Study on parameters of giant sea catfish

	NTU scientists have carried out research on biological and reproductive parameters of giant sea catfish Arius thalassinus Ruppell, 1837 along the coastline of Kien Giang province.
	The aim of this study is to collect scientific data on biological and reproductive parameters of giant sea catfish, which provide scientific information for seed production that help to reduce the pressure of over exploitation on this species. Research conducted from April, 2010 to April, 2012.

Results of the research:

- Morphology and taxonomy: D I, 6 – 8; P I, 9 – 12; V 6; A 13 – 17; C 20 - 30. L_m/L_h = 44%, E_d/L_h = 13%, L_m/L_s = 13%, E_d/L_s = 4%, D_e/L_s = 14%, L_h/L_s = 29%, H_b/L_s = 18% and L_v/L_s = 14%.

- Total length and body weight: Total length of the giant sea catfish exploited was between 448 and 1119 mm (mean±SD, 778.02 ± 133.88 mm). Body weight of the giant sea catfish exploited was between 890 and 15495 g, with average weight of 5145.98 ± 2640.80 g. Fishing season for giant sea catfish with high productivity was between May and July. The relationship between total length and body mass was estimated as equation: W_t = 0.00000877L_t^3.0121452 (R² = 0.96682027). Von Bertalanffy growth rate equation was determined as L_t = 117.6 (1 – e^{- 0.52t}). Growth performance index (ø’) was 3.857. The longevity of giant sea catfish was 5.16 years.

	*- Gastrointestinal tract and stomach content:* Gut length was from 590 to 2750 mm, with average of 1445.82 ± 317.12 mm. Relative length of gut was ranged of 0.98 to 2.46 (mean±SD, 1.76 ± 0.29). Fullness index (FI) was mostly between 0 and 1 (73.74%). Gastro-somatic index varied between 0.21 and 2.82 (mean±SD, 1.21 ± 0.51. The stomach emptiness index (CV) was 37.07%.	Eggs of the giant sea catfish
	The preys found the in stomach of giant sea catfish were 23 species, including 14 species of fish (60.87%), 6 species of crustaceans (26.09%), 1 species of mollusk (4.35%) and 2 species of starfish and holothurian (8.69%). The appearance frequency of feed groups was 60.46% for fish, 38.46% for mollusk, 32.97% for crustaceans, and 24.18% for starfish and holothurians group. The appearance frequency of feed types was 38.46% for squid, 19.78% for holothurians, 16.48% for cardinal, and 10.99% for horsehead fish. These results indicate that giant sea catfish is a carnivorous fish species.

	*- Reproductive indices:* Egg diameter was from 3 to 20 mm. Maturation coefficient of this fish was from 0.45 to 12.60% and average 3.49 ± 3.35%. Fulton coeffiecient was between 578.10^-6 and 1428.10^-6 (mean±SD, 957.10^-6 ± 117.10^-6), while Clark coefficient was between 514.10^-6 and 1340.10^-6 (mean±SD, 862.10^-6 ± 97.10^-6).	Feed of the giant sea catfish
	The smallest length and age at the first maturation in females was 779 mm and 1.89 years old, respectively. The absolute fecundity was from 85 to 153 eggs per female (mean±SD, 104.50 ± 26.27 eggs/female), and the relative fecundity was 0.0115 to 0.0215 egg per g female (mean±SD, 0.0165 ± 0.0043). Spawning season of giant sea catfish was from February to July, mainly between March and May.