Studies on the biology and aquaculture potential of feral catfish Heterobranchus bidorsalis (Geoffroy St. Hilaire 1809) (Clariidae)

Abstract

Haematological profile of Heterobranchus bidorsalis (Geoffroy St. Hilaire 1809) was determined. Haematocrit values, haemoglobin concentrations, erythrocyte and leucocyte counts, mean cell haemoglobin concentration, sodium and potassium ions concentrations were 24.75±1.23%, 5.43±0.25 g/100 ml, 1.99±0.52 10⁶/mm³ and 7.25±0.60 10⁴/mm³, 22.11±0.77%, 802.52±36.97 and 83.54±5.05 mg/1, respectively.

H. bidorsalis fingerlings were subjected to a range of salinities, 0, 3, 6, 9, 12 and 15 ppt. The optimum salinity range for survival and good growth performance was determined as 0–3 ppt. Survival was >85% from 0–9 ppt with no significant differences (P>0.05), but decreased progressively as salinity increased.

Qualitative and quantitative assays of digestive enzymes in the different regions of H. bidorsalis guts revealed an array of carbohydrases, proteases and lipases. Enzyme activity was restricted to the stomach, duodenum and ileum with fewer enzymes recorded in the stomach. The pattern of distribution and relative activity of enzymes correlated with its euryphagous diet.

Parasitological examinations conducted on the skin and internal organs of H. bidorsalis yielded a variety of parasites which included three protozoans, two monogeans, six digeneans, four cestodes, two nematodes, two annelids and four copepods. No acanthocephalan infection was detected. Protocephalus sp. (Cestoda) and Allocreadium sp. (Trematoda) had the highest prevalence (>81%) followed by digenean metacercaria (35%).

The implications of these results in relation to the aquaculture potential of this catfish is discussed.

Key Words:

• haematological characteristics
• salinity tolerance
• digestive enzymes assay
• parasite fauna
• feral catfish
• H. bidorsalis