Tank Tales Update #4

Most of our eggs have turned into alevin, and only a few have yet to make the transition! All we have to do now is wait until they absorb their yolk sacs, and then we’ll have fingerlings to start feeding. Seeing the transformation from egg to alevin makes the process very real. When we first picked up the eggs, they were tiny and motionless. Now we have small creatures resembling trout, that wriggle around in the tank with big round silver eyes. 

The alevin have been growing and getting bigger with time.

Every day the students rotate checking on the tank, recording it’s temperature, and make note of any eggs that die. When they die, they turn white and must be removed to prevent any harmful bacteria from spreading to the others.

Alevin and eggs that are dead turn white.

The biggest excitement today was a two-headed trout! The students were extremely interested in how and why this happened. Some were fascinated and loved it, while others were sickened at the sight. We’re all curious to see how this little guy progresses!

Two headed trout.

If you’re curious what the tank looks like all set up, check out the video below to see!

Tank Tales Update #3

On Friday, our fourth grade classes learned about general fish anatomy! The first thing I had the students do was to try and label the basic parts of a fish using a word key. After much debate and uncertainty of their choices, we went over the answers. For a Friday afternoon, the students were extremely engaged and excited to be learning about the animals growing in the back of their classroom. Most could identify the gills, the lateral line, and even the dorsal fin. The other fins are harder to identify, and so are some of their functions. By the end of the class the students knew what all the fins were, and why fish need them.

See below for the fins and their functions.

Caudal Fin: Pushes and steers the trout. They are made of bony spines with skin covering them and joining them together. They can be webbed, as seen in most bony fish, or similar to a flipper, as seen in sharks.

Pectoral Fins: Allows for abrupt changes in side-to-side direction and speed; also acts as brakes to decrease speed while swimming.

Dorsal Fin: Helps keep fish steady. Protects the fish against rolling, and help with sudden turns and stops.

Pelvic Fins: Helps fish swim up and down, turn, and stop quickly.

Anal Fin: Helps keep fish stable while swimming.

Lateral Line: Senses movement and vibration in the water. Helps fish be aware of their surroundings.

Adipose Fin: Soft and fleshy. Its purpose is a mystery, but it may be a sensory function and could be important for the detection and response to sound and changes in pressure.

Gills: Take in oxygen from the water, and allows fish to breathe.

After the anatomy lesson, we took out our trout eggs and alevin to do some observations. The students answered some questions, such as; do they have fins?, what’s the most interesting thing about them?, how well do they swim? etc. By far one of the most interesting things for these fourth graders, was the fact that the alevin feed off of a yolk sac.

We also discussed the life cycle stages of trout and the capabilities they have now versus the future. Currently the alevin can wiggle around, but they do not have the fins they need to swim. As our trout progress, they will begin to grow fins and will have more freedom to move around the tank.

AWWA is thrilled that the students are embracing this wonderful experience!

Tank Tales Update #2

It’s been four days since our trout were delivered to the Paul School in Wakefield. After a rough count of the eggs in the tank, it looks like we have around 230! So far we’ve only had one egg turn white and die. It is important to take out dead eggs as soon as possible, in order to keep any potentially harmful bacteria from spreading to the other eggs.

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Can you spot the egg that’s in the Alevin stage?

Most of our eggs are still in the Strongly Eyed stage and are currently 53.52% developed. We also had one egg enter the Alevin (al-e-vun) stage. At this stage the trout has emerged from the egg, and you can see that the egg sac is still attached to the trout. The trout will continue to feed off of its egg sac, which contains all of the food it needs during this step. Eventually the sac will disappear and absorb into the trout, and at this point we will have to provide them with food.


Trout in the Alevin (al-e-vun) stage.

Keep checking back in with us for more updates!

Welcome to Tank Tales!

Welcome to our latest series of blog posts! We will periodically update our blog with what’s happening in the 4th grade classrooms in Wakefield, NH, as they partake in an environmental and educational endeavor.

Yesterday was an exciting day at the Paul School. The room was buzzing as three 4th grade classes looked at me with inquisitive eyes. What could possibly be in the DSCN0393cooler? Could it be more than one? The students had a variety of guesses as to what creature(s) would be living in their classroom. With a tank set up in the corner, imaginations had a week to run wild, as the possibility of having a turtle, a shark, or even a penguin was still plausible. Luckily, the anticipation was almost over, as the big reveal was imminent. Soon, the students would find out what would be living in that tank.

As a jar emerged from the cooler, a chorus of “Eggs!” rang out, and this time the students were right. The excitement in the room was infectious as they learned about their upcoming months with their….drum roll… brook trout eggs! Eggs were passed around in clear cups so students could examine them closer with magnifying glasses. It’s great to see such enthusiasm in this group of students!





Students will track daily development as they experience brook trout evolve from egg to fry. Over the coming months they will learn about anatomy, water quality, habitat, food webs and much more. Because trout development is temperature dependent, daily tracking is necessary to determine life cycle stages. The warmer the water, the quicker they develop, and our goal is to keep the tank at a range of 35° – 38°F. Development is measured using the Brook Trout Developmental Index Chart.

Brook Trout Developmental Index 
Temp F 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
35 0.41 0.416 0.422 0.428 0.434 0.441 0.447 0.453 0.459 0.465
36 0.471 0.477 0.483 0.489 0.495 0.502 0.508 0.514 0.52 0.526
37 0.532 0.538 0.544 0.55 0.556 0.562 0.568 0.574 0.58 0.586
38 0.592 0.598 0.604 0.61 0.616 0.623 0.629 0.635 0.641 0.647
39 0.653 0.659 0.665 0.671 0.677 0.684 0.69 0.696 0.702 0.708
40 0.714 0.722 0.729 0.737 0.745 0.753 0.76 0.768 0.776 0.783

How to use the chart:

  • The left hand column is temperature in Fahrenheit; 35, 36, 37, etc.
  • The row across the top is tenths of degrees (the decimal); 35.3, 36.4, 37.5, etc.
  • The decimal figures found at the intersection of the left hand column and the row across the top represent how much the eggs developed at a certain temperature.
  • The goal is to have a cumulative total of all the daily development percentages.


  • At 35.1°F, the eggs have developed 0.416% for that day at that temperature.
  • At 35.2°F, the eggs have developed 0.422% for that day at that temperature.

Total development = 0.838%

Development Stages:

  • Weakly eyed 29%
  • Shocking 38-42%
  • Strongly eyed 47% (Our eggs are currently at this stage; approx. 52% developed)
  • Hatched 73%
  • Swim up 100%

Schools all across New Hampshire are participating in the Trout in the Classroom program, which is facilitated by the New Hampshire Fish and Game Department and in partnership with Trout Unlimited. Our eggs were provided by the Powder Mill Fish Hatchery in New Durham.

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Check back in with our blog as the Paul School 4th graders partake in this awesome educational experience!

Amy Arsenault
Program Manager