Lagocephalus suezensis, Clark & Gohar, 1953

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 : 8-10

Lagocephalus suezensis

The most invasive species, L. suezensis , were abundant at all shelf stations with bottom depths of 10–to- 125 m ( Fig. 6 ). Maximum average biomass was 300 kg /km 2 ( Fig. 6A ), and maximum abundance was 11,024 ind/km 2 ( Fig. 6B ). This species was abundantly present in all regions, particularly in R 4.

Regional differences were determined statistically for biomass distribution (p = 0.012). This difference was due to much higher biomass in R 4 (62.95 ± 16.31 kg /km 2) than in the other regions (2.75–10.09 ± 7.40 kg /km 2, Fig. 7A ). The biomass was significantly different among seasons and bottom depths (p =0.448 and 0.269, respectively). Seasonal biomass varied from 1.59 ± 9.34 kg /km 2 in August to 19.57 ± 8.41 kg /km 2 in October ( Fig. 7B ). Biomasses were tended to decrease from shallower waters (24.32 -30.62 ± 10.04 kg /km 2) to deep waters (<2.00 kg/ km 2) ( Fig. 7C ). Depths greater than 125 m were virtually devoid of L. suezensis .

Overall, there were no significant differences in abundance among regions, seasons, and bottom depths (p = 0.084, 0.191, and 0.133, respectively, Fig. 6B ). Abundance was significantly higher (2294.60 ± 762.64 ind/ km 2) in R4 than in the other regions (from 119.26 ± 355.58 ind/km 2 in R2 to 573.61 ± 334.44 ind/km 2 in R1 ). Maximum mean abundance occurred in October (1157.20 ± 376.87 ind/km 2), while minimum abundance occurred in August (56.24 ± 418.87 ind/km 2). Abundance decreased with bottom depth from high abundance in shallower waters (> 1000 ind/km 2 from 10 to 25 m and low abundance at greater depths (<100 ind/km 2 from 50–125 m).

Dominance of females over males did not differ among regions, seasons, and bottom depths (p = 0.611, 0.091, and 0.925, respectively). Regions R1 and R2 had sex ratios <2, whereas the ratios were higher in R3 (58.95 ± 33.85) and R4 (20.43 ± 61.79). The ratio was significantly higher (144.50 ± 49.03) in August than in the other seasons. Females predominated in bottom depths of 25 m (53.34 ± 33.82), then decreased to 0.14 ± 56.09 at 75 m; thereafter, no females were observed in the seaward direction .

Total length of L. suezensis varied between 4 cm and 18.5 cm during the year ( Fig. 8A ). The COST function estimated an optimum size class (bin size) of 0.52 cm for total length distribution of the species ( Fig. 8B ). The KDF determined five cohorts in total length: 4.0–5.5, 5.5–10.2, 10.2–14.3, 14.3–17.0, and> 17 cm ( Fig. 8A ). The third cohort was the dominant cohort in the population.

The lengths of the species were significantly different among regions, seasons, bottom depths, and sex (p = 1.3×10 -14, 2.5×10 -19, 2.0×10 -9, and 2.2×10 -27, respectively). The lengths were significantly shorter in R 1 (10.21 ± 0.19 cm) than the other regions (11.91 ± 0.18 to 12.44 ± 0.22 cm) ( Fig. 9A ). The shortest lengths differed significantly in October (10.59 ± 0.14 cm) and the longest individuals were present in February (13.01 ± 0.26 cm) ( Fig. 9B ). The lengths were significantly longer at bottom depths of 75 m (12.64 ± 0.44 cm) than lengths in bottom depths of 25 m (10.79 ± 0.15 cm) and 50 m (10.26 ± 1.13 cm, Fig. 9C ). Females were significantly longer (12.37 ± 0.15 cm) than males (11.35 ± 0.14 cm); however, lengths of 8.35 ± 0.40 cm could not be sexed, and juveniles were 4.93 ± 0.96 cm in length ( Fig. 9D ).

Individual weight varied between 1.10 and 82.73 g. The weight changed significantly with the regions, seasons, bottom depths, and sex (p = 2.8×10 -11, 4.1×10 -16, 5.6×10 -6 and 7.5×10 -20, respectively). Individuals were significantly heavier in R 4 (27.50 ± 1.13 g) than in R 1 (16.88 ± 1.01 g) and R 2 (23.17 ± 1.52 g). The weight in May (25.39 ± 1.07 g) was significantly higher than in October (18.32 ± 0.75 g) and lower than in February (29.97 ± 1.35 g). Individuals were significantly lighter in weight in bottom depths of 25 m (19.59 ± 0.81 g) than at 10 m (25.64 ± 0.83 g) and 75 m (26.78 ± 2.34 g). Females were heavier (27.40 ± 0.81 g) than males on average (20.88 ± 0.75 g).

The total length relationship with weight of L. suezensis regressed significantly for the females, males, and total individuals ( Fig. 10 ). The slopes of the regression lines were not significantly different from the isometric slope of 3 for total and female individuals, but significantly different for males (n = 522, t = -1.761; n = 280, t = -2.138; n = 239, t = -1.928, respectively) at p <0.05. This species grew in an isometric type of length-weight relationship.

Constants for the length-weight regression equations were significantly different by regions, bottom depths, and sex, including juveniles and individuals of undefined sex (p = 5.0×10 -7, 0.0022, and 0.0008, respectively); there was no significant difference among the seasons. The slopes and intercepts were not significantly different between males and females at p <0.05. The slope was significantly lower in R 2 than in the other regions, whereas they were not significant in R 1 and R 3 ( Table 2). Regional differences were not estimated by post-hoc tests for length-weight relationships. Like the differences among sex (excluding undefined sex and juveniles), depth-wise differences in slopes and intercepts of length-weight relations were not significantly different; greater depths were excluded due to insufficient number of L. suezensis individuals.

Figures

Fig. 6: Distribution of (A) biomass, (B) abundance (circles square-rooted), and (C) percent sex composition of Lagocephalus suezensis in time (months) and space (regions and depths). Seasonal colors on the figures are: blue = May 2014, green = August 2014, red = October 2014, and magenta = February 2015. Colors for sex composition: females follow seasonal color scheme, males are black, and juveniles are white in seasons.

Fig. 7: Post-hoc test (least significant difference, LSD) of biomasses in kg/km2 of Lagocephalus suezensis among (A) regions, (B) seasons (1 = May, 2 = August, 3 = October, and 4 = February), and (C) bottom depths. Circle = mean, horizontal bar = standard deviation, blue mark = to be tested for biomasses among regions, months and depths, red = significant difference, gray = no significant difference between vertical discrete gray lines.

Fig. 8: Lagocephalus suezensis: (A) length-frequency histogram with solution of the KDF in a size class interval estimated by (B) COST function. Asterisk * = optimum length class interval in cm.

Fig. 9: Post-hoc test (least significant difference, LSD) in total length in cm of Lagocephalus suezensis among (A) regions, (B) seasons (1 = May, 2 = August, 3 = October, and 4 = February), (C) bottom depths, and (D) sex (F = female, M = male, NI = sex not identified, and J = juvenile). Circle = mean, horizontal bar = standard deviation, blue mark = to be tested among the regions, months, and depths, red = significantly different, gray = not significantly different between vertical discrete gray lines.

Fig. 10: Length-weight relationships of males (blue), females (pink), and pooled data (red) of Lagocephalus suezensis.