Abstract
A series of investigations were performed to assess the impacts of fish sanctuaries on some important water quality parameters, bottom soil properties, abundance and diversity of plankton, macro-benthic organisms, diversity and yields of fish and prawn and length groups of Labeo calbasu (Kalibaus), Punctius sarana (Sar puti), Spereta seenghala (Guzzi ayre) and Wallago attu (Boal) in sanctuary treatments of Mohi river (T1, T2 and T3) and control treatment of Ghor river (T4); and sanctuary treatments of Dopi beel (T1 and T2) and control treatment of Chota-bora beel (T3) in Mithamain Upazilla of Kishoregonj district during 2004 and 2005. In the treatments of river, water depth and dissolved oxygen recorded in sanctuary treatments (T1, T2 and T3) during study period showed significant (P<0.05) difference from control (T4). Mean total abundance (±SE) of plankton were 13761.08±1362.48, 13969.08±1,598.27,13218.25± 1,735.44 and 8458.75±1458.38 in 2004 and 17840.33±1,262.29, 1897.00 1473.89, 16601.75±1473.78 and 12492.33± 1402.13 cellsl'' in 2005, respectively in T1, T2, T3 and T4 and exhibited significant (P<0.05) difference with control (T4) in both the years. Values of Shannon diversity indices decreased from H=0.82, 0.60, 0.61 and 0.55 in 2004 to H=0.56, 0.54, 0.55 and 0.50 IN 2005, respectively in T1, T2, T3 and T4. Mean total abundance (No.m2) of macro-benthic fauna recorded in T1, T2, T3 and T4 were 1725.92 ± 88.19, 1694.92 ± 92.35, 1221.42± 112.32 and 765.50 ± 53.1 during 2004 and 1357.58 ± 150.33, 1385.25 ± 144.10, 1185.50 ± 134.97 and 376.67 ± 42.72 during 2005 respectively. Mollusca were the largest group in all the treatments. Species diversity increased in sanctuary treatments (T1, T2 and T3) during 2005 than 2004, but decreased in control treatment (T4). Mean total abundance of macro-benthic organisms recorded in sanctuary treatments were significantly (p<0.05) higher than control (T4) in both the years. Mean values of total N and organic carbon in T1, T2 and T3 were also significantly higher (p<0.05) than the mean value of T4. Available P (ppm) fluctuated but increased in final sampling in all the treatments. Mean total yields of fish and prawn in four treatments T1, T2, T3 and T4 were 5256.74±271.23, 4815.75±33.64, 3636.24+658.28 and 204.15±30 kgha', respectively during 2005. Yearly combined yield (271.40 kgha') of all the groups and habitats obtained in Mohi river during 2005 was higher than the yield (210.50 kgha'') recorded in this river and Ghor river (204.15 kgha1) during 2004. The highest value of Shannon diversity indices was found in T1 (H=1.06). Comparatively larger fishes were recorded in sanctuary treatments (T1, T2 and T3) than control. Among all the parameters of water, total hardness showed maximum significant (22 highly and 8 simply) relationship with all the groups of fish and prawn. Again among all the treatments T, showed more significant (53 highly and 20 simply) relationships than T2, T4 and T3. In treatments of beels, mean total abundance of plankton recorded were 16380.67±2575.68, 14970.75±2,437.70 and 10188.75+ 2389.43cells' in 2004 and 23497.67±2751.55, 23996.25±3,252.36 and 12706.92+ 2484.85cells1 in 2005, respectively in T1, T2 and T3. Plankton population was significantly higher (p<0.05) in sanctuary treatments than the control. Shannon diversity indices of plankton abundance were not changed during 2005 in T, and T2 except control (T3) in which diversity was increased. During 2004 and 2005, 12 groups of macro-benthic fauna were detected in sanctuary treatments (T, and T2) and 10 groups in contro. Mean total abundances of macro- benthic fauna recorded were 1783.92 + 240.03, 1822.08 ± 229.08 and 829.83 ± 36.30 m2 in 2004 and 1787.17 ± 245.89, 1966.25 ± 266.16 and 693.58 ± 77.93 m2 during 2005, respectively in T1, T2 and T3. Macro-benthic abundance was significantly higher (p<0.05) in T, and T2 than T3. Mean total yields of 11 groups of fish and prawns were 5613.70±975.30, 8307.65±1168.05 and 112.59±17.31 kgha', respectively in T2, T, and T3. The total yields of fish and prawn in sanctuary treatments (T, and T2) were significantly higher than control (T3). Yearly combined yield of all the groups and habitats of Dopi beel obtained in 2005 (3,643.21 kgha'') was four times higher than the base line yield of 2003 (812.02 kgha1). Again combined yield of Dopi beel recorded in 2005 was more than thirty two times higher than the yield obtained in Chota-bora beel (control). Higher length groups of S. seenghala, W. attu, P. sarana and L. calbasu were recorded in T, and T2 of Dopi beel than control beel (T3). Among all the parameters of water total hardness (21 highly and 3 simply); total phytoplankton and total plankton (11 highly 13 simply) showed maximum significant relationship with all the groups of fish and prawn. Again among all the treatments T, showed higher number of significant (43 simply) relationships than T2 (33 highly and 3 simply) and T3 (17 simply and 10 highly).