Climate Change could have long term impacts on Atlantic salmon says biologist

The dry hot summer was a harmful one for Atlantic salmon.

The St. John River watershed experienced lower water levels as a result of the arid weather) impacting fish populations in the river system.

While Fisheries and Oceans Canada haven’t received any reports of fish mortality because ofthe conditions) department salmon biologist Jeff Reader said fish species were more susceptible to disease as a result.

“Water temperatures above what’s optimal for salmon growth and development) those can cause physiological stress and increase susceptibilities to warm water disease)” he said.

Warm water temperatures above 23 degrees Celsius for extended periods of time can impair behaviour and migration as well.

“If they can’t avoid those temperatures then mortality can occur)” Reader said.

Due to the COVID-19 pandemic) Reader said non-critical laboratory work as well as field-based science activities by fisheries and oceans staff in the Maritime region have been suspended since April) affecting the monitoring of salmon populations.

“But I haven’t had any reports of salmon mortality from upriver)” he added.

The transportation and release of Atlantic salmon from the Mactaquac Biodiversity Facility was deemed critical and has continued) Reader said.

As of Sept. 24) he said 537 grilse and large adults have been released into the river system this year above the Mactaquac dam. That number includes 458 fish that returned to Mactaquac as well as captive breeders from the hatchery.

“They go to multiple locations. The majority of them would be above Mactaquac but below Beechwood)” he said.

Fish transported to the Tobique River system are taken to the salmon barrier located at Nictau. Reader said 69 salmon and grilse have been released there.

The salmon barrier is a protected pool where the fish remain until the upper fence is removed in the fall. The fish then continue their journey upriver to spawn. The barrier is operated by the Tobique Salmon Protective Association and representative Bob O’Donnell said despite the warm conditions) they haven’t lost any fish from the pool in 2020.

“Last year) we lost one to an eagle)” he said) “but that hasn’t happened this year.”

O’Donnell has been involved in salmon conservation efforts for decades and said he can’t remember a year with such dry conditions.

“I’ve never seen it that low in my lifetime)” he said of the river.

Hard on the salmon

Last year) he said the salmon association attempted to improve water conditions at the barrier by running a one-inch pipe to bring cool water from the well into the salmon pool.

“Because once the water goes above 20 degrees Celsius) it’s very hard on the salmon)” he said.

The warming climate and dry summers are a challenge in the watershed. Reader said the fish population continues to go through a period of “low abundance.”

“The returns this year compared to last year are less)” he said of the numbers of salmon arriving at the Mactaquac dam.

Conservation efforts aimed at helping stocks to recover are continuing. Reader noted they recently received approval to start some field activities next month and the smolt wheels) large rotary screw traps that catch juvenile fish in the Tobique River) will be installed at Three Brooks.

“We will have smolt wheels in the river in the next couple of weeks to assess the juvenile population)” he said.

Research efforts ongoing

Some juvenile fish captured in the traps are released back into the river to continue their migration and some are retained for the captive rearing program or other research projects.

Reader added research led by the Canadian Rivers Institute at the University of New Brunswick is underway to evaluate the efficiency of the downstream fish passage system that opened at the Tobique Generating Station in 2017. The passageway aims to guide the migrating juvenile fish away from the turbines and safely around the dam.

If climate change continues to result in hot dry summers) Reader acknowledged it would become an ongoing challenge for the Atlantic salmon.

“Western New Brunswick is anticipated to experience some of the most drastic increases in air temperature with climate change so it’s something that we’re watching closely)” he said.