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Article

Overview of a Keystone Small Pelagic Fish in the North-Western Black Sea: Biometry, Age and Stock Status of Horse Mackerel Trachurus mediterraneus (Steindachner, 1868)

by
Cătălin Păun
,
Aurelia Țoțoiu
,
George Țiganov
,
Mădălina Galațchi
,
Magda Nenciu
and
Victor Niță
*
National Institute for Marine Research and Development “Grigore Antipa”, 300 Mamaia Blvd., 900581 Constanța, Romania
*
Author to whom correspondence should be addressed.
Fishes 2025, 10(8), 390; https://doi.org/10.3390/fishes10080390
Submission received: 30 May 2025 / Revised: 16 July 2025 / Accepted: 29 July 2025 / Published: 7 August 2025
Browse Figures
Versions Notes

Abstract

As a semi-pelagic fish with commercial value, Mediterranean horse mackerel, Trachurus mediterraneus (Steindachner, 1868), is highly important both for the ecosystem, as a link between trophic levels, and for fisheries and local livelihoods. This study investigates the T. mediterraneus stock along the Romanian coast for more than 10 years (2014–2024), reporting the following data on its bio-ecological characteristics and stock status: size, age, sex ratio, and estimated biomass. Horse mackerel at the Romanian coast revealed an initially slower growth rate followed by acceleration in later years, which may reflect local ecological influences such as resource availability, environmental conditions, or selective pressure. The spatial distribution of the species along the Romanian shelf indicates a clear pattern of coastal aggregation, highlighting the need for targeted and precautionary fisheries management measures, aiming to ensure a sustainable stock.
Keywords:
horse mackerel; Western Black Sea; age; growth; stock status; fisheries
Key Contribution: The study brings novel data on the overall status of Mediterranean horse mackerel at the Romanian coast.

Graphical Abstract

1. Introduction

The Mediterranean horse mackerel, Trachurus mediterraneus (Steindachner, 1868), is a semi-pelagic carnivorous fish with significant commercial value, belonging to the Family Carangidae. It is distributed in the Atlantic Ocean’s Eastern Central and Northeast areas, as well as the Black Sea and the Sea of Marmara [1]. Pelagic fish represent one of the major links between plankton and the higher trophic levels, as predatory fish, marine mammals, and seabirds rely on them as a major food source [2]. T. mediterraneus has an essential role in Black Sea fisheries and is caught by pelagic trawl, uncovered pound nets, and gillnets. For sound resource management, it is crucial to determine the structural characteristics of horse mackerel stocks, which have great importance both in the food chain and for Black Sea fisheries. This study, conducted at the Romanian Black Sea coast, discusses some biological characteristics (age, length, weight and sex composition, length-weight relationship, condition factor, and growth) of the horse mackerel population. The biological characteristics of horse mackerel have been previously characterized in different areas of the Black Sea: at the Turkish coast [3,4,5,6,7,8,9,10], Romanian coast [11,12,13,14,15], Bulgarian coast [16,17,18,19,20,21], and Russian coast [22]. In these studies, various aspects of stock status (such as population structure and abundance), biometric relationships (e.g., length-weight, length-age), and age distribution have been analyzed, offering important comparative data that support fishery management and biological assessment efforts across the region.
For a more effective management of economically important species stocks, their monitoring is essential. In this context, determining the bio-ecological characteristics of the stocks can contribute to ensuring their sustainability. The present study aimed to provide an extensive overview of horse mackerel from the Western shelf of the Black Sea, by addressing specific aspects, such as stock structure and growth parameters, as well as proposing appropriate measures to support stock levels by comparing the results with those of previous studies.

2. Materials and Methods

2.1. Fish Sampling

A total of 3737 specimens of T. mediterraneus from the Romanian Black Sea were collected monthly from pelagic trawls (22 stations) and uncovered stationary fishing pound nets (12 stations) along the Black Sea coast in the northern area (Sulina, Gura Portiței, Periboina, Vadu, Corbu, Hanul Piraților, Platforms, Midia, Camp Năvodari, Mamaia) and the southern area (Agigea, Eforie Sud, Costinești, Olimp, 2 Mai, Vama Veche) during 2014–2024 (Figure 1). The fish caught were immediately refrigerated, packed in ice boxes, and transported to the laboratory for measurements. For each fish, the total length (L) and the total weight (W) were measured, using a 10 mm scale [23]. The sex of all specimens was recorded by a macroscopic examination of the gonads as male or female, according to Follesa and Carbonara [24]. Regarding gonad characteristics, in immature female individuals, the ovary is small, rosy, and translucent, while in adults, the ovary is pink-yellow and has a granular appearance, and the eggs are easily visible. For males, in juveniles, the testes are whitish and transparent, whereas in the adult stage they are white [24].

2.2. Determining Biometric Parameters

The relationship between length and weight was established as W = aLb, where W is total body weight (g), L is total length (cm), and a and b are coefficients [25,26]. The parameters a and b of length-weight relationships were estimated by linear regression analysis on log-transformed lengths and weights. The degree of association between the variables was estimated by the determination coefficient (R2). The growth type was identified by Student’s T-test, which was applied to determine the significance of differences between the isometric growth (b = 3) and allometric growth (b ≠ 3). The Fulton index (Condition Factor) was calculated for all the individuals sampled. After taking biometric measurements and weighing individuals, the Fulton index (K) was calculated [27], according to the following formula: K = (W/ L3) × 100, where W = total weight, in grams; L = total length, in cm.

2.3. Age Reading Methodology

For age determination, all 3737 individuals were analyzed, from each 0.5 cm size interval, to represent all length groups. Age data can provide considerable insight into fish population dynamics. Data on fish size, combined with age information, provide growth rates. When fish age is known, this information gives a measure of the mortality rate due to both fishing and natural causes [28]. Stock assessments use the age data, in addition to other data, to build mathematical models of the entire population.
Horse mackerel specimens were collected by pelagic and demersal trawling during NIMRD’s biannual fishing surveys and from the stationary fishing points (pound nets).
Almost all fish bone structures can be used to determine age; however, for practical reasons, the most commonly used are otoliths and scales [29]. Otoliths are polycrystalline bodies made of calcium carbonate crystals [23]. The sagittal otolith pairs were removed, cleaned to remove the organic material, and stored in dry conditions inside a microtube to avoid breaking them. Age determination was performed using a stereoscopic zoom microscope under reflected light against a black background. Opaque and transparent rings were counted as an opaque zone together with a transparent zone, which was considered the annual macrostructure [3,15]. The best results were obtained with the otolith placed with the distal surface up and the proximal surface down (Figure 2) [23].

2.4. Estimating Stock Biomass

To assess the stock status of horse mackerel along the Romanian Black Sea shelf, a dedicated scientific survey was conducted in 2024 using a pelagic trawl. The operation covered the continental shelf up to the 70-m isobath, encompassing key habitats where the species is typically present during the warm season. A total of 30 trawl hauls were carried out systematically across the surveyed area. However, for analytical purposes, only the hauls performed up to the 50-m isobath were included in the final assessment. This decision was based on the absence of horse mackerel catches beyond 50 m, where no specimens were recorded in deeper stations. By excluding data from the deeper, non-productive zones, the evaluation focused on the effective distribution range of the species within Romanian waters, ensuring more accurate estimates of biomass and density within the horse mackerel’s known aggregation areas (Figure 3).

3. Results

3.1. Population Parameters

Overall, the sex ratio was determined as follows: 2% immature, 53% females, and 45% males (Figure 4). The observed sex ratio (F:M = 1.16:1) significantly deviated from the expected 1:1 ratio (χ2 test, p = 0.00000376), indicating a higher share of females in the sampled population. Sex distribution in various length groups is given in Figure 4.
The mean length of the analyzed individuals was 11.3 ± 2.01 cm (range between 4.48 cm and 19 cm), the mean weight was 13.31 ± 7.91 g (range between 1.1 and 61.18 g), and the Fulton Index was 0.83 ± 0.13 (range between 0.32 and 3.94). The highest number of individuals analyzed was in 2023 (1115). The highest mean of length was registered in 2015 (13.84 ± 1.24 cm), and the lowest in 2014 (8.79 ± 1.46 cm). The highest mean weight was also registered in 2015 (13.84 ± 1.24 g), and the lowest in 2014 (6.02 ± 2.49 g). Regarding the Fulton condition index, the highest value was found in 2018 (0.91 ± 0.09), and the lowest value was recorded in 2023 (0.78 ± 0.11) (Table 1).
The highest number of individuals sampled was in Camp Năvodari station (557) and Corbu (514), both collected from uncovered pound nets, and the lowest number of individuals analyzed was from Haul 12 (4) and Haul 18 (11) stations with the pelagic trawl (Figure 5).
The most numerous individuals sampled were in uncovered pound nets (2799), while 938 individuals were sampled in pelagic trawls (Figure 6).
Most individuals were sampled in June 2023 (430), and the lowest number was in September 2018 (11). Throughout the study period, the highest number of individuals was collected in October (1085), both by pound nets and the pelagic trawl. The fewest individuals were collected in March (26) and April (16), when the horse mackerel approaches the Romanian Black Sea coast (Figure 7).
The distribution of individuals by length class (Figure 8) highlights a population concentrated in the 9–13.5 cm range, with a peak frequency in the 10–10.5 cm class, which accounts for nearly 12% of the total individuals. Total length varies between the 4–4.5 cm and 19–19.5 cm classes.
The sex distribution shows a relatively balanced presence of females and males in the dominant classes, although females are slightly more numerous in the central intervals of the distribution. Immature individuals are mostly found in the smaller length classes (<10 cm), but in very low proportions. Overall, the distribution indicates a population dominated by mature individuals, with a balanced demographic structure and moderate recruitment. The low presence of very small and very large individuals suggests moderate fishing intensity and/or a natural population dynamics that favors concentration within an optimal length range.
In this study, a total of 3737 individuals were analysed. The average lengths and weights (±standard deviation) were 11.3 ± 2.01 cm and 13.31 ± 7.91 g, respectively, and the minimum and maximum values were 4.48 and 19.0 cm in length and 1.1 and 61.18 g in weight. The correlation between the average total length and total weight was statistically significant (r2 = 0.9401, p < 0.001), indicating a strong positive relationship and a positive allometric growth pattern (b = 3.0806), as shown in Figure 9. In the case of horse mackerel individuals analysed for the period 2014–2024, the length-weight correlations had positive values. Correlation takes values between 0 and 1 R2 (0;1), which can be converted to percentage values (√R2). The value of correlation becomes very important when values can be compared for a larger set of data and over a long period of time. Also, the closer the value of R is to 1, the tighter the correlation is [30]. The length-weight relationship is used to determine the body condition of the fish and the type of growth (isometric or allometric). A coefficient b = 3 signifies a linear isometric growth of the fish (length and weight increase proportionally) [26]. The length-weight relationships for T. mediterraneus were described by the equations: for females, W = 0.0069·L3.0759, for males, W = 0.0062·L3.1149, and for all individuals, W = 0.0068·L3.0806. In all cases, the slope (b) was significantly greater than 3 (p < 0.05), indicating a positive allometric growth pattern across the sampled population.

3.2. Age Structure

Figure 10 illustrates the percentage distribution of individuals by age group, divided into females, males, and immature individuals. The highest share of individuals is found in age groups 0 and I, approximately 70%, where females and males are nearly equal in number, and immature individuals appear only in group 0 (1.90%). In group I, females are significantly more numerous than males (18.92% vs. 14.56%). As age increases, the proportion of individuals gradually decreases across all categories, reaching very low values in groups IV and V. In all age groups, females are generally more numerous than males, except for group 0, where the percentages are almost equal (Table 2). This distribution suggests a young population of Mediterranean horse mackerel.
The analyzed population shows a normal and balanced growth between length and weight, with differences between sexes and a typical age structure. Sexual dimorphism is moderate but consistent, with females being more developed than males. A large number of young individuals (ages 0, I, II) is observed, which indicates a healthy population.

3.3. Stock Status

3.3.1. Overview of Catches

Horse mackerel, a commercially significant pelagic species in the Black Sea, has shown variable catch volumes over the past decade. While total catches across the Black Sea have ranged from around 8000 to over 25,000 tons annually [31], Romania’s contribution remains modest, typically well below 1% of the regional total. Between 2011 and 2024, Romania’s catches fluctuated from a low of approximately 6.6 tons in 2014 to a peak of around 54.27 tons in 2023. Meanwhile, total Black Sea catches ranged from about 9000 tons to 25,000 tons over the same period. This discrepancy highlights Romania’s relatively limited role in exploiting this species, largely due to its small-scale fleet.
Recent assessments coordinated by the General Fisheries Commission for the Mediterranean (GFCM, 2023) [31] indicate that the Black Sea stock of horse mackerel is experiencing overexploitation. Scientific modeling, including the use of Extended Survivors Analysis (XSA), suggests declining trends in spawning stock biomass and unsustainably high fishing mortality rates. In particular, 2022 assessments estimated the spawning stock biomass (SSB) at around 22,500 tons, while fishing mortality was calculated at approximately 0.73, well above the estimated precautionary threshold of 0.4. These figures highlight the urgent need for strengthened regional management and conservation actions.

3.3.2. Romanian Coastal Context

In Romania, horse mackerel is caught primarily by small-scale vessels, many of which are under 12 m in length. While this species is not a primary target for Romanian fishers, it is a regular component of multi-species catches. Biological studies conducted along the Romanian coast have shed light on the condition of the local population. Between 2013 and 2020, sampling revealed an average fish length of approximately 11.4 cm and a mean weight of 14 g. The population displayed positive allometric growth (growth coefficient b = 3.08) and a healthy condition factor (K = 0.84), indicating that fish in Romanian waters are generally in good health, even if overall numbers remain limited [14,15,32].

3.3.3. Total Biomass Estimation

In the 30 hauls carried out with the pelagic trawl, on an area of 5445 km2, the average catch values were 0.001–1.259 t/km2. The maximum values were recorded in the sectors Chituc–Sahalin (0–30 m) and East Constanța—Mamaia Bay (0–30 m). The estimated biomass of the horse mackerel aggregations in the researched area was approximately 969.68 t (Figure 11 and Table 3).
The recent survey findings offer valuable insights into the spatial ecology (Figure 12) and mean catch distribution of T. mediterraneus along the Romanian coast. An analysis of depth-stratified data reveals clear habitat preferences and notable differences in biomass concentration that carry important implications for fisheries management. The most important result is the pronounced aggregation of horse mackerel biomass in waters shallower than 30 m (Figure 13). With approximately 858.58 tons, this zone holds nearly 90% of the total estimated biomass. This concentration indicates that shallow coastal areas are critical habitats, likely used for feeding, breeding, or juvenile development. The higher average catch per square kilometer (0.349 t/km2) further confirms that these inshore zones support the densest populations. In contrast, the 30–50 m depth range, despite covering a larger area (3.440 km2), contributed only 112.10 tons to the overall biomass. The mean catch density in this zone drops to just 0.022 t/km2, suggesting that deeper areas are used less intensively or seasonally. This disparity could reflect different environmental conditions, prey availability, or behavioral traits of the species.
The extrapolated biomass estimate of 969.68 tons offers a useful benchmark (Figure 14), but it should be viewed as a point-in-time indicator rather than a static value. This assessment, made for the first time in the last decade, offers an important view of the stock at the national level, but continuous monitoring and correlations with regional assessments are very important due to the migratory behavior of the species. Regular and standardized monitoring is essential to track changes in biomass distribution over time, particularly in the context of climate variability, changing sea conditions, or evolving fishing practices.
The line chart (Figure 15) illustrates annual fluctuations in horse mackerel landings over 14 years, offering insights into interannual variability and possible underlying ecological or fishery-related dynamics. Catch volumes demonstrate notable year-to-year fluctuations, ranging from a low of approximately 8 tons (2014) to a peak of over 50 tons (2023). This level of variability is characteristic of small pelagic species, which are sensitive to changes in environmental conditions, prey availability, and fishing efforts. A significant drop occurred in 2014, marking the lowest point of the entire time series. However, the fishery quickly rebounded in subsequent years, reaching a local peak around 2017. Another sharp increase is visible between 2022 and 2023, when catch levels more than doubled. These abrupt changes may be linked to shifts in water temperature or salinity, variability in plankton abundance (a key food source), or natural population cycles of horse mackerel [33,34]. The catch peak in 2023 represents the highest recorded value within the period analyzed. Although there is a slight decrease in 2024, the level remains relatively high compared to earlier years, suggesting that stock availability or fishing efficiency improved in recent seasons.

4. Discussion

The data presented regarding the average lengths by age group for the T. mediterraneus population in the Black Sea indicate slower growth in the early life stages compared to other studies in the region. Thus, at ages 0, I, and II, the average length values (9.5 cm, 11.5 cm, and 12.7 cm, respectively) are in the lower range of the intervals reported by other research, such as those conducted by Şahin et al. [7] or Şahin and Ceylan [8] (Supplementary Material Tables S1 and S2). However, starting from age III, the values become comparable or even higher, reaching 14.3 cm at age III and 17.8 cm at age V—one of the highest values reported for this age group, similar to the data from the study conducted by Samsun [10]. This model suggests an initially slower growth rate followed by acceleration in later years, which may reflect local ecological influences such as resource availability, environmental conditions, or selective pressure. The comparability of these data with those from other sources, such as Kutsyn [22] or Yankova [19], supports the relevance of the observations and contributes to a better understanding of variations in the growth of this species across different areas of the Black Sea (Supplementary Material Tables S1 and S2).
The present study provides a robust analysis of the length-weight relationship for T. mediterraneus in the Black Sea, with the largest sample among all compared studies (n = 3737). The equation coefficients for the combined sexes (a = 0.0068, b = 3.0806) and the determination coefficient (r2 = 0.9401) indicate a well-defined relationship with a positive allometric growth pattern (b > 3).
When compared to other regional studies, the results are very close to those reported by Yankova [19], Samsun et al. [9], or Şahin and Ceylan [8], who reported b values between 3.046 and 3.0938, all indicating proportional growth. In contrast, other studies, such as those by Kasapoğlu [5] or Dürrani [4], highlighted negative allometric growth, with b values below 2.93, suggesting slower weight development (Supplementary Materials Tables S1 and S2).
Therefore, the current study contributes significantly to the characterization of growth in the analyzed population from the Black Sea, providing reliable and comparable results that align with a coherent regional pattern and support the hypothesis of a general positive allometric growth trend of the species in this area.
Regarding horse mackerel stock and catch evolution in our study area, despite fluctuations, there is no consistent upward or downward trend over the full-time span on the North-Western Black Sea shelf. The data suggest a cyclical pattern rather than a linear trajectory, which is typical for small pelagics [35,36], and highlights the importance of adaptive management based on annual stock assessments [37].
The 2024 extrapolated biomass (estimated at approximately 1000 tons) provides a useful reference point. Yet, as previously mentioned, it should be interpreted as a snapshot rather than a fixed value. This is the first such assessment conducted in the past decade in Romanian waters, offering valuable insights into the horse mackerel stock at the national level. However, continuous monitoring and alignment with regional assessments are crucial, given the species’ migratory behavior. This is essential to detect changes in horse mackerel biomass distribution over time, especially in relation to variable climate and marine environment conditions [34,38].

5. Conclusions

The current study contributes significantly to the characterization of growth in the analyzed Mediterranean horse mackerel population from the Black Sea, providing reliable and comparable results that align with a coherent regional pattern and support the hypothesis of a general positive allometric growth trend of the species in this area. The spatial distribution of horse mackerel along the Romanian shelf reveals a clear pattern of coastal aggregation, highlighting the need for targeted and precautionary fisheries management. By aligning policy with ecological realities—particularly the species’ depth preferences—Romania can contribute to the sustainable use and conservation of this valuable Black Sea resource. Horse mackerel in the Black Sea, including Romanian coastal waters, is under clear pressure from overfishing. Although Romania’s direct impact is minimal, the country plays a vital role in monitoring, research, and the implementation of regional conservation frameworks.
The horse mackerel stock along Romania’s Black Sea shelf is best characterized today as overfished and fragmented, with high year-to-year catch volatility masking an overall depletion of biomass. To reverse this trend, depth-targeted closures, tighter effort controls in shallow coastal waters, and harmonized Black Sea management measures are urgently needed. Only by realigning fishing pressure with the species’ actual distribution—and by enforcing smaller, seasonal catch ceilings—can this small but ecologically important population be guided back toward sustainable levels.
Immediate measures for conservation are outlined as follows: GFCM Framework Alignment—harmonize Romanian measures with Black Sea riparian states through GFCM-led technical committees, sharing raw survey data and agreeing on synchronous closure periods when needed; Vessel Tracking—require all trawler vessels to operate with active VMS (Vessel Monitoring Systems) and electronic catch-weighing logbooks; Observer Coverage—deploy independent observers on at least 20% of all trips, prioritizing high-density fishing hotspots identified by prior surveys.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/fishes10080390/s1: Supplementary Materials. Variations in the growth of horse mackerel across different areas of the Black Sea (Table S1. Comparative studies regarding the age-length distribution for T. mediterraneus and Table S2. Previous literature indicates the result of the length-weight relationship for T. mediterraneus in different areas).

Author Contributions

Conceptualization, V.N.; methodology, C.P., A.Ț., G.Ț. and M.G.; software, C.P., A.Ț. and G.Ț.; validation, V.N.; formal analysis, M.N.; investigation, C.P., A.Ț., G.Ț., M.G. and M.N.; resources, C.P., A.Ț., G.Ț. and M.G.; data curation, M.N. and V.N.; writing—original draft preparation, C.P., A.Ț., G.Ț., M.G. and M.N.; writing—reviewing and editing, V.N.; supervision, V.N. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Fisheries Data Collection Program (yearly contracts). Additional investigations were performed in the frame of NIMRD’s NUCLEU Programs (INTELMAR and SMART-BLUE).

Institutional Review Board Statement

We hereby confirm that ethical approval was not required to perform animal studies, as all fish sampling by trawling conducting to the results reported in this paper was performed in compliance with the scientific fishing license NIMRD “Grigore Antipa” holds (Scientific Fishing License no. CT 0001 S/04.02.2025, issued by the Romanian National Agency for Fisheries and Aquaculture). The additional pound net horse mackerel samples were collected from fishing points along the Romanian coast (commercial catches).

Data Availability Statement

Data is contained within the article or Supplementary Materials.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Sampling map for horse mackerel at the Romanian coast (Dragoș Niculescu, NIMRD, “Grigore Antipa”).
Figure 1. Sampling map for horse mackerel at the Romanian coast (Dragoș Niculescu, NIMRD, “Grigore Antipa”).
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Figure 2. Sagittal otolith pairs of Mediterranean horse mackerel visualized under the stereomicroscope (transparent rings—blue, opaque rings—red).
Figure 2. Sagittal otolith pairs of Mediterranean horse mackerel visualized under the stereomicroscope (transparent rings—blue, opaque rings—red).
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Figure 3. Monitoring stations for pelagic trawl survey along the Romanian coast.
Figure 3. Monitoring stations for pelagic trawl survey along the Romanian coast.
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Figure 4. Sex ratio of T. mediterraneus individuals sampled at the Romanian coast.
Figure 4. Sex ratio of T. mediterraneus individuals sampled at the Romanian coast.
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Figure 5. Distribution of sampled T. mediterraneus individuals per station.
Figure 5. Distribution of sampled T. mediterraneus individuals per station.
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Figure 6. Distribution of sampled T. mediterraneus individuals per fishing gear.
Figure 6. Distribution of sampled T. mediterraneus individuals per fishing gear.
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Figure 7. Distribution of T. mediterraneus individuals analyzed by years and months.
Figure 7. Distribution of T. mediterraneus individuals analyzed by years and months.
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Figure 8. Sex distribution of T. mediterraneus on length groups.
Figure 8. Sex distribution of T. mediterraneus on length groups.
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Figure 9. Length-weight relationship of the sampled individuals (total, females, and males).
Figure 9. Length-weight relationship of the sampled individuals (total, females, and males).
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Figure 10. Age structure of horse mackerel (males, females, and combined sexes) at the Romanian coast.
Figure 10. Age structure of horse mackerel (males, females, and combined sexes) at the Romanian coast.
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Figure 11. Map of the spatial distribution of horse mackerel density (in tons/km2) across trawling areas along the Romanian coast.
Figure 11. Map of the spatial distribution of horse mackerel density (in tons/km2) across trawling areas along the Romanian coast.
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Figure 12. Mediterranean horse mackerel surveyed area by depth zone, Romanian coast.
Figure 12. Mediterranean horse mackerel surveyed area by depth zone, Romanian coast.
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Figure 13. Mediterranean horse mackerel mean catch per unit area by depth zone, Romanian coast.
Figure 13. Mediterranean horse mackerel mean catch per unit area by depth zone, Romanian coast.
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Figure 14. Mediterranean horse mackerel estimated biomass by depth zone, Romanian coast.
Figure 14. Mediterranean horse mackerel estimated biomass by depth zone, Romanian coast.
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Figure 15. Total annual catch of Mediterranean horse mackerel and trend line for the last three years, Romanian coast.
Figure 15. Total annual catch of Mediterranean horse mackerel and trend line for the last three years, Romanian coast.
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Table 1. Mean values and standard deviations of the total length (L), total weight (W), and Fulton index (K) by year.
Table 1. Mean values and standard deviations of the total length (L), total weight (W), and Fulton index (K) by year.
YearNL (cm) + SDW (g) + SDK + SD
20141208.79 ± 1.466.02 ± 2.490.86 ± 0.09
201510813.84 ± 1.2422.75 ± 5.660.84 ± 0.06
201622912.04 ± 1.7915.69 ± 6.210.86 ± 0.11
201724411.05 ± 2.7814.04 ± 9.810.88 ± 0.14
201818011.86 ± 1.8116.42 ± 8.630.91 ± 0.09
201932211.8 ± 2.1315.3 ± 8.460.85 ± 0.1
202031511.02 ± 2.1911.95 ± 7.480.8 ± 0.2
202124511.65 ± 1.5713.64 ± 6.220.83 ± 0.25
202228910.68 ± 2.0411.64 ± 7.610.85 ± 0.06
2023111511.19 ± 1.8612.4 ± 8.590.78 ± 0.11
202457011.26 ± 1.2712.9 ± 4.40.87 ± 0.09
Table 2. Age, sex, mean length, and weight of T. mediterraneus from the Romanian coast.
Table 2. Age, sex, mean length, and weight of T. mediterraneus from the Romanian coast.
AgeSexNL (cm)W (g)
0I717.794.01
F6219.667.50
M6319.577.16
Combined13239.527.15
IF70711.2112.26
M54411.0611.65
Combined125111.1412.00
IIF39812.8318.05
M33712.5416.78
Combined73512.7017.47
IIIF18814.6226.68
M13114.3525.65
Combined31914.5126.25
IVF5616.0236.21
M4515.8235.63
Combined10115.9335.95
VF318.3653.39
M517.1451.32
Combined817.6052.10
Table 3. Evaluation of horse mackerel aggregations (tons), in September–October 2024, in the Romanian area.
Table 3. Evaluation of horse mackerel aggregations (tons), in September–October 2024, in the Romanian area.
Depth Interval (m) 0–30 m 30–50 m Total
Researched area (km2) 2005 3440 5445
Catch variation (t/km2) 0.006–1.259 0.001–0.240 0.001–1.259
Mean catch (t/km2) 0.349 0.022 0.185
Biomass of fishing agglomerations (t) 858.58 112.10 969.68
Biomass extrapolated to the Romanian shelf (t) 969.68
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Păun, C.; Țoțoiu, A.; Țiganov, G.; Galațchi, M.; Nenciu, M.; Niță, V. Overview of a Keystone Small Pelagic Fish in the North-Western Black Sea: Biometry, Age and Stock Status of Horse Mackerel Trachurus mediterraneus (Steindachner, 1868). Fishes 2025, 10, 390. https://doi.org/10.3390/fishes10080390

AMA Style

Păun C, Țoțoiu A, Țiganov G, Galațchi M, Nenciu M, Niță V. Overview of a Keystone Small Pelagic Fish in the North-Western Black Sea: Biometry, Age and Stock Status of Horse Mackerel Trachurus mediterraneus (Steindachner, 1868). Fishes. 2025; 10(8):390. https://doi.org/10.3390/fishes10080390

Chicago/Turabian Style

Păun, Cătălin, Aurelia Țoțoiu, George Țiganov, Mădălina Galațchi, Magda Nenciu, and Victor Niță. 2025. "Overview of a Keystone Small Pelagic Fish in the North-Western Black Sea: Biometry, Age and Stock Status of Horse Mackerel Trachurus mediterraneus (Steindachner, 1868)" Fishes 10, no. 8: 390. https://doi.org/10.3390/fishes10080390

APA Style

Păun, C., Țoțoiu, A., Țiganov, G., Galațchi, M., Nenciu, M., & Niță, V. (2025). Overview of a Keystone Small Pelagic Fish in the North-Western Black Sea: Biometry, Age and Stock Status of Horse Mackerel Trachurus mediterraneus (Steindachner, 1868). Fishes, 10(8), 390. https://doi.org/10.3390/fishes10080390

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