Because Gudrun was one of the main attractions in the Dolfinarium's performing collection, den Herder was concerned that her absence would result in a loss of profits. He therefore requested that Sea World provide two false killer whales (pseudorcas) on loan to the Dolfinarium for the duration of Gudrun's absence in order to fill their performance schedule.

On March 31, Cornell replied and offered to deliver two false killer whales to the Dolfinarium in the spring or summer of 1987 in exchange for Gudrun.

Sea World eventually delivered the false killer whales to the Dolfinarium in Amsterdam in November 1987. Lanny Cornell, James McBain, James Antrim, and Brad Andrews travelled to Japan, picked up three pseudorcas from Kamogawa Sea World and escorted them to the Dolfinarium in Amsterdam.

The issue raised by this transaction is how Sea World USA could trade animals which belonged to a Japanese marine park  for the loan of the killer whale from Amsterdam. When interviewed by FRONTLINE, Brad Andrews and Jim McBain denied knowledge of a direct exchange of Kamogawa's animals for Gudrun.

Another aspect of the transaction concerns the Japanese drive fisheries, a violent method of capture which ends in the slaughter of numerous dolphins and whales. These drive fisheries are a sensitive issue for marine parks and governments. Until recently, all the pseudorcas in captivity had been taken from Japanese drive fisheries. Animal activists ask: did the pseudorcas Sea World traded in the Gudrun transaction come from a drive fishery?

Note: The NMFS has no clear-cut position on animals from fish drives. However, in recent years, the agency has denied two marine mammal facilities permits to acquire animals caught in them, on the grounds that there were no observers on hand to guarantee that the captures were indeed humane.