Some aspects of fisheries ecology in Thomas dam, Kano Nigeria
The diversity, length-weight relationship and condition factor of fish species of Thomas Dam, Dambatta Kano were studied fortnightly between November, 2016 and February, 2017. Fish species were collected using line nets, cast nets, hooks and traps; weighted to the nearest gram and standard length measured to the nearest centimeter. A total 313 fishes comprising of 7 families and 11 species were identified. Family cichlidae was predominant(36.7%) represented by T. zilli (21.7%) and Oreochromis niloticus (15.0%). Family Claridae was the second highest in abundance with 24.7% represented by C. garipienus (8.9%), Clarias anguillaris (8.9%) and Heterobranchus sp. (6.7) while Protopteridae represented by Protopterus sp. was the least with 2.8%. Species diversity determined by Shannon Weiner index of diversity, Evenness index and Margalef’s index which revealed the highest value at site A of 1.45, 0.78 and 2.66 while site D had the least with 1.1, 0.64 and 1.72 respectively. Growth coefficient b of the length weight relationship ranged from 0.9 to 2.7 inHeterobranchussp. andClariasgariepinus. The b values of the all the fish species is less than the mean exponent b =3, indicating a negative allometric growth. Condition factor (K) for all fish species differed significantly (P<0.05) as the highest value was recorded in Mormyrus rume and Heterobranchus sp. with 1.9 each and the least were C. gariepinus and C. anguillaris, protopterus sp. and Labeo senegalensis each had 0.9 values respectively. The mean condition factor (K) by species was greater than 1, indicating that the fish species were not in good condition.
KEY WORDS: Species diversity, Length-weight relationship, Condition factor, Allometric growth, Thomas Dam, Dambatta Kano State.