Fish populations decline in region

Again this year, the results of the annual fish count show declining populations in five local river systems. Those that evaluate the results have few -- or too many -- theories to explain why.

Each spring, beginning in April, more than a hundred volunteers count fish as they swim upstream at certain points along the Essex, Ipswich, Parker, and Saugus rivers, as well as the Little River in Gloucester. The volunteers count alewives, or river herring, which reach 8 to 10 inches in adulthood.

Alewives live most of their lives in the ocean, but are born in and return to freshwater to reproduce. By counting fish, and using a mathematical formula, biologists estimate the fish population in the river.

Protecting and restoring the alewife population is considered important for a number of reasons, particularly for the fish's important role in the food chain. The species is eaten by larger commercial and recreational fish, said Tim Purinton outreach coordinator for the Massachusetts Audubon Society, who coordinated the Little River count and will report on the findings. The health of the species also may reflect the region's biodiversity, from animal, bird, and fish life to plant and plankton life, Purinton said.

For those reasons, the continued decline in the alewife population is a cause for concern for wildlife biologists and others who work on the effort.

''Every year it's a little troubling, and we don't know why," Purinton said, noting that while there are man-made dams and other impediments to alewives returning in some systems, the count was down even in the Essex River, considered to be a healthy watershed offering good potential as a spawning area.

On the Essex River, an estimated 2,420 fish were present, down from 5,600 from last year, 8,100 in 2002, and 15,900 in 2001.

Peter Phippen, who coordinated volunteers for the Essex River fish count, said that past fish counts have shown declines over a period of years, but that a tremendous number of variables made it difficult to pinpoint the reasons. Alewives may be eaten or overfished at sea, obstructed from returning by heavy water flows on a river, or discouraged by cold temperatures, water quality, or habitat issues.

''Who knows what it is?" Phippen said. ''It could be something going on in the ocean, environmental conditions in their spawning area, or weather conditions. I don't think you can say, definitely."

The Parker River, which has a recent fish count dating back to 1997, has shown a decline since 1999, when an estimated 8,000 fish were found in the river. This year's count was 2,000, following 2,400 in 2003, 3,500 in 2002, 2,200 in 2001, and 7,900 in 2000. Studies from the 1970s indicated much larger populations, including 1973, when it was estimated that the fish population was 38,100.

''At this point, we're still working on reasons and don't have any good ones," said Don Bade, president of the Parker River Clean Water Association.

The Ipswich River Watershed Association counted bluebacks and alewife from April until mid-June. Their figures indicate an estimated population of 180, which is consistent with the 1999 estimate of 168. In 2001 that estimate was 420, in 2002 it dropped to 360, and last year it was 231. Kate Taylor, a volunteer who coordinated the count, noted that the state Division of Marine Fisheries had planned to stock the river with fish taken from the Charles River, but didn't because of a shortage of fish in the Charles.

On the Little River in Gloucester, an estimated 150 fish were present, up from zero last year but well below the estimated 8,700 in 2000, 1,800 in 2001, and 500 in 2002.

Along with variables that may affect fish migration, some human variables may affect the fish count as well. For example, the Little River fish count was supported financially by Gorton's of Gloucester this year, which allowed Purinton more time and resources to recruit volunteers. The Essex River fish count had been grant funded for three years, but not this year. While Phippen still coordinated the count, as he had in other years, he had less time and fewer resources, which was reflected in fewer volunteers and fewer ''counts."

Other human-related variables can include the time of day that fish are counted, or the viewing spot. For example, the Saugus River Watershed Council is reevaluating its methods after fish counters at the Saugus Ironworks Bridge spotted just one fish this year, and none last year. Executive director Joan LeBlanc said fish have been spotted ''unofficially" at a dam near the Lynnfield-Wakefield line, and that there is spawning activity at Camp Nihan Pond.

''The good news is, we know there's a presence of alewife and hope to restore it in greater numbers," LeBlanc said. ''The bad news is, we need a new method for tracking."

In addition to the counts done by volunteers, the Division of Marine Fisheries also counts anadromous fish returns on the Merrimack River, where fish are helped upstream by fish lifts that help them navigate over dams, such as the one in Lawrence.

Phil Brady, Marine Fisheries senior biologist, noted that this year's number of 15,051 river herring is an increase over last year's 10,879, but far below the numbers of the late 1980s and early 1990s, including the high of 387,973 in 1989.