Some of the smallest bodies of water, such as a pond, can contain an unexpectedly high number of different species of fishes, the most diverse of all vertebrate animals.

At the Canadian Museum of Nature’s research facility, there’s a naturally populated pond — about the size of an Olympic-size swimming pool — which surprisingly is home to 15 species of fishes. By comparison, the museum’s little pond has almost a fifth of the species found in the entire Ottawa River watershed, which has about 80 fish species.

Aerial view of the museum’s research and collection facility. Inset: a woman standing in the pond.
It’s a small pond. The museum’s research facility is the large, white roofed, rectangular building in lower, centre-left. The pond is in front of it. In the inset, Emma Lehmberg, a museum summer student, collecting specimens in the pond. Aerial photo: Chuck Clark, © Chuck Clark. Inset: Cassandra Robillard, © Canadian Museum of Nature.

Of these fishes, eight species belong to the minnow family (Cyprinidae). Although often overlooked because they’re small, minnows have fascinating behaviours.

For example, the Golden shiner (Notemigonus crysoleucas) will sometimes lay its eggs in the nest of one of its natural predators, such as the Largemouth bass (Micropterus salmoides). Although this may seem dangerous, it benefits the Golden shiner because the Largemouth bass defends its nest from egg poachers, inadvertently protecting the Golden shiner’s eggs.

A Fathead minnow fish
A male Fathead minnow (Pimephales promelas) with prominent breeding tubercles. Image: Shalini Chaudhary, © Canadian Museum of Nature.

The Fathead minnow (Pimephales promelas), another minnow species found in the pond, displays a dramatic physical change in the breeding season. Bony tubercles grow on the male’s head, which also darkens. The male will guard the eggs lain by its mate and drive off other fishes, sometimes even his mate!

A Pumpkinseed fish
The Pumpkinseed (Lepomis gibbosus) has markings and colouration that rival tropical fishes. Image: Emma Lehmberg, © Canadian Museum of Nature.

A more familiar fish in the pond, especially to novice anglers, is the Pumpkinseed (Lepomis gibbosus). It’s one of the most colourful of local fishes and is found throughout North America. Did you know that depending on the prey available in a given body of water, the Pumpkinseed will have different body part shapes and structures? For example, Pumpkinseeds in waters with large shelled prey, such as snails, have stronger jaw muscles and crushing bone parts in their mouths than Pumpkinseeds in ponds without these molluscs.

A Brown bullhead (Ameiurus nebulosus) with its barbels fully extended to sense its aquarium environment. Image: Francesco Janzen, © Canadian Museum of Nature.

Lastly, the museum’s little pond is home to the Brown bullhead (Ameiurus nebulosus), a common catfish.

Brown bullheads, and catfish generally, have facial taste receptors with a high concentration of them on their whiskers, or barbels. This, along with its keen sense of smell, enables the bullhead to detect food in its murky habitat where visibility is poor.

Even more amazing is the fact that bullheads and other catfishes have specialized receptors embedded in their skin that can detect electricity. This includes the minute electrical activity produced by the contracting muscles of a swimming minnow, which could lead the Brown bullhead straight to its next meal.

It may be a small pond, but the fish stories it holds are truly remarkable.

Table listing the common names and species names of the fishes found in the pond.
A list of the 15 species found in the pond at the museum’s research facility. Eight species are from the minnow family, the bass and sunfish family has two representatives, and all other species are the sole members of their respective families. © Canadian Museum of Nature.