No abstract

Invasive vermiculated sailfin catfish (Pterygoplichthys disjunctivus) has an impact on highly valued native fish species.

Impacts of ineffective wastewater management on the biodiversity of receiving waters in developing countries are poorly documented. Using a before-after-control-impact methodology, we measured the effects of untreated wastewater release on the fish community in the Barnoi River, Bangladesh. In 2006, prior to untreated wastewater discharge, fish abundance, species richness and water quality were similar across sampling sites. In 2016, after 8 years of wastewater release to the downstream reach, fish abundance and species richness were reduced by >47% and >35% respectively at downstream sites compared to unaffected upstream sites and >51% and >41% lower respectively compared to the pre-wastewater discharge period. The wastewater impact was particularly severe during months of low discharge (October–December). Water transparency, dissolved oxygen and pH were lower (P < 0.001) at impacted downstream sites compared to upstream sites. Nineteen species (41.3% of all species we recorded) are threatened in Bangladesh and the abundance of these species, except one, decreased significantly (P < 0.05) at the impacted sites. We recommend improved wastewater management by applying primary treatment facilities and incorporating reedbed filtration as a mean of biological treatment, into the canals carrying wastewaters. The success of such measures should be tested with fish species that were most responsive to wastewater, using the indicator species concept.

Lack of quality carp seeds is one of the major problems for fish production in Bangladesh. This experiment was conducted during July to December 2013 to study the production and economics of carp polyculture using wild and hatchery produced seeds in ponds in Faridpur district, Bangladesh.  Seeds of native major carps (NMCs) (Catla catla, Labeo rohita and Cirrhinus mrigala) and non-native carps (NNCs) (Hypophthalmichthys molitrix, Ctenophryngodon idella, Aristichthys nobilis and Cyprinus carpio) from four different sources were tested in feed and fertilizer based polyculture ponds under controlled mesocosm trials with four treatments (T1–T4), each with four replications. Combination, weight and density of the stocked species were same for all the treatments. Water quality parameters were monitored monthly and mean values were found within suitable range for fish farming. Mean final weight, weight gain, specific growth rate and yield of L. rohita, C. catla and C. mrigala were found significantly (P < 0.05) higher with treatment T1, T3 and T2 respectively. Treatments T1, T2 and T3 varied more significantly (P < 0.05) than treatment T4 for total fish yield and cost benefit ratio.  Polyculture of wild sourced NMCs and hatchery produced NNCs were found more profitable than aquaculture of hatchery produced NMCs and NNCs.

Lack of quality carp seeds is one of the major problems for fish production in Bangladesh. This experiment was conducted during July to December 2013 to study the production and economics of carp polyculture using wild and hatchery produced seeds in ponds in Faridpur district, Bangladesh.  Seeds of native major carps (NMCs) (Catla catla, Labeo rohita and Cirrhinus mrigala) and non-native carps (NNCs) (Hypophthalmichthys molitrix, Ctenophryngodon idella, Aristichthys nobilis and Cyprinus carpio) from four different sources were tested in feed and fertilizer based polyculture ponds under controlled mesocosm trials with four treatments (T1–T4), each with four replications. Combination, weight and density of the stocked species were same for all the treatments. Water quality parameters were monitored monthly and mean values were found within suitable range for fish farming. Mean final weight, weight gain, specific growth rate and yield of L. rohita, C. catla and C. mrigala were found significantly (P < 0.05) higher with treatment T1, T3 and T2 respectively. Treatments T1-T3 varied more significantly (P < 0.05) than treatment T4 for total fish yield and cost benefit ratio.  Polyculture of wild sourced NMCs and hatchery produced NNCs were found more profitable than aquaculture of hatchery produced NMCs and NNCs.