Pesticide-contaminated feeds in integrated grass carp aquaculture: toxicology and bioaccumulation

Abstract

Effects of dissolved pesticides on fish are widely described, but little is known about effects of pesticide-contaminated feeds taken up orally by fish. In integrated farms, pesticides used on crops may affect grass carp that feed on plants from these fields. In northern Vietnam, grass carp suffer seasonal mass mortalities which may be caused by pesticide-contaminated plants. To test effects of pesticide-contaminated feeds on health and bioaccumulation in grass carp, a net-cage trial was conducted with 5 differently contaminated grasses. Grass was spiked with 2 levels of trichlorfon/fenitrothion and fenobucarb. Unspiked grass was used as a control. Fish were fed at a daily rate of 20% of body mass for 10 d. The concentrations of fenitrothion and fenobucarb in pond water increased over time. Effects on fish mortality were not found. Fenobucarb in feed showed the strongest effects on fish by lowering feed uptake, deforming the liver, increasing blood glucose and reducing cholinesterase activity in blood serum, depending on feed uptake. Fenobucarb showed increased levels in flesh in all treatments, suggesting bio-concentration. Trichlorfon and fenitrothion did not significantly affect feed uptake but showed concentration-dependent reduction of cholinesterase activity and liver changes. Fenitrothion showed bioaccumulation in flesh which was dependant on feed uptake, whereas trichlorfon was only detected in very low concentrations in all treatments. Pesticide levels were all detected below the maximum residue levels in food. The pesticide-contaminated feeds tested did not cause mortality in grass carp but were associated with negative physiological responses and may increase susceptibility to diseases.

Uptake of nitrogen from natural food into fish in differently managed polyculture ponds using 15N as tracer

“…The production is limited by loss of pond productivity due to high turbidity in the ponds caused by the constant inflow of particles eroded from surrounding intensive agriculture. Further, the production of grass carp, as the dominant species stocked in traditionally managed ponds, is endangered by the occurrence of a species-specific disease that causes mass mortalities of grass carp in Northern Vietnam (Edwards 2000;Steinbronn 2009;Pucher et al 2013) which may be linked with feeding fish with pesticide-contaminated leaf material from the fields (Steinbronn 2009;Pucher et al 2014c). To improve regional aquaculture production, modifications of the traditional pond management towards a more semi-intensive pond management were designed by researchers and introduced to farmers in the Yen Chau District, Son La Province, Northern Vietnam.…”

Effects of modified pond management on limnological parameters in small-scale aquaculture ponds in mountainous Northern Vietnam

“…In mountainous regions of Northern Vietnam, rapid agricultural intensification of cropping systems has changed the traditional integrated farming systems of small‐scale farmers (Minot, Epprecht, Anh & Trung ) and negatively affected single farming activities such as pond aquaculture which is important for food security and income generation (Steinbronn ). Exemplarily, Pucher, Gut, Mayrhofer, El‐Matbouli, Viet, Ngoc, Lamers, Streck and Focken () evaluated that pesticide contaminated leave material collected from rice paddy fields and used as feed for fish might negatively affect feed uptake and health parameters of fish. Even though demand for fish and accessibility for external high quality inputs is rising in the Northern Vietnam uplands (van Anrooy ), pond aquaculture is still performed mainly for subsistence and supply to local markets (Luu ; Steinbronn ; Minh ).…”

Primary Production

“…However, in such IAAs, an intensification of one farming activity (e.g. application of pesticides or inorganic fertilizers) has a direct impact on the efficiency of the entire system and may also affect the safety of their products (Pucher et al 2014;Schlechtriem et al 2016). A sustainable and safe expansion of this type of aquaculture needs to be well integrated into the regional situation.…”