From: Jordanna Dulaney, MONGABAY.COM
A recent study from the Biological Conservation journal brings
shocking news: every year across the globe, an estimated 400,000
seabirds are killed by gillnets.
Gillnets, a common term for any net used to entangle and catch fish,
are used all over the world, and at any depth. These nets, whether
used in subsistence or commercial fishing, trap anything that swims
through them. When unintended marine wildlife, or “bycatch,” is caught
in these nets, the results can be significant.
“Fishermen do not try to catch seabirds or other unwanted species, but
they usually set their nets in productive marine areas with abundant
fish resources, which are also home of other marine fauna,” co-author
Ramunas Zydelis told mongabay.com in an interview. “In such places
seabird habitats overlap with fishing grounds and subsequently some
diving birds accidentally entangle in fishing nets and drawn as they
cannot return to the water surface.”
The study synthesized previously collected data from around the world.
Overall, it identified 148 different seabird species at risk for
becoming gillnet victims, of which 81 have been officially reported as
bycatch.
“Bird bycatch in gillnets is net type-specific and species-specific.
Not all the nets are equally dangerous. Nets set in deep waters are
less likely to catch birds than nets in shallow places or drifting at
the surface,” Zydelis says. “Whether a bird species is likely to be
caught in fishing nets also depends highly on species foraging
behavior and diving habits.”
The birds most likely to be affected by gillnets are those that hunt
underwater, such as penguins, loons and cormorants. In particular, the
study found that auk species have the highest chances of becoming
entangled.
“The highest numbers of seabirds get caught in gillnets set in cold
sub-arctic and temperate seas of the northern hemisphere, where very
large numbers of diving birds live and rich marine resources attract
intensive fisheries.” Zydelis told mongabay.com. “High bycatch occurs
in the Russian offshore waters of the northwestern Pacific; possibly a
lot of birds get caught around Iceland; the Baltic Sea is another area
with high bycatch.”
“But sometimes even low numbers of birds dying in fishing nets could
be considered as a significant bycatch when affected bird population
are small,” Zydelis added. “Examples could be bycatch of Humboldt
penguins in Peru and Chile and bycatch of Magellanic penguins off the
southeastern coast of Brazil.” – via ENN
