Norwegian study investigates sensitivity of Atlantic salmon to endosulfan
The increasing use of plant ingredients in fish feeds can lead to exposure to higher levels of contaminants such as the pesticide endosulfan. NIFES is investigating the impact of endosulfan in feed on fish health.
Few and small changes in blood parameters in fish that received 710 microgram endosulfan per kilo feed for 49 days indicated that Atlantic salmon tolerate high dietary endosulfan levels, says Dietrich Petri, scientist at the Seafood Safety research program at NIFES.
Endosulfan is an organochlorine pesticide that is used in agriculture. Adverse effects of endosulfan on humans as well as on mammals are well documented. Fish, in particular salmonids, seem to be very sensitive to waterborne endosulfan exposure, as seen after runoff from agricultural land or accidental discharge into rivers. However, information regarding the effects of oral exposure to fish is limited. The current EU maximum level (ML) for endosulfan in fish feed is considerably lower than in feed for terrestrial farm animals (5 vs. 100 microgram per kilo feed), possibly limiting the choice of plant products by the feed industry.
Feeding experiment with endosulfan
In an initial range finding study, Atlantic salmon pre-smolt (weighing about 50 gram) received diets that contained increasing concentrations of endosulfan (4, 50 or 710 microgram endosulfan per kilo feed) or a control diet for 49 days. General growth parameters, haematology and clinical chemistry in plasma were used to detect adverse effects on fish health.
Results from experiment
The feed concentrations of endosulfan did not result in clear clinical symptoms or clear adverse effects. Only minor and transient responses were noted in the highest dose group. Condition factor, which gives information on the relationship between weight and length, was slightly but significantly reduced by day 49. Certain haematological parameters (hemoglobin, hematocrit) were significantly increased in the highest exposure group on day 35, but had returned to levels similar to controls by day 49. Elevated concentrations of a liver enzyme (ASAT) were deteceted in two fish in the highest dose group, but there was no significant difference among treatments. Similarly, the proportion of different white blood cells (leucogram) was not statistically affected by treatment, while lymphocytes of two fish in the highest group showed irregularities in the cell nuclei.
How much endosulfan is tolerated?
Few and small changes in blood parameters in fish that received 710 microgram endosulfan per kilo feed for 49 days indicated that Atlantic salmon tolerate high dietary endosulfan levels. Further analyses of fish from this study are being conducted and will give more detailed information on the impact of endosulfan on fish health.
