Lengths, length-length relationships and condition factor of Indian catfish Gagata cenia (Hamilton, 1822) in the Padma River, Bangladesh

This study described some biological parameters including lengths, length-length relationships and Fulton’s condition factors of Gagata cenia in the Padma River of Bangladesh, based on 1120 specimens collected from May to November, 2012. Maximum 39.78% female fishes were belonging to the length category of 55-60 mm whereas 51.06% male were belonging to 50-55 mm.The highest mean total lengths were found 66.51±10.28 mm (combined sex), 70.12±09.49 mm (female) and 61.08±09.45 mm (male) in the month of June. Similar findings are also presented for standard length, fork length, body depth, dorsal length, pectoral length, pelvic length and anal length. Linear relationships were also studied among mentioned lengths. Strong positive correlations were observed in all cases. Speraman’s Rank test indicated that there was a strong, positive correlation between total length and condition factor in female, which was statistically significant (rs=0.210, P=0.044). In male, there was no significant correlation between these two (rs=0.167, P=0.262). The Mann-Whitney U-test showed that the female individuals had the highest condition factor (Mean rank of 79.76). There was a statistically significant differences in the Fulton’s condition factor between males and females (two tailed, Mann-Whitney U = 1324)

Fishes of the river Padma, Bangladesh: Current trend and conservation status

The Padma River is one of the longest rivers and it is believed to be an important spawning and feeding ground for riverine fish species of Bangladesh. This study was conducted from February 2013 to January 2014 and with a view to revealing the diversity of fish fauna in the river. A total of 71 species were recorded belonging to 10 orders, 26 families and 54 genera. The most dominant fish order was Cypriniformes contributing 28 species in 16 genera. Cyprinidae was most dominant family contributing 23 species in 16 genera. Four alien species were found. Twenty eight species have been considered threatened by IUCN Bangladesh. These fishes were belonging to the following categories, Vulnerable (13%), Endangered (18%) and Critically Endangered (8%). Comparing the results with the previous findings, it was revealed that the species diversity have declined in the Padma River over time. Considering all the findings it is concluded that the Padma River could be considered a refuge for conservation of threatened freshwater fishes of Bangladesh. The conservation efforts should ensure minimization of anthropogenic impacts, especially the fishing pressure and introduction of alien invasive species

An overview of the traditional rice-prawn-fish farming in Kalia of Narail district, Bangladesh

This study was conducted in Narail district, Bangladesh between January and June, 2012; with a view to describing the status of rice- prawn-finfish based aquaculture practices. Average area of plots was 0.55±0.44 ha, of which mean ditch area was 4.35±2.02% of total land. All farmers dry their plots and made renovation prior to start of a new growing season followed by liming and fertilization. No standard stocking density was maintained, prawns were stocked at 15895 PL/ha, whereas fin fishes at 1551 seeds/ha. Commercial feed was applied in all the plots. Production of prawn, stocked and non-stocked fin fishes were found 380.34±155.25 kg/ha; 713.65±352.99 kg/ha and 51.73±24.55 kg/ha respectively. Average cost and income for fish culture were 120514.07±36758.35 BDT/ha and 232497.48±76594.80 BDT/ha respectively. Average rice production was 4229.78±856.71 kg/ha. Low growth and high mortality of PL; scarcity, high and uprising price of feeds; and floods were identified as the major problems

Do temperature and water depth influence microcrustacean hatching responses from floodplain wetland sediments?

Microcrustacea in ephemeral wetlands produce dormant eggs to escape prolonged dry conditions. These eggs can hatch on inundation, although in most cases not all eggs hatch during a single wetting event. Incomplete hatching can reflect bet-hedging strategies, but also the presence or absence of environmental cues that stimulate hatching. This study examines the effects of environmental cues likely to change for wetlands in the future, namely, temperature and water depth. Surface sediments collected from dry anabranches of the Macintyre River floodplain (eastern Australia) were inundated under two temperature regimes (warm and cool) in microcosms of two depths (shallow and deep). Hatched microcrustacea were sampled for 6 weeks. The abundance and assemblage composition of microcrustacea varied by temperature but not by depth. Although the total abundance was greater under warm conditions, the effect of temperature diminished over time. Temperature also had a greater effect on non-ostracods, with 144% more non-ostracods being hatched under warm than under cool conditions. Thus, changes to temperature during inundation periods arising from global climate change or river regulation are likely to influence the abundance and composition of microcrustacean assemblages, especially among non-ostracods, which will influence food availability for larval and juvenile native fish and, hence, recruitment

The Effects of Flood History and Environmental Cues on Microcrustaceans Hatching from Floodplain Sediment and the Predictions of the Impact of Water Resource Development and Climate Change on Microcrustacean Hatching Response

Microcrustaceans are an important component of the dryland river systems. They play a crucial role in maintaining trophic links between microbial, primary producers and higher consumers, primarily larval and juvenile fish. Due to the high variability in dryland river systems, microcrustaceans produce dormant eggs to survive prolonged dry periods, and hatch when the subsequent rewetting in the waterbody stimulates the diapausing eggs to break their dormancy. There are many factors, including physical, chemical, biological, and environmental cues that influence hatching patterns, active or adult communities in the waterbody and subsequently the dormant egg banks. Flood history is an important hydrological factor which has the potential to influence microcrustaceans’ egg bank composition in the dryland river soil which has not been investigated much in Australian dryland river systems. In addition to these factors, dryland river systems are also subject to anthropogenic alteration because of water resource development (WRD), and climate change which changes hydrological and temperature regimes in floodplain wetlands. However, the predicted influences of WRD and climate change on microcrustacean communities has not been explored widely. The aim of this PhD research project is to examine ecosystem responses to hydrological events. Specifically, the research examines: how a flood pulse event stimulates the hatching and emergence of microcrustaceans that persist through dry periods as desiccation resistant eggs. This research has four main objectives. These are to determine: a. how inundation frequency and duration influence abundance and community structure of emerging microcrustaceans; b. how water temperature and water depth act as potential environmental cues acting to influence the abundance and community structure of emerging microcrustaceans; c. how flood history and environmental cues might interact to further influence emergence patterns; d. how changes to inundation frequency and duration, temperature and depth arising from water resource development and climate may have influenced and may continue to influence emergence patterns and hence extant microcrustaceans assemblages in these systems. This study has been conducted in the Macintyre River which drains the Border Rivers catchment in south-eastern Australia and a typical of Australian allogenic lowland, dryland river system. This study determined that flood history variables such as annual return interval (ARI) and time since last flood can influence egg bank composition, with study also found more frequent flooding having a negative effect on the number of microcrustaceans hatching from the egg bank. However, the duration of inundation was found to be the most crucial factor in determining the abundance and composition of the hatched microcrustacean assemblage from egg bank. With regard to environmental cues for hatching, temperature was found to have a significant effect on the number and assemblage composition of microcrustacean hatching from sediment, with warmer temperatures resulting in a higher number of hatchlings. Importantly, temperature may have a greater effect on the hatching numbers of nonostracods compared to ostracods. However, there does not appear to be any significant effect of water depth on microcrustacean hatching. The composition of the egg bank and the hatching response of microcrustaceans are influenced by various factors, which interact to drive spatial variation in egg banks across the floodplain. The variation in egg bank composition is affected by both predictable spatial variation between shallow and deep areas within sites and unexplained spatial variation among sites. The interaction between factors influencing egg bank composition and microcrustacean hatching response is also influenced by temperature, and this interaction mainly affects the assemblage composition of non-ostracod microcrustaceans. Therefore, any changes in temperature and inundation duration can affect microcrustacean community composition and abundance. The flood pulse exerts a major influence on the structure and function of floodplain river systems However, the flood pulse has been, and continues to be, altered by water resource development (WRD) and climate change. This study predicts that WRD has greater individual impact on microcrustaceans hatching than climate change. However, the combination of WRD and climate change has the strongest impact on microcrustacean hatching. This prediction was made based on the relationships between the duration and temperature of flooding and microcrustacean hatching established in laboratory trials. In conclusion, this study highlights the critical influence of flood duration and temperature on hatching patterns of microcrustaceans from inundated sediments. Thus, changes to temperature during inundation periods arising from global climate change or river regulation are likely to influence the abundance and composition of microcrustacean assemblages, especially among non-ostracods, which will influence food availability for larval and juvenile native fish and hence recruitment. Notably, this study helped us to predict how the changes in temperature and inundation period due to WRD and climate change may influence microcrustacean communities and abundance hence the ecological integrity of dryland river systems

Lengths, length-length relationships and condition factor of Indian catfish Gagata cenia (Hamilton, 1822) from the Padma River, Bangladesh

This study described some biological parameters including lengths, length-length relationships and Fulton’s condition factors of Gagata cenia in the Padma River of Bangladesh, based on 1120 specimens collected from May to November, 2012. Maximum 39.78% female fishes were belonging to the length category of 55-60 mm whereas 51.06% male were belonging to 50-55 mm.The highest mean total lengths were found 66.51±10.28 mm (combined sex), 70.12±09.49 mm (female) and 61.08±09.45 mm (male) in the month of June. Similar findings are also presented for standard length, fork length, body depth, dorsal length, pectoral length, pelvic length and anal length. Linear relationships were also studied among mentioned lengths. Strong positive correlations were observed in all cases. Speraman’s Rank test indicated that there was a strong, positive correlation between total length and condition factor in female, which was statistically significant (rs=0.210, P=0.044). In male, there was no significant correlation between these two (rs=0.167, P=0.262). The Mann-Whitney U-test showed that the female individuals had the highest condition factor (Mean rank of 79.76). There was a statistically significant differences in the Fulton’s condition factor between males and females (two tailed, Mann-Whitney U = 1324)

Risking lives for living: a study on underwater fishing in the Padma River, Bangladesh

Different types of fishing methods and gears are being employed across the globe including Bangladesh. This study describes the underwater fishing method in the Padma River- one of the three largest rivers in Bangladesh. Standardised efforts have been made for collecting data of interest between September 2016 and May 2017. Two types of underwater fishing, with or without using oxygen cylinders, were recorded. Mean duration of fishing per effort was higher (by 382%) when fishermen used oxygen cylinders. Mean water depth of fishing sites was also higher when oxygen cylinders were used. Three species of finfish (Rita rita, Sperata seenghala and Labeo calbasu) and one freshwater prawn species (Macrobrachium dayanum) have been identified in the catch. The catch was dominated by M. dayanum in both fishing types (27 ± 9.3 [with oxygen] and 15 ± 5.2 [without oxygen]). However, all the number of caught fish species varied significantly among different sampling months in both fishing methods (P < 0.001) except L. calbasu in fishing with oxygen cylinder. A number of health issues of the fishermen were also recorded

Risking lives for living: a study on underwater fishing in the Padma River, Bangladesh

Different types of fishing methods and gears are being employed across the globe including Bangladesh. This study describes the underwater fishing method in the Padma River- one of the three largest rivers in Bangladesh. Standardised efforts have been made for collecting data of interest between September 2016 and May 2017. Two types of underwater fishing, with or without using oxygen cylinders, were recorded. Mean duration of fishing per effort was higher (by 382%) when fishermen used oxygen cylinders. Mean water depth of fishing sites was also higher when oxygen cylinders were used. Three species of finfish (Rita rita, Sperata seenghala and Labeo calbasu) and one freshwater prawn species (Macrobrachium dayanum) have been identified in the catch. The catch was dominated by M. dayanum in both fishing types (27 ± 9.3 [with oxygen] and 15 ± 5.2 [without oxygen]). However, all the number of caught fish species varied significantly among different sampling months in both fishing methods (P < 0.001) except L. calbasu in fishing with oxygen cylinder. A number of health issues of the fishermen were also recorded. Keywords: Fishing; Padma River; hand fishing; underwater fishing

An overview of the traditional rice-prawn-fish farming in Kalia of Narail district, Bangladesh

This study was conducted in Narail district, Bangladesh between January and June, 2012; with a view to describing the status of rice- prawn-finfish based aquaculture practices. Average area of plots was 0.55±0.44 ha, of which mean ditch area was 4.35±2.02% of total land. All farmers dry their plots and made renovation prior to start of a new growing season followed by liming and fertilization. No standard stocking density was maintained, prawns were stocked at 15895 PL/ha, whereas fin fishes at 1551 seeds/ha. Commercial feed was applied in all the plots. Production of prawn, stocked and non-stocked fin fishes were found 380.34±155.25 kg/ha; 713.65±352.99 kg/ha and 51.73±24.55 kg/ha respectively. Average cost and income for fish culture were 120514.07±36758.35 BDT/ha and 232497.48±76594.80 BDT/ha respectively. Average rice production was 4229.78±856.71 kg/ha. Low growth and high mortality of PL; scarcity, high and uprising price of feeds; and floods were identified as the major problems

An overview of the traditional rice-prawn-fish farming in Kalia of Narail district, Bangladesh

This study was conducted in Narail district, Bangladesh between January and June, 2012; with a view to describing the status of rice- prawn-finfish based aquaculture practices. Average area of plots was 0.55±0.44 ha, of which mean ditch area was 4.35±2.02% of total land. All farmers dry their plots and made renovation prior to start of a new growing season followed by liming and fertilization. No standard stocking density was maintained, prawns were stocked at 15895 PL/ha, whereas fin fishes at 1551 seeds/ha. Commercial feed was applied in all the plots. Production of prawn, stocked and non-stocked fin fishes were found 380.34±155.25 kg/ha; 713.65±352.99 kg/ha and 51.73±24.55 kg/ha respectively. Average cost and income for fish culture were 120514.07±36758.35 BDT/ha and 232497.48±76594.80 BDT/ha respectively. Average rice production was 4229.78±856.71 kg/ha. Low growth and high mortality of PL; scarcity, high and uprising price of feeds; and floods were identified as the major problems