Corresponding author: Sinan Mavruk ( smavruk@cu.edu.tr ) Academic editor: Alexei Orlov
© 2021 Dursun Avşar, Sinan Mavruk, Hacer Yeldan, Meltem Manaşirli.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Avşar D, Mavruk S, Yeldan H, Manaşirli M (2021) Population dynamics of an emergent invasive fish, striped piggy, Pomadasys stridens (Actinopterygii, Perciformes, Haemulidae) in the Gulf of İskenderun, north-eastern Mediterranean. Acta Ichthyologica et Piscatoria 51(1): 13-21. https://doi.org/10.3897/aiep.51.63320
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The striped piggy, Pomadasys stridens (Forsskål, 1775), is a recent invasive fish species in the eastern Mediterranean. Although its population dynamics was investigated in detail in its natural distribution area, the western Indian Ocean, an important data gap still exists in the Mediterranean. This study was carried out to determine the growth, mortality, and the length–weight and length–length relations of invasive striped piggy right after its establishment in the area. Samples were collected seasonally between April 2014 and December 2015 by using bottom trawl from 10 and 20 m depth contours off the north-western coast of the Gulf of Iskenderun. After the length, weight, and sex of fish were recorded, sagittal otoliths were extracted and examined for age determination. Then length–length, length–weight, and length at age relations, growth performance, and mortality rates were calculated for both sexes and pooled data. In the study, a total of 1131 individuals were investigated, the total length of which ranged between 7.3 and 18.9 cm. The mean length was 12.32 ± 0.11 cm. There was no significant difference between the length–weight relation (LWR) parameters of sexes and pooled data. The overall LWR was found to be TW = 0.0113 * TL^3.096 in all specimens. The von Bertalanffy growth parameters were not significantly different between males and females. The model parameters for both sexes were L∞ = 22.01 cm, K = 0.22 years–1, t0 = –1.30 years. The growth performance index (Ø′) was calculated as Ø′ = 2.03. For combined sexes, the total, natural and fishery mortality rates were Z = 1.14 years–1, M = 0.66 years–1, and F = 0.48 years–1, respectively. The exploitation rate of the stock was found to be E = 0.42. The growth performance of the invasive striped piggy population was determined to be similar to the ones reported from the Gulf of Suez where was the closest natural distribution area of the species. Although striped piggy is proper for human consumption and commercially caught in its native range, its fishery has not yet been established in the Eastern Mediterranean and we found that there was insufficient fishery pressure on the invasive population.
Exploitation, growth, Lessepsian fish, Levant Basin, mortality
Striped piggy, Pomadasys stridens (Forsskål, 1775), naturally distributed in the western Indian Ocean extending from the Pakistani coasts to the east African coasts including the Red Sea (
The Gulf of İskenderun is an important fishery ground (
Striped piggy is a small sized demersal fish species inhabiting in shallow waters with sandy and muddy bottom structure feeding on crustaceans and small fishes (
Samplings were seasonally performed in April, July, October, and December 2014 and 2015 off Yumurtalık, Gulf of Iskenderun (Fig.
In total, 1134 specimens were investigated in the context of the study. To determine the morphometric characteristics; total length (TL), fork length, standard length, body width, head width, body depth, head depth, and total weight were measured. Lengths and weights were measured to the nearest millimeter using a digital caliper, and to the nearest 0.01 g using a digital scale, respectively. The sex of specimens was determined by a visual examination when the gonads are ripe or with a stereomicroscope (Olympus SZ 60), otherwise.
The age of fish was determined by otolith investigations following the methods suggested by
The sex-based changes of length frequency distribution were tested using Kolmogorov–Smirnov test. The season and sex-based variations of the mean TL were analyzed using two ways ANOVA. TL–length and TL–girth relations were fitted using ordinary linear regressions. TL–weight (W) relations were fitted using the allometric equation given by
W = a ∙ Lb
The von Bertalanffy (
where; Lt, is the total length at age t, L∞ is asymptotic length, K is growth coefficient and t0 is theoretical age at zero length. Then the generation time was calculated using LN[3]/K equation given by
In order to determine the growth performance,
Ø′ = Ln K + 2 ∙ Ln L∞
The total mortality rate was calculated from the linearized catch curve method based on
Ln M = –0.0152 – 0.279 ∙ Ln L∞ + 0.6543 ∙ Ln K + 0.463 ∙ Ln T
where T [°C] shows the mean annual water temperature of the study area which is assumed as 23°C. After the total and natural mortality were determined, fishing mortality was calculated from equation
Z = F + M
Then the exploitation level (E) of the stock was calculated using E = F / Z equation given by
In the study, a total of 1131 individuals were examined, 445 of which were males and 471 of which were females. In 215 specimens, sex could not be determined. The total length of females ranged between 7.8 and 18.9 cm, and of males between 9.1 and 18.6 cm. The overall mean length and weight values were 12.32 ± 0.11 (95% confidence interval) cm and 29.19 ± 0.85 g, respectively. The overall mean length and weight of females were found to be 12.79 ± 0.18 cm and 32.85 ± 1.46 g, and of males were found to be 12.38 ± 0.16 and 29.18 ± 1.21 g. Length-frequency distributions of males and females were significantly different than each other (D = 0.12, P < 0.01). Females were slightly larger than males (P < 0.01). In addition, seasonal variations of the mean length were found to be significant (P < 0.001). Length frequency distributions by seasons and sexes are given in Fig.
Linear relations between the TL and fork length, standard length, head and body width, as well as maximum girth and girth at opercle are given in Table
Regression parameters of morphometric relations calculated for striped piggy, Pomadasys stridens from the Gulf of Iskenderun, by sexes and pooled data.
Total length–fork length | Total length–head width | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Par. | Ste. | t | sig. | Par. | Ste. | t | sig. | ||||
Male | a | 0.254 | 0.071 | 3.581 | <0.001*** | Male | a | 0.172 | 0.067 | 2.551 | 0.011* |
b | 0.921 | 0.006 | 162.513 | <0.001*** | b | 0.835 | 0.005 | 154.901 | <0.001*** | ||
r 2 | 0.984 | r 2 | 0.982 | ||||||||
Female | a | 0.411 | 0.092 | 4.472 | <0.001*** | Female | a | –0.040 | 0.124 | –0.320 | 0.749ns |
b | 0.909 | 0.007 | 128.037 | <0.001*** | b | 0.852 | 0.010 | 89.239 | <0.001*** | ||
r 2 | 0.972 | r 2 | 0.944 | ||||||||
Overall | a | 0.267 | 0.056 | 4.801 | <0.001*** | Overall | a | 0.065 | 0.060 | 1.083 | 0.279ns |
b | 0.920 | 0.004 | 206.002 | <0.001*** | b | 0.844 | 0.005 | 174.770 | <0.001*** | ||
r 2 | 0.974 | r 2 | 0.964 | ||||||||
Total length–standard length | Total length–girth at opercle | ||||||||||
Par. | Ste. | t | sig. | Par. | Ste. | t | sig. | ||||
Male | a | –0.736 | 0.099 | –7.451 | <0.001*** | Male | a | –0.397 | 0.085 | –4.677 | <0.001*** |
b | 0.286 | 0.008 | 35.365 | <0.001*** | b | 0.199 | 0.007 | 28.720 | <0.001*** | ||
r 2 | 0.769 | r 2 | 0.672 | ||||||||
Female | a | –0.601 | 0.084 | –7.121 | <0.001*** | Female | a | –0.152 | 0.077 | –1.972 | 0.049* |
b | 0.275 | 0.007 | 40.890 | <0.001*** | b | 0.180 | 0.006 | 29.257 | <0.001*** | ||
r 2 | 0.825 | r 2 | 0.673 | ||||||||
Overall | a | –0.691 | 0.053 | –13.138 | <0.001*** | Overall | a | –0.271 | 0.047 | –5.799 | <0.001*** |
b | 0.280 | 0.004 | 64.760 | <0.001*** | b | 0.188 | 0.004 | 48.986 | <0.001*** | ||
r 2 | 0.816 | r 2 | 0.706 | ||||||||
Total length–body width | Total length–maximum girth | ||||||||||
Par. | Ste. | t | sig. | Par. | Ste. | t | sig. | ||||
Male | a | –1.434 | 0.169 | –8.474 | <0.001*** | Male | a | –0.798 | 0.146 | –5.450 | <0.001*** |
b | 0.773 | 0.014 | 57.049 | <0.001*** | b | 0.612 | 0.012 | 52.190 | <0.001*** | ||
r 2 | 0.881 | r 2 | 0.861 | ||||||||
Female | a | –1.095 | 0.152 | –7.185 | <0.001*** | Female | a | –0.612 | 0.140 | –4.386 | <0.001*** |
b | 0.745 | 0.012 | 63.270 | <0.001*** | b | 0.600 | 0.011 | 55.597 | <0.001*** | ||
r 2 | 0.896 | r 2 | 0.868 | ||||||||
Overall | a | –1.265 | 0.094 | –13.508 | <0.001*** | Overall | a | –0.691 | 0.085 | –8.150 | <0.001*** |
b | 0.757 | 0.008 | 100.746 | <0.001*** | b | 0.604 | 0.007 | 88.740 | <0.001*** | ||
r 2 | 0.900 | r 2 | 0.875 |
The parameters of length–weight relations calculated for males, females and pooled data are given in Table
Parameters of length–weight relations calculated for striped piggy, Pomadasys stridens, from the Gulf of Iskenderun, by sexes and pooled data.
Sex | N. of samples | a | b | r 2 |
---|---|---|---|---|
Male | 445 | 0.0116 ± 0.09 | 3.087 ± 0.053 | 0.967 |
Female | 471 | 0.0123 ± 0.13 | 3.064 ± 0.069 | 0.941 |
Overall | 1131 | 0.0113 ± 0.18 | 3.096 ± 0.038 | 0.958 |
The maximum age determined for both sexes was found to be seven years. It was determined that the first age group was dominant for both sexes and pooled data constituting 62.5% of males and 52.7% of females. The von Bertalanffy growth parameters calculated for male, female, and pooled data were given in Table
Von Bertalanffy growth parameters with confidence intervals (95%) and growth performance indices calculated for males, females and combined data in this study and previous studies.
Ref. | Location | Sex | L ∞ [cm] | K [year-1] | t o [year] | Ø′ |
---|---|---|---|---|---|---|
ps | Mediterranean | M | 20.99 (± 2.56) | 0.24 (± 0.07) | –1.31 (± 0.46) | 2.03 |
ps | Mediterranean | F | 21.60 (± 2.04) | 0.23 (± 0.06) | –1.25 (± 0.37) | 2.01 |
ps | Mediterranean | C | 22.01 (± 1.63) | 0.22 (± 0.04) | –1.30 (± 0.25) | 2.03 |
1 | Mediterranean | M | 17.96 | 0.34 | –1.54 | 2.04 |
1 | Mediterranean | F | 32.70 | 0.10 | –1.14 | 2.01 |
1 | Mediterranean | C | 22.52 | 0.19 | –2.05 | 1.98 |
2 | Suez Canal | C | 16.64 | 0.51 | –0.65 | 2.15 |
3 | Suez Canal | C | 23.15 | 0.51 | –0.29 | 2.44 |
4 | Gulf of Suez | C | 20.37 | 0.28 | –1.33 | 2.07 |
5 | Gulf of Suez | C | 20.60 | 0.19 | –2.40 | 1.91 |
6 | Persian Gulf | C | 26.00 | 0.70 | –0.65 | 2.68 |
7 | Persian Gulf | C | 24.54 | 0.14 | –4.41 | 1.93 |
Mean length values, lower (CIL), and upper (CIU) limits of 95% confidence intervals calculated from von Bertalanffy growth equation.
Male | Female | |||||
---|---|---|---|---|---|---|
Age | CIL TL [cm] | Mean TL [cm] | CIU TL [cm] | CIL TL [cm] | Mean TL [cm] | CIU TL [cm] |
I | 8.50 | 8.75 | 8.92 | 8.39 | 8.82 | 9.08 |
II | 11.18 | 11.38 | 11.48 | 11.14 | 11.48 | 11.64 |
III | 13.26 | 13.49 | 13.60 | 13.21 | 13.58 | 13.76 |
IV | 14.92 | 15.17 | 15.30 | 14.86 | 15.25 | 15.45 |
V | 16.23 | 16.53 | 16.70 | 16.13 | 16.57 | 16.81 |
VI | 17.23 | 17.61 | 17.87 | 17.09 | 17.62 | 17.95 |
VII | 17.99 | 18.48 | 18.85 | 17.79 | 18.45 | 18.90 |
The total mortality (Z), natural mortality (M), fishing mortality (F), and exploitation rate (E) calculated for each sex of the P. stridens are given in Table
Here, we investigated the population dynamical parameters of an invasive fish species striped piggy (Pomadasys stridens) soon after its establishment in the study area. In the context of the study, the mean length of investigated individuals was 12.32 ± 0.11 cm ranging from 7.3 to 18.9 cm. In previous studies, the maximum length was reported as 23.5 cm by
Contrary to the above-mentioned hypothesis, the studies performed in the Gulf of Suez and the Suez Canal reported maximum length values close to our study which were 19 cm (
Although, the first specimens of the striped piggy were collected in 2009 in our study area (
Although the observed the mean length of females was found to be larger than males, no statistically significant difference was observed between the von Bertalanffy growth parameters and length at age values of sexes. Therefore, the presence of larger females in the sampling area may indicate differences between the distribution patterns of sexes. This should be investigated in further studies.
In the context of our study, b values of length–weight relation were calculated between 3.064 and 3.096. A slightly positive allometric growth profile was observed for males and pooled data; however, isometric growth was detected in females of the striped piggy population in the Gulf of Iskenderun. In general, negative allometry is prevalent for striped piggy in the studies performed in both native and introduced range of the species. From the northern Persian Gulf,
Although the asymptotic length (L∞) is a theoretical size of the infinitely old fish, its value is influenced by the number of large sized fishes in the sample. Therefore, it does not represent a reliable measure of the maximum growth potential of an average fish in a population if the population is not sampled representatively, including all available size classes. Moreover, its value directly influences the growth parameter (K), e.g., an overestimated L∞ value causes underestimation of K. Accordingly, the asymptotic length (L∞), growth coefficient (K), and theoretical age at zero length (t0) of striped piggy varied in a wide range in the both native and introduced distribution area. For example, in the Suez Canal,
In spite of the above-mentioned methodological obstacles in making direct comparisons among the growth parameters, the growth determined in different studies can be compared using the growth performance index (Ø′) of
The striped piggy populations inhabit the Suez Canal seem to have better growth performance with 2.15 (
The establishment and dispersal of an invader is a complicated process depending on a lot of intrinsic and extrinsic factors from the biological traits of the species to climate change (
The striped piggy is an invasive species, the first observation of which has been reported in 2009 in the study area (
Although striped piggy is suitable for human consumption and has economic importance in its native range (
This study was performed with the financial support of Çukurova University-Turkey, Scientific Research Coordination Unit with project number FYL-2015-3850.