Fate of stocked trout: 5 things learned from 4-year study
Editor’s Note: This is the first of five “things we learned” from our 4-year study. Check back each day this week as we reveal the entire list. AZGFD’s Zach Beard, Ryan Mann, and Andy Clark contributed to these posts.
Ever wondered what happens to the thousands of trout that the Arizona Game and Fish Department stocks into streams all around the state every year? You’re not alone.
We just completed a 4-year study (beginning in 2013) to investigate the fate of rainbow trout and Apache trout stocked into several of Arizona’s popular stream trout fisheries.
As part of this project, AZGFD biologists conducted nearly 5,000 angler interviews on six different streams (Canyon Creek, East Fork Black River, East Verde River, Silver Creek, Tonto Creek, and West Fork Little Colorado River) during the trout stocking seasons (April to September) of 2013–2016.
From these interviews, biologists estimated total harvest (number of stocked trout kept by anglers), angler effort (total time spent fishing by anglers), and angler catch rates.
Our biologists also implanted trout with radio transmitters in order to track their movements and determine how long they survived in the streams.
Here’s the first of 5 things we learned:
1. Most trout don’t survive past one week of being stocked
Soon after they’re stocked, the fish are being caught. Anglers: It seems you’re doing a great job of fishing AZ.
First, some facts during the duration of the study:
- Biologists implanted 492 trout with radio transmitters (246 rainbow trout and 246 Apache trout).
- Many of the trout — 60 percent — are no longer alive after one week in the streams.
- It was several weeks before the percent of trout remaining from a single stocking was below 20 percent.
This is why most streams on our stocking schedules call for waters to be stocked every 1-2 weeks, keeping trout in these “intensive use” systems to maintain opportunity.
Yet there are rare exceptions. In one stream, 71 percent of radio tagged trout remained alive after one week. Surprising?
Get this: The longest surviving trout was a pair of Apache trout (Fish Nos. 1C and 38C) that were still alive 123 days after they were stocked when we detected them on Dec. 4, 2015 in the East Fork of the Black River. Who’s up for the challenge of catching these hard-nosed Apaches?
Anglers were not the only ones eating stocked trout. Birds and mammals, such as ospreys, great blue herons, and raccoons, consumed between 6 to 30 percent of radio tagged trout.
Check back tomorrow for No. 2: Trout don’t move far from release locations.
Here’s background on the project from 2015 on our “AZGFD” YouTube channel: