Peter Gray Parr Project


The Peter Gray Parr Project began in 2012 on Maine’s East Machias River. The Project is based on successful salmon restoration methods used by Peter Gray on the River Tyne. Over the ensuing years,  increased egg production has had a positive impact on the number of raised fry and parr. In fact, since the Project’s inception, over 1 million fall parr have been stocked. Biologists and volunteers clip the adipose fin of each parr that leaves the Peter Gray Hatchery. These fish are easily identified during future electrofishing sampling and smolt trapping. Stream sampling shows salmon population response with juvenile salmon densities increasing from 5.3 fish/100m2 in 2013 to 14.9 fish/100m2 in 2016 (181% increase), a drainage-wide density of juvenile salmon not seen in the East Machias River since 1984. The big story is when the parr transform into smolt. As of 2018, smolt populations in the East Machias have more than quadrupled since the start of the Project.

For complete data though 2019, documented results can be found HERE


Peter Gray, the legendary British fisheries biologist, created one of the most impressive wild Atlantic salmon restoration programs in the 170-year history of Atlantic salmon conservation. Through his innovative rearing conditions in his unique streamside hatchery, he was able to strengthen salmon for survival during their epic oceanic journey. Over three decades, Gray’s efforts increased salmon returns on England’s River Tyne from 724 to over 13,000 adults. Peter Gray personally trained the biologists working on the Peter Gray Parr Project and he was actively involved in the project’s launch back in 2012.

One of the cornerstones of Gray’s methodology was a streamside hatchery that incorporates flowing river water from the salmon’s natal river. As the Peter Gray Parr Project is focused on improving runs of Downeast salmon, acquiring land and building the Peter Gray Hatchery on a Downeast river was key. In addition to the unique internal and state-of-the-art interior, the hatchery is partially solar powered and eco-friendly.


Parr collected during late-summer electrofishing assesments in the East Machias River are transferred to the United States Fish and Wildlife conservation facility, Craig Brook National Fish Hatchery. These parr carry the genetic composition of East Machias salmon and are raised at Craig Brook to adults. In the fall, eggs from the female salmon are fertilized with milt from the male salmon. The fertilized eggs are later transported to the Peter Gray Hatchery where they are placed into Heath Stack Egg Trays for 3 months. Once hatched into alevin, the salmon are transferred to Kielder substrate incubation boxes. Gray designed the boxes to include water running from the salmon’s natal river over plastic substrate mimicking a natural salmon redd.

Upon hatching from the egg, the salmon enters the alevin stage and relies on its yolk sac for nutrition. Once the yolk sac is fully absorbed, the alevin swims up and out of the substrate incubation box dropping into our rearing tanks.


The rearing tanks are painted black to keep the coloration of the salmon in the hatchery dark, just like their in-river counterparts. The water flow in the rearing tanks is continually increased as the salmon grow, which begins the conditioning process. Fry feed and swim against the current, and with every passing day, they gain both size and strength. In the fall, when the fish are stocked in the river, they will be in a condition suited for life in the wild. This strengthening program is critical as parr spend between 1 and 3 years in the river.


Each fall, before the “little athletes” are stocked, each individual salmon receives an adipose clip. They receive an adipose fin clip prior to stocking so they can be identified as coming from the Peter Gray Hatchery during future electrofishing and smolt trapping surveys.


Parr are stocked in the fall when water temperatures have dropped, and these lower water temperatures slow the fish’s metabolic rates. Since they don’t have to feed as much, the parr are able to focus their energy on finding overwintering habitat instead of feeding.

Parr remain in the river for one to three years until they reach the smolt life stage. Food availability, water temperature, and water level are examples of variables that determine the amount of time they spend in the river. When ready, they go through the process of smoltification, which allows them to live in salt water, swimming down the river in the spring to begin their life in the open ocean.

They remember the “smell” of their natal river and once they have grown for a couple of years in the ocean, they utilize the “smell” to travel back to the river of their birth to spawn.


Seabound smolt are trapped to gather one final piece of data. The PGPP team works with the Maine Department of Marine Resources (DMR) staff operating rotary screw traps borrowed from NOAA Fisheries. Each trap is made up of three basic parts – a cone, pontoons and a live car. The cone sits on its side in the river with the wide end facing up-stream. At the back of the trap, the narrow end fits into a live car which holds the smolts until the trap is tended. These traps are tended at least once per day and the salmon population is estimated using a mark-recapture study. All salmon are measured, weighed, and any markings noted. Newly captured salmon are then marked with a small tail punch and released upstream. This tail punch not only functions as a mark but also provides tissue from each fish for genetic analysis.

The number of marked fish re-captured indicates the efficiency of the rotary screw traps. Using this number, it is determined what percentage of the population is captured in the traps. The capture efficiency is one metric used to estimate the overall size of the outgoing smolt population. Because all of the fish from the Peter Gray Hatchery have been marked with a fin clip prior to release, it is known what percentage of the smolt population comes from the Peter Gray Hatchery. Gathering this valuable smolt data allows determination of ocean survival rates of returning adults.


The restoration of wild Atlantic salmon in the United States takes time, just as it did on Peter Gray’s River Tyne. Every benchmark has shown dramatic increases, from egg production to parr stocking to departing smolt. Some might reason that we wait for five years and assess the number of returning grilse and salmon, but given the proven successes of Peter Gray’s methodology, we plan to continue raising more eggs, alevin, fry, and parr. Only then can we ensure a progressive return of wild Atlantic salmon to Maine’s waters. Conservation costs money and we need your help. Please pledge today.