Investigation Some Biological Properties of Atlantic Mackerel Scomber scombrus Linnaeus, 1758 in the Sea of Marmara

NESciences, 2019, 4(2): 133-140 - RESEARCH ARTICLE – Investigation Some Biological Properties of Atlantic Mackerel Scomber scombrus Linnaeus, 1758 in the Sea of Marmara Habib Bal1* Dilek Türker2 Livestock Research Institute, Department of Fisheries, Bandırma, Balıkesir, Turkey Balıkesir University, Faculty of Science and Arts, Department of Biology, Balıkesir, Turkey 1 2 Abstract In this study, length-frequency, length-weight and length-length relationships and condition factors of Atlantic mackerel Scomber scombrus Linnaeus, 1758 were investigated. In 2016, a total of 163 individuals were examined by random sampling from commercial fishermen in the Sea of Marmara. It was determined that the total length distribution of the samples varied between 12.027.0 cm. The length-weight relationships were calculated as W=0.0040L3.2975 (r2=0.978) for females, W=0.0045L3.2537 (r2=0.973) for males and W=0.0042L3.2782 (r2=0.976) for all specimens. The t-test showed that the growth pattern was positive for all sex groups and for all samples (b˃3, P<0.05). The relationship between length-length for all sex groups was also found to be quite strong (mean value: r2=0.94; P<0.05). Fulton’s condition factor (K) was calculated as 0.938±0.11 for females, 0.909±0.10 for males and 0.947±0.09 for all samples. The sex ratio (F:M) of the population was found to be 1:0.94. Keywords: Length-weight relationship, length-length relationship, growth, condition factor. Article history: Received 26 February 2019, Accepted 10 May 2019, Available online 16 May 2019 Introduction Atlantic mackerel Scomber scombrus Linnaeus, 1758 is a pelagic species that forms swarms with rapid swimming ability and extends over a wide area of the Atlantic Ocean (Whitehead et al., 1984; Sette, 1943; Anderson, 1976). It is one of the important target species of Portuguese fishermen with the Atlantic Ocean coast (Martins, 2007). It is reported that they reach 26 cm at the end of the * Corresponding Author: Habib Bal, e-mail: Natural and Engineering Sciences 134 second year and 33 cm at the end of the fifty year (Anderson, 1973; Isakov, 1973; Stobo & Hunt, 1974). In the researches, it was found that the first maturity length was between 25-30 cm. Spawning period reported that twice a year in spring and summer close to the continental shelf, mainly in the middle part of the Atlantic Ocean (O’Brien et al., 1993; MacKay, 1967). They feed on copepods, amphipods, shrimp and decapod (Bigelow & Schroeder, 1953). Mackerel has an important role in prey-predator relations in Atlantic Ocean. There are many predators feed on mackerel such as Sharks, Atlantic cod and Sea birds (Smith & Gaskin, 1974; Scott & Tibbo, 1968; Maurer & Bowman, 1975; Bowman & Michaels, 1984). The conservation of the existing habitats of all fish species in the marine ecosystem depends on the development of sustainable fisheries management models with an ecosystem approach. Length-weight, length-length relationships, condition factors are important foundation stones for fisheries, ecology, physiology and fisheries management (Gonçalves et al., 1997). Thanks to the created growth equations comparison of environments where species are available, as well as helping to monitor vital cycles (Binohlan & Pauly, 1998; Radkhah & Eagderi, 2015). In this study, length-weight, length-length, relationships, and condition factor and sex ratio of the mackerel S. scombrus Linnaeus, 1758 samples obtained from Sea of Marmara were determined. It is foreseen that the research results will contribute to the studies to be done in Sea of Marmara, where sampling is carried out and in the other seas of our country and to the sustainable management of stocks. Materials and Methods The samples were taken randomly from fishery boats catch by purse seine nets in the Sea of Marmara (North Kapıdağ Peninsula) in 2016 (Figure 1). The fish brought to the laboratory were measured in total length (TL), fork length (FL) and standard length (SL) in cm. Total weight (TW) was measured on a digital scale with a precision of 0.01 g. Estimation of length-weight relationships was calculated using W=a.TLb (Ricker, 1979). This can be expressed in linear form after logarithmic transformation by log W=a+blogTL where W is the total weight (g) and TL is the total length (cm), a intercept, b is slope. The t-test was used to determine the growth type (Sokal & Rholf, 1987). The length-length relationship was calculated using liner regression analysis (TL=a+bFL, FL=a+bSL, SL=a+bTL). Condition factor (K)=(W/L3)*100 formula using was calculated for female, male and all samples (Froese, 2006). In order to determine the sex ratio, gonads of all samples were examined by direct observation method. For all descriptive statistics and graphical drawings Excel was used (Microsoft Excel® 2010). Natural and Engineering Sciences 135 Figure 1. Sampling area. Results Length-frequency Freguency (N) The total length of the specimens varied between12.0-27.0 cm. However, the individuals included in the 18 cm length class were densely (26.99%) represented in the population (Figure 2). 50 45 40 35 30 25 20 15 10 5 0 12 14 16 18 20 22 24 26 28 30 Total length (cm) Figure 2. Total length frequency distribution of all S. scombrus specimens from Sea of Marmara. Length-weight relationship For all samples of S. scombrus (n=163), the length-weight relationship was calculated for male and female (Figure 3). It was determined that growth was positive allometric with t test (b˃3; P<0.05). Natural and Engineering Sciences 136 Figure 3. Length-weight relationship of S. scombrus specimen. The relationship parameters for all samples were given in Table 1. Table1. Length-weight relationship parameters of mackerel fish. Length (cm) Sex F M F+M 79 84 163 Weight (g) Mean±SD 19.3±0.79 18.1±0.76 18.7±0.79 n Min-max. 12.0-25.7 12.2-27.0 12.0-27.0 Min-max. 20.0-179.9 19.6-177.1 19.6-179.9 Mean±SD 78.3±4.78 64.2±4.39 71.0±4.58 a 0.0040 0.0045 0.0042 95%CI b of b 3.29 3.09-3.31 3.25 3.17-3.30 3.27 3.14-3.29 SE(b) 0.051 0.041 0.047 r² 0.978 0.973 0.976 n: Number of individuals; F: female; M: male; SD: standard deviation; a: intercept b: slope; r 2: regression coefficient: CI: confidence intervals. Length-length relationships As the length-weight relationship, length-length relations were also found to be quite high (P<0.05). The lowest regression coefficient was found to be r 2=0.89 between fork length and standard length in the female samples. While the highest relationship was found to be r2=0.99 in the male samples between fork length and standard length. Other calculated length-length relationships parameters were given in Table 2. Table 2. Length-length relationships parameters of mackerel fish Sex n Female 79 Male 84 Total 163 Length-length relationships parameters equations a b r2 TL=a+bFL 0.89 0.68 0.96 FL=a+bSL 1.21 0.89 0.89 SL=a+bTL 0.25 0.86 0.91 TL=a+bFL 1.51 0.83 0.97 FL=a+bSL 0.03 1.06 0.99 SL=a+bTL 1.43 0.78 (...truncated)