Low Oxygen Suspected in Massive Belize River Fish Kill

The Department of the Environment says hypoxia, a severe shortage of oxygen in the water, is now the leading suspected cause of the massive fish kill in the Belize River Valley. However, officials stress that the finding remains preliminary and that further testing is required before a final determination can be made.  Appearing on the morning show today, Chief Environmental Officer Anthony Mai said the investigation has so far found no evidence that the incident was caused by a chemical spill or disease.

Anthony Mai, Chief Environmental Officer, Department of Environment: “When the Department of Environment receives a report of a fish kill we look at three possibilities. We look at the possibility of it being a disease. We look at the possibility of chemicals or toxins being deposited into the river. And we also look at the possibility of a large amount of organic matter going into the river. So those three different areas could lead to a fish kill. We sought advice from local experts in relation to the disease as a possible cause. They suggested to us that they don’t believe that it might be a disease because in fish the diseases are very specific. And so if you have a virus affecting the fish it normally targets one specific species and again the evidence is clear. There are several different species of fish that was impacted in fact to some degree turtles and crocodiles etc were also impacted. And so we have not fully ruled that out but again we focused on the other two options or causes which is looking at the possibility of any chemical related issue or organic related issue. In relation to determine if it’s a chemical input the type of work that we have done and are doing is we have collected fish species from the river. We did a necropsy on it, so we did a post mortem to determine the cause of death. That was done by a local expert as well, Dr. Ben Carias. He determined that the cause of death of the fish was hypoxia which basically died because they didn’t have enough oxygen to breathe. And there are several different evidence that shows that. Again, he suggested that it might not be chemical related because the results and the organs would have been damaged. The skin would have been darker in color and there would have been more excessive blood within the tissue itself.”

The DOE’s field assessments recorded extremely low dissolved-oxygen levels in areas where significant fish mortality occurred. Elevated conductivity, chlorophyll-a and turbidity were also detected at some locations. The department says those conditions can severely affect aquatic life and are consistent with hypoxia.  Significant mortality was observed along an approximately seventeen-and-a-half-mile stretch of the river between Isabella Bank and Grace Bank. The DOE’s wider assessment extended from near Banana Bank, upstream of Santander Farms, to the Burrell Boom Bridge.  While an obvious chemical spill and disease have been initially ruled out, Mai says the investigation is not over. Water, fish and sediment samples are undergoing further analysis to determine what triggered the oxygen depletion and whether contaminants or other environmental factors contributed to the event.

Anthony Mai, Chief Environmental Officer, Department of Environment: “So we’re in the process of collecting sediment samples from some of the farms within the area. We took for example sediment samples from Santander’s effluent pond, from their drainage network, from the canal that leads to the river, and we are taking sediment samples from the river upstream. So we will run chemical analysis of those samples. That’s water quality samples to see if there’s any connection. And not only with Santander, there’s a rice farm north of Santander about 380 acres that we’re also taking samples from. So we will do chemical analysis on the sediments. We will also do chemical analysis on the preserved fish tissue that we have to look at the possibility of it being chemical related. As you know, if it is chemical, normally the sediment will trap residues, right? So we’ll be able to detect. We have in our laboratory a GCMS, and that’s a highly accurate equipment that is able to detect chemical and chemical residues. One of the good things, again, with this approach is that we have worked extensively with several different agencies. The collaboration in this response was awesome. We had the Pesticide Control Board, for example, go into Santander to investigate the type of pesticides that they use just before the flooding event and when we run the chemical analysis we’ll compare it to whatever data they provide to us as well in relation to that. So in terms of the chemical approach, again, we’ll be running chemical analysis on the fish tissue as well. We believe that at the end of the day that will tell us a particular story. And all of these tests and studies and analysis will be done in country, in our labs. And we’re working with BAHA because BAHA has what is called an LCMS. They will assist us with running some of the fish tissue for chemical analysis as well.”

Samples were also collected from the Santander Farms drainage system and downstream locations for chemical analysis. Investigators are examining possible discharge points, nearby activities, land clearing and satellite imagery from before and during the incident.  In the meantime, the public advisory remains in effect. Residents are urged not to consume fish or other aquatic resources from the affected area or use untreated river water for drinking, cooking, livestock or pets. The warning does not apply to treated water supplied by Belize Water Services Limited.