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Introduction
Although sea cucumbers (Holothuroidea) have
been exploited for at least 1,000 years around India,
Indonesia and the Philippines (Conand 2004), their
exploitation in the Sultanate of Oman is relatively
recent (Al-Rashdi et al. 2007a). Anecdotal reports
from older fishermen indicate that a very small-
scale Holothuria scabra fishery occurred as part of
the traditional annual cycle of trade between Oman,
India and East Africa, but that the recent increase
in H. scabra landings only began in 2004 with the
establishment of a truly commercial exploitation,
involving 400 fishers and a handful of traders and
exporters, for export to the United Arab Emirates
(Al-Rashdi et al. 2007a). The fishery is restricted to a
single embayment in Mahout Bay along the Arabian
sea coast of the Sultanate of Oman (Al-Rashdi et al.
2007b). The body walls of sea cucumbers are locally
processed and exported in dry form. Because this
fishery is quite recent, there are currently no tradi-
tional or state-directed management strategies in
place (i.e. it is a fully open access fishery) (Charles
2001). Following the report of this fishery, a short
study carried out in 2005 to document the status
of stocks and the fishery’s structure (Al-Rashi et al
2007a,b), suggested that there were already some
indications of overfishing in areas easily accessible
to fishers.
This paper documents the status of sea cucum-
ber stocks five years after the start of commercial
exploitation.
Material and methods
The study area covered Mahout Bay (Ghubbat
Hashish Bay; 20°27’ N 58°0’ E), the only known area
where the sea cucumber fishery in the Sultanate of
Oman takes place (Fig. 1). The semi-sheltered bay
covers approximately 320 km2 and forms the inner-
most part of the Gulf of Masirah (Fig. 1). It has a
maximum depth of about 10 m in the southern part
but most of the bay is less than 5 m deep. Tidal ranges
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SPC Beche-de-mer Information Bulletin #30 – March 2010
Evidence of rapid overfishing of sea cucumbers in the Sultanate of Oman
Khalfan M. Al-Rashdi1 and Michel R. Claereboudt2 *
Abstract
A small, artisanal sea cucumber export fishery developed in the Sultanate of Oman in 2004. The area cov-
ered by the fishery is limited to a single shallow embayment of 320 km2 in Mahout Bay, and involves approx-
imately 400 fishers, around 50% of whom are women. The fishing season (October to May) in 2005 was the
first season to be officially recorded. However, anecdotal evidence suggests low levels of exploitation as
early as the 1970s, although catch, effort and export data for this period are unavailable. The total biomass
of the stock in 2005 was estimated at 1,500 tonnes (t) (fresh weight). In the following year, at least 14.5 t of
processed Holothuria scabra were exported to the United Arab Emirates, corresponding to approximately 145
t, or around 10%, of the recorded biomass.
Interviews with fishermen and traders revealed that in 2005, about 100 sea cucumbers per fisher per fish-
ing trip were collected, whereas by 2007, less than 20 sea cucumbers per fisher per fishing trip were col-
lected, indicating that there had been significant pressure on the resource. Over the same timeframe, the
value of an average sized H. scabra was 0.1 Omani rials (USD 0.25) in 2005, increasing to 1.5 Omani rials
(USD 3.75) in 2007, and is still increasing. Concomitantly, fishers began targeting the less valuable H. atra in
large numbers. This species commands a market price of 0.2 Omani rials (USD 0.5) per specimen. Also, an
examination of processed specimens for sale showed a significant number of very small individuals (<6 cm
processed, corresponding to around 12 cm live length).
These concurring evidences suggest a rapid decline of H. scabra populations in Mahout Bay, with a corre-
sponding increase in pressure on other species such as H. atra. Accordingly, the Ministry of Fisheries Wealth
of the Sultanate of Oman has initiated a number of projects aimed at monitoring the sea cucumber fishery
with the ultimate objective of providing a regulatory framework to ensure the sustainability of the resource.
Projects also include an evaluation of enhancement and ranching techniques.
1 Ministry of Fisheries, Aquaculture Center, PO Box 247, P.C.100, Muscat, Sultanate of Oman. Email: omanaba@yahoo.com
2 Sultan Qaboos University, College of Agriculture and Marine Sciences, PO Box 34, P.C. 123, Sultanate of Oman. Email: michelc@
squ.edu.om
*corresponding author: Michel R. Claereboudt, michelc@squ.edu.com
are 1.8 m during spring tides and
less than 1.0 m during neap tides.
The bay remains relatively pro-
tected from severe storm waves
that are generated by monsoonal
winds during the summer. A large
part of the bay’s sandy bottom is
covered with sparse to dense sea
grass beds dominated by Halodule
uninervis and Halophila ovalis (Al-
Rashdi et al. 2007a,b).
Originally, we had planned to
revisit all six fishing grounds
described in Al-Rashdi et al
(2007a,b), but the extremely low
population density observed in
2008–2009 did not allow compari-
sons between sites. During each
field survey, we interviewed fish-
ermen about the length (duration)
of their fishing trip, the number of
fishers involved, and the method
and location of the collection. We
also recorded the number and spe-
cies of sea cucumbers collected. On
several occasions, we made infor-
mal visits to processing areas to
document size and species distri-
butions of sea cucumber landings.
Since 2007 and following our first
survey, fisheries officers were
requested to record all exports of
processed sea cucumbers (beche-
de-mer) at the main office of the
Ministry of Fisheries Wealth in
Mahout.
Results
Between March 2007 and June
2008, 15.5 t of dried, processed
sea cucumbers were officially
exported from Mahout Bay.
Exports values followed a distinct
yearly cycle, with a winter maxi-
mum and a summer minimum,
ranging from 3.6 t per month in
January 2008 to 0.0 t between
July and October 2008 (Fig. 2).
According to our interviews,
prices varied with size and sea-
son, but overall, fishers received
between 1.5 and 2.0 Omani rials
(~USD 3.5–5.5) per sea cucumber
in 2007–2008.
We observed a definite decline in
sea cucumber abundance. In 2008,
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SPC Beche-de-mer Information Bulletin #30 – March 2010
Figure 1. Mahout Bay (Ghubbat Hashish: “bay of grass”)
in the Sultanate of Oman and the major fishing
areas for Holothuria scabra.
Figure 2. Volume of dried Holothuria scabra exported from Oman
to Dubai in 2007–2008. The grey area covering June-September
corresponds to the period of the southwest monsoon (Khareef),
during which most fishermen leave the area.
on all exploratory dives at the six fishing grounds
used in the 2004–2005 survey (Fig.1) (Al-Rashdi
et al. 2007a), only one or two sea cucumbers were
observed during the 30-minute dives, precluding
any use of quantitative population density or bio-
mass estimates. Similarly, shallow water quadrats
in the same locations as that of the previous survey
(Al-Naqel, Wadsumah, Al-Eigah, Al-Shagnhiah,
Al-Hofnat and Ra’s-Knasah) showed that abun-
dances were very much reduced: in Ra’s-Knasah,
we collected 3 individuals per 200 m2 and only one
individual in Al-Naqel. In the other four sites, no
sea cucumbers were recorded. In terms of catch
per unit of effort, fishers and traders reported that
in 2005, about 100 sea cucumbers per fisher were
collected during a single fishing trip (3–4 hours of
wading at low tide), whereas in 2007, less than 20
sea cucumbers per fisher were collected (Table 1).
We also observed a shift in fishing methods used
by fishermen. In 2005 (Al-Rashdi et al. 2007b), all
fishing took place at spring low tide on foot, but in
2007–2008, 30% of fishermen reported using snor-
keling and skin-diving gear to collect their catch.
Furthermore, in 2005, about 50% of the fishers were
women and children; this ratio dropped to less than
10% in 2007–2008 (Table 1).
The shift in collection methods also allowed fishers
to access deeper fishing sites. One additional fish-
ing ground was exploited in 2007–2008 in Mahout
Bay (Al-Ghynah: Fig. 1), and fishermen reported
that some populations of H. scabra near Masirah
Strait were also newly exploited.
Our observations at the processing sites revealed
that in addition to H. scabra (feik al-bahar, literally “sea
jaw”, probably in relation to the U-shape this species
tends to adopt in collection buckets), a significant
proportion of processed sea cucumbers were H. atra
(abu ar-Reyf, “father of Reyf”) and H. leucospilota (abu
ar-Reyf naqly, “fake abu ar-Reyf”). We also witnessed
large numbers of very small H. scabra (<12 cm fresh,
<6 cm processed) being processed (Fig 3).
Discussion
The rapid decline in population densities observed
between 2005 and 2008 in Mahout Bay is not excep-
tional. Most exploited sea cucumber populations
around the world experience similar declines at
the onset of commercial exploitation (Conand 1997;
Uthicke and Conand 2005). The abundance of H.
scabra observed originally in 2005 was similar to
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SPC Beche-de-mer Information Bulletin #30 – March 2010
Table 1. Changes in sea cucumber fishery indicators between 2004–2005 and 2007–2008 in
Mahout Bay, Sultanate of Oman.
Indicator 2004–2005 2007–2008
Holothuria scabra population density 1000 ind. ha-1 <1 ind. ha-1
Targeted size > 20 cm All sizes (including <15 cm)
CPUE (ind. h-1)* 25 ind. h-1 <5 ind. h-1
Price to fishers (Omani rials) 0.1–1.0 1.5–2.0
Targeted species H. scabra H. scabra
H. atra
H. leucospilota
Fishing grounds 6 recorded grounds in
Mahout Bay
7 recorded grounds in Mahout Bay
+ 2 in Masirah Strait
Fishers involved in the fishery 450 150
% of women and children 50% 15
Fishing methods Low tide collection by
hand
Low tide collection by hand (70%)
Skin-diving (30%)
* Based on a four-hour fishing trip at low tide.
Figure 3. Small, processed juvenile Holothuria scabra
on Mahout Island, October 2008. The 50 baisa coin
is 23 mm in diameter.
that of unexploited stocks of the same species in
the Red Sea (Hasan 2005), and is likely the result of
a highly productive ecosystem and a nearly unex-
ploited sea cucumber population. The decrease in
targeted size classes observed between 2005 and
2008 is an indicator of stressed (or overexploited)
populations. Fishermen now collect almost any size
of animal, including individuals well below the
size at first maturity estimated for this species (i.e.
160–180 mm) (Conand 1989; Hasan 2005; Kithakeni
and Ndaro 2002). This strategy was developed by
fishermen to maintain a constant income from the
fishery. However, because smaller size individuals
fetch a much lower price than larger ones, more sea
cucumbers needed to be caught. This in turn led to
the collection of immature individuals (Richmond
1996). The recent addition of low-value species (H.
atra and H. leucospilota) to catches indicates the poor
status of the fishery in Mahout Bay (Friedman et al.
2008). Overall, all six indicators listed by Friedman
et al. (2008) suggested that the H. scabra fishery was
in poor “health” and that an annual exploitation
of >10% of the stock was unsustainable (although
export and landing data are likely to be strongly
underestimated).
Following these observations, the Ministry of Fish-
eries Wealth gathered a team of experts to develop a
management strategy for the Oman’s sea cucumber
fishery. Future regulation will include a minimum
size at capture of 20 cm, as well as a seasonal clo-
sure (February–August). Despite these soon-to-be
implemented regulations, several closure experi-
ments in the Indo-Pacific have shown that over-
fished sea cucumber stocks were slow to recover
(D’Silva 2001). This is partially because holothuri-
ans are broadcast spawners, whose fertilization rate
drops rapidly at low population densities.
Modelling experiments indicate that individuals
separated by only a few meters do not contribute
practically to larval production because of the dilu-
tion of sperm in the water column (Claereboudt
1999). The reduction in population density due to
fishing may render the remaining individuals nearly
incapable of successful reproduction (Allee effect).
In addition, the population in Mahout Bay appears
to be nearly isolated from other populations of the
same species, and most likely self-recruits, further
increasing the likelihood of recruitment failure in
the future.
In addition to these fisheries management efforts,
the Ministry of Fisheries Wealth has also invested
in sea cucumber aquaculture research to replace or
supplement the income of fishermen involved in
the sea cucumber fishery near Mahout, as well as
to develop a large-scale sustainable production of
beche-de-mer.
References
Al-Rashdi K.M., Claereboudt M.R.and Al-Busaidi
S.S. 2007a. Density and size distribution of the
sea cucumber, Holothuria scabra (Jaeger, 1935)
at six exploited sites in Mahout Bay, Sultan-
ate of Oman. Agricultural and Marine Sciences
12:43–51.
Al-Rashdi K.M., Al-Busaidi S.S. and Al-Rassadi I.H.
2007b. Status of the sea cucumber fishery in the
Sultanate of Oman. SPC Beche-de-mer Infor-
mation Bulletin 25:17–21.
Charles A.T. 2001. Sustainable fishery systems.
Blackwell Science, Oxford. 370 p.
Claereboudt M.R. 1999. Fertilization success in
spatially distributed populations of benthic
free-spawners: a simulation model. Ecological
Modelling 121:221–233.
Conand C. 1989. The fishery resources of Pacific
Island countries. Part 2. Holothurians, FAO
Fisheries Technical Papers. FAO, Rome. p. 143.
Conand C. 1997. Are holothurian fisheries for export
sustainable? p. 2021–2026. In: Lesslos A.H. and
Macintyre A.G. (eds). Smithsonian Tropical
Research Institute, Panama. 8th International
Coral Reef Symposium, Panama..
Conand C. 2004. Present status of world sea cucum-
ber resources and utilization: An international
overview. p. 13–23. In: Lovatelli A., Conand C.,
Purcell S., Uthicke S., Hamel J.-F. and Mercier
A. (eds). Advances in sea cucumber aquacul-
ture and management. FAO Fisheries Techni-
cal Paper, Geneva. D’Silva D. 2001. The Torres
Strait beche-de-mer (sea cucumber) fishery.
Beche-de-Mer Information Bulletin 15:2–4.
Friedman K., Purcell S.W., Bell J.D. and Hair C. 2008.
Sea cucumber fisheries: A manager’s toolbox.
Australian Government. Australian Center for
International Agricultural Research, Canberra,
Australia. 32 p.
Hasan M.H. 2005. Destruction of a Holothuria scabra
population by overfishing at Abu Rhamada
Island in the Red Sea. Marine Environmental
Research 60:499–511.
Kithakeni T. and Ndaro S.G.M. 2002. Some aspects
of the sea cucumber, Holothuria scabra (Jaeger,
1935), along the coast of Dar-es-Salaam. West-
ern Indian Ocean Journal of Marine Science
1:163–168.
Richmond R.H. 1996. Introduction and overview.
p. 2–6. In: Richmond R.H. (ed). Suggestions for
the management of sea cucumber resources in
Micronesia. Results of the Workshop. A egional
Management Sustainable Sea Cucumber Fish-
ery for Micronesia. University of Guam Marine
Laboratory, Technical Report101. 75 p.
Uthicke S. and Conand C. 2005. Local examples of
beche-de-mer overfishing: An initial summary
and request for information. SPC Beche-de-mer
Information Bulletin 21:9–14.
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SPC Beche-de-mer Information Bulletin #30 – March 2010
