How do I write off the loss for a boat in my fishing business I won in a tournament and sold for less than the value indicated on the MISC-1099?

In 2017, I won a boat and sold it.  The selling price was below the value indicated on the MISC-1099.  I've reported fishing income and losses for years on my tax returns using Schedule C.  I'm curious if I can write off the difference as a loss and if so, how.