An unusually warm fall in 2017 overlapped with the spawning of brown trout in the New Gloucester Fish Hatchery, killing a large number of eggs that season.
In a normal year, up to 90 percent of the eggs survive. But the warmer water that came with the higher air temperature dropped the survival rate to 20 percent, said David Russell, fish pathologist at the Maine Department of Inland Fisheries and Wildlife Fish Health Laboratory in Augusta. The so-called New Gloucester strain of brown trout’s whole brood population ovulates within one week of each other, so there was no chance for another spawn that season to compensate for the losses.
“The event was one of several factors that resulted in us switching to the Seeforellen strain [of brown trout], which has a protracted spawning season,” he said. “If temperatures are too warm at the start of the season, the later spawning brood can make up the difference.”
Warming waters caused by the changing climate are threatening Maine’s hatcheries, which raise fish that are released into rivers and lakes in the state where fish are scarce for anglers to catch. The hatcheries are a key part of Maine’s freshwater fishing economy, which the Maine Department of Inland Fisheries and Wildlife and the Maine Office of Tourism estimated was worth $319 million in 2013, the most recent data available. To protect the industry, the state is figuring out ways to adapt and protect the fish from the effects of climate change.
Fishing is increasingly popular in Maine. The number of fishing licenses, which pay for the state’s hatchery operations, increased in 20 of the last 25 years, according to Maine Department of Inland Fisheries and Wildlife spokesperson Mark Latti. Since 2013, they rose 20 percent to 373,000 licenses in 2022.
The New Gloucester Hatchery is one of the eight state fish hatcheries that are used to stock more than 1 million trout and salmon in 800 Maine lakes and rivers each spring and fall. All eight face temperature challenges.
At the Enfield Hatchery, for example, the temperature during the first two weeks of spawning season starting at the end of October rose from an average of 49 degrees Fahrenheit in 2013 to almost 54 degrees in 2023. Water temperatures at other hatcheries vary with location depending on where they get their water. The Enfield Hatchery is supplied with lake water that can be subject to unusually warm autumns, while the Governor Hill Fish Hatchery in Augusta is spring fed with reliably cooler water, Russell said.
“Temperature anomalies that have impacted our spawning operations over the past few decades are still an issue and seem to be occurring with increasing frequency,” Russell said. “The last three years have been particularly notable, with average water temperatures during our critical spawning window for trout and salmon being several degrees warmer than ideal.”
Another big fish loss occurred in 2016 at the Grand Lake Steam Hatchery in Washington County, before the state built a pipeline to access cold water from the depths of West Grand Lake to mitigate deaths caused by warming waters. A prolonged period of temperatures above 80 degrees Fahrenheit killed 30,000 brook trout at the hatchery, he said. The deepwater pipeline, installed in 2018, lets the hatchery mix in colder water from the depths of the lake with warmer water from its shallow water pipeline to maintain ideal water temperatures for the fish. The hatchery in Casco had a similar deep water pipeline installed before the one in West Grand Lake.
Warmer water temperatures decrease egg quality and survival dramatically, Russell said. The greater the temperature difference, the worse the result. It only takes a few degrees for some of the more sensitive species, such as the brown trout, to have a bad egg year.
There is no option to wait for cooler weather. So the hatcheries are looking for ways to cope with warming waters. They include piping in cooler water from deep parts of lakes and increasing the amount of fish used for breeding, Russell said. In some cases, eggs in jars are moved from one hatchery to another with better conditions.
The state also plans to dedicate $20 million of the American Rescue Plan funding it received for several hatchery projects, including replacing antiquated infrastructure at the 88-year-old New Gloucester Fish Hatchery. The money also will go toward creating capacity at Grand Lake Stream Hatchery to manage fish disease threats and conserve the native population of landlocked Atlantic salmon. And it will go toward improving the water quality leaving all eight of its fish hatcheries.
Maine grows six species at its hatcheries, spawning about 3,000 fish annually from 10 captive and two wild broodstock populations. The state-run hatcheries are in Casco, Dry Mills, Augusta, Grand Lake Steam, Embden, Enfield, New Gloucester and Palermo.
The state’s first fish hatchery, started in 1871, was at Craig Brook in East Orland, according to the Maine Memory Network. A new law in 1895 allowed the state to buy or lease land for fish hatcheries. The state ran about 50 hatcheries between 1895 and 1956. Russell said scientific advances and modernization of the hatcheries allowed that to shrink to today’s eight locations, which have the best water volume, quality and temperature to grow the fish.
Brook trout make up about 70 percent of the fish the state stocks at its hatcheries, followed by 13 percent brown trout, 11 percent landlocked salmon, 3 percent splake (a hybrid of lake and brook trout), 3 percent rainbow trout and the remainder, lake trout.
The Maine Department of Inland Fisheries and Wildlife said it stocks waterways to maintain healthy populations of trout and landlocked salmon that otherwise would not be there because the location is not suitable for spawning, or there are competitor fish or predators such as mink.
The waters that are stocked are away from those with naturally occurring populations in strong numbers, Russell said. They are stocked in the fall and the spring, from the end of April through June and in late September through October.
In the spring the department stocks some brooks in York and Cumberland counties where fish survive for the season but cannot live year-round. In the fall it stocks large yearling trout, typically brook trout, that open water anglers can catch in the fall, ice anglers in the winter and spring anglers at ice-out. Those fish are usually two to three years old, or 12 inches to 15 inches long, when they are stocked and are brightly colored, so even beginners can find and catch them, according to the department, which posts daily updates on its website of fish stocks by county.
“Because of the resources, we have some operational flexibility to kind of roll with whatever climatic punches are thrown our way,” Russell said.
Lori Valigra is an investigative environment reporter for the BDN’s Maine Focus team. She may be reached at lvaligra@bangordailynews.com. Support for this reporting is provided by the Unity Foundation and donations by BDN readers.