PROVIDENCE — Mid-March, about 140 years ago, the first river herring, while making its yearly migration up the Woonasquatucket River, was rudely introduced to the Rising Sun Mills dam. Since then, thousands of fish each year have been prevented from migrating upstream to ideal spawning habitat. That changed, however, in 2007 when the Woonasquatucket River Watershed Council had a fish ladder built that allows herring and other fish to pass freely from one side of the dam to the other.

Since the fish passage restoration project began five years ago, the Woonasquatucket River Watershed Council (WRWC) has remediated four dams along the lower Woonasquatucket River. Ladders were added to the Rising Sun Mills dam and the Atlantic Mills dam at Riverside Park; the Paragon and Dyerville dams were removed.

The fifth and final dam the WRWC plans on remediating is the Manton dam. Unlike the other sites, the Manton dam will be bypassed by a stream-like fishway built around the dam.

In 2010, the WRWC began a fish counting program to measure the success of the Rising Sun Mills dam ladder. During the first year of counting, the WRWC estimated that more than 25,000 herring used the ladder to migrate to upstream spawning grounds. In 2011, after the removal of the Paragon dam further upstream, the count dropped substantially to an estimated 7,000 fish. That lower number of counted fish, however, is nothing to be disappointed about, according to Alicia Lehrer, executive director of the WRWC.

She said the high count in 2010 occurred because fish, confronted with the Paragon dam just upstream, likely spent the season in the vicinity and traveled through the ladder multiple times. In 2011, after the Paragon dam was removed, the fish were able to keep swimming upstream and, thus, only passed through the ladder once.

The number of fish counted is expected to rise in the coming years, according to Phillip Edwards of the state Department of Environmental Management (DEM). First, because river herring naturally swim upstream to calmer, less brackish and more spacious spawning habitat, their offspring should be biologically programmed to return and spawn there as well. Second, since the dams have become passable, the WRWC has been stocking the upstream spawning habitat with new fish. Those fish should also be programmed to return to the upstream habitat once they are sexually mature, Edwards said. He said he expects counts to rise by tens of thousands, possibly reaching 100,000 fish.

Volunteer fish counters
The WRWC fish counting program has developed something of a following. Registration and training to count fish this year was held March 19 and 20, and the turnout was high. In the hour I spent at the Rising Sun Mills fish ladder, next to Donigian Park, 15 volunteers became trained fish counters. The training was anything but grueling.

It includes a 10- to 15-minute session during which five trainees stand on the ladder’s viewing platform and learn to measure the height and temperature of the water and where to look to count the fish. The fish are counted in 10-minute time intervals. At least two counts are necessary each day, one in the morning and one in the afternoon. If extra counts are conducted, the totals are averaged. The more counts taken, the more accurate the data.

I signed up to count fish once a week from March 27 through May 17. At the outset, I expected the counts to rise and fall in a bell curve, starting out slow, spiking toward the middle, and then tapering off at the end. I counted zero fish during my first two outings, and could tell from the log that my fellow counters were having no better luck. Lehrer quickly went into damage control sending out an e-mail to all counters with the subject, “Fish Counting Patience,” in which she blamed a cold snap for the lack of fish using the ladder.

I continued to make my once-a-week journey to the ladder, sometimes in the rain, sometimes in the sun, sometimes in the morning, sometimes in the afternoon, but frustratingly, weeks later I still hadn’t seen any fish. I began to wonder if something had gone wrong. My completely unscientifically educated mind started coming up with wild scenarios to explain how all the fish simply disappeared.

Maybe they all got swallowed up by the out-of-state pair-trawlers reported to have taken huge catches off Rhode Island’s shores earlier in the year — it turns out the pair-trawlers were targeting a different kind of herring. Perhaps they all snuck by a month early because of the mild winter. Perhaps the drought-like conditions during the early part of spring were making the water too shallow downstream for the fish to swim up the river.

It was with thoughts like these lurking in my mind when I arrived at the fish ladder just a few weeks from the end of the counting season. I dutifully took the temperature of the water, measured its heights and started my 10-minute count.

And then, a fish! And another, and another.

By the end of the 10-minute session, I had counted 15 fish passing through the ladder. The pair-trawlers hadn’t gotten them all! They hadn’t snuck past when no one was looking. The dry spring hadn’t left them all gasping for water down stream. I recorded my results, with a smile on my face.

As the season closed out, I counted two fish on one other occasion. My personal results looked nothing like the bell curve I expected, but I would have to wait until early June for the numbers to be crunched to learn the overall findings.

A good year
It turns out, that despite the many fishless days reported from the Rising Sun Mills fish ladder, 2012 was a pretty standard year. The total fish estimated to have passed the ladder at Rising Sun Mills was 9,264, about 2,000 more fish than were counted in 2011. According to Edwards, this growth in population is modest. The yearly increase in population is expected to rise sharply when the stocked fish begin to return to the Woonasquatucket River spawning grounds over the course of the next year or two. Herring generally do not start to reproduce until their fourth year.

The weather played a substantial role in when the fish moved up the river. The mild winter caused the run to start about three weeks early. Then, the cold snap that occurred in late March and early April, just as the counting began, sent fish counts plunging in rivers all over the state. A few heavy days of rain also were responsible for slow fish counting days, as the fish prefer not to struggle upstream against the higher velocity water generated by the rain.

This season marked the first in which fish were counted at the Atlantic Mills dam ladder further upstream. Few fish traveled through that ladder, but there were accounts of 10 fish passing during some counts. As data for the Atlantic Mills ladder is accumulated during the next few years, the WRWC will be able to tell how many fish are spawning beyond the first three remediated impasses.