Student Resource Pages - Dangerous for Fish
When fish die, special kinds of detectives investigate. They ask, "Hmmm...did the fish die naturally? Or, was pollution the killer? Or, did a harmful algal bloom do it?"
Sometimes natural causes killed the fish since, like humans, fish can just get sick and die. A fish's age is the biggest clue for detectives wanting to know if it died of natural causes.
Greg Southard, a TPWD scientist, shares a really cool way to figure out the age of fish.
Scientists count the rings of otoliths to find the age of a fish. That provides a clue about whether or not the fish died of natural causes.
Check this out:
"Texas Parks and Wildlife Department biologists can age fish by counting the rings on a structure called an "otolith" (oh-toe-lith) within the inner ear of fish - much in the same way that trees are aged by the rings in the tree's trunk."
If pollution killed the fish, investigators ask, "Do we blame nonpoint source or source pollution?"
Nonpoint Source Pollution
Pollution that can't be traced to just one person or place. It comes from many different sources.
Some rainwater goes straight into our lakes, rivers, and streams, but a lot of it falls on roads and in yards first. We call
Runoff brings icky stuff like oil from the streets and fertilizer from our yards with it when it flows into lakes, rivers, and streams. That's "nonpoint source pollution."
Pollution that can be traced to one person or place. You can "point" your finger at it. Source pollution happens when people put things into the water on purpose. Throwing bottles, tires, candy wrappers, or dumping paint or used motor oil right into the water all give examples of source pollution.