The Thin End

For all the fish that are in the sea, the herring is the fish for me!  These are the words of a song my mother used to sing, and the whole family would join in the chorus.  But how many fish are in the sea?  Estimates of the numbers of fish in the oceans vary, of course. How could it be an exact measure? One figure given by scientists places the number of fish in the ocean at 3,500,000,000,000.  That is a lot of fish?  So, what about 'the fish for me', the herring? Archaeologists counting herring bones  along North America's west coast recently found evidence that herring that had been abundant for thousands of years.   Like so many, they are in decline due to overfishing.  Herring collapse has signifcant knock-on effects both for humans and for ecological balance.  Over time, there have been serveral periodic collapses.  Sometimes the recovery has been slow.  Herring is the fish for me could be a standard for seabirds, With lo...

We are more aware than ever before that microplastics (plastic particles under 5 mm) are an abundant type of debris found in salt and freshwater environments.  They can be readily ingested along with food and enter the 'food' chain.   It is not yet clear what harm if any the ingestion of microplastics has in the food chain, although some studies have found depressed growth and lethargy. In a Limnology & Oceanography Letters study, researchers demonstrated the transfer of microplastics through the food chain between microscopic prey and larval fish that live in coastal ecosystems. They also found that microplastic ingestion interferes with healthy growth in fish larvae. The investigators also looked at the effects of a common pollutant (the pesticide DDT) that attaches to microparticles in coastal waters. Organisms were not able to detect or discriminate against ingesting microparticles with high levels of DDT. "Even short exposure to high levels of micropl...

Scientists are increasingly warning that prescription drugs can affect wildlife and ecosystems when they find their way into the environment. In a new Environmental Toxicology and Chemistry study, investigators found that the anxiety and depression drug Escitalopram—at concentrations similar to those measured in the environment—can inhibit fish foraging and eating behaviour. Interestingly, the team noted that the two sexes respond differently to the drug. Specifically, the inhibitory effect of the drug was more pronounced in males than in females. zebrafish “It is disturbing that psychoactive drugs affect vital life processes in aquatic wildlife,” said corresponding author Erik Baatrup, PhD, of Aarhus University, in Denmark. These psychoactive drugs (Selective Serotonin Reuptake Inhibitors) have been found in natural waters around the world and have been found to inhibit fish feeding behaviour.  These researchers monitored the effect of escitalopram on zebrafish swim...

New research published in Environmental Toxicology & Chemistry reveals that low doses of a commonly used pesticide potentially harm the Northern Leopard frog by inhibiting their brain development. Case against chlorpyrifos stacks up The pesticide,  chlorpyrifos, which has been used since 1965 in both agricultural and non-agricultural areas, had clear effects on Northern Leopard tadpoles’ neurodevelopment, even in situations where the pesticide did not cause a decline in the amphibians’ food source. Diagram by Sara McClelland. Developmental exposure to chlorpyrifos The leopard frog ( Lithobates pipiens ) tadpoles were reared through metamorphosis in artificial ponds containing either 0 or 1 µg/L chlorpyrifos and either chlorpyrifos‐resistant or chlorpyrifos‐sensitive Daphnia pulexzooplankton.  Developmental exposure to chlorpyrifos resulted in metamorphs with a relatively wider optic tectum, medulla, and diencephalon compared with controls, and this resu...

A new study suggests exposure to residues persisting in the environment from pesticides banned fifty years ago is associated with autism. The new study provides the first biomarker-based evidence in humans that maternal exposure to DDT residues in the food chain may increase the risk of autism in their children. DDTs (organochlorines) were widely banned as pesticides from the late 1970s,  but residues persist in the food chain. These persistent organic pollutants can be transferred from the mother across the placenta to the fetus, resulting in fetal blood concentrations ranging from 30% to 50% of levels found in maternal blood.   The investigation ,  published online in the American Journal of Psychiatry, was derived from the Finnish Prenatal Study of Autism, a large national birth cohort with maternal serum specimens from early pregnancy tested for levels of the organochlorine DDT (dichlorodiphenyl-trichloroethane) and its metabolite DDE (dichlo...