Cod stocks off Newfoundland's south coast are not improving, but they're not worsening, either, a research report released Wednesday shows.

John Brattey, a research scientist with the Department of Fisheries and Oceans, said the latest assessment of cod in the area shows no clear trend on where the stock is headed.

"It's certainly frustrating from everyone's perspective, from our own and from the fisheries managers and indeed from the fishermen, too," Brattey told CBC News.

"But we don't feel that a single mathematical model can reconcile the information into a single assessment of the stock as a whole, so we don't feel it would be appropriate to do it at this point."

Cod stocks off the south coast have been among the healthiest in Newfoundland and Labrador, but only because other stocks — particularly the northern cod stock, off the island's northeast coast — remain so weak even after more than 15 years of a commercial fishing moratorium.

Fishermen have been catching cod off the south coast that are bigger and older than in recent years, which Brattey said indicates the area is not being overfished.

He said, however, that it is too early to tell how many younger fish will survive to maturity.

The fishing zone, which is known in the industry as 3PS, has been in steady decline since 2000.

The assessment is based on a variety of data, including landings, trawl surveys and logbooks. The assessment will be used by fisheries managers before commercial quotas are set for the coming year.