Learning the shocking truth about trout

BALDWIN – Periodically DNR biologists survey coldwater streams like the Pere Marquette to learn the “shocking truth” about how the populations of trout and other species are faring there. The biologists learn the truth - the trout get the shock.

Biologists use electro-surveying methods to catch the trout to measure them, count them, take biological samples and then return the trout, alive, back to the stream.

Using electric prod poles to reach under banks, into log jams holes and other cover where trout hide out, the team was able to put a controlled amount of electric shock into the surrounding water. When the shock waves zap a trout, it comes rolling out, stunned and momentarily unable to swim away.

Stunned fish are scooped up in nets, laid on a measuring board to record length, identified by species, scale samples taken to age some fish, and then all are released back to the stream to recover and swim for cover none the worse for their handling.

On one site (the Pere Marquette River’s ‘flies only’ water) biologists surveyed about one acre of water, an index site, to get a population estimate. Each fish was given a tail fin clip, and biologists came back the next day to re-survey the same area - to see how many are recaptured and how many new fish are collected, explained Jan Sapak, then a DNR fisheries technician who headed up the survey team of DNR and Forest Service workers. (Stupak was later promoted to biologist and heads up rearing activities at the Platte River hatchery today.)

Two representatives of the Pere Marquette Watershed Council, who are also forest service cooperators, aided the team in netting the shocked fish.

A fisheries technician from the Harietta fisheries research office handled the measuring and identification of the fish. Each fish was measured and its species information recorded by another team member.

They clip a tail fin at this point to identify this as a captured fish when re-surveying the site again.

They also note the fish that are stocked by other fin clips, so they’ll know how many are wild trout and how many are stockers.

These index surveys are important to keep track of populations. Biologists have learned that most planted fish do not live more than two years, while many wild trout may live from three to four years on the average.

Other fish species present were identified so that the total fishery of the stream is known. These other species also give biologists an idea of stream health and condition. If too many warmer water species are found, for instance, it suggests that stream conditions may be marginal for trout to thrive in any numbers.

The DNR does not survey the same areas every year, but periodic re-surveys of these index sites give biologists an idea of the population trend on a given stream.

If surveys over time show a drop in populations, then they must look for the reasons for it – degraded habitat, pollution, increased encroachment of competing warmwater species or other causes to be determined.

With the survey information to direct them, biologists can make better use of their finite manpower and resources.

Sometimes what is learned from these surveys might shock anglers. But never as shocked as the trout being surveyed.