Much like a whale, a porpoise is not a fish but a sea mammal that surfaces regularly to breathe. Photo Shutterstock After a dead porpoise tagged by Wageningen Marine Research scientist washed ashore last summer, disaster has hit again: during a new transmitter study, one of the captured animals drowned in the net.
The first incident could not be proven to be related to the transmitter study. The most recent incident, which took place in the Marsdiep last week, there is no escaping the link. The animal was found dead in the net the researchers used to catch two other porpoises. One of these was successfully fitted with a transmitter; the second animal was released in accordance with the protocol before a transmitter could be attached because it displayed signs of stress. A third animal was not immediately identified and appeared to have drowned when the researchers freed it from the net.
Precisely what happened and how that may have caused the animal to perish will be diligently investigated, says WMR director Tammo Bult. ‘The researchers also want to know. A transmitter study being fatal to the animal is just about the worst nightmare.’ Internal and external experts, including the animal testing committee, will contribute to this investigation. In legal terms, fitting animals with a transmitter constitutes testing on animals.
Experts on board
Fitting wild porpoises with transmitters is new in the Netherlands. Denmark and Greenland have more experience in this department. This project aims to find the best approach for the Netherlands so that the method can later be applied more extensively to study porpoises in the North Sea, which is becoming increasingly busy. To this end, WMR enlisted the help of Scandinavian experts, two of whom were on board at the Marsdiep, as well as the vet, who is always present to assess whether an animal is sufficiently fit to be tagged.
The Utrecht University Faculty of Veterinary Medicine will perform an autopsy on the porpoise. The same faculty also performed the autopsy on the tagged porpoise from the Oosterschelde. In that case, no link was found between the tagging and the animal’s death. It should be noted, however, that the body was already decomposing. Given the fact that the animal was 11 years old, according to observations by the Delta Bruinvis foundation and the Rugvin foundation, the animal passing within a month after being tagged could easily be a coincidence. Most porpoises do not live past twelve years.
Three months of data
The tagging initiative was halted immediately following the incident at Marsdiep. Whether or not the project will be resumed is to be determined after the evaluation is concluded. Bult was unable to confirm when the outcome of the evaluation is expected. Meanwhile, the porpoise that was successfully tagged last week is being followed. The tagging in the Oosterschelde also yielded one tagged porpoise, a male. His tag provided data for three months.
