Thats what they say about Piranhas and then some idiot dumps them into the columbia and next thing you know a fisherman catches a 2' Rhom. Remember it takes a great while for water temp to drop so while your 3 weeks of harsh 40's might not be to great for a ray the waters still 67. Just a thought.
You keep saying they are illegal but all you have to do is go get a permit.
Here... I've done all the work for you.
Region 1: California, Guam, Hawaii, Idaho, Nevada, Oregon, & Washington
U.S. Fish & Wildlife Service
Office of Law Enforcement
911 NE 11th Avenue
Portland, OR 97232-4181
Tel: (503) 231-6125
Fax: (503) 231-6197
Email: permitsR1LE@fws.gov