A fish out of water

At full size, these small fish are around ten centimetres and although dull from a distance, they have vivid horizontal coloured stripes stretching along their body. Males and females can be distinguished fairly easily by their colouration; males tend to be brighter and have distinctive pale orange edges to the tail, while the female’s tail has a darkened tip.

Jumping guabines are found throughout TT as well as in northern Venezuela. They thrive in a variety of habitats, from muddy road-side puddles to the shallow edges of large rivers.

Despite the name, they are not closely related to the much larger and fiercer “guabine” (Hoplias malabaricus), which is actually one of their main predators. Instead they are a type of killifish, one of more than 320 species belonging to the family Rivulidae. Killifish have representatives throughout Asia and Africa as well as the Americas, and most are known for their ability to withstand harsh environments. Many species are popular in the aquarium trade, due to their bright colour, small size and algae-controlling abilities.

As the name suggests, this fish has the ability to launch itself completely out of the water. The ability to beach yourself may not seem like much of an evolutionary advantage, but this fish has another trick up its sleeve – it can breathe atmospheric air through its tail, which is covered in capillaries. As such, a jumping guabine can “jump” out of water on to land and survive for a considerable time, as long as it does not dry out entirely.

This allows these fish to travel short distances over land to new bodies of water, and it is not unusual to find a few individuals in isolated puddles, often some distance away from permanent water.

Dr Doug Fraser of Siena College, New York, has been studying jumping guabine movements in the Northern Range for many years, along with various colleagues. They have discovered that jumping guabine seem to have something akin to a “personality”, which determines whether they prefer to be “shy stay-at-homes” or “bold explorers”. In other words, they found that fish with a bolder personality are more likely to travel long distances from their home.

Travelling outside of water is also the reason they are often the only fish found in the highest stretches of rivers in the northern range – pools that even guppies have failed to colonise. Jumping guabines can simply make multiple jumps to scale the sheer rock face of a waterfall!

Another advantage of jumping is that it allows hungry individuals to hunt prey that may be otherwise out of reach – on overhanging vegetation or at the water’s edge, such as ants. Incredibly, they have been recorded jumping as high as 14 centimetres, more than their total body length, to catch prey. While in the water, they are ravenous predators of small aquatic invertebrates, small fish and tadpoles. As a result, in an example of excellent parenting, Trinidad stream frogs, Mannophryne trinitatis, will always check for jumping guabine before depositing their tadpoles in a pool to ensure the safety of their young.

Female jumping guabine scatter their eggs in aquatic vegetation. On hatching, the young fish (at one centimetre long), tend to bury quickly into the sediment to avoid predation. Unlike guppies, these fish do not shoal in groups for protection. Instead they have an incredibly quick escape response – indeed, often all you see is a flicker as they dart for cover on sensing your approach, but with patience you will see them venture back after a few minutes.

This speedy response not only helps them to catch prey but also to avoid becoming prey themselves. I recently witnessed a large spider (Dolomedes sp) capture an adult jumping guabine from the water’s edge, so it is not only fish and bird predators they have to stay alert for!

It is easy to overlook some of our most common wildlife species, because we see them so frequently. However, with this fish, the very fact that it is found everywhere is what makes it fascinating. Next time you see a jumping guabine, take a closer look – is she a dull bold-explorer or is he a colourful stay-at-home?

This feature was written by Amy Deacon. For more information on our natural environment, you can contact the Trinidad and Tobago Field Naturalists’ Club at admin@ttfnc.org or visit our website at www.ttfnc.org. The club’s next monthly meeting will be held today at St Mary’s College, Port-of-Spain. This month’s lecture: Human impacts on mangrove wetland systems in TT by Erin Mangal.