The Guppy Project: Studying fish in Trinidad

A few years ago I had the opportunity to work as a field technician in Trinidad studying guppies for The Guppy Project. Guppies don’t sound too interesting to most, but they are an extremely fascinating and unique species.

Guppies are one of the best species to study adaptive evolution because they have very short generation times (they mature very quickly), they live in environments that can be easily manipulated (waterfall barriers restrict migration), and they vary in many other traits, like physiology, life history and appearance within populations.

In Trinidad, guppies live in streams, some separated by waterfalls that neither the guppies nor their predators can cross. The most common predator of guppies in our focal streams was rivulus harti. My crew worked in both high-predation and low-predation streams. In high-predation streams, the male guppies tended to be smaller and more cryptic to avoid being eaten by predators. In low-predation streams, the males were larger and more colourful. Predators play an important part in the evolution of guppy populations. These males were able to evolve bright colours to attract females. 

Living in Trinidad was such an amazing experience for me because I had the chance to see my family again while at the same time, working on fun and interesting work outdoors. Most of the people from the local community knew us as the “guppy people” and would wave to us in town as we drove around in our beat-up truck. 

Guppies also give birth to live young. In fact, we caught a pregnant female who sadly gave birth to 14 dead guppies, shown below.

Members of the local community knew quite a bit about guppies as they are very common in Trinidad. There was even a news article written about part of our work shortly after I left to go back home to Canada. The article described how female guppies can store sperm cells in their system for up to 10 months. Their ability to perform selective-fertilization helps to ensure the growth and genetic diversity of the populations over time. My cousin sent me a photo of the article below. One of our top scientists, Andres Lopez Sepulcre, discovered this in a focal streams experiment.

I had the absolute privilege of working with an amazing group of people that I learned so much from and experienced so many great times with. We worked together, ate together, hiked up hills and waterfalls together, and laughed together. Lastly, we learned how remarkable this little species can really be!

-MK