After back-to-back spawns that helped to boost striped bass stocks into fully "recovered" status, this year's juvenile index returned to levels that were near its 41-year average.
Maryland's 1995 "young-of-year" index of 9.3 is just slightly below its average of 9.6. It followed indices of 16.1 last year and 39.6 in 1993 the best back-to-back spawning years on record. Over the past four years, the index average has been at its highest for any four-year period since the early 1970s.
"These numbers show that we are achieving the levels necessary to maintain the striped bass fishery over the long term," said Maryland Department of Natural Resources Secretary John R. Griffin. "The last few years of high juvenile indices have provided an enormous number of small striped bass in the Chesapeake Bay and its tributaries."
The state's young-of-year index, the average catch for a standard seine net haul at 22 monitoring stations in four major spawning areas, is considered the best predictor for future rockfish populations. About 90 percent of the Atlantic Coast's striped bass stock is spawned in the Bay.
The sharp turnaround, only a decade ago, Maryland imposed a moratorium on striped bass fishing while other states sharply curbed their catches, spurred the Atlantic States Marine Fisheries Commission earlier this year to declare rockfish stocks "recovered."
That action by the ASMFC, a compact of East Coast states which develops management plans for migratory fish, cleared the way for states all along the coast to raise their catch limits as long as they stay within guidelines intended to ensure a sustainable stock.
"I think they're out of the woods for sure," said Bill Goldsborough, a fisheries scientist with the Chesapeake Bay Foundation. "The juvenile index being back down to average level this year is not surprising and it should not be of concern. If you just look at the historical record of that index, it's up and down all over the place."
Because good conditions are critical to a successful spawn, the striped bass recovery strategy of the 1980s and early 1990s was aimed at restricting harvests to ensure that enough fish survived to spawning age to take advantage of those conditions when they do occur.
Larger populations coupled with good conditions resulted in unusually large spawns, known as "dominant year classes", in both 1993 and 1994. Before that, Goldsborough said, having back-to-back dominant year classes had been "unheard of" in the 41-year history of the index.
"Historically, even when the stocks were high, on the average you only hit a dominant year class every six years because that was the frequency with which you hit those conditions just right," Goldsborough said. "So I don't think we have a problem."
Still, he added, a striped bass population that is truly recovered in a biological sense would need a better age distribution among spawners than is now found in the Bay. The spawning stock should range from 8-to-30 years old, but spawners in today's stock mostly range from 8-to-13 years, older striped bass are few because they were subject to greater fishing pressure before the new restrictions were imposed. Generally, older fish produce more eggs than younger fish.
Nonetheless, Goldsborough said the ASMFC's current striped bass management plan would allow more fish to survive to older ages over time, improving the spawning mix. "We don't need to worry as long as we maintain fishing mortali ty in the sustainable range," he said.
This year's survey showed that three of the four major spawning systems produced better than average numbers when compared with the 41-year average. The Choptank River had the highest index at 17.7, well above its average of 12.5. The Nanticoke River, which had produced relatively poor numbers for 20 years, was at 10.4, above its average of 6.5 for the third consecutive year, and the Potomac River was at 8.7, better than its average of 7.2.
The upper Bay was the only system with a below average level of 4.4. Its average since 1954 was 12.2, and in 1993 and 1994 it had reached 23 and 23.5 respectively. Fisheries biologists say the 1995 figure may have reflected poor spring survival conditions for eggs and young in that area. But they said the previous two year's success indicate a successful long-term reproductive rate f or that area.
To produce the index, samples are taken from each site three times during July, August and September and involve biologists making two sweeps, a half-hour apart, with a 100-foot long, 4-foot deep seine. The young-of-year index is calculated by dividing the total number caught by the number of seine hauls.
This year's fish will be large enough to be harvested in the 1998-99 season.