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Gill Raker
Trade
Manta and mobula rays are large filter
feeding
animals,
whose
flesh
is
considered to be of relatively poor
quality by humans all around the
world. As a result these animals have
not been widely targeted for human
A specialist fish monger at a fish market in Sri Lanka expertly removes each of this oceanic
mantas ten gill rakers from the head of the animal in half sections.
consumption through commercial fisheries in the past. However, in recent years this has changed. Manta rays
and their close relatives are now rapidly becoming a more desirable product, making them a target for fishermen
all over the tropical and temperate oceans of the world. So what has happened? Why the sudden change of
fortunes for these unfortunate rays? The underlying answer to these questions is not a new story, in fact it's a
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tale of depressing repetition played out in our oceans and throughout our planet on a regular basis. The
difference this time is that the latest targets are the mantas, which are paying the price of becoming the latest
commodity in the often senseless and environmentally destructive Chinese Medicinal Trade. The ray's feathery
gill rakers, which they use to filter the plankton from the water, have become a product and as a result these
harmless animals are paying the price of humanity's selfish ignorance......
What are Gill Rakers?
The gill rakers, or branchial filaments, are
thin cartilage filaments that enable the
manta and mobula rays to filter plankton out
of the water column. Every manta or mobula
has five pairs of gills, each protected inside a
gill slit. Inside each of the ten gill slits there is
one complete feathery gill raker which forms
This image shows the complete set of gill rakers inside the
mouth of a spine-tail mobula ray.
a circle around the periphery of the slit,
trapping their planktonic food as it is
funnelled through the mobula or manta ray's mouth and out through these gill rakers.
A close up image of the raker
filaments shows their feathery
structure which aids the filtration
of their planktonic food from the
water.
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The Fishery
These rakers, once dried, are the most valuable parts of the mobulid rays and
drive the commercial fishery of these rays around the world, with particularly
large fisheries present in India, Sri Lanka and Indonesia. Although the rakers
comprise just a tiny percentage of a manta or mobula's mass, they sell for
significantly more than the rest of the body parts put together. While rakers
are used from both mobula and manta rays, the gill rakers from mantas
(usually oceanic manta rays; M. birostris) fetch the highest prices, followed by
the larger species of mobulas (generally M. tarapacana and then M.
One removed from the manta and mobula rays, the gill rakers
are laid out to dry in the sun for several days.
japanica),
with
the
price
reducing as the size of the
rakers decreases. The demand for gill rakers is so high that in certain countries, such as Sri Lanka,
fisherman who used to avoid catching mobulid rays, due to their propensity to destroy and
entangle fishing nets, are now driven to fill their boat's holds with mobulid rays when returning
to harbour. This demand, coupled with the dwindling supplies of more desirable fish catches
(such as sharks, tunas and billfishes) now gives the fishermen even greater incentives to actively
target mobulid rays in order to maintain their livelihood.
A bag of dried mobula gill rakers on sale at a
retail market in China advertises the raker's
supposed medicinal properties.
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Chinese Medicine
The international trade in mobulid gill rakers which is being driven by the current demand in the
Chinese Medicine trade appears to be a relatively new phenomenon, with demand significantly
increasing in the last couple of decades. Those selling or promoting the use of this product claim the
rakers can treat health issues ranging from asthma, to skin rashes, chicken pox and even cancer.
Some of the practitioners also maintain that rakers reduce toxins, boost the immune system and aid
in the detoxification of the bloodstream. However, reviews of available literature, along with
interviews of well respected practitioners have revealed that there is no evidence to support any of
these claims, with some practitioners even admitting that gill rakers are not effective and that many
other alternatives are available. Gill rakers are often consumed in a soup (locally called “Peng Yu Sai”)
which is made from a few main ingredients (gill rakers,
ginseng and dried pipefish) and is not considered
“prestigious”, like shark fins, but solely as an ingredient
This pile of manta and mobula gill
rakers, representing many hundreds of
individual rays, was on display outside
just one retail shop in mainland China.
collection of
in a medicinal product.
It appears that the increasing demand which has arisen
in the last few decades is due to product marketing by Chinese retailers who have seen an
opportunity, created by a relatively available commodity, to market a new product into the
traditional medicine industry, falsely “reviving” this remedy which in reality does not even exist in
the traditional literature. It appears as though one of the marketing strategies plays on consumers
Gill rakers soup 'Peng Yu Sai' consists
mainly of pieces of raker, some ginseng
and a few pipefishes.
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fears over the increasing prevalence of modern disease outbreaks such as
Bird Flu, Swine Flu and SARS. The sales pitch suggests that as these fishes
are able to filter particles from the water with their gill rakers, if
consumed, these rakers will therefore aid in the detoxification and
purification of the consumer's body by filtering these diseases or toxins
from the human body. Most consumers are unaware that the product
comes from manta and mobula ray, indeed most consumers are not even
aware of what a manta or mobula rays is, therefore they have no idea of
the impact their consumer choices are having on these increasingly
vulnerable species.
A handful of gill rakers is the only body part of the entire manta ray
which is worth anything of real value. The rest of the carcass is sold
for virtually nothing and often processed for animal feed.
In order to maintain this supply of gill rakers, large numbers of manta and
mobula rays are being landed at fish markets around the world. This is
having dire effects on the populations of mobulid rays and reports have already been published on decreases, or complete crashes, of ray
populations around the world. It also appears that the giant oceanic manta ray (M. birostris) is likely to be the most heavily affected by this
unsustainable and senseless fishery.
Want to know more? (Visit our website: www.mantatrust.org)