Length-weight, condition factors, age, and growth of Scomber japonicus (Houttuyn, 1782) from the Egyptian Mediterranean Sea

Length-weight, condition factors, age, and growth of Scomber japonicus were investigated. The specimens were collected monthly from Alexandria landing centers during 2017 and caught using night purse seine ranging from 12.9 to 34.4 (TL) (average, 21.00 ± 4.1) cm and from 15.10 to 391.49 (TW) (average, 92.81 ± 59.17) g. The exponent “b” of the length-weight relationships were “>3” for females (b = 3.24), males (b = 3.25), and all samples (b = 3.15), reflecting the positive allometric mode of growth. Moreover, the positive allometric mode of growth was observed for the relationship between forked length (FL) and standard length (SL) with weight. The annual average of absolute condition was 0.89 ± 0.06, with the highest value during April (0.96 ± 0.05). The annual average relative condition was 1.01 ± 0.06, with the highest value (1.10 ± 0.10) during August. The absolute condition (Kc) increased with the increasing length. However, the relative condition showed an inverse trend. The age of S. japonicus was determined using length-frequency analysis giving five age groups at mean lengths of 14.09, 19.29, 23.82, 28.25, and 31.76 cm for the 1^st, 2^nd, 3^rd, 4^th, and 5^th age groups, respectively. The third age group (III) was the most frequent one (38.89%). The estimated growth parameters were L∞ of 38.11 cm; W∞, 534.74; K, 0.33 year-1; growth performance (Ø), 2.68; and t-max, 8.89 years. In conclusion, the present data reflected a good stock status with the suitability of living habitats. Further continuous monitoring is recommended for better fishery management and conservation.