Features
Sustainable caviar production: save our sturgeon!
26 Oct 2011
By Myra Armson, BSc, Higher Scientific Information Officer, IFIS
Caviar, the salted roe of sturgeon, is considered a delicacy
worldwide. It is traditionally obtained from wild species caught
mainly in the Caspian Sea, and is prepared by sieving their egg
masses, and adding 4-6% salt as a preservative and flavour
enhancer. Demand for caviar, and the prices it obtains, is high,
but supplies may be running out.
The trouble is that caviar is typically produced from unripe,
unovulated sturgeon eggs, which can only be harvested by
sacrificing fish. Sturgeon are slow growing creatures that may take
20 years to reach sexual maturity (depending on species) and, even
then, do not spawn every year. In the absence of adequate
management systems, particularly since the decline of the USSR,
they have been harvested faster than they can reproduce, resulting
in their near extinction. Twenty-seven species are on the IUCN Red
List of Threatened SpeciesTM and of these, 63% are
listed as critically endangered. Sturgeon have also been listed in
Appendix II of the United Nation's Convention on International
Trade of Endangered Species of Wild Fauna and Flora (CITES) since
1998. This limits the international trade of sturgeon and their
products, but the slow maturation of the fish means that
populations could take many years to recover. The use of wild
sturgeon for caviar production is not sustainable.
Alternatives are available though. Imitation caviar is the name
given to roe from fish other than sturgeon (e.g. capelin, lumpfish,
salmon) which are consumed as caviar. The eggs from these fish are
processed like authentic caviar, but may also be seasoned and
coloured. Although the resulting products may be delicious in their
own right, they are usually quite different from sturgeon caviar.
Beluga caviar consists of pea-sized, black-grey eggs which burst in
the mouth releasing a smooth, buttery flavour. Salmon eggs, in
comparison, are orange-red, larger in size and taste strongly of
salmon; they do, however, offer a similar "popping" mouthfeel. In
contrast, lumpfish and capelin caviars comprise much smaller eggs,
which may be dyed black, but are crunchy and briny or chewy and
mild, respectively. There are, of course, many other substitutes,
with varying qualities, but what if only the "real thing" will
do?
Sturgeon aquaculture is proving to be valuable on two counts -
replenishing wild stocks which may not be able to recover on their
own, and ensuring a regular supply of caviar to meet consumer
demand. There are challenges to overcome, however; not least the
limited supplies of broodstock and the long maturation period. With
a typical wait of 5-10 years before a female reaches maturity and
produces eggs under culture conditions, it is simply not efficient
to farm sturgeon for just one egg harvest as would be
traditional.
Fortunately, whilst it is conventional to sacrifice sturgeon to
obtain their eggs, it is not essential. Roe can be harvested from
live sturgeon through a caesarean-style incision or, if ultrasound
is used to locate them within the fish, through the urogenital
opening by massage. The latter requires only a 2 mm cut to be made
to relax the muscles and the fish can subsequently be returned to
its tank and stripped again when it has produced more eggs. Using
this technique, it is claimed that sturgeon may well fulfil their
natural lifespan, which could be up to 200 years!
Unfortunately, stripping methods may yield eggs that are
significantly closer to being spawned than those obtained by
sacrificial methods. The associated physiological changes can alter
their properties and make caviar production difficult. Ovulated
sturgeon eggs become sticky when they contact water. They adhere to
one another and when salt is added, they burst forming a thick mass
which is far from the typical beads of caviar produced from
unovulated eggs.
To prevent the waste of sturgeon eggs considered to be "too ripe",
a technique has been developed in Germany for making their outer
membranes more resilient without altering their desirable
properties. In nature, spawned eggs harden in response to
fertilisation. Fertilised eggs are not permitted for use in caviar
production, but the hardening process involves a series of
reactions triggered by specific signalling molecules, which may be
utilised. Two of them, hydrogen peroxide and calcium ions, can be
applied externally to ripe sturgeon roe, resulting in successful
membrane hardening. The eggs can then be processed like
conventional caviar, and become a comparable product. CITES has
recommended this process as a way to relieve the burden on
threatened wild sturgeon populations.
So, whilst caviar production from wild sturgeon stocks is not
sustainable, it appears that we neither have to give up the fishy
treat nor opt for second best. Caviar production is moving on. It
may not be traditional, but change is good.especially for wild
sturgeon.
Examples of some FSTA records related to caviar
JOURNALS
- A new technique that could revolutionise the caviar
market.
Eurofish Magazine
- Identification of caviar from increasing global aquaculture
production. Dietary capric acid as a labeling tool for CITES
implementation in caviar trade.
Aquaculture
- Lumpfish caviar - from vessel to consumer.
FAO Fisheries Technical Paper
- Quality attributes and microbial storage stability of caviar
from cultivated white sturgeon (Acipenser transmontanus).
Journal of Food Science
PATENTS
- Method for producing sturgeon and salmon caviar
substitute.
PCT International Patent Application
BOOKS
- Caviar in the retail market. (Kaviar v obchodni
siti.)
