Dry Summer Has Stressed Fish


Dry summer is causing river levels to drop and stressing out fish
UNB graduate student Antoin O'Sullivan says low water levels impact fish, but also bacteria, plants and bugs

By Jordan Gill, CBC News Posted: Oct 10, 2017 10:43 AM AT

A dryer than normal couple of months has had a negative impact on rivers in the province according to a University of New Brunswick graduate student.

Antoin O'Sullivan, a PhD student who works with the Canadian Rivers Institute, said the province has seen very little rain between June and September.

For example, 151 mm of rain fell on Fredericton in that time, according to Environment Canada. The normal rainfall amount is 343.8 mm. This represents a 44 per cent decrease in expected rain totals.

The lack of rain has dropped river levels through the province.

O'Sullivan said that while the lower water levels can have a direct impact on the fish in the rivers, including salmon and trout, but there is other damage being done.

"Look at the bacteria, and the plants, the bugs, everything that are food sources for salmon," said O'Sullivan.

"If they're in trouble then it goes up the ladder. That's what I would be worried about."

Warm water

In addition to the rivers having less food for the fish to eat, the lower water levels can hurt the fish in two additional ways.

Lower river levels in the summer means higher water temperatures, which send fish looking for deeper pools, which can be difficult to find when the river levels are low.

"If it gets too hot, these fish get stressed out and they'll move into what are called cold water refuges," said O'Sullivan.

"But if you don't have enough water in the river for fish to get from one pool to another, or from one warmer spot to a colder spot, then that's not good for the species."

O'Sullivan said while salmon and trout are resilient and able to adapt, it only goes so far.

"There's a ceiling to that right. You can adapt to so high but these are cold water species, they're not going to survive at 35 C," said O'Sullivan.

Climate models point to trend

A before and after photo show a pond at Windy Hill Organic Farm slowly drying up after five weeks with little rain. (Windy Hill Organic Farm/Facebook)

While the dry weather isn't unheard of, Sullivan said it does point to a growing trend.

"There was a Miramichi 1825 fire and it didn't rain from June until October that year. So you can assume [the rivers were] pretty low then too," said O'Sullivan.

"What the concern is, I guess, is [climate models] are saying that we're going to have these periods of long drought."