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CARIBBEAN RESEARCH INSTITUTE
COLLEGE OF THE VIRGIN ISLANDS
ST. THOMAS, VIRGIN ISLANDS 00801
SPECIAL REPORT
ECOLOGICAL RESEARCH CENTER
CARIBBEAN RESEARCH INSTITUTE
COLLEGE OF THE VIRGIN ISLANDS
DR. NORWELL HARRIGAN, DIRECTOR, CRI
DR. ARTHUR A. RICHARDS, PRESIDENT
JULY 15, 1980
ECOLOGY AND POTENTIAL ECONOMIC IMPORTANCE
OF SHRIMP OF THE GENUS ACETES IN THE CARIBBEAN
by
DR. M.J. CANOY
Acetes amerlcanus
ECOLOGY AND POTENTIAL ECONOMIC IMPORTANCE
OF SHRIMP OF THE GENUS ACETES IN THE CARIBBEAN
ABSTRACT:
During the period 1972-75 five specimens of the planktonic
shrimp Acetes were collected near Puerto Rico. Collection was
incidental to other efforts and raises the question of a poten-
tial fishery with proper exploration.
The species of the genus Acetes are small planktonic shrimp
living mainly in the estuaries and coastal waters of the tropical
and subtropical regions. Fourteen species and five subspecies
are recognized. Ten species are distributed in the Indo-West
Pacific, and the Indo-Malayan region is particularly rich in
species. One species is restricted to Pacific America and two
species are found in Atlantic America and the Caribbean. No
species are known either from East Atlantic-Mediterranean or
from the islands of the Central Pacific. Available information
on geographic distribution is summarized for each species.
Specific relationships, biogeography, fishery and economic
potential for the Caribbean are discussed.
Acetes affords a major source of protein to some of the
people in Asia and East Africa. Present status of the Acetes
fishery in various countries is reviewed. The shrimp is mainly
fished with various kinds of push nets and bag nets set near the
shore against the flow of the tide. Boat seines and shore seines
are used, too. The average world catch is estimated at 170,000
metric tons per year or about one-half the potential sustained
yield. It accounts for 26% of the total shrimp catch in the
Indo-West Pacific and 15% of that of the world. Only a very
small proportion of the catch is sold as fresh shrimp, but the
greater proportion is dried, salted or fermented with salt for
food in various ways. A shrimp paste is manufactured exten-
sively throughout Southeast Asia. The products represent a high
quality protein supplement.
The fishery is characterized by a restricted fishing season
during the year and the catch fluctuates considerably. The fish-
ing season corresponds with the swarming season in the area where
the Acetes fishery is carried out. During the season local
catches may exceed a ton a day with small boats.
The Caribbean and South Atlantic fishery is estimated, on
the basis of area of suitable habitat, at about one-third that of
the world fishery or 60,000 metric tons. With a dock-side price
of 40 per kilogram as a lower limit, the fishery value would run
$24,000,000 per season. The parameters of the fishery potential
and the need for further information are discussed.
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BIOGEOGRAPHY AND ECOLOGICAL NOTES
Ten of 14 existing species in the genus Acetes are found
in the Indo-West Pacific, and the Indo-Malay archipelago region
is particularly rich in species. The latitudinal range is be-
tween 41ON and 34 S. Acetes chinensis occurs as far northward
as Po Hai (Gulf of Chihli), China, whereas A. sibogae australis
is distributed along the coast of New South Wales, Australia.
No species have yet been recorded from New Guinea and the
Persian Gulf areas, but this may be largely due to the lack of
survey. Three species, A.americanus, A. marinus, and A. parag-
uayensis, are restricted to Atlantic America, the last species
occurring in fresh water. The latitudinal range in the Atlantic
is between 35 N (A. a. carolinae)and 32 S (A.a. americanus). In
Pacific America A. binghami is recorded from the Gulf of Panama
and the Gulf of Guayaquil. No species are known either from
East Atlantic-Mediterranean or from the islands of the Central
Pacific including Hawaii and New Zealand.
FLEMINGER and HULSEMANN (1973) state that epiplanktonic
copepods occurring in the lower equatorial latitudes, i.e.
species with their breeding range restricted to lower latitudes
between the equator and 20-30north and south, tend to show
regional provincialisms. A similar tendency emerges from the
distribution of Acetes whose northern and southern limits fall
roughly between the 300 parallels. All species of Acetes are
restricted to either Atlantic, Indo-West Pacific, or the eastern
tropical Pacific Ocean. In addition to continental barriers to
the spread of the species, the coastal habitats favored by Acetes
may be equally or even more significant in isolating populations
and in producing short-range species and subspecies.
Morphological characters of the species of the genus Acetes
indicate that all present species were derived from two common
precursors. One gave rise to the erythraeus group and the other
produced the japonicus group. Probably the precursor of the
erythraeus group was associated primarily with equatorial (trop-
ical) waters and that of the japonicus group with tropical-sub-
tropical (tropical-warm temperate) waters. It is considered
that the two precursors were distributed widely in the Tethys
Sea, both in the Indo-European province and American province,
during the Eocene and Oligocene. Because of the late tertiary
climatic deterioration, however, these precursors disappeared
from East Atlantic-Mediterranean. The formation of the land-
bridge between Asia and Africa also divided their habitat into
two regions, namely Atlantic-East Pacific and Indo-West Pacific
(UMBGROVE, 1930). After that they developed gradually on
different lines in the two separate regions.
The climatic change after middle of Miocene took place on the
American side, though it was not so catastrophic for the tropi-
cal fauna (EKMAN, 1953: 71). However, it might have caused
immigration of tropical-subtropical species (the Americanus
subgroup) to the lower equatorial latitudes, and forced the
equatorial species (the paraguayensis subgroup) to take refuge
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o Acetes Species
Distribution records for Acees species
in the new world.
in the new world.
Figure 1.
in rivers and estuaries of central and northeastern South
America. Acetes paraguayensis in the Parana basin could have
been introduced directly from the upper region of the Amazon
basin without passing through the sea.
The fact that A. binghami shows stronger morphological
affinity to A. Americanus indicates that they must have been
recently derived from a single subtropical precursor. JORDAN
(1908) introduced the term geminatee species" or "twin species"
for amphi-American species having a common ancestor. Until
Pliocene the Pacific had a direct connection with the Atlantic
across the present Central America. Presumably, simultaneous
development of A. americanus and A. binghami occurred after
formation of the Panama Isthmus.
Attention has often been called to the faunistic resemblance
between the Indo-West Pacific and Atlantic America and the
faunal richness of the Indo-Malayan region, as demonstrated in
Acetes, as well as various other common families and genera
such as the decapod shrimp genus Lucifer, the squid genus Sppio-
teuthis and the eel genus Anguilla. The faunal richness of the
Indo-Malayan region is sometimes explained by the assumption
that this region is a center for the generation of marine organ-
isms. However, EKMAN (1953:79) notes that the explanation is
rather that, in contrast to the Atlantic, the Indo-Malayan
region has been able to preserve this inherited richness until
the present time, and that in addition new forms have been
able to develop continuously.
Acetes is a typical neritic, epipelagic shrimp and it is
common in estuaries and backwaters where fresh water from the
land greatly influences the situation. It can withstand a
great change of salinity. For instance, adults of A. erythraeus
are found in water where the salinity fluctuates seasonally be-
tween 1.5 and 35.00/00 (LE RESTE, 1970). Other common environ-
mental features correlated with appearance of the species are:
1) the sea is shallow for a great distance from the shore;
2) the area is separated from the open ocean by a peninsula,
submarine sills or numerous islands; 3) the tidal range is con-
siderable; 4) the bottom is covered with mud or sandy-mud.
Acetes is generally distributed in depths shallower than 50m;
swarming and gregariousness are usually found from the surface
to a depth of 20m. The swimming activity of the shrimp becomes
highest at night. In the shallow area of the Seto Inland Sea
(10-20m in depth), A.japonicus often intimately associates with
the bottom during daytime, but in Toyama Bay where the bottom
slope is very steep, the species aggregates at depths of 40-90.
It is probable that Acetes produce a steady emission of
greenish-blue light. Fishermen in various localities always
point out the occurrence of massive blue-green glows from
swarms of Acetes. No instrumental method has yet been devel-
oped for swarm location based on the glow.
ABUNDANCE AND CATCHES
Catches of pelagic crustaceans like sergestids, galatheids,
euphausiids, and mysids are not recorded in the FAO's "Yearbook
of Fishery Statistics" as a result of the lack of statistical
data on these fisheries. Therefore, it would be worthwhile to
estimate the amount of commercial catches of Acetes at present
and to evaluate the potential of Acetes as a fishery resource.
Approximate average annual catches of Acetes and their propor-
tions to the catches of total shrimps in seven Asian countries
are summarized in Figure 2. The catches of Acetes in the table
total 130,000 tons, but these records must be considered as
minimal because reliable statistics are only available for a
few of the larger markets. Although data is not complete as
yet, Acetes certainly supports a subsistence fishery of consid-
erable importance in North Korea, Taiwan, Hong Kong, Philip-
pines, North Viet Nam, Cambodia, Burma, Singapore, and indonesia.
It is probably fished in Bangladesh, Pakistan, and Sri Lanka.
Catches from Kenya, Tanzania, Mozambique, and Madagascar may
not be ignored. In South America, a small amount of A.amerigan-
us is consumed in Surinam and French Guiana (HOLTHUIS, 1959).
I would judge the Acetes harvest from areas not reporting region-
al fishery statistics to exceed 40,000 tons per year. Therefore,
the world catch of Acetes is estimated to be at least 170,000
tons per year.
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Figure 2
Approximate Recent Annual Catches of Acetes and Their Contri-
bution to the Shrimp Fishery in Seven Asian Countries
Total Other ** Acetes Acetes
Country Year Acetes Shrimps*Crusts. to ttl. to ttl;
(tons) (tons) (tons) Shmps.% Crust.%
China 1955 71000 --- ---- --
South Korea 1965-68 10700 13700 3900 78.1 60.8
Japan 1968-72 800 57700 92300 1.4 0.9
South Viet Nam 1972 10000 54300 19.4
Thailand 1968-72 13600 75000 35700 18.1 12.2
Malaysia (West) 1970-72 9400 52200 2000 18.0 17.3
India 1959-68 14500 81700 3000 17.7 17.3
*Natantia
**Panulirus, Portunus, Scylla, Paralithodes, etc.
The annual catch of total shrimps (Natantia) excluding
planktonic forms reached about 474,000 tons in 1970 in the Indo-
West Pacific; it was 930,000 tons in the world (FAO, 1971). If
the present estimate is correct, Acetes accounts for 26% of the
total shrimp catch in the Indo-West Pacific and 15% of that in
the world. Furthermore, Acetes probably exists in potentially
exploitable quantities in other areas but is not fished due to
lack of appropriate method of food processing, the richness of
other fishery resources, and/or the small size of the local
market.
The life span of Acetes is less than 3-10 months and the
adult dies soon after spawning. Thus, the adults represent an
emphemeral stock with very rapid turnover, new individuals being
consistently recruited from the nearby waters. Since planktonic
shrimps such as Acetes, Peisos, and Lucifer often occupy a key
trophic level in neritic communities (OLIVIER et al., 1968;
AMORI, 1974), the exploitation should be carefully managed so
that it is not excessive and does not unbalance the food web.
However, it seems reasonable to conjecture that a potential world
fishery of 50,000-100,000 metric tons of Acetes would not be
excessive. The potential New World fishery probably does not
equal the Asian fishery, and may be as little as 20,000 metric
tons. No data exists for making a reasonable estimate.
PROCESSING AND UTILIZATION
Many kinds of Acetes products are marketed, but they can
be classified into the following types: 1) raw; 2) boiled;
3) dried in the sun; 4) dried after boiling and sometimes pro-
cessed further by having the carapace removed from each shrimp;
5) pickled in salt; 6) fermented with salt (shrimp paste and
shrimp sauce).
Generally, only a very small proportion of the Acetes
catch is sold as fresh shrimp, but the greater proportion is
dried, pickled or fermented for food in various ways. The
dried shrimp is marketed in all countries of Asia and it
appears the exclusive use of Acetes in Africa, In Japan
"Amizuke" (Ascetes pickled whole in salt and fermented) is
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the main product; a similar product is very common in South
Korea. In China and Southeast Asia, Acetes is highly desired
in the form of fermented shrimp paste and shrimp sauce.
Figure 3
Sample Water Carbon Nitro- Ash
(%) gen %
(dry wgt.)
Blachan 26.9 32.3 7.9 22.7
Acetes japonicus
(8 Aug. 1972: Suruga Bay) 79.8 42.9 11.5 13.3
(25 Oct. 1973: Ariake Sea) 79.1 42.3 11.0 10.7
The paste includes "Xiajiang" in China, "Mam-tep" in Viet
Nam, "Blachan' in Malaysia and Singapore, 'Gapi' in Thailand,
and "Ngapi" in Burma. Blachan is manufactured in the following
way. Fresh Acetes is mixed with salt and dried in the sun for
5-8 hours. It is then put through a mincer and packed tightly
in a wooden tub which is covered with burlap and set aside for
a week to cure. The paste is then removed from the tub and
again spread out to dry in the sun. This is followed by a
second mincing and again the paste is packed into the tub,
covered and allowed to cure for about a month. The process of
fermentation, mincing, and drying is repeated at least three
times and finally the product is pressed into a hard mass.
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Blachan is deep purple in colour and has a salty strong shrimp
flavour (Plate 1-e, f). This product remains in good condition,
for 2 months or more. The biochemical composition of the Blach-
an from Penang was determined and compared with that of fresh
A. japonicus (Fig. 3). The results indicate that about 3.7 kg
of fresh shrimp are needed to make 1 kg of Blachan and that
Blachan is a highly nutritive product containing 36% protein.
In the market 1 kattee (about 600 g) of good Blachan cost 100
yen in 1973. About 80% of the Acetes landed in West Malaysia
was used to make Blachan and the amount of production, mainly
from Selangor, Johor, and Penang, attained 4,072 tons in 1972.
The taste and nutritional value of Blachan is highly favoured
by people of Southeast Asia, and a considerable amount is ex-
ported from Malaysia to Singapore and Thailand.
DISCUSSION
Little is known about Acetes, its propagation, growth,
migration, swarming behaviour, feeding habits, etc. Acetes is
assumed to play a significant role in the food web of coastal
waters. In particular, it must be important in the dynamics
of ecosystems in lagoons, sea-grass beds, and mangrove swamps
which extend over vast areas in tropical and subtropical
regions.
Acetes certainly affords a major source of protein to
sore of the people in the Indo-West Pacific. Among 14 species
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of the genus, A chinensis, A. Erythraeus, A. Indicus, A. Japon-
icus, and A. Vulgaris are most important in the plankton fishery.
In the report on the crustacean resources of the countries border-
ing the South China Sea, MISTAKIDIS (1973) mistakenly lists
Sergestes spp. in place of Acetes spp. as one of the most impor-
tant commercial shrimps in the area. No species of the genus
Sergestes have so far been exploited in Southeast Asia.
The possibility of using plankton as a food source for
mankind has been discussed for a long time. While much interest
has focused on the practicality of fishing Antarctic krill,
Euphausia superba, few seem aware th&t planktonic fisheries have
existed for many years utilizing the pelagic crustaceans, Acetes
spp., Sergia lucens, Neomysis intermedia, Acanthomysis mitsururii,
and Euphausia pacifica (see MURANO, 1963; KOMAKI, 1967; OMORI
et al., 1973) and the jelly fish, Rhopilema esculenta and Stomo-
lophus nomurai. Harvesting krill is technologically feasible.
During 1974/75 season two Japanese exploratory stern trawlers took
a combined catch of about 3,000 tons of krill in Antarctic waters.
Some scientists suggest that a potential of at least 20-30 mill-
ion tons of krill exists for the world fishery. At present, how-
ever, a satisfactory large-scale method for processing krill for
human consumption is lacking, although various possibilities of
industrial and agricultural use, e.g. as meal for cultivated
animals, as a source of lipids for pharmaceuticals, as a source
of protein flour for human consumption, etc., are considered.
So-ution of this problem is indispensable for development of com-
mercial fishery of Macrozooplankton.
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