Water and sediment quality parameters in the Chalan Beel, the largest wetland of Bangladesh

A study was conducted to investigate the status of the water and sediment quality in the Chalan Beel——a major fresh water fish reservoir of the country for a period of one year from July 2007 to June 2008. The mean values of water quality parameters(depth: 214.73±152.22 cm, temperature 27.68±4.26℃, transparency 123±82 cm, p H 9.7±0.47, total alkalinity 137±42 mg/L, conductivity 307±147 μs/cm, total dissolved solids 183±89 mg/L, ammonia-N 0.27±0.39 mg/L, nitrate-N 0.09±0.07 mg/L, phosphate-P 2.01±2.53 mg/L) and sediment quality parameters(p H 7.21±0.35, organic matter 2.59±0.52%, total nitrogen 0.09±0.04%, available phosphorus 5.4±3.6 Meq./100 g and exchangeable potassium 0.43±0.14 Meq./100 g) were within the range recommended for most of the inland fishes of Bangladesh. Although the water and sediment quality parameters except ammonia and phosphate are in the suitable range, the overall results suggest that better management techniques should be practiced in order to overcome the declining trend of associated aquatic life(fauna and flora) of this important fresh water body of Bangladesh.

A multidisciplinary method to assess the reproductive biology of Mystus bleekeri

The study aims to afford a deeper knowledge on reproductive biology of Mystus bleekeri from Surma River,Bangladesh in a multidisciplinary way.Though,the species is in demand as food and ornamental fish in Bangladesh but still now comprehensive details on reproductive biology of this species is scanty.Total 600 fish samples were derived from commercial catches from July 2018 to June 2019.Periodic differences in sex ratio,size distribution,condition factor(Kn),fecundity,gonadosomatic index and gonadal maturation cycle were assessed.The results showed 384(64%)female and 216(36%)male with an overall sex ratio of 1.77:1(female:male).Mean total length(TL)and body weight(BW)of all fish studied were 14.85±3.38 cm TL and 27.54±15.76 g,respectively.The Kn varied with length groups,the highest(1.45±0.23)and lowest(0.89±0.18)values obtained in 16.0-16.9 and 10.0-10.9 cm TL groups,respectively.The highest Kn was documented in October while the lowest was in January.Monthly GSI values showed two peaks in July and November for both the sexes.The fecundity was found to vary from 1120 to 14790 eggs with average value of 4968±3047 with 14.4-18.3 cm in TL and 19.97-34.7g in BW.The relationship of fecundity with TL and BW was F=1.385TL13.405,r^(2)=0.885 and F=5.201BW^(4.827),r^(2)=0.944.Partial behavior of spawning together with allochronic oocytes development has also been found through histology.The results of this study could be used for predicting the response of populations of fish in Surma River and/or other where to human interferences and environmental change.

Effects of temperature and diet on length-weight relationship and condition factor of the juvenile Malabar blood snapper(Lutjanus malabaricus Bloch & Schneider, 1801)

In this study we aimed to analyze the effects of water temperature and diet on the length-weight rela- tionship and condition of juvenile Malabar blood snapper Lutjanus malabaricus over a 30-d experimental period. The experiment was conducted in the laboratory using a flow-through-sea-water system. The fish were subjected to four different temperatures （22, 26, 30, and 34 ℃） and two diets （commercial pellet and natural shrimp）. Fish were fed twice daily. L. malabancus exhibited negative allometric growth （b〈3） at the beginning of the experiment （Day 0） at all temperatures and both diets except for 22 ℃ fed with shrimp, which showed isometric growth （b=3）. Conversely, at the end of the experiment （Day 30） fish showed isometric growth （b=3） at 30 ℃ fed with the pellet diet, indicating that the shape of the fish did not change with increasing weight and length, and a positive allometric growth （b〉3） at 30 ℃ fed with shrimp diet, which indicated that fish weight increases faster than their length. The rest of the temperatures represented negative allometric growth （b〈3） on both diet, meaning that fish became lighter with increasing size. The condition factors in the initial and final measurements were greater than 1, indicating the state of health of the fish, except for those fed on a pellet diet at 34 ℃. However, the best condition was obtained at 30 ℃ on both diets. Nev- ertheless, diets did not have a significant effect on growth and condition of juvenile L. malabaricus. The data obtained from this study suggested culturing L. malabaricus at 30 ℃ and feeding on the pellet or shrimp diet, which will optimize the overall production and condition of this commercially important fish species.