Fisheries surveys show Delaware River holding wild brown, rainbow trout
So you want to catch some fish, huh?
Well, here’s a tip. Start by casting your line where the fish are.
Pretty sage stuff there, I know. Confucius-esque, almost.
But if you want to catch fish, you’ve got to know what waters the fish call home and in what sizes and numbers.
The good news is, there’s a way to pin that down. Biologists with state fish and wildlife agencies each year survey lakes, streams and rivers to get a handle on fish populations. They don’t get to every water every year. Indeed, in many cases, they go years between looks.
But the survey reports are a starting point, a sort of CliffNotes for anglers.
And we’ve got them. Each week or so over the next few months, we’ll provide the lowdown on the latest fisheries surveys from across Pennsylvania.
Here’s episode #3.
It’s a tricky business, managing the Delaware River watershed’s wild trout.
It all comes down to water.
The fish need consistent flows of sufficiently cold water to thrive. They get it via releases from New York City’s water supply reservoirs.
That involves competition.
The city, together with officials from the states of New York, Pennsylvania, New Jersey and Delaware, cooperatively determine how much to release and when. Historically, all want varying amounts of that water for various purposes at varying times.
Those sometimes divergent demands haven’t always been great for trout.
But those entities value the Delaware’s browns and rainbows — an increasingly important source of tourism dollars in the region — more than in the past. So two states are trying to figure out how many there are and where.
Pennsylvania’s Fish and Boat Commission and New York’s Department of Environmental Conservation are right in the middle of a three-year effort to document wild trout numbers and reproduction. Their “joint fisheries investigation plan” began in 2018 and runs through 2020.
Biologists from each state, together with volunteers, are doing electroshocking surveys to monitor populations and counting redds, or fish beds, to see where natural reproduction occurs.
The results so far show a pretty nice fishery.
The 2019 version of the work is ongoing.
But details from the 2018 surveys are available. Commission biologists sampled four sites on the West Branch Delaware River. They collected 178 wild brown trout and 25 wild rainbows.
“Size distribution varied, but a majority of the fish captured were 12-inch to 18-inch in length,” said a commission report. “A 24.1-inch brown trout (caught at Laurel Bank) and a 19.1-inch rainbow trout (caught at Shehawken) were the largest trout captured.”
Biologists suspect that total catch under-represents the actual fishery, however, given high waters that reduced the effectiveness of their work.
New York biologists began some preliminary trout sampling in 2017. They said the overall number of trout in the river — and young of the year trout in particular — was a surprise “because historical surveys did not collect the high numbers of trout” seen over the past two years.
Commission biologists resurveyed the river in June, using night boat electrofishing. That turned up 474 brown trout and 49 rainbows. The Laurel Bank site produced the most fish, and downstream sites — Airport Road, Balls Eddy and Shehawken, in that order — offered fewer.
“The improved catches of trout observed in June likely reflect better electrofishing catchability rather than an increasing trout population in the West Branch, as lower flows experienced during the June sampling allow for an easier capture of trout,” biologists wrote in their report.
Size of the wild trout was again good, though.
Seventy-one percent of the brown trout and 59 percent of the rainbows exceeded 12 inches in length. Twenty-six percent of the browns and 10 percent of the rainbows measured 16 to 19 inches.
Fish longer than 20 inches were “relatively infrequent,” biologists said. But they collected a 26.2-inch brown and a 19.1-inch rainbow.
As for where those fish are spawning, biologists from the two agencies, together with volunteers from assorted sportsmen’s groups, counted trout redds, or spawning beds, last year.
Rainbows spawn in spring, typically in April. Browns spawn in fall, usually in October.
Both species use shallow, fast-moving waters with gravel substrate, with rocks measuring 1 to 3 inches in diameter. Females dig a small depression, surrounding it with an elevated gravel bar, and lay their eggs inside it.
Crews looked for redds by kayaking and wading. That’s unique in itself.
New York biologists said “it’s unknown” when the river last was surveyed that way.
Volunteers examined the first half-mile upstream of the upper Delaware River tailwaters on 21 tributaries looking for redds.
Biologists canceled work planned for October, looking for brown trout redds, because of high water. But they completed their work in spring, looking for evidence of spawning rainbows.
Volunteers counted 82 redds in total. They were not equally spaced, however.
“Oquaga Creek, tributary to the West Branch, had the single highest red count. Read Creek, tributary to East Branch, had the second highest red count,” biologists wrote.
Volunteers found 22 redds in Oquaga, 17 in Read Creek.
“Most of the other tributaries surveyed typically had less than 10 redds observed,” the report said.
Some didn’t have any. Several of those examined have “unsuitable bottom substrates i.e. large cobble,” within the first half mile of reaching the rivers. They were Roods Creek, Sands Creek, Cadosia Creek, Campbell Brook and Hoolihan Creek.
As a result the first half-miles of those waters won’t be surveyed next time.
And biologists missed out on examining some others last spring. High flows made it impossible to count redds in the mainstems of the East Branch and West Branch Delaware.
The hope is to get to them this year.
Then, after 2020’s work is done, biologists will recommend how best to manage the Delaware and its wild trout.
Next week: A look at the Susquehanna River’s channel catfish.