MINISTRY OF EDUCATION AND TRAINING
CAN THO UNIVERSITY
SUMMARY OF PhD THESIS
Major: Aquaculture
Major code: 62620301
NGUYEN MINH TUAN
SPECIES COMPOSITION OF GOBIIDAE AND
ELEOTRIDAE AND BIOLOGICAL ASPECTS OF
SOME COMMERCIAL SPECIES DISTRIBUTED IN
THE COASTAL AREAS OF BEN TRE PROVINCE
Can Tho, 2016
A
THIS STUDY HAS BEEN COMPLETED AT
CAN THO UNIVERSITY
Supervisor: Assoc. Prof. Dr. Tran Dac Dinh
The thesis was confirmed at the defence committee of Can Tho
University
Venue: ………………………………………………….
Time: ………………………………………………….
Reviewer 1:
Reviewer 2:
Reviewer 3:
This thesis is available at:
Learning Resource Centre, Can Tho University.
Vietnam National Library.
B
Chapter 1: INTRODUCTION
1.1 General introduction
In the Mekong Delta, the fish composition of Gobiidae and
Eleotridae is high diversity with 66 species living from fresh to marine
water (Tran Dac Dinh et al., 2013). Of these fishes, Glossogobius giuris,
Oxyeleotris urophthalmus, Boleophthalmus boddarti are important
commercial fishes for food and are widely distributed from inland to
estuarine regions (Murdy, 1989; Clayton, 1993) and from tropical to
subtropical areas (Chotkowski et al., 1999, Blaber et al., 2000).
Boleophthalmus boddarti (Pallas, 1770) and Glossogobius aureus
Akihito and Megugo, 1975 are two commercial fishes that contribute to
the local fisheries products.
The coastline of Ben Tre Province is the downstream of Tien
River comprise four estuaries with large areas of muddy flats. The
gobiids of Gobiidae and Eleotridae are important for food in this region,
but there has been little published work on these fishes. Therefore, this
study was conducted to provide useful information on gobiid
composition and biological characteristics that will be a basis for
sustainable exploitation of the gobiid resources in the region.
1.2 Study objectives
- General objectives: determine the fish composition and
biological characteristics of gobies (Gobiidae and Eleotridae) using for
fishery management and sustainable development in the Mekong Delta
in generally and Ben Tre Province in specifically.
- Specific objectives:
+ Contribute to the fish composition of Gobiidae and Eleotridae
families along the coastline of Ben Tre Province.
+ Provide new information on food and feeding habit, growth and
reproductive biology of Glossogobius aureus Akihito and Megugo, 1975
and Boleophthalmus boddarti (Pallas, 1770).
1.3 Study contents
- Investigate the fisheries status and economic species of Gobiidae
and Eleotridae families along the coastal areas of Ben Tre Province.
- Determine the species composition of Gobiidae and Eleotridae
families along the coastline of Ben Tre Province.
- Determine some biological characteristics of Glossogobius
aureus and Boleophthalmus boddarti, including:
+ Digestive morphology characteristics and diet composition.
1
+ Growth pattern: length-weight relationship and von Bertalanffy
curves.
+ Reproductive biology: gonadal stage, sex ratio, gonadosomatic
(GSI), hepatosomatic (HSI), condition factor (CF), fecundity, spawning
season and length at first mature (Lm).
1.4 The significance of the thesis
The results update the basic knowledge about the species
composition of Gobiidae and Eleotridae distributed in coastal
mudflats, status of fisheries and important comercial species;
findings on biological characteristics of growth and reproduction
of G. aureus and B. boddarti. The results can be applied for
artificial breeding for aquaculture development of G. aureus,
B. boddarti in the coastal areas.
1.5 The Significant Results
- The species composition of Gobiidae and Eleotridae distributed
in coastal areas in Ben Tre Province are 35 species, including 28 species
of Gobiidae (80%) and 7 species of Eleotridae (20%).
- There are 13 important commercial species of Gobbiidae and
Eleotridae.
- The results provide some biological characteristics of G. aureus
and B. boddarti include:
+ G. aureus have digestive organs morphology suitable for fish
species, animal feed and feed ingredients common crustacean and small
fish predominate (86.8%); meanwhile, B. boddarti have digestive organs
morphology consistent with herbivorous species and common properties
of food ingredients dominant diatom (87.84%).
+Length-weight relationship showed that G. aureus grows
allometrically, meanwhile B. boddarti grows isometrically. The results
also showed the growth parameters of G. aureus are L∞ = 300 mm;
K = 0.77 / year and t0 = -0.02 years, and thoese of B. boddarti are
L∞ = 160 mm; K = 0.55 / year and t0 = -0.01 years; which can be
identified the relationship between length and age of those species.
+ Results showed that spawning season of G. aureus and
B. boddarti in the rainy season, the absolute fecundity are high and
fecundity G. aureus is higher than of B. boddarti. Determine the length
at first maturity to help fishermen to catch fish larger than the length at
first maturity in order to maintain the fish populations.
2
Chapter 3: MATERIALS AND METHODS
3.1 Methods
3.1.1 Time and region study
Fish specimens were collected from 4/2012 to 3/2014 along the
coastal areas of Ben Tre Province (downstream of Tien River). The pH
and salinity were also recorded.
Specimen analysis: at the field and the Laboratory of Fisheries
Resources, College of Aquaculture & Fisheries, Can Tho University.
3.1.2 Materials
Fishing gear: gill net, bag net and others; camera, macroscopic and
microscopic, GPS (Global Positional System); electronic scale, ruler and
fish surgery equipment; thermometer (pH–506) and refractometer
(TI–SAT100(A)); formalin, alcohol (70%) and other chemicals.
3.2 Study 1: Investigate the fishing status of fish species of
Gobiidae and Eleotridae along the coastal areas of Ben Tre
Province.
3.2.1 Time and study areas: information on fishing status of
gobiids was collected from 3/2012 to 4/2012 at 3 districts such as Binh
Dai (30 samples), Ba Tri (30 samples) and Thanh Phu (30 samples).
3.2.2 Data collection method: the questionnaire was used to obtain
the fishing status from fisherman based the method of Froese and Pauly
(2012).
3.2.3 The content of questionnaire
- Species composition;
- Fishing gears, size of fishing species (g/fish);
- Yield (kg/yr); price (VND/kg);
- Fishingground;
- Fishing season (month);
- The change of yield compared to 5 yrs ago (±%). The main reason
lead to the variation of each fish yield;
- Potential fish species for aquaculture.
3.3 Study 2: Species composition determination.
3.3.1 Fish collection and fixation
Collection
Specimens were monthly collected from 4/2012 to 12/2013 using
gill and bag nets at the muddy flat and mangrove forest along the coastal
areas of Ben Tre Province. 5-10 specimens/species were used for
identification; and the temperature, pH and salinity were also recorded.
3
Fixation
Specimens were fixed using formalin (10%) after collection before
transport to the Laboratory of Fisheries Resource, College of
Aquaculture & Fisheries, Can Tho University for analysis.
3.3.2 External determination
Fish external was determined based on the method of Pravdin
(1973). The fish taxonomy was identified using the taxonomic suggested
by Froese and Pauly (2015).
3.4 Study 3: The digestive morphology determination for
G. aureus and B. boddarti.
3.4.1 Fish collection and fixation
Time and study area:
+ Glossogobius aureus: this study was conducted from 1/2013 to
12/2013 at Thanh Phu.
+ Boleophthalmus boddarti: this study was conducted from
4/2012 to 3/2013 at Ba Tri.
Number of specimens:
+ Glossogobius aureus: 411 individuals and 35 individuals were
used for length-weigh relationship analysis and diet composition
analyses, respectively.
+ Boleophthalmus boddarti: 436 individuals and 30 individuals
were used for length-weigh relationship analysis and diet composition
analyses, respectively.
The gill nets with 15 mm mesh size of the cod end (2a) were used
to collect G. aureus, whereas the bag nets used to collect the B. boddarti.
Fish were fix in formalin (10%) after collection and transport to the
Laboratory of Fisheries Resource, College of Aquaculture & Fisheries,
Can Tho University for analysis.
3.4.2 Specimen analysis
3.4.2.1 Digestive morphology and structure: Fish tooth,
mouth,… structures were observed, and the gut and fish length ratio (was
calculated based on the method of Al-Hussainy (1949).
RLG = gut length (cm)/fish length (cm)
3.4.2.2 Diet composition:
The occurrence and gravimetric methods were applied for
G. aureus, whereas the occurrence and point methods were used for
B. boddarti based on the method of Biswas (1993).
3.5 Study 4: Growth pattern of G. aureus and B. boddarti
3.5.1 Length-weight relationship
4
W = a*Lb (Jennings et al., 2001)
where:
W: fish weight (g);
L: total length (cm);
a: initial growth constant;
b: growth parameter.
3.5.2 The von Bertalanffy growth equation
The parameters (L, K and to) of the von-Bertalanffy equation
were determined using FiSAT II software based on the 12-month length
frequency data (Gayanilo et al., 2006).
Lt = L (1-e-K (t-to))
where:
Lt : the length of fish at t age
L∞: asymptotic length;
t0: the age at which egg is fertilised;
K: growth parameter.
* The index of growth performance:
Φ’ = logK+2log L (Pauly and Munro, 1984).
* The longevity (tmax):
tmax = 3/K (Taylor, 1958):
3.6 Study 5: The reproductive biology of G. aureus and
B. boddarti
A total of 607 G. aureus and 559 B. boddarti were collected
monthly during a period of 18 months were used for this study.
Gonadal development determination
* The gonadal development was determined based gonads’
external and histologically based on the method of Nikolsky (1963).
* The gonadal histologically was done based method of Drury and
Wallington (1980) and Gabe (1976). The development of oocytes was
determined based on scale of Pham Quoc Hung et al. (2014).
Sex ratio determination
Fish specimens were sexually differentiated based the external
morphology of gonads that were removed from specimens after surgery.
The sex ratio was calculated as:
Sex ratio = number of females/number of males
Gonadosomatic index:
GSI (%) = (GW/W)*100
where: GW: gonad weight (g);
W: fish weight (g).
Hepatosomatic index:
HSI (%) = (LW/W)*100
5
where:
LW: liver weight (g);
W: fish weight (g).
Condition factor:
CF = W/Lb (King, 1995)
where:
W: fish weight (g);
L: total length (cm);
b (growth parameter) and a (initial constant) obtained
from length-weigth relationship;
Spawning season
The spawning season was determined based on the variation of
GSI, HSI and CF.
Fecundity
* Absolute fecundity (F):
F = (n*G) /g
where:
F: fecundity;
G: gonad weight (g);
g: representative gonad weight (g);
n: number of eggs in the representative gonad weight.
* Relative fecundity
Relative fecundity (egg/g) = absolute fecundity/weight of fish)
Length at first mature (Lm)
The length at first mature is the length at which 50% fish reach
maturity (King, 2007):
P = 1/{1+exp[-r(L-Lm)]}
where: P: Proportion of maturity;
r: relative constant;
L: mean of fish length;
Lm: length at first mature.
3.7 Data analysis
Mean, standard deviation, max, min and χ2 test were performed
using Excel. FiSAT II (FAO) was used to obtain the von Bertalanffy
curve parameters, and Lm determined using STATISTICA 8.0.
Chapter 4: RESULTS AND DISCUSSION
4.1 The fishing status of Gobiidae and Eleotridae families in
Ben Tre Province.
4.1.1 Fish species composition
Thirteen commercial fish species of Gobiidae (9) and Eleotridae
(4) families has been caught in the study region (Table 4.1).
6
Table 4.1: Thirteen commercial fishes in the study region.
No.
I
1
2
3
4
II
Scientific name
TP
Eleotridae
Butis butis (Hamilton, 1822)
Eleotris melanosoma (Bleeker, 1853)
Oxyeleotris marmorata (Bleeker, 1852)
Oxyeleotris urophthalmus (Bleeker, 1851)
Gobiidae
5 Acentrogobius viridipunctatus (Valenciennes, 1837)
6 Boleophthalmus boddarti (Pallas 1770)
7 Glossogobius aureus Akihito & Meguro, 1975
8 Oligolepis acutipennis (Valenciennes, 1837)
9 Parapocryptes serperaster (Richardson, 1846)
10 Periophthalmodon schlosseri (Pallas 1770)
11 Pseudapocryptes elongatus (Cuvier, 1816)
12 Mugilogobius chulae (Smith, 1932)
13 Trypauchen vagina (Bloch & Schneider, 1801)
*Note: TP:Thanh Phu; BT:Ba Tri; BD: Binh Dai.
Occurrence
BT
BD
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
4.1.2 Fishing status and economic values
The information on fishing status and price of 13 commercial
fishes based on the survey of 90 fishermen (Table 4.2).
Table 4.2: Fishing status and economic values of 13 fish species.
Species
B. butis
E. melanosoma
O. marmorata
O. urophthalmus
A. viridipunctatus
B. boddarti
G. aureus
O. acutipennis
P. serperaster
P. schlosseri
P. elongatus
M. chulae
T. vagina
Ave
14.6
7.45
347
18.7
24.8
24.2
28.4
7.8
28
112
20.8
2
16.5
Weight
(g/fish)
max
min
25
7.5
20
1
900
30
40
10
35
15
50
12
80
10
10
4
50
15
400
5
40 14.5
3
1
20
10
Total length
(mm)
ave max min
98.4
175
45
48.2
80
10
214
270 120
105
150
30
115
160
75
138
200 100
127
300
75
71
80
50
183
250 110
189
250 100
33.6
200
15
25
30
20
147
200 110
Yield
(kg/yr/family)
min
ave
max
373 1092
20
217
700
2
335 2500
10
361 1500
5
1071 2548
50
463 1700
2
809 4500
10
180
700
10
299 1000
2
375 1500
1
811 5000
20
250
300 200
265
576
35
Price
(Thousand VND/kg)
ave
max
min
34
60
12
48
110
15
237
400
80
58
80
20
25
40
13
78
110
30
61
100
30
32
60
20
80
135
50
85
135
30
100
135
65
170
250
90
24
35
13
There are many types of fishing gear such as gill net, bag net, trawl
net, casting net, and hook and line were used to catch fishes. Of them,
bag net was the main fishing gear for mudskipper catching at the muddy
flat whereas other fishes were caught by other gears. Nguyen Bach Loan
(2003) reported that mudskippers had sub-respiration organs that enable
7
they can move on the mud regions (Macnae, 1968; Clayton and
Vaughan, 1988).
Oxyeleotris marmorata was the largest size ranged from 347 g (214
mm in TL) to 900 g (270 mm in TL) among these species, and it is the
most important fish and currently aquaculture in Ben Tre Province,
whereas Acentrogobius viridipunctatus and Trypauchen vagina were low
price. Although the goby G. aureus and B. boddarti cost from 60.000
VND/kg and 80.000 VND/kg respectively, their yield was high. They
were also potential aquaculture fish due to high demand for food,
especially G. aureus has been farming in some extensive shrimp at
Thanh Phu district. However, the yield of this fish was low since the fry
or juvenile were collected from the wild in the Mekong Delta. Therefore,
there is a need to study on the reproductive biology of G. aureus that will
be a basis for artificial reproductive study supplying the fry for
aquaculture.
Comparing to 5 years ago, the yield of 13 commercial fishes
decreased gradually due to high exploitation, suggesting that aquaculture
for gobiids was the fundamental demand. Among these fishes,
P. elongatus and O. marmorata have been farming in this region and
G. aureus and B. boddarti were two potential fish for future aquaculture.
4.2 Environmental factors and fish composition of Gobiidae
and Eleotridae families in Ben Tre Province.
4.2.1 Environmental factors
The temperature and pH were not significantly different between
seasons whereas the salinity was dramatically higher in the dry that in
the rainy season. In the annual salt effect regions, salinity increased
gradually from 12/2012 to 3/2013 reaching the highest point of 28±1‰,
but there was a downtrend of salinity from 4/2012 onward and dropping
the lowest point of 8±2,7‰. In the seasonal salt effect, the salinity grew
to 14,2±4‰ from 1/2013 to 3/2013 after decreasing from 5/2012
onwards and stabilising at 0‰ during a period of 5 months (8/2012 –
12/2012). The variation of salinity caused by the heavy precipitation in
the rainy season and the intrusion of marine water to freshwater in the
dry season. The change in salinity was one of the factor lead to the
diversity of fish composition in this study area.
4.2.2 Fish composition
A total of 35 species belonging to 24 genera was recorded in the
study region (Table 4.3).
8
Table 4.3: Fish composition of Gobiidae and Eleotridae families
No.
Scientific name
R
I
Eleotridae
1
Bostrychus scalaris Larson, 2008
2
Butis butis (Hamilton, 1822)
3
Butis humeralis (Valenciennes, 1837)
4
Butis koilomatodon (Bleeker, 1849)
5
Eleotris melanosoma Bleeker, 1853
6
Oxyeleotris marmorata (Bleeker, 1852)
7
Oxyeleotris urophthalmus (Bleeker, 1851)
II
Gobiidae
8
Acentrogobius canius (Valenciennes, 1837)
9
“Acentrogobius” globiceps (Hora, 1923)
10
Acentrogobius viridipunctatus (Valenciennes, 1837)
11
Amoya moloana (Herre, 1927)
12
Aulopareia unicolor (Valenciennes, 1837)
13
Boleophthalmus boddarti (Pallas 1770)
14
Brachygobius sabanus Inger, 1958
15
Caragobius urolepis (Bleeker, 1852)
16
Eugnathogobius microps Smith, 1931
17
Glossogobius aureus Akihito & Meguro, 1975
18
Glossogobius giuris (Halminton, 1822)
19
Glossogobius sparsipapillus Akihito & Meguro, 1976
20
Gobiopterus chuno (Hamilton, 1822)
21
Gobiopsis macrostoma Steindachner, 1861
22
Mugilogobius chulae (Smith, 1932)
23
Oligolepis acutipennis (Valenciennes, 1837)
24
Parapocryptes serperaster (Richardson, 1846)
25
Periophthalmodon schlosseri (Pallas, 1770)
26
Periophthalmodon septemradiatus (Hamilton, 1822)
27
Periophthalmus variabilis Eggert, 1935
28
Periophthalmus gracilis Eggert, 1935
29
Pseudapocryptes elongatus (Cuvier, 1816)
30
Pseudogobius yanamensis (Rao, 1971)
31
Redigobius chrysosoma (Bleeker, 1875)
32
Stenogobius mekongensis Watson, 1991
33
Stigmatogobius pleurostigma (Bleeker, 1849)
34
Taenioides gracilis (Valenciennes, 1837)
35
Trypauchen vagina (Bloch & Schneider, 1801)
*Note: R: River; Mu: Muddy flat; Ma: Mangrove forest
Ecology
Mu
Ma
+
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+
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+
Gobiidae family with 28 species and 20 genera mainly contributed
to fish composition in the present study region (80%), which was 4 times
higher than that of Eleotridae family (7 species and 4 genera, 20%).
These fishes widely distributed from estuarine to mudflat and mangrove
forest regions, but Boleophthalmus boddarti và Periophthalmodon
schlosseri mostly occurred at the muddy and mangrove forest habitats.
4.2.3 The variation of fish composition between seasons
9
The fish composition was more diversity (35 species) in the rainy
season than in the dry season (22 species). Gobiidae family displayed
more variation in fish composition compared to Eleotridae family
between dry and rainy seasons. In the dry season, B. scalaris,
A. globiceps, A. viridipunctatus, A. unicolor, B. sabanus, E. variegates,
G. macrostoma, P. yanamensis, R. chrysosoma, S. mekongensis,
S. pleurostigma, T. gracilis, T. vagina were not found, resulting from the
difference in salinity and prey items in the environment.
4.2.4 The variation of fish composition between habitats
The fish composition was high diversity in the seasonal salt effect
region (31/35 species) than in the annual salt effect region (22/35
species). Some species was only found in the later region as they were
brackish species that cannot live in the former area (Table 4.4).
Table 4.4: Species only found at the seasonal or annual salt effect
regions
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Scientific name
Bostrychus scalaris
Oxyeleotris marmorata
Oxyeleotris urophthalmus
Brachygobius sabanus
Eugnathogobius microps
Amoya moloana
Gobiopsis macrostoma
Mugilogobius chulae
Periophthalmodon septemradiatus
Pseudogobius yanamensis
Redigobius chrysosoma
Stenogobius mekongensis
Stigmatogobius pleurostigma
Periophthalmodon schlosseri
Periophthalmus variabilis
Periophthalmus gracilis
Trypauchen vagina
Tổng:
A
+
+
+
+
+
+
+
+
+
+
+
+
+
13
B
+
+
+
+
4
*Note: A: seasonal salinity effect areas; B: salinity areas.
4.2.5 The variation of fish composition between fishing gears
The fish composition varied with fishing gears due to different
feeding habit of fishes, and most of fishes (29/35 species) were caught
by gill net and the bag net is the effective gear for mudskipper catching.
It could be concluded that gobiids were wide range of salinity as
they can live from fresh to marine water.
4.3 Digestive morphology and diet composition of G. aureus
10
and B. boddarti
4.3.1 Digestive morphology
4.3.1.1 Glossogobius aureus
This species was carnivore based on its digestive morphology such
shape tooth, wide mouth, J-shape stomach, short gut,… and low value of
RLG which was 0.26 (<1).
4.3.1.2 Boleophthalmus boddarti
This species was herbivore based on its digestive morphology
such unshaped tooth, narrow mouth, long gut,… and high value of RLG
which was 1.77 (>1).
4.3.2 Diet composition
4.3.2.1 Glossogobius aureus
Small crustacean (40.46%) and small fish (46.3%) predominantly
occupied the stomach content whereas detritus contributed 12.87% to the
diet composition, conforming that this species was carnivorous category
based on the scale of Das (1934). Similarly, the goby G. giuris mainly
fed on small crustacean and small fish (Pham Thi My Xuan, 2012;
Achakzai et al., 2015; Rao and Rao, 2002; Hora, 1935; Mookerjee,
1947).
4.3.2.2 Boleophthalmus boddarti
Diatoms (87.84%) were the main prey found in the fish stomach,
followed by blue algae (11.31%), indicating that this species was
herbivore. In the mangrove forest in Pichavaram, India, this species was
also fed mainly on diatoms (Ravi, 2013). This assumption was
confirmed by the previous studies of Macnae (1968), Fenchel (1969).
Heald and Odum (1970) showed that diatom was the most important
prey in the mangrove forest ecosystem.
4.4 Growth of G. aureus and B. boddarti
4.4.1 Length-weight relationship
The G. aureus weight ranged from 7.76 g (9.3 cm TL) to 219.95 g
(30.1 cm TL), and B. boddarti weight was 7.9–44.2 g (10.3–16.5 cm
TL). Both fishes displayed a positive relationship between weight and
length. However, the former showed negative isometric growth
(W = 0.012*L2.85, R2 = 0.958), whereas the later displayed isometric
growth based (W = 0.007*L3.09, R2 = 0.8547) based on the scale provide
by Froese (2006).
4.4.2 von Bertalanffy curve
4.4.2.1 Glossogobius aureus
Pauly (1987) suggested that the analysis on the structure of a fish
11
population requires at least 1500 fish specimens collected over six
months, and the length frequency distribution should display distinct
peaks over time. In this study, a total of 2.395 individuals collected
during 12 months that adopted to the sampling criteria. The von
Bertalanffy curve parameters showed that L∞ = 300 mm; K = 0.77/yr,
t0 = -0.02 yr, and total growth parameter Φ’ = 2.84. The longevity of this
goby was 3.9 yr that was affected by mortalities (Dinh, 2008). The age
and fish length relationship was recorded in Table 4.5
Table 4.5: Age and length relationship of G. aureus.
Age
1+
Standard length (mm)
162
2+
237
+
270
3
4.4.2.2 Boleophthalmus boddarti
A total of 6884 individuals collected during 12 months adopting
to the sampling criteria was used to obtain the von Bertalanffy
parameters (L∞ = 160 mm; K = 0.55/yr and t0 = -0,01 yr) and total growth
constant (Φ’ = 2.15). The longevity of this fish was 5.5 yr. The age and
fish length relationship was recorded in Table 4.6.
Table 4.6: Age and length relationship of B. boddarti.
Age
1+
2+
3+
4+
5+
Standard length (mm)
69
107
130
142
150
The goby G. aureus reached 300 mm in total length at 3.9 year
old. Compared to other gobiids, G. aureus grew faster but slower than
that of Gobio gobio and Gobius niger (Table 4.7). Froese and Pauly
(2015) showed that B. boddarti reach 220 mm TL, but in this study
reached 160 mm TL, and this fish grew slowly compared to
Periophthalmus babarus (Table 4.7). The variation in the longevity of
some gobiids was recorded Table 4.7.
12
Table 4.7: Population parameters of some gobiids.
Species
Gobio gobio
Gobius niger (male)
Gobius niger (female)
Gobius paganellus
Periophthalmus papilio
Periophthalmus babarus
Pseudapocryptes elongatus
Glossogobius aureus
Boleophthalmus boddarti
L∞
(mm)
106
117
151
138
193,9
216
255
300
160
K
(/yr)
0,99
0,91
0,91
0,73
0,51
0,55
0,71
0,77
0,55
t0
Φ’
0
0,32
0,32
-0,22
n.a
n.a
-0,09
-0,02
-0,01
2,05
2,1
2,32
2,14
2,28
2,41
2,66
2,84
2,15
Sources
Bowker (1996)
Vesey và Langford (1985)
Vesey and Langford (1985)
Azevedo and Simas (2000)
Etim et al. (1996)
Etim et al. (2002)
Tran Dac Dinh et al. (2008)
Present study
Present study
4.5 Reproductive biology of G. aureus and B. boddarti
4.5.1 Sex ratio
The male and female G. aureus ratio was 1:0.93 based on a total
of 607 G. aureus (315 males and 292 females) collected during 18
months analysis, indicating that the sex ratio of this goby was close to
1:1
(χ2 = 0.87; p > 0.05). Although the number of female B.
boddarti (302) collected was larger than that in males (257), the sex ratio
of this fish (1:1.18) was not significant different with 1:1 (χ2, p > 0.5).
However, the proportion of female Gobioides rubicundus was higher
than that of males in the spawning time (April to July), whereas the
revised case occurred post-spawning period (November to December)
(Kader et al., 1988). The sex ratio is effected by spawning behaviour like
male or female tend eggs (Miller, 1984; Rogers, 1988; Polgar and Crosa,
2009). The similar in the sex ratio of G. aureus and B. boddarti
suggested that they shared the same spawning behaviour, or they may
not do egg tending.
4.5.2 Gonadal development
The goby G. aureus spawned from August to December due to
stage IV of gonad mainly appeared in this period, whereas the
B. boddarti released eggs monthly as its stage IV of gonad appeared
during 12 months.
4.5.3 Gonadosomatic (GSI) and hepatosomatic Index (HSI)
4.5.3.1 Glossogobius aureus
Both male and female G. aureus shared the same pattern in the
GSI variation. Females’ GSI increased from July and reached a peak in
October (8.52±3.77%) before decreasing from November onward and
droping to the low point from January to June. By contrast, the HSI was
stabled lower point during a period of 4 months (September to
13
December), matching with mature ovaries predominantly appared in that
time.
4.5.3.2 Boleophthalmus boddarti
The variation in GSI of males was similar to females. The female
GSI grew from July to October 2012 and reached the highest point in
October 2012 (4.87±3.02%) before declining from November 2012
onward and dropping to the lowest point in January 2013. The GSI of
females stabled high value during 4 months (September to December),
but HSI reached low point in this period, matching with mature ovaries
during this period.
Duong Tuan (1981) and Miller (1984) reported that during the
maturity period, the energy was stored in muscle and liver, and the
energy was supplied for gonad development during the spawning time. It
lead to the variation in GSI and HSI of G. aureus and B. boddarti.
4.5.5 Condition factor (CF)
The CF of male and female G. aureus varied monthly and
increased from November to June and decreased from March to June.
Similarly, the CF grew from October to June and declined from March to
June in both male and female B. boddarti. The change of gonad weight is
one of the factors affecting the variation in CF (King, 1995; Froses,
2006). The low value of CF from January to February of G. aureus CF
showed this is the post-spawning time of this gobiid.
4.5.6 Spawning season
This goby G. aureus spawned from September to Decmber,
releasing mainly eggs in two months (November to December), whereas
B. boddarti reproduced during 12 months, laying eggs mostly from
October to November based on the GSI, HSI and CF analysis. The high
precipitation in rainy season leads to an abundance of food supplied for
fish and its fry (Nedeco, 1993; Nguyen et al., 2000; Dinh, 2008). It could
result in the spawning season of G. aureus and B. boddarti coincided
with the rainy season.
4.5.7 Fecundity
The absolute fecundity of G. aureus was 69006±25616 eggs
(35175–149932 eggs), and its relative fecundity was 1122±148 eggs/g,
whish was higher than that of B. boddarti. The fecundity of B. boddarti
was 18.224 2.940 eggs (12.607 – 27.270 eggs), and its relative
fecundity was 724 104 eggs/g. The fecundity of fish is species-specific
as Eciota lacrimae fecundity was less than 100 eggs (Sunobe and
Nakazono, 1995) whereas Awaous guamensis fecundity was higher than
14
500000 eggs (Ha and Kinzie, 1996). The fecundity of two gobiid species
in the present study was higher than that of other gobiid such as
Neogobius melanostomus (84 – 606 eggs) (Macinnis and Corkum, 2000)
Crystallogobius linearis (300 – 700 eggs) (Caputo et al., 2003), Gobius
vittatus (560 – 3045 eggs) (Kovačić, 2007), and Periophthalmus papilio
(508 – 15,700 eegs) (Lawson, 2011). However, the fecundity of
G. aureus and B. boddarti was lower than that Parastromateus niger
(71,305 – 3,895,449 eggs) (Dadzie et al., 2008). The goby fecundity of
P. elongatus (10,200 – 113,100 eggs) (Dinh, 2008) was higher than that
of B. boddarti but lower than that of G. aureus. The diffences in fish
fecundity among these gobiids was affected by differences fish size of
eggs size of regions (Pham Thanh Liem and Tran Dac Dinh, 2004).
4.5.8 Length at first mature
The goby G. aureus reached 142 mm TL for males and 122 mm TL
for females at firs mature. The length at first mature of B. boddarti was
128 mm and 126 mm TL for males and females, respectively.
Chapter 5: CONCLUSION AND RECOMENDATION
5.1 Conclusion
The fish composition of Gobiidae and Eleotridae families in the
present study region was high diversity and fishes widely distributed
from estuarine to mangrove forest habitats and from fresh to marine
water. Of 35 species, 13 commercial fishes were being caught, and
P. elongatus and O. marmorata has been farmed.
The goby G. aureus was carnivore since small crustaceans and
fish were found in its stomach, whereas B. boddarti was herbivore as its
stomach contained mainly diatoms and bluealgae. The former showed
negative allometric growth whereas the later displayed isometric growth
and both these fishes belonged to fast growth pattern category,
suggesting that they were potential fish for future aquaculture.
The sex ratio of two gobiid species in this study was close to 1:1.
They were multiple-spawner laying eggs mainly in the main rainy
season. The goby G. aureus reached 142 mm TL for males and 122 mm
TL for females at firs mature. The length at first mature of B. boddarti
was 128 mm and 126 mm TL for males and females, respectively.
5.2 Recommendation
- There was a need to find the suitable method to conserve the
fishery resources of E. microps and G. macrostoma due to few fish
caught.
15
- The length at first capture should be higher than 142 mm and 128
mm TL for G. aureus and B. boddarti for future sustainable exploitation
and management.
- Future artificial aquaculture and reproduction of G.aureus and
B. boddarti should be conducted based on initial knowledge on its
feeding habit and reproductive biology.
16
PUBLICATIONS
Journal
1. Nguyen Minh Tuan, Tran Dac Dinh, Nguyen Hoai Anh, Tran
Trung Kien and Hoang Lam Truc, 2013. The species composition of
goby (Gobiidae and Eleotridae) and some feeding, reproductive biology
characteristics of the goby Boleophthalmus boddarti (Pallas, 1770), in
the Bentre coastal areas. Science and Technology Journal of Agriculture
& Rural Development, (12/2013): 175-182.
2. Nguyen Minh Tuan, Huynh Thi Ngoc Lanh, Nguyen Thanh
Phuong and Tran Dac Dinh, 2014. Some Biological Characteristics Of
The Glossogobius aureus Akihito and Meguro, 1975 Distributed In Ben
Tre Province, Journal of Science, Can Tho University (2014): 169-176.
Conferences
1. Nguyen Minh Tuan, Tran Dac Dinh, Nguyen Hoai Anh, Tran
Trung Kien and Vo Hoang Lam Truc, 2013. The species composition of
goby (Gobiidae and Eleotridae) and some feeding, reproductive biology
characteristics of the goby Boleophthalmus boddarti (Pallas, 1770), in the
Bentre coastal areas. National Scientific Workshop on marine fisheries in
2013, Hai Phong November 2013.
2. Nguyen Minh Tuan, Huynh Thi Ngoc Lanh, Nguyen ThanH
Phuong and Tran Dac Dinh, 2014. Some Biological Characteristics Of
The Glossogobius aureus Akihito and Meguro, 1975 Distributed In Ben
Tre Province, Aquatic Science Meeting times V in Can Tho University
August 2014.
3. Nguyen Minh Tuan, Tran Dac Dinh, 2014. Species
Composition of Gobiidae và Eleotridae and Some Biological Aspects of
Glossogobius aureus Akihito and Meguro, 1975 Distributed in The
Coastal Areas Of Ben Tre Province, Mekong Delta, Vietnam.
International Fisheries Symposium 2014 “Development of Fisheries and
Marine Technology for Sustainable Biodiiversity Conservation and
Respoonsible Aquacuture Industries”. Surabaya, Indonesia. October 3031th, 2014. 6-O-18.
17
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