Species of the Month

These species have been featured in our FYI newsletter as "species of the month."

• Brook Lampreys
• Snapping Turtle (Chelydra serpentina)
• Spotted Salamander (Ambystoma maculatum)
• Eastern Hog-nosed Snake (Heterodon platirhinos)
• Blue Ash (Fraxinus quadrangulata)
• Brook Trout (Salvelinus fontinalis fontinalis)
• Wood Frog (Rana sylvatica)
• Smooth Serviceberry (Amelanchier laevis)

Brook Trout (Salvelinus fontinalis fontinalis)

The distinctively marked adult brook trout.

The brook (AKA speckled) trout is one of the most colourful and attractive freshwater fish and a highly prized gamefish. They are particularly colourful at this time of the year, as they are sporting their spawning colours. This species is the only native fall spawning fish species found naturally in the Thames watershed. Brown trout and Pacific salmon are introduced fall spawners.

Brook trout can be identified by the worm-like markings on their backs, coloured spots surrounded by white halos on their sides, and reddish lower fins with white leading edges defined by a black stripe. While much larger in northern lakes and rivers, Thames brook trout inhabit small drains and creeks and typically reach lengths of 15 to 20 cm with occasional “trophies” exceeding 30 cm.

Sampling over the last decade has indicated brook trout are surprisingly widespread in the Thames watershed. They have been found at almost two dozen locations, including a main Thames tributary in London, four South Thames tributaries in the Dorchester to Ingersoll corridor, several Middle Thames tributaries and a couple of North Thames tributaries. The largest concentration of remnant trout are in the North Thames and Trout Creek and their tributaries, in the area east of St. Marys.

Although widespread, most of the fish are in small, isolated headwater streams and drains and are present in relatively low numbers. As such, these populations would support little or no harvest and could be destroyed by moderate angling pressure. Catch and release or just observing this attractive little fish is recommended.

Brook trout have been found at nearly two dozen locations in the Thames watershed.

Several additional Thames tributaries have been identified that may have the potential to support brook trout – the primary requirement being cold, clear flows with temperatures that rarely rise much above 22º C. Temperature measurements or the presence of other coldwater species (mottled sculpin, pearl dace and American brook lamprey) were used to locate these habitats. A cooperative project with the Thames River Anglers and the OMNR to (re)-introduce trout to these waters is being considered.

Contact: , Aquatic Biologist

Like the brook trout, the mottled sculpin (above), pearl dace (left top) and American brook lamprey (left bottom) need cold, clear flowing water.

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