Watts: Chesapeake wildlife in the balance

In November, the Atlantic States Marine Fisheries Commission (ASMFC) will decide on the path forward for managing the Atlantic menhaden fishery. At issue is whether to increase target population levels, which would effectively reduce commercial harvests of menhaden. At risk are populations of birds and other wildlife enjoyed by millions of residents throughout the tidal reach of the Chesapeake Bay.

Menhaden, often called the "most important fish in the sea," are the energy changers of bay waters. They filter plankton, converting it into oil-rich tissues and making this vast energy reserve available to consumers higher up on the food chain. Demand for this energy-rich oil is at the heart of the conflict between commercial menhaden fisheries on the Atlantic Coast and many recreational anglers who claim that menhaden harvest levels have greatly compromised the health of striped bass and other prized species that depend on menhaden for food.

But striped bass and commercial harvesters are not the only ones chasing menhaden. Menhaden are critical prey for many of our bird populations as well, including bald eagles, osprey, brown pelicans, royal terns, and common loons — species that provide the sights and sounds of the visible living fabric that we identify with the Chesapeake Bay experience.

The current ASMFC regulation allows for harvests down to 8 percent of the projected unfished population (or conversely, catching up to 92 percent of all menhaden in the bay and ocean). The population is technically classified as overharvested if it is driven below the 8 percent threshold. Even with this alarmingly generous threshold, a recent scientific assessment has indicated that menhaden have been overfished in 32 of the past 54 years. Allowing menhaden stocks to be harvested to such low levels has implications for other consumer communities.

In 1971, during the height of the DDT era, Bob Kennedy worked with breeding osprey in Mobjack Bay as a graduate student at the College of William and Mary under Mitchell Byrd. Kennedy determined that osprey pairs were producing chicks at a rate well below that needed to maintain the population, largely because DDT in their system made their eggshells too thin to be viable. Only one in four eggs hatched due to DDT contamination, but of the chicks that hatched, nearly eight of 10 survived to fledge.

During the next few decades, three additional William and Mary graduate students would work with osprey in Mobjack Bay and provide a portrait of a changing population. The United States ultimately banned DDT, and by the early 1980s osprey pairs were producing more than twice as many chicks as in the early 1970s, and their population was growing.

Surprisingly, however, by 2006 osprey productivity in Mobjack Bay had declined again back to levels not seen since the DDT era. This time the underlying cause had changed.

More than 35 years after DDT, graduate student Andy Glass found that nine of every 10 eggs hatched, but only four of every 10 chicks survived to fledge. Chicks were hatching, but they were starving in the nest.

Why? In the 1970s adult osprey were delivering nearly three times more fish to nestlings than in 2006. In the 1980s during the period of highest productivity, more than 70 percent of the fish delivered to nests were menhaden. By 2006 menhaden represented less than 27 percent of the diet. None of the other fish species in the osprey's diet are equivalent to menhaden in energy content. So the adults were providing fewer fish to their chicks, and the fish were of poorer quality.

Significantly, over the same four decades, the menhaden population as measured by haul seines in Maryland had declined by more than 90 percent.

What is now before the ASMFC are proposals to make no change, as well as one to increase the population threshold from 8 percent to 15 percent of unfished levels. Though that would represent a modest change, it would be a welcome movement toward considering the needs of fish, birds, marine mammals and the broader bay ecosystem.

The Chesapeake Bay is a tremendous and shared resource. We all have a voice in how that resource should be used for the highest public good. Let ASMFC hear your voice.