I think that the salmon were "as big as an ell" or in modern terms, as long as your arm.
The old way of measuring cloth was to stretch it between arms length and your nose. The Anglo Saxon for arm is "ell" (hence "elbow" -the bend in the arm) so before yardsticks were standardised, you would buy cloth by the ell (from the most gorilla-like draper you could find)
Cheers
Dave