How to Milk a Fish

Friday, May 16

Yes, I said "milk a fish".  The fish guys have been spending the last few days electroshocking fish to get lots of gravid grayling females as well as lots of males. (Gravid just means full of eggs.)  Friday was to be the day they planned to milk the fish for eggs and milt (sperm) and fertilize the eggs.  Some of these eggs would be put in special little pens over  gravel  with different amounts of silt added,  to see if the amount of silt in a stream is a factor in successful egg hatching. The rest of the eggs will be put in our little fish hatchery, that is made of 5-gallon buckets. (More on that  in a later blog.)

While Dick and I were transporting a male  fish to Widgeon Lake (last blog topic), our boss, Bill, called us on the radio to tell us it was time to come watch the milking. We hurried back and then spent the next hour or so waiting for the fish guys to come down the stream with their boat that has the electroshocking equipment and bins in which to put the fish they have caught.

Waiting for the show to start

Here they come!

 
The first thing to happen was to divide the fish into two pens that sat in the water, one of males and one of females.  These were holding their previously caught fish.  Unfortunately, this spring has been unusually warm here and the fish were about a week ahead of schedule. So a lot of the caught fish had already been upstream to lay their eggs and were headed back downstream.

Sorting male and female Arctic grayling into separate pens

Another view of sex separation

WOW! Look at this grayling's awesome fin.

Meanwhile the milking expert guy was setting up his tent and laying out his supplies.  The person in the background is going to tag, and collect  data from each fish.

The fish milker  - he does the milking in the tent to keep the eggs and milt shaded

Fish waiting to be milked

When the milking started the milker, was handed a female fish which he dried off with a towel and then squeezed her from the gills to the vent.

Readying a fish for milking - he dried each one with a towel so he could hold on tightly

The milking in process 

Data was collected on each fish - many were already tagged

This are the eggs from two females and the milt (the white part) from one male

As soon as the milker milked two females and then two males, a little saline was added and the bowl was swirled around for several seconds. Then the fertilized eggs were rinsed with fresh water from the stream and added to a water cooler.  They had to sit still and harden up for an hour before they could be hauled to the fish hatchery or added to the experiment on the effect of silt on eggs.

One of my jobs is to sometimes tend the developing eggs.  We started that project the next day.  You'll have to wait for next Sunday's blog to learn about that.