Scomber Scombrus Research Articles

Gelibolu Yarımadası’ndan (Kuzey Ege Denizi, Türkiye) Avlanan Palamut (Sarda sarda Bloch, 1793), Uskumru (Scomber scombrus Linnaeus, 1758) ve Kolyoz (Scomber colias Gmelin, 1789) Balıklarının Toplam Boy, Toplam Ağırlık, Maksimum Vücut Çevresi ve Operkulum Çevresi Arasındaki İlişkiler

Bu çalışma Gelibolu Yarımadası açıklarında (Kuzey Ege Denizi, Türkiye) Ocak 2017-Aralık 2017 tarihleri arasında palamut (Sarda sarda Bloch, 1793), uskumru (Scomber scombrus Linnaeus, 1758) ve kolyoz (Scomber colias Gmelin, 1789) türlerinin boy-ağırlık ve boy-çevre ilişkilerini ortaya çıkarmak için ticari balıkçılar tarafından avlanan öü balıkları kullanmak suretiyle gerçekleştirilmiştir. Boy-ağırlık ilişkisi palamut, uskumru ve kolyoz balıkları için, sırasıyla, W=0.0143TL2.84 (R2=0.89), W=0.0059TL3.11 (R2=0.92) ve W=0.0059TL3.11 (R2=0.92) olarak tahmin edildi. Yine sırasıyla bu türlerin boy-operkulum çevre ilişkileri Gope=0.3988TL+0.2512 (R2=0.78), Gope=0.3528TL+0.8122 (R2=0.84) ve Gope=0.4295TL-0.5991 (R2=0.94) olarak hesaplanırken boy-maksimum vücut çevre ilişkileri ise Gmak=0.5993TL-4.1237 (R2=0.79), Gmak=0.4206TL+0.2732 (R2=0.83) ve Gmak=0.4676TL-0.168 olarak saptanmıştır. Bu çalışma Karadeniz’i de kapsayacak şekilde tüm Akdeniz Havzası için bu türlerin boy-operkulum ve boy-maksimum vücut çevresi ile ilgili ilk bilgileri içermektedir.

Estimation of growth parameters of the Atlantic chub mackerel (Scomber colias Gmelin, 1789) off Gallipoli Peninsula (Northern Aegean Sea, Turkey)

This study was carried out to reveal the age and growth of the atlantic chub mackerel (Scomber colias Gmelin, 1789) in Gallipoli Peninsula (northern Aegean Sea, Turkey). The individuals of sampled S. colias from commercial fishmongers randomly each month were taken during the period January 2016-December 2016. A total of 348 otoliths were aged successfully. The total length and weight of aged specimens ranged from 16.0 to 28.0 cm and from 31.72 to 222.68 g, with a mean of 22.0 cm and 101.23 g, respectively. The length-weight relationship was estimated as W = 0.0060TL3.20 (R2 = 0.97). The von Bertalanffy growth equations were computed to be 𝐿∞ = 32.0 cm, k = 0.30 year-1, 𝑡0 = -1.72 year for all samples. The growth performance index (𝛷′) was found as 2.49. The present study provides the first information on the growth parameters of the species so as to define the current state Scomber colias population for Gallipoli Peninsula (northern Aegean Sea, Turkey).

Integrating complementary survey methods to estimate catches in Norway’s complex marine recreational hook-and-line fishery

Abstract Marine recreational fishing is popular in Norway, but current estimates of the catches by resident and tourist anglers are lacking due to several challenges, in particular Norway’s long and intricate coastline with no defined access points and the large tourist fishery. To test methods for long-term monitoring of boat-based marine recreational anglers, estimate their catches, and characterize the fishery, we conducted a roving creel survey based on a novel spatial sampling frame and a survey of tourist fishing businesses in Troms and Hordaland County. These surveys showed that cod (Gadus morhua) and saithe (Pollachius virens) dominated the catches in Troms, while mackerel (Scomber scombrus) and saithe dominated the catches in Hordaland. The estimated total annual harvest of cod by all marine recreational anglers was 2 160 tonnes (relative standard error, or RSE 44%) in Troms and 73 tonnes (RSE 29%) in Hordaland, of which ∼40% (in weight) were landed in registered tourist fishing businesses, based on data from the tourist fishing survey. The results indicate that recreational anglers in Hordaland harvest more cod in coastal waters than commercial fishers. This study provides information for developing marine recreational fisheries monitoring in challenging survey situations to support science-based fisheries management.

Improved bycatch reduction in the mixed demersal trawl fishery for Norway pout (Trisopterus esmarkii)

In this study, we compared the bycatch reduction capacity of a trawl fitted with a standard rigid sorting grid with that of a trawl fitted with a newly developed, flexible system called the Excluder. We conducted the fishing trials in the Norway pout (Trisopterus esmarkii) small-meshed trawl fishery in the North Sea. Catch data were analysed by species and length using the catch comparison and catch ratio method. The Excluder significantly reduced the bycatch (in weight) relative to the standard grid for blue whiting (Micromesistius poutassou) (−35.6%), mackerel (Scomber scombrus) (−93.3%), horse mackerel (Trachurus trachurus) (−99.3%), herring (Clupea harengus) (−89.9%), haddock (Melanogrammus aeglefinus), (−98.6%), whiting (Merlangius merlangus) (−99.3%), cod (Gadus morhua) (−97.1%), European hake (Merluccius merluccius) (−98.0%), and greater argentine (Argentina sphyraena) (−24.5%). For Norway pout there was a marginal decrease in the overall catch efficiency of −1.4%. The observed bycatch reduction efficiency is explained by the larger sorting area of the Excluder relative to the grid's area and by the differences in behaviour between Norway pout and the bycatch species. While it contributes to reduce bycatch of quota regulated species, the Excluder also can potentially affect the profitability of the fishery.

Screening the Implementation of HACCP Principles in the Romanian Seafood Industry. Case Studies and Optimisation Scenarios

HACCP (Hazard Analysis and Critical Control Points) is considered an efficient tool for both the food industry and health authorities in preventing foodborne diseases. Seafood and fishery products in particular may harbor biological, chemical and physical hazards, as their chemical composition makes them much more perishable than meat products and constitute better substrates for growth of pathogenic bacteria. In this context, the aim of this paper was to perform an in-depth analysis of the HACCP implementation for the major shellfish [rapa whelk Rapana venosa (Valenciennes, 1846) and Black Sea mussels Mytilus galloprovincialis Lamarck, 1819] and marine/freshwater fish species [Danube shad Alosa immaculata Bennett, 1835; sprat Sprattus sprattus (Linnaeus, 1758); mackerel Scomber scombrus Linnaeus, 1758; various carp species] processed by the Romanian seafood industry at the Black sea coast. Field visits to the processing plants were performed in February and March 2022 and the application of the HACCP plan was documented, in order to identify potential weaknesses and drawbacks. Optimization scenarios for each of the two case studies were considered, to foster the safe and responsible development of the sector in Romania.

Remote acoustic sizing of tethered fish using broadband acoustics

Remote fish sizing is desirable in fisheries (e.g., pre-catch) and research (e.g., platforms without biological sampling capacity) applications. In those contexts, the high spatial resolution of pulse compressed broadband echoes combined with narrow beamwidth transducers makes it feasible to resolve the scattering from different parts of the fish body and hence can be used to measure the body size. A motorized apparatus was used to suspend individual fish in the acoustic beam of two laterally oriented transducers (45–90 kHz, 160–260 kHz, 12.2 m range) with precise control of rotation angle. Broadband scattering was measured from tethered Atlantic mackerel (Scomber scombrus), saithe (Pollachius virens), and pollack (Pollachius pollachius) ranging in standard length from 239 to 491 mm as a function of orientation angle to validate sizing based on the acoustic resolution of fish body parts. Under these controlled conditions, fish size was underestimated by 11–19 mm, varying with broadband pulse characteristics, orientation angle, species, and fish size. The best remote acoustic sizing results were obtained using 160–260 kHz pulses with a slow rise and fall of pulse amplitude (aka, taper).

Vitality as a measure of animal welfare during purse seine pumping related crowding of Atlantic mackerel (Scomber scrombrus)

The impacts of wild capture fishing on animal welfare are poorly understood. During purse seine fishing for Atlantic mackerel (Scomber scrombrus), catches are crowded to high densities to facilitate pumping onboard. This study aimed to monitor fish welfare during crowding events in the Norwegian purse seine fishery, and to identify relevant drivers. We first correlated a suite of neuro-endocrine, physiological and physical stress responses (integrated into a single measure of welfare using multivariate analysis) to the behavioural vitality of individual mackerel in controlled crowding trials in aquaculture cages. Vitality was found to be a useful measure of welfare. We then assessed individual fish vitality onboard a commercial purse seiner. Catch welfare, measured using vitality, was observed to be negatively impacted during pumping related crowding. Larger catches and longer crowding exposure times resulted in greater negative impacts. Vitality was not significantly impacted by crowding density or dissolved oxygen concentrations inside the net, although methodological limitations limited accurate measurement of these parameters. Blood lactate levels correlated negatively with vitality, suggesting that high-intensity anaerobic locomotory activity was associated with the reduction in welfare. Based on these findings, catch welfare could be improved by targeting smaller schools to minimise crowding exposure times.

Drivers of Atlantic herring decline and evidence basis for fisheries closures and rebuilding plans

Atlantic herring ( Clupea harengus) are economically and ecologically significant but have been in decline in Atlantic Canada due to an uncertain combination of environmental recruitment controls, predation, and fishing (commercial fishery and poorly documented bait removals). Fisheries and Oceans Canada partially closed Atlantic mackerel ( Scomber scombrus) and herring fisheries in March 2022 amid controversy and disagreement. Here, we develop a conceptual model for natural and anthropogenic controls on herring abundance centered on the southern Gulf of St. Lawrence (sGSL) and evaluate the likely importance of each. We provide the first estimates of the magnitude of bait fishery withdrawals in the sGSL. The decline in sGSL herring is likely driven by natural predation exacerbated by fishing. Bait fishery removals were 182 tonnes in 2021, suggesting that previous estimates for removals of spring-spawning herring were ∼30% too low. Fisheries closure is consistent with a precautionary approach given uncertainties and irreversibility of stock collapse. Ecosystemic models are needed but will be difficult to develop given the incomplete understanding of prey substitutability and net effect of interacting environmental processes.

Spatial variability of life-history parameters of the Atlantic chub mackerel (Scomber colias), an expanding species in the northeast Atlantic

Atlantic chub mackerel is a pelagic species present in the Atlantic Ocean that in recent decades has expanded northwards in the eastern Atlantic. Fish samples were collected in scientific surveys and commercial catches between 2011 and 2019. We analysed the geographical variation of the biological parameters (age, length, weight and condition), as well as the length-weight relationship, maturity-at-length and spawning season onset and duration in five geographical areas (from south to north): the Canary Islands, Gulf of Cadiz, western Portuguese coast, northwestern Spanish coast and Cantabrian Sea. The influence of sea surface temperature (SST) on fish length was modelled as a potential driver of geographical variability. All biological parameters increased progressively northwards, while the spawning season was delayed and prolonged with increasing latitude, from January in the Canary Islands to May-August in the Cantabrian Sea, when SST was between 15°C and 19°C. SST had a positive effect on length in three study areas and a negative one in two of them, suggesting that each group is at a different position within their thermal tolerance range. Deviance from the geographical pattern of some biological parameters in the Gulf of Cadiz suggests that it could be a hinge or mixing zone between Atlantic African, Mediterranean and Atlantic Iberian population components.

A review of the importance of various areas for northern contingent West-Atlantic mackerel spawning

Abstract 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.

Heavy metals determination and microbial assessment of some species of frozen fish sold at Utako Market, Abuja, Nigeria

This work assessed heavy metals [Copper (Cu), Iron (Fe), Cadmium (Cd), Zinc (Zn) and Lead (Pb)] concentrations and microbial load in the tissue (skin, fillet and gills) of some frozen fishes [Clupea harengus (herring), Scomber scombrus (Mackerel), Urophycis tenuis (White hake)] sold in Utako market using Flame Atomic Absorption Spectrophotometer (AAS) and standard microbiological procedures. The results obtained revealed that the concentrations of all the heavy metals determined except Zinc (Zn) were above the Food and Agriculture Organization (FAO) and World Health Organization (WHO) permissible limits in fresh water fish and fishery products. The total aerobic plate count (APC) was between 2.15×103 cfu/g and 47.6×103 cfu/g, total coliform count ranged from 1.85 × 103 cfu/g to 2.03 × 103 cfu/g and fungal counts ranged between 6.02x102 cfu/g and 18.3x102 cfu/g. The microbiological study showed that the skin had more load compared to other studied tissues and in all, the microbial load except APC also exceeded the FAO/WHO acceptable limits for frozen fish products. This study indicated that the products were not ideal for consumption due to bioaccumulation of these heavy metals and the issue of post-harvest contaminants that can multiply in case of defrosting which may impact negatively on the consumers. It is recommended that there should be proper handling and examination of frozen foods and they should be properly cooked before consumption.

A Fast and Simple DNA Mini-barcoding and RPA Assay Coupled with Lateral Flow Assay for Fresh and Canned Mackerel Authentication.

The online version contains supplementary material available at 10.1007/s12161-022-02429-6.

Species acclimatization pathways: Latitudinal shifts and timing adjustments to track ocean warming

Poleward distributional shifts and phenological adjustments are universal ecological responses to ocean warming. Though they are commonly addressed as independent processes, phenology usually depends on the latitudinal location where an organism lives. Such interaction can mask the actual impacts of warming and may even constrain the ability of a species to cope with ocean warming. We propose a framework to analyse alternative acclimatization pathways that accounts for pure distributional shifts, pure phenological adjustments, and mixed response. We tested this analysing drivers of observed changes in the spawning of horse mackerel (Trachurus trachurus) and Atlantic mackerel (Scomber scombrus) in northeast Atlantic in 1992–2019. Since species had contrasting population trajectories, data from the same survey is suitable to test whether shifts are driven by warming or density-dependence. Species showed contrasting responses to warming; horse mackerel spawned earlier (11.7 ± 1.5 days/°C of warming), whilst Atlantic mackerel shifted northward (367 ± 22 km/°C of warming). The narrower reproductive thermal niche of horse mackerel resulted in a tight coupling between latitude and timing of spawning that is consistent with geographical attachment, and an acclimatization constrained to an earlier phenology. The northward shift of Atlantic mackerel might be associated to its wider thermal reproductive niche, which enables prolonged migrations and almost synchronous spawning along the Atlantic margin. Results support our framework underpinning that acclimatization can combine or exclude timing and poleward shift, which could depend on species traits. These new insights are useful for fisheries management and to improve habitat projections under climate change.

Micobacteriose em uma cavala atlântica aparentemente curada (Scomber Scombrus, L.) e potencial zoonótico

ABSTRACT Mycobacteriosis was detected in seven out of one Atlantic mackerel (Scomber scombrus) that was purchased for human consumption from a fish market. The fish was apparently healthy but during cleaning, several granulomatous foci were noticed in the visceral organs. Histopathological examination of the lesions revealed numerous foci characterized by caseous necrosis in the center of the lesion surrounded by epithelioid giant cells. Ziehl-Neelsen staining revealed the presence of rod-shaped, acid-fast bacteria. Furthermore, immunohistochemical examination revealed the presence of a protein of mycobacterial origin in giant cells and macrophages. Based on gross and microscopic findings, mycobacteriosis was diagnosed. This report showed that due to its zoonotic potential, mycobacteriosis should be considered even in healthy-appearing fishes for human consumption.

Navigating sustainability and health trade-offs in global seafood systems

Seafood is expected to play a key role in improving access to healthy diets while providing food products with relatively low rates of greenhouse gas emissions. However, both nutrients and carbon footprints vary among species and production methods, and seafood consumption is further influenced by price and consumer preference, such that it is unclear which species are best placed to provide low-emissions nutritious seafood. Here, we use seafood production data to assess the nutritional value, carbon emissions, sustainability, affordability, and availability of seafood available to UK consumers. Globally, most seafood products are more nutritious and emit lower greenhouse gases than terrestrial animal-source foods, particularly small pelagic fishes and bivalves that contributed to recommended intakes for 3–4 essential dietary nutrients at the lowest emissions. For seafood products relevant to UK markets and consumers, Atlantic mackerel had the highest availability (i.e. landings) of all wild-caught UK seafood and lowest carbon footprint of all finfish, with one fillet portion exceeding recommended intakes of three nutrients (selenium, vitamins B12 and D). We found that price and sustainability of UK seafood, both factors in consumer demand, had considerable trade-offs with nutrients, carbon footprint, and availability. Farmed salmon, for example, were produced in large volumes but were relatively more expensive than other seafood, whereas highly nutritious, low-emissions farmed mussels had limited production volumes. The UK’s seafood system is therefore not currently optimised to produce nutritious, low-emissions seafood in large amounts. Policies that promote local consumption of affordable species already produced in high volumes, such as mackerel, could improve intakes of nutrients that are deficient in the UK population at relatively low environmental cost.

Novel Plasmid Carrying Mobile Colistin Resistance Gene mcr-4.3 and Mercury Resistance Genes in Shewanella baltica: Insights into Mobilization of mcr-4.3 in Shewanella Species.

Shewanella species have been identified as progenitors of several clinically important antibiotic resistance genes. The aim of our study was to analyze Shewanella baltica strains isolated from the gut contents of wild Atlantic mackerel (Scomber scombrus) for the presence of both known and novel variants of antibiotic resistance genes (ARGs), using Illumina-based whole-genome sequencing (WGS). Thirty-three S. baltica strains were isolated from Atlantic mackerel collected in the northern North Sea. WGS revealed the presence of several new variants of class C and class D beta-lactamases. Nearly 42% (14/33) of the strains carried the mobile colistin resistance gene mcr-4.3. To understand the genetic context of mcr-4.3, we determined the complete genome sequence of strain 11FHM2, using a combination of Oxford Nanopore- and Illumina-based sequencing. The complete genome sequence is 5,406,724 bp long, with one contig representing a chromosome of 5,068,880 bp and three contigs representing novel plasmids (pSBP1, 194,145 bp; pSBP2_mcr4, 86,727 bp; and pSBP3, 56,972 bp). Plasmid pSBP2_mcr4 contains the mobile colistin resistance gene mcr-4.3, as well as the mercury resistance operon merRPAT. Plasmid pSBP1 carries genes encoding resistance against copper, zinc, chromium, and arsenic. Plasmid pSBP3 does not carry any antibiotic or heavy metal resistance genes. Analysis of the flanking region of mcr-4.3 suggests that a phage integrase may be involved in the mobilization of mcr-4.3 in Shewanella spp. Our results provide insights into the mobile mcr-4.3 present in Shewanella spp. and highlight the importance of the marine environment in the emergence and dissemination of clinically important resistance genes. IMPORTANCE We identified two new plasmids in Shewanella baltica isolated from wild Atlantic mackerel (Scomber scombrus) collected from the northern North Sea, one plasmid carrying the mcr-4.3 gene for colistin resistance and the operon merRPAT for mercury resistance and the other carrying multiple heavy metal resistance genes. The marine environment has been recognized as a source of new resistance genes that are found in human pathogens. Selection pressure from heavy metals is seen in the marine environment, especially associated with human activities, such as waste discharge, mining, and in aquaculture settings. This would help maintain and disseminate these plasmids in the environment. Our study provides insights into the mobilization of colistin resistance genes in Shewanella spp. and highlights the importance of the marine environment in the emergence and dissemination of clinically important antibiotic resistance genes.

Space-time recapture dynamics of PIT-tagged Northeast Atlantic mackerel (Scomber scombrus) reveal size-dependent migratory behaviour

Based on GIS-mapping and semi-parametric modelling of recaptures from PIT-tag experiments in the North Sea nursery area (September 2011), the Celtic Seas spawning area (May-June 2014-2021) and the Icelandic Waters feeding area (August 2015-2019), we argue that the distribution of Northeast Atlantic (NEA) mackerel is influenced by a size-dependent migratory behaviour. The time-space recapture dynamics revealed that larger mackerel tended to migrate a longer distance between spawning and feeding areas, either through a western route from the Celtic Seas into the Icelandic Waters and the Greenland Sea or by following the main route northwards through the Faroe-Shetland Channel into the Norwegian Sea. This long-distance travel resulted in turn in delayed arrival in the North Sea wintering area. During the return spawning migration into the Celtic Seas, larger individuals remained in the front, likely heading to spawning grounds farther south than smaller conspecifics. Migration patterns also evolved with time at liberty as the mackerel grew older and larger, while possibly covering a progressively wider area over its annual migration cycle as suggested from the tagging data. However, the study also showed large inter-annual variability in the recapture patterns which likely reflect changes in environmental condition (prey availability and ocean current), NEA mackerel population demographics, and the spatial fishery dynamics.

Appropriateness of three fish species (Scomber scombrus, Sarda sarda, and Thunnus thynnus) from the Scombridae family in terms of shape and hydromechanics in designing the body of a robotic fish

In this study, we first identify seven criteria for the design of biomimetic robotic fish and focus on two of these tasks: shape and hydromechanics. For this purpose, fish body part measurements were obtained using previous work and also captured and harvested fish samples to construct computer-aided design (CAD) models of three fish species: Scomber scombrus, Sarda sarda, and Thunnus thynnus. Dead body drag and caudal fin flapping were considered as two separate problems. Computational simulations were carried out to determine drag and propulsive performance. Body drag simulations showed that the Reynolds dependence of the drag coefficient of three different species can be adequately expressed by a single laminar scaling correlation. At the same length and swimming speed, the Atlantic mackerel experiences the least drag. Caudal fin deformation simulations showed that the Atlantic bluefin tuna offers the highest thrust and efficiency. Peak efficiency is in the range of 31–35 percent observed at the same optimal Strouhal number, St = 0.5, for all species. It is shown that the aspect ratio as the main length scale influences propulsion performance.

Genome sequence of Vibrio anguillarum isolates carrying a novel class A β-lactamase VAN-1: do migratory fish transport novel resistance factors?

The aim of the study was to understand the genetic basis of resistance of five β-lactam resistant Vibrio anguillarum isolates obtained from the gut content of Atlantic mackerel (Scomber scomberus), using whole genome sequencing and to characterize a novel β-lactamase (VAN-1) from these isolates. Antibiotic sensitivity pattern was determined using Sensititre™ plates and whole genome sequencing was carried out using Illumina MiSeq-based sequencing. The blaVAN-1 gene was synthesized and expressed in Escherichia coli Top10 cells. Five isolates obtained (out of 73) from the gut content of Atlantic mackerel were identified as Vibrio anguillarum. Whole genome assemblies ranged from 3.894 to 3.906 million bases in length with an average of 50 contigs. A novel β-lactamase blaVAN-1, sharing 77.7% nucleotide identity with a known mobile β-lactamase from Vibrio species was detected. The blaVAN-1 gene in these isolates is flanked by a truncated IS5 family transposase on one end and a hypothetical protein and outer membrane protein followed by another IS5 family transposase on the other end, suggesting its potential for mobility. The blaVAN-1 gene was absent in V. anguillarum type strain (ATCC 14181) and V. anguillarum isolates from bivalves and sea water in Norway. VAN-1 conferred ampicillin resistance when expressed in E. coli, thus confirming the functionality of this gene. Our study highlights the importance of the marine environment as a reservoir of new antibiotic resistance genes. Our results suggest that migratory fish may transport novel antibiotic resistance determinants over long distances.

Effects of capture-related stress and pre-freezing holding in refrigerated sea water (RSW) on the muscle quality and storage stability of Atlantic mackerel (Scomber scombrus) during subsequent frozen storage

Crowded (stressed) and unstressed Atlantic mackerel with or without pre-freezing holding in refrigerated sea water (RSW) were stored at −19 °C for ∼12 months and analysed for nucleotide degradation (K value), muscle pH, water holding capacity (WHC), fillet firmness, cathepsin B/L like activity, lipid oxidation and fillet colour. The frozen storage showed the largest and most consistent direct effects on the quality metrics leading to increased lipid oxidation, discolouration (yellowing) and reduction on WHC and cathepsin activity. RSW treatment promoted nucleotide degradation and reduced WHC and fillet firmness in interaction with frozen storage and affected fillet colour lightness and saturation. Although showing only marginal main effects, crowding stress modified WHC, cathepsin activity and fillet firmness and colour through significant interactions with the frozen storage and RSW treatment. Further studies with larger sample sizes would be needed to elucidate their complex effects and interactions on the quality and storage stability of mackerel.