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Mark and Recapture: Brook Trout Tagging Study in Nova Scotia

By Matt Dort

I have been involved with several scientific “mark and recapture” studies for trout in Nova Scotia over the past few years. These studies are very valuable as they allow us to collect biological data on the fish and help us understand the health of the populations. It also provides data to help determine proper management for the long term success of the species.

Nova Scotia has a popular spring fishery for sea run speckled trout (Salvelinus fontinalis). These speckled trout, also known as brook trout, are native to our province and are the Provincial Fish. Sea run trout migrate into estuary waters to take advantage of the abundant forage present in tidal waters. Angler catches of large trout, exceeding 2 kg have been reported from sea run fisheries in Nova Scotia. As in other sea trout fisheries, much of the angling activity takes place in the spring of the year, when the trout are in the tidal, lower reaches of river systems.

The brook trout is native to eastern North America but has been introduced elsewhere in North America and to other continents. They can also be found in Iceland, Europe and Asia. In Europe, it has been established since the latter half of the nineteenth century. The brook trout is the state fish of nine U.S. states: Michigan, New Hampshire, New Jersey, New York, North Carolina, Pennsylvania, Vermont, Virginia, and West Virginia.

These fish are identifiable by a distinctive pattern called vermiculation present on their body. Their skin is green to dark brown on the back and sides, with light-colored, wavy lines on upper back, dorsal fin and upper part of the caudal (tail) fin. Red spots surrounded by blue halos and many light spots are usually present on the sides. The belly is lighter, white to yellow in females, or reddish in males. The leading edges of the lower fins have a bright white border followed by a black border and reddish coloration. When the brook trout is in the tidal water, they will have a silver colored stomach.

In recent years, angler and river association groups have expressed concern about a decline in the status of the sport fishery in some of the watersheds within Nova Scotia. This concern initiated the mark and recapture studies. For these studies, members of the local river associations, volunteers, and Nova Scotia Department of Inland Fisheries and Aquaculture (DIFA) staff angle for trout during the Spring season. Trout that are captured are anesthetized using clove oil; afterwards, several data points are gathered and later analyzed. All captured trout are measured to the nearest millimeter in fork length, weighed to nearest gram, marked with individually numbered Carlin tags, scale sampled, adipose fin clipped, and then released. Adipose fins are stored in 99% ethanol for DNA analysis. Effort and catch per hour during the tagging (marking) period is also calculated. Water temperature loggers are also deployed at multiple sites throughout the rivers.

One of the things I like sharing with people is that when proper catch-and-release techniques are used, fish have a high probability of being recaptured by other anglers over multiple years. If a tagged trout gets recaptured later in the season, anglers are asked to call Nova Scotia DIFA with the number on the tag and provide details around the location. This is something I have personally experienced, and in one scenario, the trout was recaptured 25 miles upstream from the point of initial tagging.

I encourage you to get involved with local conservation groups and volunteer for these very valuable studies.

about the author

Matt Dort is a Sage Elite Pro who resides in New Glasgow, Nova Scotia. This location gives him access to over a dozen Trout and Atlantic Salmon rivers located along the North Shore of Nova Scotia. Matt has 30 years of fly fishing experience for Atlantic Salmon and Trout, is very passionate about the sport and commits a lot of his time towards conservation initiatives and projects. Fishing is in his blood and his experience is diverse: from night time Brown Trout fishing to Sea Run Brookies, to estuary Striped Bass and the King of them all; the majestic Atlantic Salmon. Most of all he enjoys being on the river fishing with his children and teaching them to love and respect Mother Nature’s gifts. Several photos used taken by Andrew Lowles.