013 in the northern North Sea. The age range represented 92% of the mackerel stock size (age 3+). During the most recent decade, mackerel length- and weight-at-age continually declined. In 2013, the average mackerel was 3.7 cm shorter and weighed 175 g less than the average individual in 2002. Individual weight-at-length, demonstrating annual summer feeding success, continually declined during the most recent 5 years, whereas somatic growth of cohorts aged 3-8 continually declined for the last 11 of 25 cohorts investigated. Growth of the latest cohort was 34% of the maximum cohort growth recorded. Both weight-at-length and cohort growth were negatively affected by mackerel stock size and Norwegian spring-spawning herring (Clupea harengus) stock size (weight-at-length: r² = 0.89; growth (length): r² = 0.68; growth (weight): r² = 0.78), while temperature was not significant. Conspecific density-dependence was most likely mediated via intensified competition associated with greater mackerel density. Negative effects of herring were likely mediated by exploitative competition for shared food resources rather than direct competition due to limited spatio-temporal overlap between mackerel and herring during the feeding season. Herring begin their seasonal feeding migration at least a month before mackerel; therefore, herring consumption influences prey availability for the later-arriving mackerel. Record low mackerel growth and negative effects of mackerel and herring stock size suggest that the carrying capacity of the Norwegian Sea and adjacent areas for plankton-feeding fish stocks have been reached. However, compounding effects of a less productive Norwegian Sea during the 30-year period cannot be excluded. [ABSTRACT FROM AUTHOR]

Mackerel (Scomber scombrus) in early life stages were captured in 2000 in the north and northwest of the Iberian Peninsula (ICES Divisions VIIIc and IXa North). Daily rings on their otolith sagittae were identified. Otoliths from 377 larvae and post-larvae caught in April and May 2000, ranging in length from 2.3 to 23.7 mm LS (Standard length) and ranging in age from 7 to 38 days after hatching were analysed. Additionally, 68 otoliths from juveniles and pre-recruits caught between July and October 2000 with a length range of 121-202 mm LS and aged between 65-186 days after hatching were analysed. Gompertz and Logistic growth models were fitted to the pooled length at age data of the larvae-postlarvae and juveniles-pre-recruits. As length at hatch is assumed in the literature to be 3.0 mm, the models were applied in two ways; not forced to pass through L0=3.0 mm and forced to pass through L0=3.0 mm. The unforced logistic growth curve appeared to be the most suitable for describing growth during the first year of life of mackerel (L? = 191.6 mm; K= 0.070; t0= 66.7 d).

In the course of the past two decades, Atlantic mackerel, Scomber scombrus, have expanded their summer feeding distribution in the Norwegian Sea substantially, and now potentially overlap with pelagic larvae of Norwegian spring-spawning herring, Clupea harengus, as these drift northwards. Mackerel are known to be opportunistic predators, and the aim of this study was to evaluate mackerel predation in an area of overlap between mackerel and herring larvae, with particular focus on predation on herring larvae. In early June 2013, we followed a predefined transect in the expected core larvae distribution area on the Norwegian coastal shelf between about 66°N and 69°N. The transect was repeated twice, and samples of mackerel for stomach analyses and subsequent herring larvae samples were obtained at pre-defined stations. Mackerel were caught in all but one of the trawl hauls, but were hardly ever observed acoustically, suggesting that they were dispersed close to the surface throughout the study area. Herring larvae were caught in all samples. Calanoid copepods were the dominant prey of the mackerel, but 45% of the mackerel guts contained herring larvae, with a maximum of 225 larvae counted in a single gut. Both the frequency of guts containing herring larvae and the average amount of herring larvae increased in line with increasing abundance of larvae. On the other hand, no spatial correlation between mackerel abundance and herring larvae abundance was found at the station level. The results suggest that mackerel fed opportunistically on herring larvae, and that predation pressure therefore largely depends on the degree of overlap in time and space. Rough a real projections suggest that the mackerel would be capable of consuming the herring larvae present in the investigation area in 6-7 d, and that such predation therefore could have regulatory effects on stocks of Norwegian spring-spawning herring. [ABSTRACT FROM AUTHOR]

This research focuses on biochemical changes related to quality losses observed in Atlantic mackerel ( Scomber scombrus) muscle stored under commercial frozen storage conditions (9 months, −18 °C) when subjected to high-hydrostatic pressure (HHP) treatments (125, 150, 175, and 200 MPa for 0 min) before freezing. After freezing, free fatty acid (FFA) formation (lipid hydrolysis assessment) showed a marked inhibition in HHP-treated fish and during frozen storage of samples treated at 175 MPa. Fluorescence ratio (FR) assessment of tertiary lipid oxidation showed a partial inhibitory effect during the 0-9-month period for samples treated at 175 and 200 MPa. After a 3-month storage of samples treated at these pressure levels, one-dimensional SDS-PAGE analysis of the sarcoplasmic protein fraction revealed the disappearance of a band; additionally, samples treated at 150 MPa showed the same effect at month 9. After gel excision, trypsin digestion, tandem mass spectrometry (MS/MS), and sequence database analysis, the band was identified as phosphoglycerate mutase 2 (28.7 kDa). On the other hand, HHP processing did not show a significant effect on trimethylamine (TMA) values, primary and secondary lipid oxidation, PUFA levels, 1-D myofibril protein pattern, and the activity of acid phosphatase and cathepsins B and D. Biochemical quality indices such as FFA, TMA, and FR and the activity of acid phosphatase and cathepsin B showed a progressive increase throughout the frozen storage of all samples. [ABSTRACT FROM AUTHOR]

Atlantic mackerel and its processing wastes were hydrolyzed separately using four commercial proteases, namely: Protamex, Neutrase, papain, and Flavourzyme. Mackerel and its by-products hydrolysates were rich in essential amino acids such as lysine, leucine and phenylalanine (3.44-7.81 mg g-1). Hydrolysis using protamex, neutrase or papain generated a high number of small peptides (300-700 Da). Both crude hydrolysates of mackerel and its by-products (lmg mL-1) inhibited at least 40% of Listeria innocua HPB13 and Escherichia coli MC4100 growth, with crude by-products hydrolysate obtained by papain and neutrase being the most antilisterial with 69.7% and 65.2% of inhibition, respectively. Dose-dependent inhibition curves were obtained and complete inhibition of both L. innocua and E. coli was obtained after acetone fractionation of whole mackerel and its by-products hydrolyzed with protamex at 20 mg mL-1. Due to its high nutritional value, coupled with excellent functional properties mackerel by-products are of interest as functional foods. [ABSTRACT FROM AUTHOR]

The aim of current studies was to determinate the levels of heavy metals like Zn, Pb, Ni and Cd in flesh of some important fish species - mackerel (Scomber scombrus); European sprat (Sprattus sprattus); horse mackerel (Trachurus mediterraneus ponticus) and bluefish (Pommatomus saltatrix). The received concentrations are analyzed and compared against the maximum levels allowed for fish, purposed for human consumption and nutritional value of fish was evaluated. The concentration of heavy metals were, measured by atomic absorption spectrophotometry after digestion of the samples, using heating digester. The muscles of mackerel were characterized by the highest content of protein (19.20%), which was higher respectively with 1.4%, 6.8% and 5.31% compared with its content in horse mackerel, sprat and bluefish. The lipids in mackerel's muscles showed the highest content (18.09%) compared with its value in the muscles of horse mackerel, sprat and bluefish and it was higher respectively with 37.5%, 63.0% and 33.1%. The highest concentration of metals in the muscles of the studied fish species were determinate for Zn, and the lowest for Cd. The highest levels of Pb, Cd and Zh were found in muscles of sprat and the content of Ni was found to be highest in the muscles of horse mackerel. The examined fish were safe for human consumption, regarding the daily intake and safety aspect. [ABSTRACT FROM AUTHOR]

Density dependence of somatic growth has an important, but overlooked, impact on fisheries management advice. We therefore examined how growth relates to abundance in a case where growth has been observed to vary substantially in recent years, namely North East Atlantic mackerel, one of the most widespread and commercially important fish stocks in the North Atlantic. Growth of juvenile and early adult North East Atlantic mackerel was found to be decreasing since the late 1990s. Modelling showed that growth was related to density. Mean growth rate during the first year was tightly correlated with the density of juveniles and especially with juveniles from the previous cohort. This putative effect of juvenile density could be tracked in the length-at-age up to adult mackerel at commercially targeted sizes. However, as the mackerel grew towards adulthood, the effects of the same cohort became dominant. The effect of adult density was minor, but increasing with age. The ontogenetic progression in density dependant regulation of growth appeared to reflect the spatial dynamics (migration patterns) in the feeding season. This is the first time growth patterns quantified in the adult mackerel population have been linked to density related processes occurring within the nursery areas during the first year. These aspects of mackerel production have a substantial and direct impact on the management plan evaluations used when fisheries scientists provide advice for fisheries management. [ABSTRACT FROM AUTHOR]

There are currently no dedicated recruitment survey data available in support of the assessment of the abundance and distribution of Northeast Atlantic (NEA) mackerel (Scomber scombrus), one of the most widespread and commercially important fish stocks in the North Atlantic. This is despite the fact that an estimate of recruitment is an important requirement for the provision of advice to fishery managers. The work here addresses this by compiling catch rates of juvenile mackerel from bottom-trawl surveys conducted between October and March during 1998-2012 and applying a log Gaussian Cox (LGC) process geostatistical model incorporating spatio-temporal correlations. A statistically significant correlation between the modelled catch rates in adjacent quarters 4 and 1 (Q4 and Q1 ) demonstrates that bottom-trawl surveys in winter are an appropriate platform for sampling juvenile mackerel, and that the LCG model is successful in extracting a population abundance signal from the data. In this regard, the model performed appreciably better than a more commonly used raising algorithm based on survey swept-area estimates. Therefore, the LCG model was expanded to include data from the entire survey time-series, and a recruitment index was developed for use in the annual ICES stock assessment. We hypothesize that catchability is positively density-dependant and provides supporting evidence from acoustic observations. Various density-dependant transformations of the modelled catch rates were furthermore found to improve the correlation between the derived annual recruitment index and recruitment estimated by back-calculation of adult mackerel data. Square root transformation led to the strongest correlation, so this is recommended for further analysis of mackerel abundance. Finally, we provide maps of spatial distributions, showing that the most important nursery areas are around Ireland, north and west of Scotland, in the northern North Sea north of 59°N and, to some extent, also in the Bay of Biscay. [ABSTRACT FROM AUTHOR]