Study on species composition and some biological characteristics of eleotridae living in the bassac river

1.2 General objective of study The overal objective aims to determine of species, abundance of Eleotridae and biological characteristics of gobies living in Bassac river in the contribu

MINISTRY OF EDUCATION AND TRAINING

CANTHO UNIVERSITY

SUMMARY OF PhD THESIS Major in Aquaculture Identification code: 62620301

B

THIS STUDY HAS BEEN COMPLETED AT

Supervisors: Assoc Dr Tran Dac Dinh

Reviewer 1:

Reviewer 2:

Reviewer 3:

This thesis is available at:

Learning Resource Centre, Can Tho University

Vietnam National Library.

CHAPTER 1: INTRODUCTION 1.1 General introduction

Goby has been the largest fish group with about 220 genera and 1,875 species belonging to five families (Eleotridae, Gobiidae, Periophthalmidae, Apocrypteidae and Gobioididae) (Healey, 1971) Among them, Eleotridae has comprised 31 genera and 178 species (Froese and Pauly, 2014) In the Mekong river basin, there have been 34 genera and 101 species belonging

to five families (Rainboth, 1996) These five fish families are also found in Vietnam, and Eleotridae consist of three genera and seven species (Mai Dinh Yen, 1992; Nguyen Huu Phung, 1997; and Nguyen Nhat Thi, 2000)

Similarily, Tran Dac Dinh et al (2013) showed that there were seven species in Mekong Delta (MD) including: Eleotris melanosoma (Bleeker, 1853); Butis butis (Hamilton, 1822); Butis humeralis (Valenciennes, 1837);

Oxyeleotris marmorata (Bleeker, 1852); Oxyeleotris urophthalmus

(Bleeker, 1853); Bostrychus scalaris (Larson, 2008) and Butis

koilomatodon (Bleeker, 1849) Some species had economic values such as

O marmorata, O urophthalmus and E melanosoma usually living in

inland areas and estuaries (Murdy, 1989), and in tropical and subtropical

areas (Chotkowski et al., 1999) Many spcecies came there for spawning and completing lifecycle (Blaber et al., 2000) Species of O marmorata

was raised and catched at fishing areas along in Bassac river, in which

species of O urophthalmus and E melanosoma had economic values

because of meat delicious and highly productive (MOFI, 1996) However, they were not been much studying and only some studies were done on species of diversity and their biological characteristics Presently, knowledge of those species, the abundance of species of Eleotridae living in Mekong river basin, as well as nutritional characteristics and reproductive

biology of O urophthalmus and E melanosoma were not much announced

although they were among of the groups with high economic values in the

MD So, study on species composition of Eleotridae and biological characteristics of gobies were very essential

1.2 General objective of study

The overal objective aims to determine of species, abundance of Eleotridae and biological characteristics of gobies living in Bassac river in the contribution to the protection of aquatic resources products and providing the basis for researching on artificial breeding of some gobies having economic value in the future

2

1.3 The significance of the thesis

The results of this thesis to supplement scientific data about the species of Eleotridae and biological characteristics of gobies living in Bassac river These results were used as resources for teaching and scientific researching

in order to manage, restore and regenerate fisheries resources in general and particular groups of goby

1.4 The significant results

i) Survey resulted some ecological parameters showed that the salinity was

related to the living in gobies of Eleotridae, especially species of E

melanosoma and B butis Catch per unit effort (CPUE) of these species

had seasonal fluctuations and depended on the diversity of aquatic species, flow speed and water depth

ii) There were five species of Eleotridae living in Bassac river, in which

species of E melanosoma, O urophthalmus and O marmorata appeared more in upstream and middle while B Butis appeared in the middle and downstream, especially species of Butis humeralis appeared only in the downstream However, catched by trawl net showed that species of E

melanosoma appeared in the upstream and middle, while B butis just

appeared in the downstream CPUE of E melanosoma was more B

Butis The abundance in rainy season was more in dry season

iii) Species of E melanosoma and O urophthalmus had morphological

gastrointestinal tract matching animal feeding Although there were four groups of food appeared in nutritional spectrum, but only three groups were considered as the favorite food for these species (crustaceans, molluscs and fingerling) The ratio of kinds of food also changed with increasing the total length and width of their mouth

iv) The value of gonadosomatic index (GSI) of E melanosoma and O

urophthalmus was high from May to October, while the hepatosomatic

index (HSI) was low in July; conditional factor (CF) was highest in April and November showing that reproductive seasonality of this two species was along from May to October and concentrated from May to

July The results also showed that the fecundity species of E

melanosoma ranged from 49 to 930 eggs/g of female and higher than O urophthalmus (from 44 to 477 eggs/g of female) Absolute fecundity of

E melanosoma from 2,981-19,520 eggs/ female and O urophthalmus

from 1,290-9,999 eggs/female Length of maturity (Lm) of E

O urophthalmus was 11.36 cm (in male) and 7.96 cm (in female)

CHAPTER 3: MATERIALS AND METHODS

3.1 Time and site study

This study was carried out from August 2012 to December 2014 The study sites were in the upstream (An Giang province), middle (Can Tho city) and downstream (Soc Trang province) in Bassac river (Figure 2.1)

Figure 2.1: Diagram sampling areas in Bassac river

(www.maps.google.com, accessed on 05/06/2012)

3.2 Materials and methods of study

3.2.1 Study 1: Identify some ecological parameters (temperature, pH, salinity, water flow, water depth, phytoplankton, zooplankton and zoobenthos) in Bassac river

Identifying some ecological parameters in the target areas was performed from August 2012 to June 2013 at the same time and place of gobies that collected by trawl net in the upstream, middle and downstream in Bassac river Each area collected five points, sampling cycle two months, in which: a) Value of pH, temperature and salinity of the water were determined by the used of specialized equipment: pH meter, thermometer, refractometers at the field (Figure 2.2)

b) Water flow was determined by the flowmeter (23090; Paul and Sally, 1977): Water flow (km/h)=distance measurement (km)/measurement time (hours); in which: (i) distance measurement=(number of rotor ring turned rotor x coefficient)/999999; and (ii) coefficient for flowmeter rotor (23090)=26,873 (Paul and Sally, 1977)

c) The depth of water in the survey was measured in the field with a water depth measurement device (model PS-7FL Hondex) (Figure 2.2)

4

Figure 2.2: Some of devices used to collection of ecological parameters

d) Species composition of phytoplankton, zooplankton and zoobenthos by phytoplankton net (mesh size of 30 micrometers), zooplankton net (mesh size 60 micrometers) and bottom Petersen (0.028 m2) combined with grating (500 micrometers), was collected at 15 points in three areas on Bassac river After collecting the sample in 110 ml plastic bottle with formaline fixed concentration of 2-8% (Petersen, 1990), phytoplankton samples were formaline fixed within 2%, zooplankton 4% and zoobenthos 8% Then they were analyzed by microscope objective lens in observing E10 at laboratories, Colledge of aquaculture and fisheries, Can Tho university

+ Determining the species composition of phytoplankton, zooplankton and zoobenthos was based on Shirota (1966), Duong Duc Tien and Vo

Hanh (1997), and Carmelo et al (1996)

+ Determining the density of phytoplanktons, zooplanktons and zoobenthos was based on Boyd and Tucker (1992)

 Density of phytoplanktons:

X (ind./L) = (T*1.000*Vcondensed *103)/(A*N*Vsample)

Vcondensed: Volume of condensed sample A: Area of one cell of sedgewick rafter cell S50 N: Number of cell of sedgewick rafter cell S50

V sample : Volume of sample collection by phytoplankton net

 Density of zooplankton:

X (ind./m3) = (T*1.000*Vcondensed*106)/(A*N*Vsample)

V condensed: Volume of condensed sample A: Area of one cell of sedgewick rafter cell S50 N: Number of cell of sedgewick rafter cell S50

Vsample: Volume of sample collection by phytoplankton net

 Density of zoobenthos:

D (ind./m2) = X/(N*d)

N: Number of collection by zoobenthos Petersen

3.2.2 Study 2: Determine species of Eleotridae and abundance (CPUE)

of gobies living in Bassac river

Samples were collected by fishing, gillnet, trawl and directed collection of fishermen from fishing activities in study sites include the type of fishing such as bottom nets, fishing, put swamps nets, rubs and trawl Fish samples kept with ice and analyzed at the laboratory of fisheries resources, Can Tho university These indicators of morphological analyzed consists of:

+ Rate of standard length (cm) / head length (cm)

+ Rate of standard length (cm) / body height (cm);

+ Rate of head length (cm) / distance of between eyes(cm);

+ Rate of head length (cm) / snout length (cm);

+ Rate of edges length (cm) / height edges (cm);

+ Rate of body height (cm) / height edges (cm)

Table 2.1: Number of sample to determine of morphological criteria of Eleotridae

Unit: individual/species

melanosoma

Oxyeleotris urophthalmus

Oxyeleotris marmorata Butis butis Butis humeralis

The classification system in this study weas identified from level of family (Eleotridae) according to Lindberg (1971) (cited by Kanayama, 1991), the species level was mainly based on Smith (1991) Also, refer to the documents classified by the authors as: Cuvier and Valenciennes (1828-1848), Cantor (1848) (cited by Manilo and Bogorodsky, 2003), Taki (1974), Vuong Di Khang (1962) Three genus of Eleotridae were determined according to the following classification keys:

1.a- Skeletal gill covers front edge after one spiky toward to front … Eleotris

2.a- Thin scalp, the forehead between the eyes, skull clearly emerged It was

covered by scales comb The lateral line along was 26-30 Butis

2.b- Thick scalp, skull covered Head and body covered the front of circular scales, flakes coated part after brush The lateral line along was 60-90

6

In this study, refer to the documentation of Mai Dinh Yen (1992), Truong Thu Khoa and Tran Thi Thu Huong (1993), Nguyen Nhat Thi (2000), Tran Dac

Determining the extent of relative abundance (CPUE) of Eleotridae was collected by trawl net with technical parameters: width at 4.5 m, height at 0.5 m, mesh size in the mouth and body at 25 mm, in refuge at15 mm, with cycle sampling in two months Location of sampling points in Bassac river

on tributaries river (from the main river enters 1 km, was located along the main river) started from upstream and downstream in the area of An Giang, Can Tho and Soc Trang; each area collected five points, three points earned

in main river and tributaries at two collection points, location of points earned was determined by GPS (Global Positional System)

A) Pelvic fins separately B) No lateral

C) Two separate dorsal fins, include hard rays and soft rays

D) Films bring discontinuous

Figure 2.3: Some of major morphological characteristics of goby (Tran Dac Dinh at al., 2013) 3.2.3 Study 3: Study on nutritional characteristic of Eleotris

melanosoma and Oxyeleotris urophthalmus

Gobies samples were collected from June 2013 to May 2014, sampling cycle was once for two months at different size groups Each group collected at least 30 individuals per species (Table 3.2)

Table 3.2: Number of samples analyzed nutritional spectrum of E melanosoma and O urophthalmus

Unit: individual/species/month

Gobies samples were fixed in formaline fluid with concentrations of 10%, then brought to the laboratory of aquatic resources fisheries, Can Tho University to analyze Method of determining feeding habits of goby based

on morphological and structure of the digestive organs (shaped teeth, mouth, combs bearing, intestine length and types of food in the digestive tract) Food was removed from the gastrointestinal tract to 1 liter of distilled water, shake well and take 100 ml continuing shake, then take 1 ml for counting chamber (sedgewick rafter cell S50) and put on the microscope observation, analyzed by the method of frequency of occurrence (Hynes, 1950) and methods of weigth (Pillary, 1952)

2.2.3.1 Method of determined the morphological and structure of digestive organs

Samples of E melanosoma and O urophthalmus obtained from Table 3.2

were analyzed identifying indicators: the width of mouth, length and body length of their intestine (Pravdin, 1973) To determine their feeding habits based on the correlation between the length of intestines and body length of gobies (relative length of the gut-RLG) RLG was calculated according to Al-Hussaini (1949): RLG=length intestine (cm)/ body length (cm) (RLG<1: feeding animals; RLG=1: omnivorous; RLG>1: herbivorous)

2.2.3.2 Method of determining the nutritional spectrum

+ Methods of frequency of occurrence: The number of goby stomach presence of every type of food was calculated The percentage (%) of total number in stomach was observed, according to classified documents about the animal and aquatic plants of Shirota (1966), Duong Tien Duc and Vo

Hanh (1997) and Carmelo et al (1996)

+ Method of weight: Most species of Eleotridae food ingredients of animal origin with a large weigth, so this study method was used in conjunction with the weigth and frequency of occurrence method to determine the food

spectrum of E melanosoma and O urophthalmus in two steps: (i) use of

electronic scales (3 decimal places) of the total mass balance of each type of food in the stomach of fish; and (ii) the weigth of each type of food to be converted into a percentage (%) of the total weigth of each food in stomach

3.2.4 Study 4: Study on reproductive biology characteristic of Eleotris

melanosoma and Oxyeleotris urophthalmus

Samples were collected from August 2012 to July 2013 and sampling cycle was once a month The analysis criteria includes:

(i) Stages of sexual maturity: based on six steps sexual maturity recommended by Nikolsky (1963) and combined with histological methods of Drury & Wallington (1980) and Kiernan (1990)

(ii) Rate of male and female: observed morphological characteristics and of gobies gonads to determine gender

(iii) Gonadosomatic index (GSI): defined for each month, GSI (%)=(GW/BW)*100 (GW: weigth of fish gonad; BW: body weight) (iv) Hepatosomatic index (HSI) was also determined for each month HSI(%)=(LW/(BW)*100 (LW: liver weigth; BW: body weight of fish) (v) Correlation of length-weight, condition factor (CF): determining to the correlation between the length-weight based on Huxley (1924): W=a*Lb (W: total weight; L: total length; a and b: coefficients) Condition coefficient (CF) was determined: CF=W/Lb (W: body

CHAPTER 4: RESULTS AND DISCUSSION

4.1 Identify ecological parameters (temperature, pH, salinity, water flow, depth, phytoplankton, zooplankton, zoobenthos) in Bassac river 4.1.1 Physical indicators (pH, temperature, salinity)

Results showed that the pH value was little changed through six times survey (7.6-8.1), temperature from 29.1-30.9oC, salinity in the downstream appeared only in February, June and December, salinity in rainy season from 0 to 7.6 ‰ and fluctuate less than the dry season (2-10.8‰) Results also showed that pH and temperature fluctuates seasonally (Figure 4.1)

According to Cees et al (1995), some gobies living in salinity up to 25‰,

but they lived in various types of water basins with different salinity, and they lived in an environment with temperature fluctuating large (28.7-31.9oC) even to 36.8oC

Surveyed areas

Figure 4.1: Fluctuations of pH, temperature and salinity in three areas surveyed

4.1.2 Water flow and water depth

Water flow had many variations (0.1-1.3 km/hour); the locations of water

flow in the middle and downstream was lowest (0.1 km/hour) and highest in the upstream (1.3 km/h) (Figure 4.2)

The water depth at the three regionals fluctuated (4.3-14.4 m), in which the water depth in the middle was highest (8.7±2.7 m) and lowest in the

upstream (6.8±3.0 m) (Figure 4.2) According to Dang Ngoc Thanh et al

(2002), distribution of benthos organisms depended on the water depth, vertical hydro static water bodies in coastal areas with sediments, molluscs and shellfish groups developed more depths

Upstream Middle Downstream

Surveyed areas Dry season Rainy season

Figure 4.2: The water flow and water depth in the three areas surveyed

4.1.3 Species of aquatic

4.1.3.1 Phytoplankton: There were 31 species of phytoplankton appeared at

upstream, 22 species appeared at middle and 15 species appeared at downstream; in which cyanophyta, bacillariophyta and chlorophyta dominated (18-41%), while euglenophyta, dinophyta and chrysophyta less (1- 9%) (Figure 4.3)

Bacillariophyta (29%)

Chlorophyta (41%)

Cyanophyta (18%)

Chrysophyta (9%) Euglenophyta

Figure 4.3: Structure of phytoplanktons in the three areas surveyed

Frequency of occurrence species of phytoplanktons in rainy season higher

in dry season In which, cyanophyta, bacillariophyta and chlorophyta more and concentrated in the upstream and middle (Figure 4.4)

Figure 4.4: Frequency of occurrence of phytoplanktons in three areas surveyed

10

Density of phytoplanktons in the upstream and downstream higher middle (Table 4.1) In the upstream highest in dry season (28,545±20,190 ind./L), euglenophyta was lowest (1,646±720 ind./L), highest in the middle of chlorophyta (5,333±3,479 ind./L) and lowest of euglenophyta (1,633±809 ind./L), highest in downstream (25, 59±28,583 ind./L) and lowest was cyanophyta (86±33 ind./L) and density of bacillariophyta highest in the upstream and downstream, lowest in the middle

Table 4.1: The average density of phytoplanktons in three areas in Bassac river

Unit: individual/Liter

4.1.3.2 Zooplankton: Structure of zooplankton species occured in three

areas, rotifera appeared total 111 species and 53 genus; in which protozoa has 51.4%, rotifer has 25.2%, copepoda has 18.9 and cladocera has 3.6% However, veliger (class of bivalvia larvae) appeared very few (0.9%) in the upstream and middle (Figure 4.5) This results was similar to Duong Tri Dung and Nguyen Hoang Oanh (2011), zooplankton species in the middle (canal Cai Khe) has 79 species and 54 species, in which rotifer was highest; however, this results higher of Ngo Duc Chan (2010) in the downstream has

48 species

Protozoa (51,4%) Rotifera

(25,2%)

Cladocera (3,6%)

Copepoda (18,9%)

Veliger (0,9%)

Figure 4.5: Structure of zooplanktons in the three areas surveyed

Protozoa Rotifera Cladocera Copepoda Veliger

Density of zooplanktons in rainy season was higher in dry season, the

lowest in the middle and highest in downstream (Table 4.2) In which, density of Cladocera in the upstream highest (3,793±3,760 individuals/m3), Copepods in upstream lowest (1,037±361 individual/m3), density larval of Nauplius highest in the middle (2,741±1,935 individual/m3), while density

of Protozoa was lowest in the middle (696±630 individual/m3), and density

of Protozoa highest in downstream (35,408±38,256 individual/m3)

Table 4.2: The average density of zooplanktons in three areas in Bassac river

Unit: individual/m 3

Area Season Protozoa Rotifera Cladocera Copepoda Nauplius Upstream Dry season 1,334±1,218 1,111±868 3,259±3,532 1,037±361 1,518±525

Rainy season 696±630 2,822±2,437 3,793±3,760 3,437±3,879 2,741±1,935 Middle Dry season 493±237 492±240 1,137±376 696±333 1,222±446

Rainy season 956±656 2,185±1,022 637±342 815±334 2,274±1,344 Downstream Dry season 13,935±14,391 2,796±1,881 178±308 537±465 4,702±3,500

Rainy season 35,408±38,256 7,058±6,204 894±1,344 3,081±2,543 9,584±10,147

3.1.3.3 Zoobenthos: There were 73 species (upstream: 17 species, middle:

23 species, downstream: 33 species) with 6 classes: Gastropoda, Bivalvia, Crustacea, Insecta, oligochaeta and Polychaeta In which, there were 12 species of Gastropoda highest (36%), Bivalvia 8 species (24%), Oligochaeta 4 species (12%), Crustacea 4 species (12%), Polychaeta 3 species (9%), Insecta 2 species (6 ,%) This result was higher than the downstream (16 species) (Vu Ngoc Ut and Duong Thi Hoang Oanh, 2013)

Oligochaeta (12%) Polychaeta (9%)

Gastropoda (36%) Bivalvia

(24%)

Crustacea (12%) Insecta (6%)

Figure 4.7: Structure of zoobenthos in the three areas surveyed

0 2 4 6 8

0 2 3 5 6 8

Density of zoobenthos in rainy season was higher compared to dry season

In which, in the upstream and middle higher downstream (Table 4.3) In the upstream Oligochaeta has the highest density (82±57 ind./m2) and lowest was Gastropoda (7±1 ind./m2); in the middle density of Bivalvia highest (58±17 ind./m2) and lowest was Insecta (1±1 ind./m2), while downstream