As striped bass begin their annual to migration to the Chesapeake Bay and other spawning grounds, local fishermen can look forward to another few years of decent fishing. But a sudden drop in the number of juveniles in 2012 will eventually reverberate up the coast.

This year’s juvenile index, announced in October, was the highest since 2011 and the eighth highest on record. The average number of juveniles counted at 22 sites around the bay was 24.2, more than double the 60-year average of 11.9. The figure has increased every year since 2012.

The young-of-year index, compiled by the Maryland Department of Natural Resources, has varied between around one and 60 since 1954 when the counts began. The numbers tracked the collapse of the striped bass fishery in the 1970s and 1980s and its recovery in the 1990s following a coast-wide moratorium.

Gary Nelson, fish biology program manager for the state Division of Marine Fisheries, said this week that the annual counts closely follow the pattern of catch rates in Massachusetts, although it takes four or five years for the fish to arrive in local waters.

He estimated that about 70 per cent of the local catch comes from the Chesapeake Bay, with the rest arriving from the Hudson and Delaware Rivers.

Juvenile counts in the Chesapeake Bay have been above average for 10 of the last 20 years, but were below average between 2012 and 2014, with 2012 having the lowest count on record. “So we’ll have good fishing the next few years until the 2011 year class is fished out and then we’ll have a little decline and then that 2015 year class should move through,” Mr. Nelson said.

Atlantic striped bass inhabit coastal waters between the Gulf of Mexico and the Saint Lawrence River, returning to rivers and estuaries to spawn in the spring. Females take four to six years to mature, while males take two or three years. The oldest striped bass on record is a 31-year-old female from the Chesapeake Bay.

Some biologists believe that a decline in recruitment in the bay between 2004 and 2010 was the result of less rainfall, since cold, rainy springs tend to produce larger year classes. The young-of-year index hit 34.6 in 2011, the fourth highest count on record, but Mr. Nelson said the cause was a mystery, as was the decline in 2012.

The Atlantic States Marine Fisheries Commission last year approved new catch limits and commercial quotas for striped bass along the coast in an effort to protect the spawning females and encourage larger year classes.

A stock assessment this year by the ASMFC projected a slightly slower decline than was previously charted. But if a stock assessment next summer shows further improvements, then states may want to revert to the old regulations.

Mr. Nelson said communities in the Chesapeake Bay in particular were pressing for softer regulations, since the fish there are generally smaller and people have observed an abundance this year. The larger fish usually leave the bay by springtime and make their way up the coast.