Preliminary study on age, growth and reproduction of Mustelus mustelus (Elasmobranchii: Carcharhiniformes: Triakidae) inhabiting the Gulf of Iskenderun, north-eastern Mediterranean Sea

Abstract

Ozcan E.I., Başusta N. 2018. Preliminary study on age, growth and reproduction of Mustelus mustelus (Elasmobranchii: Carcharhiniformes: Triakidae) inhabiting the Gulf of Iskenderun, north-eastern Mediterranean Sea. Acta Ichthyol. Piscat. 48 (1): 27-36.Background. Shark populations within the eastern Mediterranean are declining due to overfishing. Unfortunately, our knowledge on the biology of sharks and specifically dogfishes within eastern Mediterranean is extremely limited due to the lack of landings. Mustelus mustelus (Linnaeus, 1758) is one of such deficiently known cartilaginous fishes and the relevant information on its age and growth in the eastern Mediterranean is missing. The understanding of growth and reproductive behaviour is important for management and conservation of this species. The presently reported study was intended to determine age, growth, and some reproductive parameters of Mustelus mustelus collected in the Gulf of Iskenderun, the north-eastern Mediterranean Sea. Materials and methods. In this study, a total of 155 Mustelus mustelus were caught in the north-eastern Mediterranean Sea between March 2012 and October 2015. Fish age was determined based on band counts of sectioned vertebrae. The periodicity of band pair formation was examined using the marginal increment analysis. Growth parameters for all specimens were then determined by fitting the observed and the length-at-age data using the von Bertalanffy Growth Equation. The size and age at which 50% of both sexes reached maturity was estimated by a logistic model for maximum likelihood process and the gonadosomatic index was determined.Results. The total length and weight of the specimens examined ranged from 44.3 to 162.6 cm and from 241.3 to 12 060 g, respectively. The presently reported study provides new maximum lengths (162.6 cm) for M. mustelus from the north-eastern Mediterranean. The fish studied represented age groups from 0 through 25. The observed sex ratio was 1 ÷ 1.04 (females ÷ males). Von Bertalanffy growth parameters were estimated to be L ∞ = 195.13 cm, W ∞ = 20 060 g, K = 0.06, and t 0 = −4.27 for all specimens. Length-weight relation was found to be W = 0.0027L 3.0054(R 2 = 0.98) and 95% confidence intervals of b = 2.936-3.075, t-test P < 0.05. All studied specimens of M. mustelus represented isometric growth (b = 3). Condition factor ranged from 0.148 to 2.87 for females and from 0.103 to 1.024 for males. The length at 50% maturity and the age at 50% maturity were 109 cm and 8 in females and 92 cm and 7 in males, respectively. It was observed that mean GSI values were low in September and July, reaching a maximum in January to February. Conclusion. The results of this study could give useful insight for management plans and conservation of M. mustelus in the Mediterranean coast of Turkey.

Contrasting life‐history traits of two sympatric smooth‐hound species: implication for vulnerability

“…In both species, the L 50 values reported were smaller in the Gulf of Gabès ( M. mustelus : males: 97.1 cm, females: 117.2 cm, Saïdi et al ., ; M. punctulatus : males: 81.4 cm, females: 95.6 cm, Saïdi et al ., ) than those in the northern Adriatic Sea. Similar results were obtained for M. mustelus in the Gulf of Iskenderun in Turkey ( L 50 of the males: 92 cm, L 50 of the females: 109 cm; Ozcan & Başusta, ). This result is in line with a latitudinal pattern of maximum size and size at sexual maturity observed in the Mediterranean Sea in the small‐spotted catshark Scyliorhinus canicula L 1758 (Finotto et al ., ) and, among the few other sharks for which data are available, in the starspotted smooth‐hound Mustelus manazo Bleeker 1855 in the Pacific Ocean (Yamaguchi et al ., ).…”

“…Indeed, the former present a larger maximum size and size at maturity than the latter. Data on maximum age and age at maturity are available only for M. mustelus (Ozcan & Başusta, ). Larger maximum sizes and sizes at maturity may be related to higher maximum age and age at maturity; nonetheless, the lack of data for M. punctulatus does not allow comparisons of maximum age, growth rate and age at maturity between the species.…”

Some Growth Parameters of Capoeta umbla (Heckel, 1843) Population Living In The Pülümür River

“…When the t-test results was used for the significance condition of the regression coefficients, it was identified that length data could be used in highly reliable to estimate weight (Özcan and Başusta, 2018). Condition factor was calculated for sexes (Table 2) and all age-groups.…”

Age and growth of the phaeton dragonet, Synchiropus phaeton (Actinopterygii: Perciformes: Callionymidae), from the Gulf of Iskenderun, north-eastern Mediterranean, Turkey

“…The regression analysis has shown that fish length had a highly significant correlation with weight (P < 0.001). The t-test results indicated that length data could be used to estimate weight in high reliability (Ozcan and Başusta 2018). Condition factor.…”