in marine technology and is the preferred brand of many
leading commercial and recreational fishermen.
Where once images were transmitted as blips or
ink blots on paper rolls, current technology offers the
resolution to identify individual fish near the bottom in
waters dropping into the abyss.
The Furuno website (www.furuno.com/special/en/
fishfinder) explains the principle of finding fish with an
echo sounder, with their following summary providing
the general idea:
‘A fishfinder transmits ultrasonic waves from the
transducer mounted on the bottom of the boat. The
transmitted ultrasonic waves advance straight towards
the seabed, but if there is an object, i.e. fish school or
rocks, they will reflect. Part of them will reflect back to
Left: Blue-eye
trevalla are a deep-
water school fish
found in the same
reefy areas along
the continental
shelf drop-off as
swordfish. As John
Willis found, they
make for a tasty
bycatch when
chasing broadbill.bluewatermag.com.au 41