Int. J. Aquat. Biol. (2021) 9(5): 297-308
ISSN: 2322-5270; P-ISSN: 2383-0956
Journal homepage: www.ij-aquaticbiology.com
© 2021 Iranian Society of Ichthyology
Original Article
Evaluation of the fisheries and resource of sea cucumbers in the coastal waters of
Trincomalee district, Eastern Sri Lanka
Kasun Randika Dalpathadu*1
Marine Biological Resources Division, National Aquatic Resource Research and Development Agency, Crow Island, Colombo, Sri Lanka.
s
Article history:
Received 22 June 2021
Accepted 4 October 2021
Available online 2 5 October 2021
Keywords:
Sea cucumber
Stock assessment
Depletion
Exploitation
Abstract: Though sea cucumber is one of the key export-oriented fishery resources in Sri Lanka,
there is some evidence for the population depletion of most of the sea cucumber species in the shallow
coastal waters. The present study was aimed to study the status of the sea cucumber fishery in the
Irrakkakandi coastal area, eastern Sri Lanka, and carry out a stock assessment on the critical sea
cucumber species presently harvested in this area. In order to achieve the objectives, logbook records
based survey was conducted to cover the fishing season in 2019, from late February to the end of
September. The harvest was collected by skin diving from shallow nearshore waters and Scuba diving
from distal coastal waters about 5 km away from the shore. Thelenota anax was the dominant species
in the catch from both fishing grounds, with a relative abundance of 86.82% in shallow waters and
91.30% in distal waters. The average Catch Per Unit Effort (CPUE) during the fishing season in 2019
for SCUBA diving and skin diving was 50±8.59 individuals /boat/day and 8±1.12 individuals
/diver/day, respectively. The dominant stock of the T. anax in the distal fishing ground was assessed
using the depletion method. The initial stock size of T. anax at the onset of the fishing season was
estimated at 112,067 individuals, and about 25% of the initial stock had been fished by the end of the
fishing season in 2019. The estimated catchability coefficient (q) was 0.00046. The study revealed
that the stock of T. anax along with other recorded threatened species in the Irrakkakandi coastal
waters might be led towards extinction if the fishery prevails without proper management.
Introduction
Sri Lanka is an island nation located in between 5°55’
and 9°55’N and 72°42’ and 81°52’E, south of the
Indian subcontinent. It has a total land area of 65,000
km2 and a coastline of 1,770 km in length, containing
several bays and shallow inlets (Kumara et al., 2005;
Dissanayake et al., 2010). The continental shelf area
is 30,000 km2, which is relatively narrow and small in
the area when compared with other island nations
(Kumara et al., 2005). Fishing activities are carried out
all around the coast, but primarily within the
continental shelf, which rarely extends more than 40
km and averages 25 km (Dissanayake et al., 2010).
Though there are nearly 200 known species of sea
cucumbers found in the waters around Sri Lanka,
about 75 species inhabit shallow coastal waters, while
nearly 50 species are abundant in intertidal areas
(Kumara et al., 2005). Among them, 21 species are
*Correspondence: Kasun Randika Dalpathadu DOI: https://doi.org/10.22034/ijab.v9i5.1265
E-mail: kasun.randika@yahoo.com
considered commercially important (Dissanayake and
Athukoorala, 2010; Dissanayake and Stefanson,
2010). As in many Asian countries, the sea cucumber
fishery in Sri Lanka is an artisanal fishery confined to
the shallow coastal waters (Dissanayake et al., 2010;
Dissanayake and Stefanson, 2012). At the present, the
sea cucumber fishery is confined to the north-western
(Puttlam and Mannar districts), eastern (Trincomalee
to Ampara districts), northern (Jaffna district) and
north-eastern (Mullaitivu district) coastal areas of the
island. Sea cucumbers were initially harvested by
hand picking along the coast during the low tide
period, and since the 1980’s fishers moved further
offshore using snorkelling and at present by scuba
diving as stock became depleted in shallow waters
(Kumara et al., 2005). Fishing activities for sea
cucumbers in Sri Lanka are highly seasonal which
affected by the monsoon wind patterns. Generally, the
298
Dalpathadu / Evaluation of the fisheries and resource of sea cucumbers in eastern Sri Lanka
fishery for sea cucumbers in north-eastern and eastern
coastal areas are carried out from the end of March to
the end of September, while in north-western coastal
areas, those prevail from the onset of October to onset
March. As in the many parts of the Asia region, all the
harvest is exported as the ‘Beche-de-mer’, mainly to
Singapore, Hong Kong and China (Dissanayake et al.,
2010; Dissanayake and Stefanson, 2010).
Holothurians are now considered valuable species
worldwide (Conand, 2008), and the recovery of
depleted populations are slow and sporadic (Kinch,
2002). Even though there is a long history of sea
cucumber fishery in Sri Lanka which dated back to
about 1000 years back (Dissanayake and Wijeyaratne,
2007; Dissanayake and Stefanson, 2010), baseline
data on the species composition, stock status, catch,
effort etc. are very scarce. Thus, the fishery for sea
cucumbers in Sri Lanka has developed neither
regulations nor precautionary approaches except
diving and transportation licenses (Dissanayake and
Wijeyaratne, 2007; Dissanayake and Athukoorala,
2010; Dissanayake and Stefanson, 2010, 2012).
Furthermore, some of the biological characteristics of
the sea cucumbers, such as their lack of hard parts for
ageing, difficulty in marking them, and plastic size
and shape, may cause difficulties in conventional
stock assessment methods (Perry et al., 1999; Uthicke,
2004). Making the situation worse, due to the less
availability of facilities for conducting the fishery-
independent surveys of resources, no one has
attempted to carry out a stock assessment for sea
cucumber resources in the Trincomalee district,
eastern Sri Lanka, via such method.
Based on the observations, it is evident that intense
exploitation rates generally induce sharp depletions in
abundance after the main recruitment within a year.
The depletion model is designed to capture such
within-season dynamics and can be used to track in
real-time the depletions in abundance under fishing
pressure, allowing in-season adaptations of
management measures (Pierce and Guerra, 1994;
Agnew et al., 1998). Thus depletion models (Leslie
and Davis, 1939; De Lury, 1947) are good candidates
for in-season monitoring and management of
invertebrate fisheries such as sea cucumbers (Trianni,
2000; Hoggarth et al., 2006; Prescott et al., 2013).
Therefore, in this study, the present status of the sea
cucumber fishery in the Trincomalee District, eastern
Sri Lanka, was assessed. Further, the stock of
dominant sea cumber species in the commercial catch
was assessed by the depletion method. To my
knowledge, this is the first effort to assess the sea
cucumber fishery and the application of depletion
methods for sea cucumber stock assessment in the
Trincomalee district, eastern Sri Lanka. The findings
of this study will help to understand the sea cucumber
fishery and the current status, and the exploitation
rates of the sea cucumbers in the region. The results
will be beneficial for the preparation and
implementation of appropriate management strategies
for a sustainable fishery for sea cucumbers in the
region.
Materials and Methods
Study area: A fisheries dependent survey of fisheries
logbook records was carried out in 2019 in
Irrakkakandi coastal area, Trincomalee district,
eastern Sri Lanka. A single collector was responsible
for carrying out the fishery for sea cucumbers in the
Irrakkakandi coastal area (Fig. 1).
Data collection: The fishing season for sea
cucumbers in the Trincomalee district was initiated in
late February till September 2019. Thus the logbook
data collection was carried out during this period. Sea
cucumber collectors typically maintain their logbooks
in which they record daily species wise catch per boat.
Accordingly, data on the total landed catch per boat by
species in terms of the number of individuals and the
total number of boats operated each day was extracted
from the daily logbook records of the collector. In
addition, some of the fishers had involved in skin
diving for collecting sea cucumbers in near shore
shallow waters. The collector had recorded the daily
species wise catch per each skin diver. Those data
were also available separately in the logbook records,
which was used to assess the nearshore stocks of the
dominant sea cucumber species. As the collector had
recorded the species by their local names, scientific
299
Int. J. Aquat. Biol. (2021) 9(5): 297-308
identification of the species was made in the field
using available published literature and species
identification guides (Conand, 1998; Dissanayake and
Athukoorala, 2010; Purcell et al., 2012; Dissanayake
and Nishanthan, 2016). Further information was
gathered via interviewing the divers and boat skippers.
Total monthly catch estimate by species
For scuba diving: For the present study, a single
fishing trip was considered as one unit of effort.
Therefore, for each sea cucumber species, the monthly
mean Catch Per Unit Effort (CPUE) in terms of catch
in the number of individuals per boat per day was
estimated based on the logbook data. Accordingly, the
total monthly collection of sea cucumber species by
scuba diving was estimated by summing up the daily
catch records of the particular month.
For skin diving: The total effort of a skin diver in a
single day was considered one unit of effort. For each
sea cucumber species, the monthly mean CPUE in
terms of catch in the number of individuals per diver
per day was estimated based on the logbook data.
Accordingly, the total monthly collection of sea
cucumber species by skin diving was estimated by
summing up the daily catch records of the particular
month.
Stock assessment by depletion method: The
depletion method consisted of modelling the depletion
of stock during the main fishing season and analysing
the influence of cumulative effort on an abundance
index (Royer et al., 2002). This method allows
interpolation of the total initial stock size during each
fishing season (Leslie and Davis, 1939; De Lury,
1947). Models were based on a biological
understanding of the fishery. Although not optimal,
this was the best compromise between using the high
resolution of the catch data and the lower resolution of
the biological data (Keller et al., 2015). The model
estimates the following parameters: the initial
population (N1) and the current stock size, the
expected catches for each time step during the
depletion event (all in numbers), the catchability
coefficient (q) and the goodness of fit measure (Rt). It
was assumed that the population was a closed one
because natural mortality would be low in the
relatively short fishing season (Gould and Pollock,
1997). Further, the catchability coefficient (q) was
assumed to be constant during the study period.
The assessments were conducted using the Leslie-
DeLury DMs with the Catch and Effort Data Analysis
(CEDA) Version 3.0 software package (Kirkwood et
al., 2001). The CEDA software package assumes that
the index (e.g. CPUE) is simply proportional to the
Figure 1. Sea cucumber landing site in Irrakkakandi area, Trincomalee district, eastern Sri Lanka (Sri Lankan map inset).
300
Dalpathadu / Evaluation of the fisheries and resource of sea cucumbers in eastern Sri Lanka
stock size (Hoggarth et al., 2006). For the analysis, ‘No
recruitment’ model type was used as per availability
of the data over a short period, certainly less than one
year, and based on the assumption of the closed stock
(Trianni, 2000; Kirkwood et al., 2001; Hoggarth et al.,
2006). Thus it was assumed that there is no
recruitment to the stock after the first data point but a
constant natural mortality rate ‘M’ (Kirkwood et al.,
2001; Hoggarth et al., 2006). For the analysis, ‘M’ was
assumed to be not significantly different from zero
over the period for which the model was fitted, which
was generally of the order of about seven days (Parkes
et al., 1996; Hoggarth et al., 2006; Prescott et al.,
2013). The depletion model is as follows:
𝑁𝑁𝑡𝑡+1 = 𝑁𝑁𝑡𝑡 𝑒𝑒−𝑀𝑀 − 𝐶𝐶𝑡𝑡 𝑒𝑒
−12𝑀𝑀
Where Nt is the abundance in terms of numbers of
sea cucumber at the start of time t, C is total catch
taken over time t, and M is natural mortality. The ‘No
recruitment’ model type is as follows (Kirkwood et al.,
2001):
𝑁𝑁𝑡𝑡+1 = 𝑒𝑒−𝑀𝑀𝑁𝑁𝑡𝑡 − 𝑒𝑒
−12
𝑀𝑀
𝐶𝐶𝑡𝑡
𝑁𝑁
𝑡𝑡+12
= 𝑒𝑒−
1
2
𝑀𝑀
𝑁𝑁𝑡𝑡 −
1
2
𝐶𝐶𝑡𝑡
Where Nt is the abundance in terms of numbers of
sea cucumber at the start of time t, C, is total catch
taken over time t, and M is natural mortality.
There are three error models in the CEDA software
package; least squares, gamma, log transform, deal
with the measurement errors in the catch component
of CPUE, or, if a single abundance index is being used,
in the abundance index itself (Kirkwood et al., 2001),
to achieve the best model fit (Keller et al., 2015).
Considering the three error models in the CEDA
software package, a preliminary analysis was
conducted to understand the effect of each error model
on the results and determine the most suitable one. The
best error model for the analysis with the available
data set was decided after analysing the “residuals”
graphs of the observed and expected values of catch
and CPUE (Kirkwood et al., 2001; Hoggarth et al.,
2006). Further within the selected error model,
Numerical measures of goodness of fit (R2) was used
to decide how well the model fits (Kirkwood et al.,
2001; Hoggarth et al., 2006; Keller et al., 2015).
Results
Fishery, fishing season and fishing methods: The
fishing season for the sea cucumbers in the
Trincomalee district was from February to the end of
September 2019. After that, fishing for sea cucumbers
could be carried out day and night. However, since a
complete ban on night diving activities in sea
cucumber fishery has been executed by the
Department of Fisheries and Aquatic Resources
(DFAR) of Sri Lanka since April 2019, all fishing
operations conducted targeting sea cucumber were
confined to the daytime. Fishing operations were
usually carried out by 6 to 7 m long outboard motor
Fibre Reinforced Plastic (OFRP) boats. Under the
collector in the Irrakkakandi area, there were 15 OFRP
boats available for sea cucumber fishery though all of
them had not operated in a single day. The collector
used his boats interchangeably for the ease of service
and repairs of the boats and engines. The catch had
collected mainly by scuba divers by the method of
hand-picking. According to the regulations
implemented by the Department of Fisheries and
Aquatic Resources (DFAR), Sri Lanka, two scuba
divers and the boat operator were allowed to
participate in one fishing operation by scuba diving.
Furthermore, a boat could carry a maximum of 10
oxygen cylinders per single fishing operation.
Usually, boats left from the landing site around 7.00
am and reached the landing site with the catch by
around 2.00 pm. The fishing ground for scuba diving
was about 5 km away from the shore, about 20 m
depth.
In addition, few skin divers had engaged in sea
cucumber collection in shallow waters on a more or
less daily basis. There was no specific time for skin
diving; thus, they had carried out the skin diving in
search of sea cucumbers when the near shore waters
got calm. Those skin divers just swam towards the
fishing ground, located within 1 km distance from the
shore and collected the catch. Then the catch was sold
to the collector. The sea cucumber catch was
processed at the collection centre to produce beach-
301
Int. J. Aquat. Biol. (2021) 9(5): 297-308
de-mer.
Species composition in the present catch in
Irrakkakandi area: Five species belonged to two
families were recorded from the catch of the
Irrakkakandi waters on the eastern coast of Sri Lanka.
Considering the fishery by scuba diving, Thelenota
anax Clark, 1921, was the dominant species with
91.30% relative abundance in terms of the number of
individuals (Table 1). Holothuria atra Jaeger, 1833
was recorded the lowest abundance with 0.14%
representation in the catch in 2019. In addition,
Actinopyga miliaris (Quoy & Gaimard, 1834),
Bohadschia sp. and Stichopus chloronotus Brandt,
1835, had contributed to the rest of the catch (Table
1).
The catch of skin divers was composed of the same
species as in the scuba diving but with different
relative abundances. Thelenota anax was the
dominant species with 86.82% relative abundance in
terms of the number of individuals and S. chloronotus
recorded the lowest abundance with 0.17% relative
abundance in 2019 (Table 1).
The fishing effort, CPUE and production in the sea
cucumber fishery
Scuba diving: The average effort during the fishing
season in 2019 was estimated at 3.37±2.07 boat days.
Figure 1. Location map of Ashtamudi Lake showing the study sites (Station I-Perumon Lake, Station II-Thekkumbhagam Lake).
Table 1. Species composition of the sea cucumber fishery based on the landed catch from in Irrakkakandi area in 2019.
Family Species Common name Local name % in the catch
Global conservation
status
Scuba diving
Skin
diving
Stichopodidae
Thelenota anax
Clark, 1921
Amber
fish Poona attaya 91.30 86.82
DD
(Conand et al., 2013a)
Stichopus
chloronotus Brandt,
1835
Greenfish Dambala Attaya 0.85 0.17
LC
(Conand et al., 2013c)
Holothuriidae
Actinopyga miliaris
(Quoy & Gaimard,
1834)
Hairy
blackfish Kalu gal attaya 3.20 4.74
VU
(Conand et al., 2013b)
Bohadschia sp. Sandfish Nool attaya 4.51 7.79
Holothuria atra
Jaeger, 1833 Lollyfish Nari Attaya 0.14 0.48
LC
(Conand et al., 2013d)
Figure 2. The monthly variation of the average Catch per Unit Effort (CPUE) in 2019 in the sea cucumber fishery by scuba diving in the
Irrakkakandi area.
302
Dalpathadu / Evaluation of the fisheries and resource of sea cucumbers in eastern Sri Lanka
The average CPUE in the sea cucumber fishery was
50±8.59 individuals /boat/day. Considering the CPUE
for the species caught by Scuba diving, a gradual
declining trend could be identified for T. anax from
March towards the end of the season. A gradual
incline till May and then after a declining trend
towards the end of the season in the CPUE was
observed for A. miliaris and Bohadschia sp. (Fig. 2).
The total production from the fishing ground for
scuba diving in the Irrakkakandi area was estimated at
31,014 individuals of sea cucumber species in 2019.
Among them, 28,317 individuals were represented by
T. anax. Considering monthly variations in the total
production by scuba diving, a sharp increment in the
catch till May then gradually decreased towards the
end of the fishing season (Fig. 3). The highest
production was recorded in May 2019. The three most
dominant species in the catch, T. anax, A. miliaris and
Bohadschia sp. showed a similar production trend,
which increased rapidly till May and then decreased
Figure 3. The monthly production of sea cumber fishery by SCUBA diving in the Irrakkakandi area in 2019.
Figure 4. The monthly variation of the average Catch per Unit Effort (CPUE) in 2019 in the sea cucumber fishery by skin diving in the Irrakkakandi
area.
303
Int. J. Aquat. Biol. (2021) 9(5): 297-308
gradually to the end of the season in September.
Stichopus chloronotus was recorded only in May and
June.
Skin diving: The average effort for skin diving fishery
during the fishing season in 2019 was estimated at
4.00±2.29 diver days. The average CPUE in the sea
cucumber fishery by skin diving was estimated at
8±1.12 individuals /diver/ day. The highest average
CPUE was recorded in May, and a gradual decline in
the CPUE was observed then after towards the end of
the fishing season for A. miliaris and Bohadschia sp.
The average CPUE for T. anax remained almost
constant from May to the end of the fishing season
(Fig. 4).
The total production of sea cucumbers via skin
diving in 2019 was estimated at 5,836 individuals,
among which 5,067 individuals were represented by
T. anax. Considering the monthly variation in the total
production by skin diving, the total production was
boosted from February to March, and then a drop-
down was observed in April. Then, it gradually
increased till July and recorded the highest production
in 2019. After that, it decreased steeply in August. The
most dominant species, T. anax, followed a trend
similar to the total production. Considering other
species in the catch, the production of Bohadschia sp.
and A. miliaris exhibited an increasing trend till May
and then decreased gradually towards the end of the
season (Fig. 5).
Stock assessment for Thelenota anax in deep water
fishing ground (scuba diving) in the Irrakkakandi
area: According to the results, the stock at the onset
and end of the fishing season was estimated at N1 =
112,067 and N30 = 83,750 (R2 = 0.94). The estimated
catchability coefficient (q) was 0.00046. Thus,
25.27% of the T. anax stock thrived in the distal waters
fishing ground was harvested by the end of the fishing
season in 2019 (Fig. 6). Log transforms error model
assumptions frequently showed minimisation failure
in the stock assessment process for the other species
recorded in the catch by the CEDA software package.
Discussions
Harvesting and exporting coastal ecosystem
associated organisms such as sea cucumbers have
contributed substantially to the country's foreign
exchange earnings while providing essential
livelihood to the coastal fishing community (Choo,
2008; Kumara et al., 2008; Dissanayake and
Stefansson, 2012). Considering the fishery for sea
cumbers in the Irrakkakandi area, Trincomalee
district, eastern Sri Lanka, hand-picking by scuba
diving was the main fishing method while OFRP boats
were used fishing craft. Those are the main fishing and
Figure 5. The monthly production of sea cumber fishery by skin diving in the Irrakkakandi area in 2019.
304
Dalpathadu / Evaluation of the fisheries and resource of sea cucumbers in eastern Sri Lanka
craft types for sea cucumber fishery in Sri Lanka
(Dissanayake and Athukoorala, 2010; Dissanayake
and Stefansson, 2012). In addition to the hand-picking
by scuba divers, some fishers involved in the hand-
picking of sea cucumbers in nearshore shallow waters
by skin diving. At the beginning of the sea cucumber
fishery in Sri Lanka, hand-picking while wading or
using snorkel gears were the main fishing methods
(Kumara et al., 2005). However, due to the
overexploitation of the nearshore sea cucumber
resources, fishers had to exploit resources located in
far deeper areas by scuba diving (Kumara et al., 2005;
Dissanayake and Athukoorala, 2010). Therefore, it
was evident that the sea cucumber resource in
nearshore shallow waters in the Irrakkakandi area had
not been over-exploited to date.
Though about 21 sea cucumber species are
considered commercially important (Dissanayake and
Stefanson, 2010) in Sri Lanka, only five species
belonging to two families were recorded during this
study. Among them, the representation of Holothuria
atra in the catch from the deep distal waters was lower
than that from the nearshore shallow waters. It may be
attributed to the habitat preference of this species as it
inhabits in aggregated populations in shallow waters
where skin diving operated while it inhabits in more
scatter in the deeper waters where the scuba diving
operated (Conand, 1998). Further, this scattered
nature of occupancy in the habitat may be the reason
behind the lowest representation of H. atra in the
catch from the scuba diving fishery. Furthermore, the
lowest representation of S. chloronotus in the catch
from the skin diving may also be attributed to its
habitat preference. This species generally occurs
on back reef hollows (Conand and Mangion, 2002)
and in areas with boulders mixed with live corals
(Choo, 2008), making it difficult to be spotted by the
skin diver. However, due to the absence of scientific
records of previous studies in sea cucumber fishery in
Trincomalee district, Sri Lanka, it is challenging to
state whether the relatively low abundance of
S. chloronotus, A. miliaris, H. atra and Bohadschia
Figure 6. The results of the catch and effort data of Thelenota anax with the 'log transform error model' in CEDA software package version 3.0 for
SCUBA diving fishery in the Irrakkakandi coastal waters in 2019.
305
Int. J. Aquat. Biol. (2021) 9(5): 297-308
sp. in the catch was due to depletion of the resources
in the area or due to other factors such as the ecology
of these species.
The lowest production from both fishing methods
in February may be attributed to the lowest total
fishing effort in February, as the fishing season started
in the last week of the month. The Easter day terrorist
attack in Sri Lanka on 21st April 2019 made a larger
impact on Sri Lankan society, including the fishing
community. It might be the reason behind the low
production in April, as most of the fishing activities
were seized for about two weeks due to security
reasons. However, a continuous decline in the total
monthly production was observed from May to
September. The sharp decline in production could
presumably be attributed to the depletion of the sea
cucumber resource in the scuba fishing ground in the
Irrakkakandi area. When considering the fishery for
sea cucumbers by skin diving, the sudden drop of the
production from July to August and also the
comparatively low production in September may be
due to either the depletion of the resources or
unfavourable weather conditions for skin diving
activities in rocky shore area in Irrakkakandi or due to
the combination of both reasons. However, lacking
historical data on the sea cucumber fishery in this area
obstructed to conclude on either trend in the
production or the fishing effort.
According to the collector in the Irrakkakandi area,
the price paid for a diver per individual of different
species in 2019 was 300-500 LKR (based on the size
of the specimen) for T. anax; 400 LKR for A. miliaris
and 200 LKR for Bohadschia sp. Therefore, when
considering the species composition, production and
CPUE for both harvesting methods, T. anax was
dominated while Bohadschia sp. holds the second
highest species in the catch. Though A. miliaris has
higher economic value than Bohadschia sp, the higher
percentage of Bohadschia sp in the catch probably
explained by the fishers' behaviour which aims to
catch valuable species first, and when such species are
not abundant or not found, they attempt to harvest
low-value species (Hasan, 2019).
Actinopyga miliaris was the third abundant species
in the catch from both fishing methods in the
Irrakkakandi area. According to the global
conservation status of this species, it has been
categorised under the 'Vulnerable' category, which is
one of the 'threaten categories' in the IUCN criteria
(Conand et al., 2013b). The price paid for an
individual of A. miliaris was as same as for T. anax.
Furthermore, unlike T. anax, A. miliaris can be easily
collected from their habitats (Conand et al., 2013b).
Therefore, the very low abundance in the catch most
probably attributed to the very low stock abundance in
the habitat. Thus prevailing fishing pressure may lead
this species towards extinction from its local habitats.
However, as there is a lack of historical data and
unavailability of the stock assessment results from the
present study for A. miliaris, it cannot be concluded on
the present status of A. miliaris in the Irrakkakandi
area.
Some studies (Purcell, 2010; Koike, 2017) have
proven that the decreasing trend in the CPUE might
indicate the decrease in the abundance of the target sea
cucumber species in their habitat. However, the
degree of confidence in CPUE as an index of species
abundance varies with behavioural interactions
between the harvested sea cucumber species and the
collectors (Purcell, 2010; Dissanayake and Stefanson,
2012).
The stock assessment results revealed that around
25% of the stock of T. anax had been removed at the
end of the fishing season via scuba diving. Though
there might be other factors that affected the reduction
of the stock, several studies have proven that the
contribution of those factors on the decline in the
abundance of sea cucumbers are probably negligible
(Conand, 1990; Uthicke and Benzie, 2000; Hasan,
2019). Therefore, the marked reduction in the size of
the stock could result from the high fishing mortality.
Due to some of the biological traits of sea cucumbers
such as late maturity, density-dependent reproduction,
and low rate of recruitment of sea cucumbers
(Dissanayake and Stefanson, 2012; Hasan and El-
Rady, 2012), some studies have suggested
maintaining the exploitable level at a lower rate such
as around 5% of the initial stock size to avoid the
306
Dalpathadu / Evaluation of the fisheries and resource of sea cucumbers in eastern Sri Lanka
collapse of the fishery due to overexploitation
(Uthicke, 2004; Purcell, 2010). If the fishery collapses
due to over-exploitation of the resources in the
particular area, it will take several decades to regain
the stocks to their original condition (Purcell, 2010;
Hasan and El-Rady, 2012; Hasan, 2019). As the
current exploitation level is higher than the
recommended level in the scuba fishing ground, there
is a high risk of extinction of the T. anax in the habitat
susceptible to scuba diving fishing if the current
exploitation level remains unchanged in future.
In this assessment, the Depletion Model used
several assumptions. Sea cucumber species exhibit
minimal movements and a slow growth rate (Conand,
1998; Trianni, 2000). Therefore, the T. anax
population in the Irrakkakandi coastal area would
probably not have experienced any significant
immigration or emigration during the seven-month
harvest period, thus validates the assumption of a
closed population. One of the fundamental
assumptions in this method is constant catchability (q)
over time. The constant catchability assumption
would depend upon weather and the management unit
fished (Trianni, 2000). For sea cucumber fishing
operations by scuba diving in Irrakkakandi coastal
area, the environmental conditions remained
unchanged to some extent during the fishing season in
2019, and fishers used their fishing locations within
the same fishing ground for the collection of sea
cucumbers. Moreover, the number of divers who were
on-board for sea cucumber collection and the number
of oxygen cylinders used for scuba diving per fishing
operation also remained constant. Therefore, the
magnitude of change in catchability is expected to be
low.
However, it is imperative to formulate a proper
management plan and implement appropriate
management strategies to ascertain the sustainability
of the sea cucumber fishery in the Trincomalee
district, eastern Sri Lanka. The results of this study
could be use of when preparing such a management
plan. Further, it is highly recommended to implement
a monitoring mechanism for the sea cucumber fishery
in the Trincomalee district to understand its existing
trend.
Acknowledgements
This study was undertaken using allocated funds to the
National Aquatic Resources Research & Development
Agency (NARA), Sri Lanka, by the Ministry of
Finance, Sri Lanka. The authors are grateful to S.S.K.
Haputhantri (Head of the Division), C. Karunarathne
and U. Prasad, and all other staff members of the
Marine Biological Resources Division (MBRD) of
NARA who assisted in the fieldwork and office work.
I would like to express my sincere thanks and gratitude
to D.R. Hearth of MBRD for her support in
proofreading this paper. I would like to express my
great appreciation for the divers and collector
involved in the sea cucumber fisheries in Trincomalee
district, Sri Lanka, who supported in the field by
providing with their logbook data.
References
Agnew D.J., Baranowski R., Beddington J.R., Des Clers S.,
Nolan C.P. (1998). Approaches to assessing stocks of
Loligo gahi around the Falkland Islands. Fisheries
Research, 35: 155-169.
Choo P.S. (2008). Population status, fisheries and trade of
sea cucumbers in Asia. In: M.V. Toral-Granda, A.
Lovatelli, M. Vasconcellos (Ed.), Sea cucumbers. A
global review on fisheries and trade, FAO Fisheries
Technical Paper No. 516. FAO. Rome. pp: 81-119.
Conand C. (1990). The fishery resources of Pacific Island
countries. Part 2 Holothurians: FAO Fisheries
Technical Paper 272. 2. FAO. Rome. 142 p.
Conand C. (1998). Holothurians. In: K. Carpenter, V. Niem
(Ed.). FAO species identification guide. The marine
living resources of the Western Central Pacific.Vol.2
cephalopods, crustaceans, holothurians and sharks.
FAO. Rome. pp: 1157-1190.
Conand C., Mangion P. (2002). Sea cucumbers on La
Reunion Island fringing reefs: Diversity, distribution,
abundance and structure of the populations. SPC Beche-
de-mer Information Bulletin, 17(17): 27-33.
Conand C. (2008). Population status, fisheries and trade of
sea cucumbers in Africa and the Indian Ocean. In: V.
Toral-Granda, A. Lovatelli, M. Vasconcellos (Ed.). Sea
cucumbers. A global review of fisheries and trade, FAO
Fisheries Technical Paper No. 516. FAO. Rome. pp:
307
Int. J. Aquat. Biol. (2021) 9(5): 297-308
143-193.
Conand C., Purcell S., Gamboa R. (2013a). Thelenota
anax. The IUCN Red List of Threatened Species 2013:
e.T180324A1615023. Available from: https://dx.Doi.
org/10.2305/IUCN.UK.2013-1.RLTS.T180324A1615
023.en. Retrieved 27/04/2021.
Conand C., Purcell S., Gamboa R. (2013b). Actinopyga
miliaris. The IUCN Red List of Threatened Species
2013 e.T180265A1607822. Available from: https://
dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T180265
A1607822.en. Retrieved 27/04/2021.
Conand C., Gamboa R., Purcell S. (2013c). Stichopus
chloronotus. The IUCN Red List of Threatened Species
2013:e.T180477A1635468. Available from:
https://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T1
80477A1635468.en. Retrieved 28/04/ 2021.
Conand C., Gamboa R., Purcell S. (2013d). Holothuria
atra. The IUCN Red List of Threatened Species 2013:
e.T180421A1628832. Available from: https://dx.doi.
org/10.2305/IUCN.UK.2013-1.RLTS.T180421A162
8832.en. Retrieved 28/04/ 2021.
De Lury D.B. (1947). On the estimation of biological
populations. Biometrics, 3: 145-167.
Dissanayake D.C.T., Wijeyaratne M.J.S. (2007). Studies
on the sea cucumber fishery in the north-western coastal
region of Sri Lanka. Sri Lanka Journal of Aquatic
Science, 12: 19-37.
Dissanayake D.C.T., Athukorala S., Amarasiri C. (2010).
Present status of the sea cucumber fishery in Sri Lanka.
SPC Beche-de-mer Information Bulletin, 30: 14-20.
Dissanayake D.C.T., Athukoorala A.A.S.H. (2010). Status
and Management of Sea Cucumber Fishery in Sri
Lanka. National Aquatic Resources Research and
Development Agency. Colombo. 109 p.
Dissanayake D.C.T., Stefansson G. (2010). Abundance and
distribution of commercial sea cucumber species in the
coastal waters of Sri Lanka. Aquatic Living Resources,
23: 303-313.
Dissanayake D.C.T., Stefansson G. (2012). Present status
of the commercial sea cucumber fishery off the north-
west and east coasts of Sri Lanka. Journal of the Marine
Biological Association of the United Kingdom, 92(4):
831-841.
Dissanayake D.C.T., Nishanthan G. (2016). Fresh and
Processed Sea cucumbers of Sri Lanka: Identification
Guide. The University of Sri Jayewardenepura and
National Research Council. Colombo. 37 p.
Gould W.R., Pollock K.H. (1997). Catch-effort maximum
likelihood estimation of important population
parameters. Canadian Journal of Fisheries and Aquatic
Sciences, 54: 890–897.
Hasan M.H., El-Rady S.E.A.A. (2012). The effect of
fishing pressure on the ecology of sea cucumber
populations in the Gulf of Aqaba, Red Sea. SPC Beche-
de-mer Information Bulletin, 32: 53-59.
Hasan M.H. (2019). Destruction of sea cucumber
populations due to overfishing at Abu Ghosoun area,
Red Sea. The Journal of Basic and Applied Zoology,
80(5): 2679.
Hoggarth D.D., Abeyasekera S., Arthur R.I., Beddington
J.R., Burn R.W., Halls A.S., Kirkwood G.P., McAllister
M., Medley P., Mees C.C., Parkes G.B., Pilling G.\M.,
Wakeford R.C., Welcomme R.L. (2006). Stock
assessment for fishery management – A framework
guide to the stock assessment tools of the Fisheries
Management Science Programme (FMSP), FAO
Fisheries Technical Paper. No. 487. FAO. Rome. 261 p.
Keller S., Robin J.P., Valls M., Cabanellas-Reboredo M.,
Quetglas A. (2015). The use of Depletion Methods to
assess Mediterranean cephalopod stocks under the
current EU Data Collection Framework. Mediterranean
Marine Science, 16(3): 513-523.
Kinch J. (2002). The beche-de-mer fishery in the Milne
Bay Province of Papua New Guinea. A Report to the
National Fisheries Authority, Port Meresby, P.N.G. &
CSIRO, Queensland. Australia. SPC Beche-de-mer
Information Bulletin, 17: 2-15.
Kirkwood G.P., Aukland R., Zara S.J. (2001). Software -
Catch Effort Data Analysis (CEDA) Version 3.0.
Marine Resources Assessment Group (MRAG) Ltd.
London, UK.
Koike H. (2017). Fishery ecology of Seychelles’ sea
cucumber fishery. PhD. Thesis, The University of
Hawaii. 182 p.
Kumara P.B.T.P., Cumaranathunga P.R.T., Linden O.
(2005). Present status of the sea cucumber fishery in
southern Sri Lanka: A resource depleted industry. SPC
Beche-de-mer Information Bulletin, 22: 24-29.
Leslie P.H., Davis D.H.S. (1939). An attempt to determine
the absolute number of rats on a given area. Journal of
Animal Ecology, 8: 94-113.
Parkes G., Moreno C. A., Pilling G., Young Z. (1996). Use
of the Leslie stock depletion model for the assessment
of local abundance of Patagonian toothfish
(Dissosticejus eleginoides). CCAMLR Science, 3: 55-
77.
308
Dalpathadu / Evaluation of the fisheries and resource of sea cucumbers in eastern Sri Lanka
Perry R.I., Walters C.J., Boutillier J.A. (1999). A
framework for providing scientific advice for the
management of new and developing invertebrate
fisheries. Reviews in Fish Biology and Fisheries, 9:
125-150.
Pierce G.J., Guerra A. (1994). Stock assessment methods
used for cephalopod fisheries. Fisheries Research, 21:
255-285.
Prescott J., Vogel C., Pollock K., Hyson S., Oktaviani D.,
Panggabean A.S. (2013). Estimating sea cucumber
abundance and exploitation rates using removal
methods. Marine and Freshwater Research, 64: 599-
608.
Purcell S.W. (2010). Managing sea cucumber fisheries
with an ecosystem approach: FAO Fisheries and
Aquaculture Technical Paper: No. 520. FAO. Rome.
157 p.
Purcell S.W., Samyn Y., Conand C. (2012). Commercially
important sea cucumbers of the world: FAO Species
Catalogue for Fishery Purposes. No. 6. FAO. Rome.
223 p.
Royer J., Peries P., Robin J.P. (2002). Stock assessments of
English Channel loliginid squids: updated depletion
methods and new analytical methods. ICES Journal of
Marine Science, 59: 445-457.
Trianni M.S. (2000). Evaluation of the resource following
the sea cucumber fishery of Saipan, Northern Marianas
Islands. In: M.K. Moosa, S. Soemodihardjo, A.
Soegiarto, K. Romimohtarto, A. Nontji, Soekarno,
Suharsono (Eds.). Proceedings of the 9th International
Coral Reef Symposium, Vol. 2. Bali, Indonesia. pp:
829-834
Uthicke S., Welch D., Benzie J.A.H. (2000). Slow growth
and lack of recovery in overfished holothurians on the
Great Barrier Reef: evidence from DNA fingerprints
and repeated large-scale surveys. Conservation
Biology, 18: 1395-1404.
Uthicke S. (2004). Overfishing of holothurians: lessons
from the Great Barrier Reef. In: A. Lovatelli, C.
Conand, S. Purcell, S. Uthicke, J. Hamel, A. Mercier
(Ed.), Advances in sea cucumber aquaculture and
management, FAO Fisheries Technical Paper 463.
FAO. Rome. pp: 163-172.