Biology and some aspects of life history of Pla Dang (Kryptopterus bleekeri Gunther, 1864) Pisces:Siluridae

Studies on biology and some aspects of life history of fishes are hard work consuming a lot of time and energy as well as being a tiresome piece of work. Eventhough they are challenge works for any one who likes to study, but there are still a very few number of researchers interested in this type of work. Pla Dang (Kryptopterus bleekeri), however is an economic fish of Thailand. Thus, it must be studied in order to gain basic information that could be used in fishery management, conservation as well as in aquaculture. Results of the study could be concluded as follows: 1) Studies on integument, skeleton, muscular, digestive, secretory, reproductive, respiratory, circulatory, neural and endocrine systems were performed by dissecting specimens; fresh and preserved ones in formalin and/or in alcohol. The results were contained in this thesis; 2) The diagnostic characters (as compared with Pla Nam Ngern) are:- a longitudinal black streak along the base of anal fin, caudal and anal fins with black rims while Pla Nam Ngern has no black streak and rims on such fins. Pla Dang has 13-14 branchiostegal rays while the second one has 15-16 branchiostegal rays; 3) Pla Dang are carnivorous and nocturnal fish. The stomach contents were comprised of small fish (54 percent), shrimp (29 percent), worm and aquatic insects (3 percent) and grass (14 percent). The relationships between total length and intestinal length could be represented by the following equation:- LogLt = 0.810979+0.519894 LogLi. The relationships between total length and weight of small fish, male and female fishes could be represented by the following equations:- LogW = -2.6067258+3.1947752 LogL, LogW = -1.9650108+2.7317475 LogL and LogW = -2.23373+2.91954 LogL, respectively. Finally, the relationships between total length and fecundity, and body weight and fecundity could be represented by the following equations:- LogF = -2.65932+4.5022 LogL and LogF = 0.8243525+1.42732837 LogW, respectively; 4) ecology of the Chao Phraya River, her habitats, some biological parameters and fisheries at sites of the study of Pla Dang were also done.