Study of fish populations in Saint John harbour shows 'surprising diversity'

ACAP Saint John workers Shauna Sands, left, Khoa Ngo, centre, and Shayelin Braydon search for small fish and shrimp in a beach seine net (Steven Webb/CBC - image credit)
ACAP Saint John workers Shauna Sands, left, Khoa Ngo, centre, and Shayelin Braydon search for small fish and shrimp in a beach seine net (Steven Webb/CBC - image credit)

When ACAP Saint John set out on a four-year study of fish life and water quality in the Saint John Harbour, the environmental group wasn't setting out to answer any big questions.

The study, which began in 2018, was designed to set a baseline for the general health of fish populations in the harbour.

No one had made an effort to see how many species of aquatic life were in the tidal waters of the harbour, and in what numbers.

Roxanne MacKinnon, the executive director of ACAP, said they were surprised by what they found.

Submitted by Roxanne MacKinnon
Submitted by Roxanne MacKinnon

"I think that we were mostly surprised at the abundance of fish we've been able to catch," MacKinnon said.

"We've caught, in our four years of sampling, we've caught a little over 35,000 fish, which, for the small amount of effort we put in, that's a lot of fish."

ACAP researchers visited eight sites once each month, from May until October.

While at each site at low tide, they haul a seine net along the sea bottom for three minutes, and set up a larger net, called a fyke net, that would be left for 24 hours to catch bigger species.

Steven Webb/CBC
Steven Webb/CBC

They found 34 species, but the vast majority were either Atlantic silverside, a tiny bright silver fish, and sand shrimp, small invertebrates that live in the harbour mud.

On this day at the mouth of Hazen Creek, MacKinnon and her team find lots of both, but there are also juvenile Atlantic tomcod, a few young winter flounder and two green crabs.

The crabs have to be killed, because they can't be returned to the water.

"We catch a lot of green crabs in our fishing. Unfortunately, they are an invasive species, so they're pretty good at competing with our native crab population, so they're doing quite well."

Steven Webb/CBC
Steven Webb/CBC

Not far from this site, the team does a similar seining at the mouth of Little River.

Practically situated in the shadow of the Irving Oil refinery and the Courtenay Bay power plant, the estuary doesn't appear healthy at first glance, despite the flock of Canada geese swimming upstream.

"It has these mats of algae growth, [the water's] kind of like a Mountain Dew colour and you frequently, when you step in it, you kind of kick up black oily substance," MacKinnon said.

That black substance also can be seen along the shore.

Steven Webb/CBC
Steven Webb/CBC

It is the site that produced the fewest fish over the first three years of the study — just 328. Most of them were reported as appearing "unhealthy or injured."

"The first time we fished in Little River and actually caught fish, we were quite surprised that we were able to actually catch things in the section of Little River that we fish in." she said.

The report of findings published on ACAP Saint John's website said "it appears that Little River is inhospitable to organism health to some extent."

It said both Little River and Marsh Creek showed poor water quality and "these locations should be targeted for not only continued monitoring but also more active management and restoration."

Steven Webb/CBC
Steven Webb/CBC

MacKinnon hopes this kind of study of fish populations can continue in the future, so the general health of Saint John Harbour can be measured over time.

But that will depend on whether Fisheries and Oceans Canada will decide to fund future efforts.

In the meantime, her teams will continue to gather data until October of this year.

The study is available on ACAP Saint John's website at acapsj.org, or on the St. Lawrence Global Observatory website, at ogsl.ca.

Steven Webb/CBC
Steven Webb/CBC