Barrie Gull Spectacle and Emerald Shiners

Gull Feeding Frenzy continued into the second week of January 2016 at Heritage Park in Barrie, where hundreds of gulls see video fed on an abundance of Emerald Shiners, a small minnow. A good breeding season concentrating the minnows in one area near shore and warm temperatures keeping Lake Simcoe open until the middle of January brought about this event. 8 January 2016.

To understand better, Peter Mills provided this information about the life cycle of Emerald Shiners from Mandrak and Crossman's Freshwater Fishes of Canada

Spawning occurs in summer
Fish are short-lived (three years maximum)
They are typically a pelagic species, but move inshore in autumn, sometimes aggregating off docks, piers, and river mouths in countless numbers
"These large schools in inshore waters are usually composed of young-of-the-year"
"As the season advances, they move to deeper water for overwintering"
"Evidence suggests that emerald shiner populations fluctuate widely in abundance from year to year"
"...periods of scarcity followed by great abundance have been characteristic of the populations for over 50 years"
This cyclic pattern is attributed to "high mortality rates causing drastic changes in age-class structure of populations".

Gulls were plunge-diving gannet-style, coming up with bills full of fish. Please click on photo or link to see video. 8 January 2016.

Depredation: "so many creatures prey upon emerald shiners it would be impossible to list them all". Known species include: Burbot, Blue Pike (now extinct), lake trout (64% of the diet in one study), Smallmouth Bass, etc.
"In Lake Simcoe, McCrimmon (1956) noted that the Emerald Shiner was the most common minnow and served as an important food item of most sport fishes at some season of the year...Many fish-eating birds, such as gulls, terns, mergansers, and cormorants feed heavily upon emerald shiners, whose surface swimming habits makes them particularly susceptible to this kind of predator."

Commercial bait fishermen took huge numbers of Emerald Shiners away in large containers on the back of pickup trucks. Individuals were also filling pails presumably for personal use. It was disheartening to see piles of these small fish dumped on the shore - wasted.

Emerald Shiners Dying belly-up at Barrie's Heritage Park

On 8 January 2016, Ron Pittaway and I witnessed an extraordinary event: Emerald Shiners (minnows) were thick in the water of the harbour at Barrie's Heritage Park. They became agitated and bubbled to the surface where they died belly-up. What caused this? Masses of them died this way. Theories such as lack of oxygen and abrupt change in water temperature have been proposed.

The shiners were thick and dying. Link to Video