I believe this problem could be solved with my theory about the flood.
Aquatic life, insects, amphibians and small, semi-aquatic animals such as otters and monitor lizards would not need to be on the ark as they could survive either in the flood waters or on floating vegetation mats. As reasonably large populations of these would have survived, there is no visible bottleneck. Evolutionists have criticized this, saying that the mix of salt and fresh water would kill off most life, but the fact that the original animal kinds were more resistant to change than today's animal species and the fact that the fresh flood waters would float on top of the saltwater oceans refutes this.
As for the ark animals, there is a bottleneck. Evolutionists have discovered an allegedly 70,000 year-old one in humans, chimpanzees. orangutans, macaques, cheetahs, tigers and gorillas (look for "Toba catastrophe theory"). More genetic research will probably reveal more. The micro-evolution of the original animal kinds and diversification of the human race that occurred after the flood probably caused scientists to think the bottleneck was 70,000 years old, rather than 4,300 years old.