UV Exploration - Salmon Eyesight Part 1

Since fishing season is getting underway again the number of podcasts will start to drop off, but never fear! We've got dozens of projects we are working on to post about. We aren't going to put the time into audio editing, etc for the Podcasts, so we will tease you with data and adventure as we pursue it. We are collecting the audio and video, though, so look for the podcasts to show up... as soon as the fishing slows down!

One project we've been working for a few years now is measuring the amount of light the salmon and sturgeon are exposed to. There have been more and more biological studies highlighting the ability of Salmonoids to see and respond to ultraviolet - UV light. In the Ocean, salmon hunt and live deeper than most visible light can penetrate. UV, however, dives deep, and science has shown that the UV recepters in salmon eyeballs dramatically increases the first year the smolt hit saltwater. So, lets use it!

More and more products in the market are targetting UV light - you've probably noticed it. I bought a black-light to look at some of our lures and it is very interesting how DIFFERENTLY the lures look in blacklight/UV spectrum. Here is the normal image of some common salmon lures.

Here is an attempt to photograph the same lures with UV/blacklight illumination. Something to consider...

A few years back, I rigged up this light-level meter that we drop into the water to measure both visible light levels as well as Infrared (IR) light. We have a video camera we use in the water, and wanted to see if the IR was visible to salmon or not. I don't think Sturgeon can see much of anything - more on that in another post ;-)

The circuit uses older TI Sensors - TSL230 and TSL245 - these chips take light and turn it into a frequency out to my microcontroller to measure how much light is available. The PIC16F688 records the Max/Min/Average values into an EEPROM memory chip, and displays the values on the LCD. I've since put it on a PCB board and powered it using AA batteries.

The kids and I have collected several seasons worth of data. Not much IR or visible light down below 30 feet... and we fall-fish as deep as 55feet! UV light is down there, though, so that is why I carry the blacklight in G.I.Joes.

I'll publish the circuit and some of our data in a future posting. We are also putting video cameras down deep and recording what the lures are doing - most underwater cameras have IR to help see in the dark... but I've started tearing mine down to use UV LEDs instead! Shh - its a secret.