Lagocephalus sceleratus (Gmelin, 1789)

Mutlu, Erhan, Meo, Ilaria de & Miglietta, Claudia, 2020, Spatio-temporal distribution of pufferfish (Tetraodontidae) along the Turkish coast of the Mediterranean Sea Abstract, Mediterranean Marine Science 22 (1), pp. 1-19 : 5-6

Lagocephalus sceleratus

Lagocephalus sceleratus was found at seafloor depths of 10, 25, and 75 m in all regions. The highest biomass was 135 kg /km 2 in February and the highest abundance was 150 ind/km 2 in October and February, particularly obvious in R 1 ( Fig. 2 ). Populations were dominated by males May–October, while females were abundant mainly in February.

Biomass did not differ significantly among regions, seasons, and bottom depths ( ANOVA, p = 0.675, 0.373, and 0.780, respectively).The highest biomass was highest in R1 (X ± SD: 5.43 ± 3.10 kg /km 2) and lowest in R3 (0.03 ± 3.16 kg /km 2, Fig. 2 ). Biomass increased from a minimum in May (0.13 ± 3.34 kg /km 2) and August (0.46 ± 3.79 kg /km 2) to a maximum in October (1.74 ± 3.41 kg /km 2) and February (7.97 ± 3.59 kg /km 2). Biomass increased with depth: 0.97 ± 4.12 kg /km 2 at 10 m, 3.69 ± 4.43 kg / km2 at 25 m and 9.72 ± 4.27 kg /km 2 at 75 m ( Fig. 2A ).

Abundance of L. sceleratus did not differ significantly among regions, seasons (months), and depths (p = 0.252, 0.215, and 0.269, respectively). Maximum abundance was found in R1 (17.35 ± 5.28 ind/km 2) and R4 (13.20 ± 12.04 ind/km 2) and minimum abundance in R2 (3.43 ± 5.61 ind/km 2) and R3 (4.92 ± 5.38 ind/km 2). Abundance increased gradually from May (1.77 ± 5.73 ind/km 2) through August (3.88 ± 6.51 ind/km 2), and experienced abrupt spikes in October (13.90 ± 5.86 ind/km 2) and February (16.95 ± 6.16 ind/km 2). In contrast to biomass, abundance decreased with depth from 20.40 ± 6.91 ind/ km 2 at 10–25 m to 11.36 ± 7.16 ind/km 2 at 75 m ( Fig. 2B ).

Sex ratios did not differ significantly among regions, seasons, and depths (p = 0.338, 0.718, and 0.909, respectively); however, an increase in p values from west (0.09 ± 0.22) to east (1.00 ± 0.44) was observed suggesting strength of dominance of the females. Females were mostly absent in May and August, whereas the ratio of females:males was twice as high in October (0.50 ± 0.25) than in February. The ratio had the same value at 10 and 25 m (0.34 ± 0.29 – 0.33 ± 0.29) and the lowest value at 75 m (0.16 ± 0.36, Fig. 2C ).

The total length of L. sceleratus varied between 5.4 and 62.5 cm. The COST function estimated an optimum length class interval (i.e., bin size) of 14.28 cm. More than half of the total number of fish were longer than 15 cm. The KDF assessed three cohorts from the total length frequency histograms. The number of cohorts was fixed at four size classes (<20, 20–33, 33–50, and> 50 cm); one class had no length measurements because the bin size increased to 30 classes. The length differed significantly among seasons, depths, and sexes but not regions (p = 0.019, 0.0001, 0.0002, and 0.103, respectively); however, post-hoc tests showed that mean lengths were significantly smaller (7.03 ± 5.80 cm) in R 3 than in the other regions (20 cm in R 1, 29 cm in R 2, and 25 cm in R 4) which were not significantly different from each other. The length in February was significantly longer (25.12 ± 2.83 cm) than that in October (10.63 ± 3.39 cm). The lengths in the pairs between other seasons were not significant between seasons (TL; 15 and 18 cm). The total length was significantly longer (33.03 ± 3.51 cm) at 75 m bottom depth than similar lengths (13.24 ± 3.25 cm) at the other two depths (10 and 25 m). Lengths of female individuals were significantly longer (36.16 ± 4.23 cm) than that of males (18.27 ± 2.49 cm).

Individual weights of the fish ranged from 2.04 to 3700 g during the year. There were significant differences in weights among bottom depths and sex (p = 0.004 and 0.001, respectively). There were no significant differences in individual weights by region. The weights varied between a minima (5.26 ± 299.02 g) in R 3 and a maxima (440.81 ± 366.22 g) in R 2. The increase in individual weights did not increase significantly from 65.51 ± 50.59 g in May to 88-94 g in August–October to 481.05 ± 149.20 g in February. However, the weights were significantly heavier (855.64 ± 185.22 g) at depth (75 m) than the weights (39–143 g) at coastal depths (10–25 m). Individual mean weights of females were significantly higher (1168.5 ± 213.15 g) than that of males (149.44 ± 125.71 g).

Length-weight (L-W) relationship was estimated for males, females, and pooled data ( Fig. 3 ). Fish showed isometric growth (b = 2.89) because the slopes were not significantly different from the constant (b = 3) for males, females, and remaining individuals (n = 44, student t = -0.075; n = 30, t = -0.279, and n = 8, t = -0.160, respectively). The length-weight relationship was not significantly different between sexes ( ANCOVA, p = 0.307). There was no significant difference in the length-weight regressions among regions (mean log 10 -transformed intercept, a = -1.66 ± 0.15 (X ± SE) and slope, b = 2.79 ± 0.13). Slope and intercepts of the regression changed significantly with seasons and bottom depths (p = 0.005 and 0.019, respectively). The slopes were 3.447, 2.847, 2.791, and 3.032 in R1 , R2 , R3 , and R4 , respectively, whereas the intercepts were 0.0031, 0.0163, 0.022, and 0.0111, respectively. The slopes were 2.827 at 10 m bottom depth, 2.787 at 25 m, and 3.004 at 75 m depth and the intercepts were 0.0189, 0.0226, and 0.0125, respectively.

Figures

Fig. 2: Distribution of (A) biomass, (B) abundance (circles square-rooted), and (C) percent sex ratio of Lagocephalus sceleratus in time (months) and space (regions and depths). Seasonal colors on the figures are: blue for May 2014, green for August 2014, red for October 2014, and magenta for February 2015. Colors for sex ratio: females follow seasonal color scheme, males are black, and juveniles are white in seasons.

Fig. 3: Length-weight relationships of males (blue), females (pink), and pooled data (red) of Lagocephalus sceleratus.