Biology and population dynamics of the freshwater puffer fish, Tetraodon lineatus (Linnaeus, 1758), from the River Nile, Aswan, Egypt

A fresh water pufferfish Tetraodon lineatus in Egypt has limited information available. A total of 350 specimens were collected monthly from the river Nile, Aswan (2019). Specimens were 13.5–38.5 cm in total length with an average of 22.16 ± 5.02 cm and a total weight of 61.7–1456 g with an average of 339.86 ± 248.85 g. The length-weight relationship showed negative allometric growth, and both absolute and relative conditions decreased after March towards September, represents the spawning period. The sex ratio of 1 male to 1.28 females showed the predomination of females (56.23%) over males (43.77%) over the year. Males dominated the first length classes of 14–19 cm. The gonadosomatic index (GSI) was elevated from April to August, with its highest peak in June, and the unimodal curve indicated spawning once per year. The hepatosomatic index showed an inverse trend against the increase of GSI. Length at maturity was 18.7 cm for males and 18.2 for females. The lifespan of the fish was determined by the counting the growth rings of vertebrae No 3 was five years for both sexes at mean lengths of 14.5, 21.2, 26.3, 31.2, and 34.2 cm for 1st, 2nd, 3rd, 4th, and 5th, years respectively. Age group III was the most abundant followed by age group II. Asymptotic length was 46.29 cm, condition was 0.242 year−1, and to was −0.609 year−1, growth performance was 2.71, and longevity was 11.78 years. Our results are among the first biology and population dynamics data on the freshwater pufferfish in Egypt, and they indicate a satisfactory growth rate and ability to live longer than their age at maturity. These data could be utilized as the basis for scientific studies of physiology and toxicology, and useful in further management.