Police in riot gear, dogs, video cameras: not a sight Islanders are accustomed to on the local news. The largest police action in Island history played out on the Souris wharf one year ago, and it seems there is nothing to stop history from repeating itself this year.

It's all about herring, and a line in the water drawn by the federal Department of Fisheries and Oceans. On the inshore side of that line fishermen based on Prince Edward Island catch herring to harvest the roe, and for bait, using small boats and small nets. On the ocean side of the line herring seiners, based in New Brunswick, are free to use their large boats to cast their large purse-style nets.

The inshore area is also where lobsters - worth $108 million to the Island economy - live, lay eggs and, wander into lobster traps for a bite of bait.

The Island fishermen claim the herring seiners are damaging lobster-fishing grounds and depleting the stocks. The seiners respond that their nets never touch the bottom, where the lobster traps lie. And they point to DFO science that says the herring stocks are healthy.

Pointing at science doesn't do much good when a Souris-based fisherman sees a big boat rumble over the lobster ground he's fished for years. In fact, what little science there is on the herring fishery was quickly lost last year behind the din of diesel engines, shouting crowds and the boom of the Mounties' bullhorns.

Nor does science seem to appease the Island's fisheries minister, the P.E.I. Fishermen's Association or the families of the men who pull traps off the eastern shore of the Island.

A Line in the Water explores the issues, how the herring fishery works and what's at stake for both sides. Continuing coverage of the herring dispute is available on CBC Radio, CBC TV and CBC Online, here on www.cbc.ca/pei.