Mackerel Population Research Articles

Are Indian mackerel (Rastrelliger kanagurta) populations in the eastern Indian Ocean truly homogeneous? Insights from geometric morphometric analysis

The boundaries of Indian mackerel (Rastrelliger kanagurta) populations/stocks in the three Large Marine Ecosystems (LMEs) in the eastern Indian Ocean (Arabian Sea, Bay of Bengal, and Andaman Sea) are not clearly discriminated or delineated, resulting in conflicting population boundaries. Inherent limitations of the methodologies adopted could be the major reason behind this lack clarity in the population boundaries. Geometric morphometric analysis (GMA) using landmarks has been found to be the most appropriate approach under these conditions. Thus, the present study aims to differentiate between the populations of R. kanagurta in the eastern Indian Ocean (Arabian Sea, Bay of Bengal, and Andaman Sea) by employing GMA of body shape. The results indicate significant differences in body shape between the populations of R. kanagurta inhabiting the eastern Indian Ocean. The variations are primarily observed in the relative sizes of body depth, head, dorsal and anal fins, and the position of eyes, mouth, pectoral, anal, and dorsal fins. The Bay of Bengal populations were mainly characterized with a deeper body, large heads, dorsally oriented eyes, posterior pectoral fins and longer anal and second dorsal fin. Andaman populations were characterized with a more streamlined body, anterior pectoral fins, ventral eyes and shorter anal and second dorsal fins. Arabian Sea population possess an intermediate shape between Bay of Bengal and Andaman populations. These observed variations confirm that R. kanagurta constitutes a discrete population in the eastern Indian Ocean. This study provides valuable information on the population structure of R. kanagurta in the Arabian Sea, Bay of Bengal, and Andaman Sea, which can be useful in fisheries management and conservation efforts.

Atlantic mackerel population structure does not support genetically distinct spawning components.

The Atlantic mackerel, Scomber scombrus (Linnaeus, 1758) is a commercially valuable migratory pelagic fish inhabiting the northern Atlantic Ocean and the Mediterranean Sea. Given its highly migratory behaviour for feeding and spawning, several studies have been conducted to assess differentiation among spawning components to better define management units, as well as to investigate possible adaptations to comprehend and predict recent range expansion northwards. Here, a high-quality genome of S. scombrus was sequenced and annotated, as an increasing number of population genetic studies have proven the relevance of reference genomes to investigate genomic markers/regions potentially linked to differences at finer scale. Such reference genome was used to map Restriction-site-associated sequencing (RAD-seq) reads for SNP discovery and genotyping in more than 500 samples distributed along the species range. The resulting genotyping tables have been used to perform connectivity and adaptation analyses. The assembly of the reference genome for S. scombrus resulted in a high-quality genome of 741 Mb. Our population genetic results show that the Atlantic mackerel consist of three previously known genetically isolated units (Northwest Atlantic, Northeast Atlantic, Mediterranean), and provide no evidence for genetically distinct spawning components within the Northwest or Northeast Atlantic. Therefore, our findings resolved previous uncertainties by confirming the absence of genetically isolated spawning components in each side of the northern Atlantic, thus rejecting homing behaviour and the need to redefine management boundaries in this species. In addition, no further genetic signs of ongoing adaptation were detected in this species.

Some biological aspects of indian mackerel (Rastelliger kanagurta Cuvier, 1817) in Bali Strait waters

Indian mackerel (Rastrelliger kanagurta Cuvier, 1817) is a small pelagic fish species which is the main catch commodity in purse seine and jukung fleets in the Bali Strait waters. Sustainable management is urgently needed for indian mackerel populations in Bali Strait waters to remain sustainable fishery. The availability of basic information such as biological aspects is very important as a fundamental resource in the management of indian mackerel in Bali Strait waters. The aims of this study were to reveal several biological aspects of mackerel such as growth patterns, condition factors, sex ratio, and size at first maturity of indian mackerel in Bali Strait waters. Sampling was carried out in May-September 2018. Samples of fish were taken from purse seine and jukung fleets using trawl nets and gill nets. Fish sample was measured, weighed and dissected to observe the sex and the gonadal maturity stage. The total number of indian mackerel samples was 167 individuals. Mackerel in the Bali Strait waters has a positive allometric growth pattern with fish in good condition. The sex ratio was in an unbalanced condition with the number of male fish being more than the female fish. The size at first maturity was 19.34 cm for male fish and 19.76 cm for female fish.

Recent Variations in the Size and Age Structure of the Population of Horse Mackerel <i>Trachurus mediterraneus</i> (Steindachner, 1868) on the South-Western Shelf of Crimea

The influence of the average annual sea surface temperature (SST) on the development of horse mackerel Trachurus mediterraneus on the south-western Crimean shelf has been shown. The changes in the main indicators of the population and their relationship with the change in the average annual SST (0.055°C/year) in 2000–2020 have been identified. Against the background of the observed increase in SST in recent years, the state of the horse mackerel population has improved: there has been an increase in the average age and, accordingly, the proportion of larger, well-fed individuals, and, in general, the average size and weight of fish. It has been shown that according to the nature of the change in the average annual SST, three periods can be distinguished: 2000−2007, 2008−2013 and 2014−2020.

Stock Identification of Short Mackerel (Rastrelliger brachysoma) in the Upper and Middle Gulf of Thailand by Morphological Characters

Rastrelliger brachysoma, a short mackerel, is a significant pelagic fish that is common in the fisheries in the Gulf of Thailand. The management of fish stocks is a prerequisite for fish conservation strategies and profitable fisheries. Morphological character differences between stocks of species provide a method for identifying fish stocks. This study was aimed to identify stock population of short mackerel in the Upper and Middle Gulf of Thailand. The fish specimens were collected from four different locations: Chonburi and Prachuap Khiri Khan (central provinces of Thailand), Chumphon and Surat Thani (southern provinces of Thailand). Twelve morphometric characters of fish were assessed to determine the stock populations by stepwise discriminant analysis. The results showed that 12 morphometric characters were significantly different among the four populations. In the discriminant function analysis, the first function explained 61.30% of total variations, whereas the 2nd and 3rd functions were 26.50% and 12.20%, respectively. The characters included total length, standard length, folk length, head length, post – orbital length, pre – dorsal length, pre – pelvic length, 1st dorsal to 2nd dorsal length, pelvic to anal length, pre – anal length, head depth, and greatest depth, all of which can be used to differentiate these populations. According to the results of the discriminant analysis, the populations of short mackerel were predicted and subsequently classified with an accuracy rate of 54.88%.

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.

DNA barcoding and morphometric of Rastrelliger spp. in North Maluku Sea, Indonesia

High exploration activity is feared to have an impact to mackerel populations. A sustainable management approach should be taken to provide information about the status of mackerel populations. Study of mackerel population status can be carried out through genetic information. The DNA of the fish samples were collected at traditional fish markets (Morotai, Bacan and Ternate). Laboratory works such as extraction, amplification, electrophoresis and DNA sequencing were analysis at the Indonesian Biodiversity Laboratory (Bionesia). The molecular characteristics of Rastrelliger kanagurta were 374 base pairs (bp). The composition of nucleotides showed the similarity of frequencies between species. Phylogenetic relationship of R. kanagurta in North Maluku Sea suggested that there was any differentiation. The genetic diversity of R. kanagurta was high with a total number of haplotypes and diverse nucleotide diversity. The minimum spawning networks (MSN) found 5 haplotype networks from a total of 12 samples. Morphological measurements of standard length, head height, body width, pectoral fin length and tail were found to have variable values. The length of the weight of the fish is obtained of b = 3, indicating that the growth pattern was isometric or weight gain was equivalent to the growth of the fish length.Keywords: Biodiversity, conservation, ecology, morphology, species

Stochastic Modelling to Assess External Environmental Drivers of Atlantic Chub Mackerel Population Dynamics

The population dynamics of small and middle-sized pelagic fish are subject to considerable interannual and interdecadal fluctuations in response to fishing pressure and natural factors. However, the impact of environmental forcing on these stocks is not well documented. The Moroccan Atlantic coast is characterized by high environmental variability due to the upwelling phenomenon, resulting in a significant abundance and variation in the catches of small and middle-sized pelagic species. Therefore, understanding the evolution of stock abundance and its relationship with different oceanographic conditions is a key issue for fisheries management. However, because of the limited availability of independent-fishery data along the Moroccan Atlantic coast, there is a lack of knowledge about the population dynamics. The main objective of this study is to test the correlation between the environment conditions and the stock fluctuations trends estimated by a stock assessment model that does not need biological information on growth, reproduction, and length or age structure as input. To achieve this objective, the fishery dynamics are analyzed with a stochastic surplus production model able to assimilate data from surveys and landings for a biomass trend estimation. Then, in a second step, the model outputs are correlated with different environmental (physical and biogeochemical) variables in order to assess the influence of different environmental drivers on population dynamics. This two-step procedure is applied for chub mackerel along the Moroccan coast, where all these available datasets have not been used together before. The analysis performed showed that larger biomass estimates are linked with periods of lower salinity, higher chlorophyll, higher net primary production, higher nutrients, and lower subsurface oxygen, i.e., with an enhanced strength of the upwelling. In particular, acute anomalies of these environmental variables are observed in the southern part presumably corresponding to the wintering area of the species in the region. The results indicate that this is a powerful procedure, although with important limitations, to deepen our understanding of the spatiotemporal relationships between the population and the environment in this area. Moreover, once these relationships have been identified, they could be used to generate a mathematical relationship to simulate future population trends in diverse environmental scenarios.

Revealing Spanish mackerel’s diversity in Indonesian through local commodities in the fish market

Abstract. Widayanti R, Nugroho HA, Megarani DV, Widiasih DA, Pakpahan S. 2021. Revealing Spanish mackerel’s diversity in Indonesian through local commodities in the fish market. Biodiversitas 23: 624-630. The objective of this study was to explore the diversity of Spanish mackerel in Indonesian Archipelago based on commodities offered in local fish markets. Eighteen specimens were collected from six different fish markets around the Indonesian archipelago. According to Wallace Line, the cytochrome B sequence was used as a genetic marker to reveal diversity from West Indonesia to East Indonesia. Gene amplification was performed using the polymerase chain reaction followed by Sanger sequencing. Based on DNA sequence analysis, we identified three species of Spanish Mackerel available at various fish markets around the region. The first group is related to Scomberomorus commerson, which was sold in both Western and Eastern Indonesian fish markets; the second group is related to Scomberomorus semifasciatus, which was sold in Eastern Indonesian fish markets; and the third group is related to Scomberomorus koreanus, which was sold in Western Indonesian fish markets. The genetic differences amongst Spanish Mackerel populations ranged from 0 to 17% and the average evolutionary divergence in the overall populations was determined to be 4%. The data collected can be utilized to initiate map mackerel diversity based on CYT B sequence throughout the Indonesian Archipelago, as well as for further study and application in the identification of foods produced from mackerel.

Age and Growth of Japanese Mackerel in the High Seas of the Northwest Pacific Ocean

Japanese mackerel (Scomber japonicus) is one of the important economic species in the pelagic light seine fishery in China, but few studies have been reported on the age, growth and management recommendations of Japanese mackerel in the high seas of the northwest Pacific Ocean. In this study, we fitted expressions for the relationship between fork length and body weight of Japanese mackerel based on fork length and body weight data of Japanese mackerel in the high seas of the Northwest Pacific Ocean from 2018 to 2019, and calculated growth parameters and growth characteristics of Japanese mackerel von Bertalanffy growth equation by identifying otolith age data combined with the least squares method. The results showed that the relationship between fork length and body weight of Japanese mackerel in the open sea of the Northwest Pacific Ocean was W = 2.0 × 10-6 L3.289 (r = 0.9764, n = 2833); the growth parameters were L = 447.61∞, K = 0.264, t = -1.060; the growth rate reached the maximum when the bodyweight growth rate was 122 g/yr, at which the inflection point age was 3 years old, the inflection point body weight was 310 g, and the inflection point length was 309 mm. We recommend 2 years of age start fishing with a fork length of 250 mm (±10 mm). The growth parameters of Japanese mackerel in the open sea of the Northwest Pacific Ocean were not significantly different from those of the Japanese mackerel population on Japan’s coast (P > 0.05), Finally, based on the knowledge of biological research and resource evaluation, we suggest that the age of opening trap should be 2 years old and the length of fork should be 250 mm (±10 mm).

Northern Gannets (Morus bassanus) breeding at their southern limit struggle with prey shortages as a result of warming waters

AbstractNorthern Gannet (Morus bassanus) colonies near the species’ southernmost limits are experiencing plateaued or declining population growth and prolonged poor productivity. These trends have been linked to reductions in the availability of the species’ key prey, the Atlantic mackerel (Scomber scombrus). Declines in mackerel availability have been associated with warming ocean temperatures and over-fishing. Here, we assessed the influence of prey availability, abundance, and sea surface temperature (SST) during the breeding season on Northern Gannet reproductive success over a multi-decadal time span at their southernmost colony at Cape St. Mary's, NL, Canada. We demonstrate that warming SST affects reproductive success differently in early vs. late chick-rearing, but that overall, declining mackerel availability (landings and biomass) due to warming SST and over-exploitation has resulted in poor productivity of Northern Gannets at their southernmost limit. Our study is consistent with previous findings in other colonies in Atlantic Canada and France, and contrasts with findings in more northern colonies where mackerel population increases and range expansion are coinciding with gannet population growth. This implies that warming SST is having opposing influences on Northern Gannets and mackerel at the different extremes of the gannets’ breeding range.

A morphometric approach into mackerel (Rastrelliger spp.) diversity in Fisheries Management Area 711 as a management base

Rastrelliger spp. is a small pelagic fish with important ecological and economic value in Indonesia. Genus Rastrelliger has three species with different distribution patterns, so they have diversity in morphology and populations in several waters. The study aimed to analyze the morphometric diversity of mackerel (Rastrelliger spp.) in Bintan, Bangka, and Ketapang waters (Fisheries Management Area 711) using standard morphometric methods and truss network analysis. 310 samples were collected from all locations based on simple random sampling. The growth pattern of Rastrellliger spp. was negative allometric in each location. The cluster analysis showed that the mackerel populations from Ketapang and Bangka formed one group, while Bintan tended to be different. Based on the discriminant analysis, there are overlapping populations between Ketapang and Bangka. The difference of morphometric characters on mackerel (Rastrelliger spp.) can indicate different species, so there is potential for more than one population or stock in FMA 711.

Prediction of Fish Migration Caused by Ocean Warming Based on SARIMA Model

Herring and mackerel are two of the most important pillars of Scottish fisheries. In recent years, global warming has caused a gradual rise in ocean temperatures. In order to survive and reproduce, herring and mackerel populations will migrate. This will have a huge impact on Scotland’s fisheries. Therefore, we need to predict the relocation of fish stocks in advance, make timely adjustments to the fishing range, and minimize the loss of the fishing industry. In this article, we subdivide the research target sea area into 39 regions, establish the optimal SARIMA model for each region based on the collected seawater temperature time series data, and take region 13 and region 15 as examples to fit the ARIMA (3, 3, 1) (1, 2, 1) and ARIMA (2, 3, 1) (0, 2, 1) models with a period of 12. The results show that the SARIMA model fits well in all regions and predicts the temperature changes in the studied sea area from 2021 to 2050. Finally, according to the predicted sea temperature in different periods, the migration position of the fish school is predicted.

Обоснование параметров близнецового лова дальневосточной скумбрии и дальневосточной сардины среднетоннажными судами с учётом их промыслово- биологических характеристик

In the Northwestern Pacific Ocean, in recent years, there has been an increase in the populations of eastern mackerel (Scomber japonicus) and Far Eastern sardine (Sardinops sagax). In the Far East, large-tonnage fishing trawlers capable of successfully harvesting (catching) mackerel and Far Eastern sardines are engaged in fishing for pollock and other traditional objects of fishing. The purpose of this article is to show how underutilized stocks of mackerel and Far Eastern sardine can be developed by medium tonnage vessels using twin fishing techniques. For the biotechnological substantiation of the parameters of the twin trawl system according to the degree of influence on the object of production (catch), it was divided into 7 zones, in each of which the object of production (catch) has one or another behavioral reaction. The article substantiates the necessary (optimal) vertical opening of the mouth of the trawl for complete vertical fishing of schools of fish based on echometric diagrams of the vertical distribution of schools of mackerel and Far Eastern sardine and the accepted response distances of fishing objects to elements of the trawl system. The biotechnical substantiation of the parameters of the twin trawl system for the extraction (catch) of Pacific mackerel and Far Eastern sardine has been carried out. The length of the twin trawl, the angle of attack of the upper, lateral and lower layers of the trawl shell, the length of the wings of the trawl are determined, the necessary ratio of the shaded area of the shell of the trawl to its fictitious area for mediumtonnage vessels with different traction characteristics is determined. Based on the speed parameters of fish in different zones of the trawl system, the distance between twin vessels, the length of the cords and the length of the cables are determined.

Genetic mixed-stock analysis of short mackerel, Rastrelliger brachysoma, catches in the Gulf of Thailand: Evidence of transboundary migration of the commercially important fish

Short mackerel, Rastrelliger brachysoma, is one of commercially important marine species in the Gulf of Thailand. The mackerel resource has been faced with overfishing and sharply declined. Here, genetic mixed-stock analysis was performed using eleven microsatellite loci on 1675 short mackerel individuals caught, in 2014, from its four major fishing grounds of Thai waters in the Gulf of Thailand. Short mackerel populations from Thai, Cambodian, Vietnamese and Malaysian waters in the Gulf of Thailand were used as baselines. The mixed-stock analysis revealed that these populations significantly contributed to catches of the four fishing grounds in Thai water. The Samut Songkhram population, representing sedentary behavior, was the major contributor (52.71 %) to the total catch from the Inner Gulf of Thailand. The Surat Thani population dominantly contributed 46.23 % to the total catch from lower part of the Central Gulf of Thailand, where the fishing ground surrounds its spawning ground. The populations from Cambodia and Malaysia corporately contributed of 70.95 % and 87.88 % to the total catches from the Eastern Gulf of Thailand and upper part of the Central Gulf of Thailand, respectively. According to these analysis results, the populations from neighboring countries to Thailand displayed transboundary migration and significantly contributed to fishery catches in the Thai water. Therefore, profound sub-regional cooperation from Gulf of Thailand countries is required for effective fishery management of the short mackerel resource to be sustainable.

Northwest Atlantic mackerel population structure evaluated using otolith δ18O composition

Abstract The Northwest Atlantic mackerel (Scomber scombrus) population is comprised of northern and southern contingents, each with distinct natal regions in the United States and Canada. We tested hypotheses on natal origin and contingent mixing by analysing natal otolith δ18O values, evaluating the approach through an out-group comparison with the Northeast Atlantic population. Otolith δ18O values varied according to expectations between the Northeast (higher) and the Northwest (lower) Atlantic basins, and between contingents within the Northwest Atlantic stock, although contingent differences varied between years. Most adults (age-3+ years) sampled from US waters (1999–2003) represented the northern contingent (Canadian spawning site). The confirmation of the seasonal mixing of older and larger fish between the two contingents provides support and justification for the development of bi-national (United States–Canada) assessment and management of Northwest Atlantic mackerel.

Estimating fish population abundance by integrating quantitative data on environmental DNA and hydrodynamic modelling.

Molecular analysis of DNA left in the environment, known as environmental DNA (eDNA), has proven to be a powerful and cost-effective approach to infer occurrence of species. Nonetheless, relating measurements of eDNA concentration to population abundance remains difficult because detailed knowledge on the processes that govern spatial and temporal distribution of eDNA should be integrated to reconstruct the underlying distribution and abundance of a target species. In this study, we propose a general framework of abundance estimation for aquatic systems on the basis of spatially replicated measurements of eDNA. The proposed method explicitly accounts for production, transport and degradation of eDNA by utilizing numerical hydrodynamic models that can simulate the distribution of eDNA concentrations within an aquatic area. It turns out that, under certain assumptions, population abundance can be estimated via a Bayesian inference of a generalized linear model. Application to a Japanese jack mackerel (Trachurus japonicus) population in Maizuru Bay revealed that the proposed method gives an estimate of population abundance comparable to that of a quantitative echo sounder method. Furthermore, the method successfully identified a source of exogenous input of eDNA (a fish market), which may render a quantitative application of eDNA difficult to interpret unless its effect is taken into account. These findings indicate the ability of eDNA to reliably reflect population abundance of aquatic macroorganisms; when the "ecology of eDNA" is adequately accounted for, population abundance can be quantified on the basis of measurements of eDNA concentration.

Growth of horse mackerel populations in the western parts of the Black, Marmara, and Aegean seas

Abstract This study estimated the growth of horse mackerel, Trachurus mediterraneus (Steindachner), populations from the western parts of the Black, Marmara, and Aegean seas. Dependencies of individual daily weight gain at age were determined. The calculations showed that in the area studied the highest absolute weight gain was 45.4 mg day−1 for fish at the age of 2.46 years from Zonguldak (Black Sea). The relative annual increase in the population biomass of T. mediterraneus inhabiting different areas of the Black, Marmara and Aegean seas was determined. It was revealed that the annual relative increase in the biomass of horse mackerel caught in the Black Sea exceeded that in the Marmara and Aegean seas. At the same time, the highest relative annual biomass increase (94.8%) was observed in populations from the Varna-Bourgas region and in the coastal waters of Sevastopol (70.9%) in the Black Sea.

SEASIM-NEAM: A Spatially-Explicit Agent-based SIMulator of North East Atlantic Mackerel population dynamics

In 2018 we published a spatially-explicit individual-based model (IBM) that uses satellite-derived maps of food availability and temperature to predict Northeast Atlantic mackerel (Scomber scombrus, NEAM) population dynamics. Since then, to address various ecological questions, we have extended the IBM to include additional processes and data. Throughout its development, technical documents have been provided in the form of e.g. supplementary information to published articles. However, we acknowledge that it would be difficult for potential users to collate information from separate supplementary documents and gain a full understanding of the current state of the IBM. Here, we provide a full technical specification of the latest version of our IBM. The technical specification is provided in the standard ODD (Overview, Design concepts and Details) format, and supplemented by a TRACE (TRAnsparent and Comprehensive model Evaludation) document. For the first time, we give our model the acronym SEASIM-NEAM: a Spatially-Explicit Agent-based SIMulator of North East Atlantic Mackerel population dynamics. This article supersedes previous documentation. Going forward we hope that this article will stimulate development of similar models.•This article collates improvements that have been made to SEASIM-NEAM over time.

A general approach to incorporating spatial and temporal variation in individual-based models of fish populations with application to Atlantic mackerel

Fish population dynamics are affected by multiple ecosystem drivers, such as food-web interactions, exploitation, density-dependence and the wider environment. While tactical management is still dominated by single-species models that do not explicitly account for these drivers, more holistic ecosystem models are used in strategic management. One way forward in this regard is with individual-based models (IBMs), which provide a single framework in which these drivers can be represented explicitly. We present a generic marine fish IBM that incorporates spatial and temporal variation in food availability, temperature and exploitation. Key features of the model are that it (1) includes realistic energy budgets; (2) includes the full life cycle of fish; (3) is spatially-explicit and (4) incorporates satellite remote-sensing data to represent the environmental drivers. The rates at which individuals acquire and use energy depend on local food availability and temperature. Their state variables, including life stage, size and energy reserves, are updated daily, from which population structure and dynamics emerge. To demonstrate the use of the model we calibrate it for mackerel (Scomber scombrus) in the North East Atlantic. Most parameters are taken from the literature, except the background early mortality rate and the strength predator density dependence, which were estimated by fitting the model to data using Approximate Bayesian Computation. The calibrated model successfully matches the available data on mackerel population dynamics and structure. We demonstrate the use of the model for management purposes by simulating the population effects of opening and closing a sector of the North Sea to mackerel fishing. Our model uses basic principles of behavioural and physiological ecology to establish how spatial and temporal variations in ecosystem drivers affect the individuals in the population. Population dynamics and structure are calculated from the collective effects on individuals. Application to a test case shows the method can fit available data well. Individual-based approaches such as this study have potential for use in strategic management because they can account for spatial structuring, food-web interactions, density dependence, and environmental drivers within a single framework.