Herring species are characterized by great fluctuations in abundance, and in the Gulf of Maine there has been much variation since the 1800s. Modern pressures, however, may have led to the widespread global collapses of Atlantic herring stocks during the 1960s and 1970s.

	Irish and Russian herring trawlers

The Norwegian, Icelandic and North Sea herring stocks totally collapsed in the late 1960s, after which restrictions were placed on fishing. Possibly as a result of these restrictions, the Icelandic population began to recover soon after.

In the Northwest Atlantic, there was a significant decrease in herring stocks concurrent with intensive offshore fishing pressure by a large foreign fleet that arrived in the early 1960s. Before its collapse, the Georges Bank population sustained the largest herring fishery in the northwestern Atlantic. [1] The foreign fleet was largely responsible for a peak in Georges Bank herring landings that reached 374,000 tons in 1968. [2]

Over-fishing and the lack of any credible management strategy led to the complete collapse of Georges Bank herring stocks by 1977, at which time reported landings were below 2,000 tons. [3] (While the decline in Maine herring stocks may have been due to over-fishing by foreign fleets, some researchers point out that the herring landings correlated fairly well with coastal temperature variation.)

In response to trends like these, the United States passed the Magnuson Fisheries Conservation and Management Act in 1976, giving the U.S. sole jurisdiction of waters up to 200 miles offshore (including Georges Bank). The Georges Bank herring population began to recover in the mid-1980s, but the juvenile herring fishery in the Gulf of Maine remains a shadow of its former strength.

References:

[1] Melvin, G.D., F.J. Fife, M.J. Power, and R.L. Stephenson. (1996) The 1996 update on Georges Bank 5Z herring stock. DFO Atlantic Fisheries Res. Doc. 96/29. 54pp.

[2] NEFMC. (1978) Final Environmental Impact Statement/Fishery Management Plan for the Atlantic Herring Fishery of the Northwest Atlantic. Appendix 1. Description of Stocks.

[3] Maine Department of Marine Resources WiteSite, Herring Landings.
http://www.state.me.us/dmr/commercialfishing/herring.htm.