Scientists seek mystery fish-breeding ground

Fish scientists need help figuring out whether striped bass is a threatened species in need of protection under federal law.

Striped bass used to breed in three rivers that empty into the Bay of Fundy; the Annapolis and Shubenacadie Rivers in Nova Scotia and the St. John River in New Brunswick.

Hydro dams on the Annapolis and the St. John Rivers have damaged breeding grounds. Scientists used to believe the Shubenacadie River system was the only place left for the fish to breed, and were worried that damage to the last breeding ground could lead to the extinction of the local population.

• NOVA SCOTIA DEPARTMENT OF AGRICULTURE AND FISHERIES: Factsheet - Striped Bass

But Department of Fisheries and Oceans scientists say recent genetic testing has shown hints of another breeding population of fish.

DFO fish scientist Rod Bradford says DNA testing on striped bass from the fish ladder below the Mactaquac Dam found specimens that were different from other known populations.

Bradford says testing found fish genetically identical to Shubenacadie fish and known American populations. But they also found another, unique population that scientists believe could mean there is another breeding ground in the Bay of Fundy river system.

"You have this other group that's not related to either one, which is a pretty good indication that there's another population somewhere," said Bradford.

Bradford says nobody knows which river is being used as a breeding ground. He says the fish like to mate and lay their eggs in large rivers where fresh and salt water mix, and migrate everywhere to breed.

Given that the fish were taken from the Mactaquac Dam, it might be simple to assume that the fish are spawning somewhere in the St. John River, but Bradford says that's not necessarily true.

"Striped bass are highly migratory," said Bradford. "Until we actually document spawning areas, we can't relate these fish to a possible origin. But given the history of known spawning in the St. John and the Annapolis, those are at least two local candidates."

Striped bass are one of the most prized sport fish on the Eastern Seaboard. The ocean-going, migratory fish can reach 30 kilograms and put up a big fight on the end of an angler's line. If they are protected under the federal Species At Risk Act, that fishery would be eliminated.

Anglers on the St. John River have long suspected that a new, or unique, genetic species of striped bass existed. They have found large numbers near a group of islands below the Mactaquac Dam and at Gagetown. The anglers reported catching much smaller specimens, leading many to wonder whether they were too young to have made the journey from the Bay of Fundy and were therefore breeding nearby.

Bradford is now asking people to keep a close eye on the the Annapolis and St. John Rivers in May and June for breeding fish and to send any reports of spawning to his department. He says the sight of mating striped bass is unmistakable, with lots of activity and a great deal of splashing at the surface of the water around the mouths of rivers.

Bradford wants to hear detailed stories about striped bass breeding on these rivers from the last three years, and any historic spawning reports, because scientists don't know the exact location of the former breeding grounds.

Public consultations about whether to protect striped bass are currently going on across the Maritime provinces. A committee will decide in 2007 whether to place striped bass on the threatened species list.