Study on biological characteristics and seed production techniques of snakehead (channa lucius cuvier 1831)

The results of this study will contribute to enriching the basic research on biological characteristics, traits of developed gastrointestinal tract and the food choices of Channa lucius

MINISTRY OF EDUCATION AND TRAINING

CAN THO UNIVERSITY

ABSTRACT OF DOCTORAL DISSERTATION

AQUACULTURE AND FISHERIES

The work was completed at the College of Aquaculture and Fisheries, Can Tho University

Scientific supervisors:

Supervisor 1: Dr Bui Minh Tam

Supervisor 2: Assoc.Prof Dr Tran Thi Thanh Hien

The dissertation was defended before the committee marking the university-level dissertation

Meeting at………

Time………Date………

Reader 1: ………

Reader 2:………

Reader 3:………

The dissertation available at:

1 The LRC, CTU

2 The National Library

GENERAL DESCRIPTION OF THE DISSERTATION 1.1 Introduction

Channa lucius Cuvier 1831 which belongs to snakehead is found in freshwaters like rivers,

lakes, canals, rice fields and forests of nature conservation in the Mekong River Delta (MRD) Channa lucius meat that is tasty and appetizing people has respiratory organs with natural air, so it

is easy to feed and the fish can live well in water from 5.5 to 6.0 low pH (Rainboth, 1996; Lee and

Ng, 1994) Many people feeding fish in the MRD think that the fish has very promising development of commercial products, especially cultured in ponds, pens and cages Currently, the

main sources of Channa lucius fries are exploited naturally in small quantities and with

insustainable quality Meanwhile, the studies of this species is not much and the information is only limited in the initial basic research on biological characteristics and natural reproductive

techniques Therefore, the study of growing Channa lucius into a new cultured species which will

have a great effect in the diversification of cultured species, thus contributing to reducing risks in farming and food supply needs for society, is a matter of urgency As a result, the topic "Study of

biological characteristics and seed production techniques of channa lucius Cuvier 1831" is

performed

1.2 Goal

It is to provide scientific arguments about the biological characteristics, and reproductive

and rearing techniques of Channa lucius The success of the project will contribute greatly to the development process of Channa lucius hatchery to supply artificial fish for aquaculture systems

and renewable fish resources in the wild in the Mekong Delta as well as in the whole country

1.3 Research content

- Research on the biological characteristics of Channa lucius

- Research on feeding Channa lucius to grow out in the pond

- Research on stimulating Channa lucius to reproduce artificially

- Research on the development characteristics of the digestive tract and the optional index of feed of fry

- Research on timing to substitute fresh food by processing food (PF) in the fry stage

- Assessing the possibility of using efficient industrial pellets in the phase rearing fish fry to breeding

1.4 The scientific and practical significance of the dissertation

The dissertation is a systematic and comprehensive research on Channa lucius The results

of the dissertation is the important scientific database and good reference source for teaching and further studies The results of this study will contribute to enriching the basic research on

biological characteristics, traits of developed gastrointestinal tract and the food choices of Channa

lucius in Vietnam

The results of the growout techniques for brood, stimulating fish reproduction and

techniques rearing Channa lucius from fry stage to fingerling are the original science-based

support for the practical local apps in highly effective productivity

1.5 The breakthrough of the dissertation

The thesis is the first comprehensive study on the biological characteristics of Channa lucius

as follows: identifying ecological features, growth characteristics, nutrition and reproductive biology

Channa lucius are mature in the pond by growout with cheap fish (75.0%) and industrial

pellets (72.7%) It is able to identify the measures to stimulate effective reproductive Channa

lucius from a combination of physiological and ecological factors At 2,000 UI HCG kg-1 male and 500UI HCG 2 mg combination with cerebral lobes kg-1 females at pH 5.5 to 6.0, 28-29oC

temperature, dissolved oxygen 5-6 mg/l and the substrate for fish nesting slender vegetables, after injecting females 37-40 hours, the percentage of spawning with farrowing rate is 83.3%, the recovery rate is 95.3% and hatchability is 82.6%

The development of the digestive tubeof Channa lucius is complete when the fish is 20 days

old; the thesis has identified food choice index from fry stage to 30 days old; it is determined that the time of the 16th day is suitable for the replacement of live food by processing food (20% degree of substitution of FP/day) to ensure high fish survival rate and good growth

In particular, the thesis has been successful in using industrial pellets to run Channa lucius

from fry to breed These results contribute to solving the problems of fresh food in the nursery, help reduce costs, improve production efficiency and expand scale of commercial fish farming in the Mekong Delta

The success of the thesis is a huge motivation and a basis to accelerate breeding career of

initiative development of Channa lucius, fish supply seeds for regeneration of Channa lucius

natural resources and aquaculture in order to create a lot of fresh fish products to meet the needs

of society

* The layout of the thesis

The thesis consists of 139 pages (excluding appendices) which include the following sections: Chapter 1: Introduction of 4 pages; Chapter 2: Overview of 26 pages; Chapter 3: Materials and Research Methods of 25 pages; Chapter 4: Results and discussions of 68 pages; Chapter 5: Conclusions and recommendations of 2 pages; (5) References of 14 pages; The thesis has 36 tables and 51 figures

RESEARCH METHODS 3.1 Time, place and subject of research

The study was conducted in 2010-2014 The study of biological characteristics was done with 968 samples in U Minh District-Ca Mau Province and Long My District-Hau Giang Province The studies were conducted in freshwater fish farms, the CAF Laboratory, the College of

Agriculture and Applied Biology, Can Tho University The research is on Channa lucius (Channa

lucius Cuvier, 1831)

3.2 Research Methods

3.2.1 Research chart: The research on biological characteristics was conducted first, then

the next research contents were conducted as subsequent growout, spawning and fish hatchery

3.2.2 Research Methods of biological characteristics

3.2.2.1 Methods of analysing morphological characteristics

Body shape, head shape, location and size of the mouth of Channa lucius specimens were

studied by the method of Pravdin (1973); Rainboth (1996) The quotas counted as scales and fin rays followed Holden and Raitt (1974) The morphological indicators were measured according to Lowe-McConnell (1971), Grant and Spain (1977) (quoting Pham Thanh Liem and Tran Dac Dinh, 2004) The research on digestive systems of fish focused on organs like the mouth, teeth, comb gills, esophagus, stomach, intestine, cecum (Lagler et al., 1977) and Bond (1996)

3.2.2.2 Methods of analysing the growth characteristics

The correlation equation between length and weight is determined by the formula of the

a Relative Lengh of the Gut RLG (RLG - Relative Lengh of the Gut)

The Relative Lengh of the Gut between intestinal length and body length is calculated according to the formula of Al-Hussainy (1949)

RLG = L i / L

Where: Li: length of the fish intestine; L: length of the fish body

b Determination of Channa lucius nutrition spectre

Nutrition spectre of mature Channa lucius is determined by the volume method of Biswas

(1993) Determination of the dry weight and of each food sample by analytical method AOAC (2000)

3.2.2.4 Methods of analysing reproductive biological characteristics

* Determining the condition factor (Condition factor-CF)

Determination of condition factor by sex and formula-based King (2007)

CF = W/L b

Where: W: Weight of fish body (g); L: fish body length (cm) b: the growth factor is determined from the equation W = aLb (a is condition factor)

* Gonado Somatic Index (GSI)

Gonado Somatic Index is defined by gender and by the formula of Biswas (1993)

GSI (%) = 100 * W g / W

Where: Wg: gonads weight (g);W: Body Weight (g)

Determining the stage of gonad development is based on hierarchy of sexual mature of fish

Where: Fr: Relative fecundity; Fa: Absolute fecundity;W: Weight of fish body (g)

* The average length of first maturity

The average length of first maturity (Lm) calculated by the formula King (2007)

3.2.3.1 Survey on aquatic environment where Channa lucius reproduce naturally

The work conducted a survey on environmental factors on Long My II channel (KC.II), 2 channels of grade III (KC.III) and three interior canals (K.ND) in regions of 2 communes Luong Tam and Luong Nghia, Long My district, Hau Giang province The environmental survey period

lasted from January to June, 2011, monthly water was measured twice: in phase 1 it was measured

on days 14, 15, 16 (al) and in phase 2 it was measured on days 24, 25, 26 (al), each channel surveyed 2 points (the beginning and the end of the sources) and at each measurement point 3 indicators are pH, temperature, dissolved oxygen Determination of pH and temperature indicators was measured by the ECO pH (HI 9813-5) and Oxygen indicators were measured by HANNA (HI 9142)

3.2.3.2 Research methods of broodstock growout

*Testing Systems

Broodstock Channa lucius growout experiments were conducted for 4 months (12/2011 to

3/2012) The experiment was arranged in a grid system (2x4x1,5 m) with a mesh size of 0.5 cm and put in the earth pond with an area of 500 m2, 1.2-1.5 m deep, the water in the pond is exchanged regularly according to tide and a minimum water level of 1 m was maintained

* Experiment Fish: Healthy fish with uniform size of about 90-115 g / head

* Dietary treatments: Trash feed was ground and mixed with 1% wool to increase adhesion

and industrial pellets are moistened with water before feeding Feed was put on the floor and

placed in the grids in feeding period

* Arranging experiment

The experiment was completely random, including two treatments (trea) Each treatment was repeated 3 times, and each iteration has 30 pairs of Breeders: Treatment 1 (trea 1) used 100 % trash fish feed; Treatment 2 (trea 2) used 100% industrial feeding pellets

* Feeding

Positive growout period was in 2 months and feeding in all treatments was as follows: 6%/day (pellets); 10%/day (trash); growout period maturing in 2 months left feeding 3%/day (pellets), 5%/day (trash fish meat)

* Analysing indicators

Before the experiment layout, we randomly collected 20 fish breeders in the fish's anatomical experiments to determine the initial biological indicators During growout periodically

on the last day of each month we collected 20 broodstock (randomly by gender) in each treatment

to analyze some indicators of reproductive biology (maturation rate, GSI, CF, fecundity) and measured environmental factors (pH, temperature, dissolved oxygen)

3.2.3.3 Methods of spawning

a) The experiment probe

We chose healthy broodstock, with ripe gonads and 90-450g weight The fish were injected with reproductive stimulants right of chest fin position Then, the fish were put in the grids (0,5m3)

in an area of 2m3 cement tanks, each tank had 2 grids

Experiment 1: Stimulating Channa lucius to reproduce with HCG

Table 3.3: Dosage of HCG injections for broodstock

Treatment HCG injection on females (UI)/kg HCG injection on males (UI )/kg

Females (number) Dosage Males (number) Dosage

The experiment consists of 3 treatments with completely random layout, and each treatment has 3 pairs of broodstock Females and males are injected at the same time and with the same HCG dosage presented in Table 3.3

Experiment 2: Stimulating Channa lucius to reproduce by LH-RHa + DOM

The experiment consists of 3 treatments with completely random layout, and each treatment has 3 pairs of broodstock In the laboratory experiments, the male fish are injected with LH-RHa + DOM before the females, in the control treatment the males and and females are injected with only physiological saline water(0.9%) The injectable time and dosage with LH-RHa + DOM is presented in Table 3.4

Table 3.4: The injectable time and dosage with LH-RHa+DOM for broodstock

Treatment Injection with LH-Rha on the males

(µg)/ kg

Injection with LH-Rha+DOM on the

females (µg+mg)/ kg number

in Table 3.5

Table 3.5: The injectable time and dosage with HCG + PE for broodstock

Treatment Injection with HCG on the males

(UI/ kg cá)

Injection with HCG + PE on the females (UI+mg)/kg number

are injected before the females are In the controlled treatment both the males and females only receives 0.9% physiological saline water The time, dosage and interval between 2 injections of hormone are shown in Table 3.6

b Main experiment: stimulating Channa lucius to reproduce

This experiment was designed based on the results of the exploratory study on stimulating fish spawning in the experiments 1, 2, 3, 4 and selecting the best exploration results such as selecting concentrations of HCG + PE and methods of injection in treatments 1 and 2 of experiments 4 to arrange this experiment The experiment was conducted with completely random layout consisting of 3 treatments, and each treatment had 12 pairs of brood stock and each pair was located in the same grids set in a cement tank of 2 m3 The time, dosage and the gap between the male and female injections are presented in Table 3.7

Table 3.7: The injectable time and dosage with HCG and PE lobe and the injection for broodstock are combined with reducing water pH (5.5 to 6.0) in the main experiments

Treatment number

(unit)

Rate male/female

HCG on the males (UI/kg)

The water used in the experiment was over filtered and adjusted pH dropping from 7.0-8.0

to 5.5-6.0 with phosphoric acid (H3PO4), 28-29 oC temperature, dissolved oxygen 5-6 mg/l and

the substrate for fish nesting with slender vegetables

c The criteria for assessing reproductive outcomes

Effective time (hours), spawning rate (%), fertility rate (%), hatching rate (%)

3.2.4 Methods of development characteristics of gastrointestinal tract and selecting

indicators of fish feed for fry Channa lucius

* Testing Systems: The fish, after eating the yolk, was transferred to spawning in small

ponds with the size 2x3x0,5m, the pond bottom with 25 cm thick layer of mud, the stocking density of 2/liter; the water in the pond is aired slightly to ensure dissolved oxygen for fish to grow

* Sources of food: Before stocking fish in the pond, the water is breeding natural food by

mixing concentrated feed (42.2% protein) with water at a dose of 10 g/m3 and successive fertilizers for 2 days During the nursery, we hang fabric bags containing fish fry 5 g/m3 to maintain the natural food in the duration of the experiment

* Collecting and analyzing morphological samples of digestive tract

- Collecting samples: Fish samples are collected in the old days 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15,

20, 25, 30 and 10 specimens are collected each day to observe life and photograph the development stage of gastrointestinal tract, intestinal length measurement, body length, yolk size and the open mouth of the fish

- Method of analysis: Individuals from the age of 1-15 days are observed shapes of the digestive tube on a microscope with eyepiece micrometer to capture and measure the length When the fish are 16-30 days old, the digestive tube indicators are measured by the naked eye on

a ruler with an accuracy of 1 mm

* Method of determining the width of the fry mouth

Shirota (1970) describe fish mouth widths by the following formula

MH (90o) = AB x 2

Where: - AB is the length of the upper jaw; MH is the width of the mouth (mm)

* Method of determining RLG

RLG is the ratio between the length of the intestines on the body length which is calculated

according to the formula of Al - Hussainy (1949)

* Method of histological analysis of gastrointestinal tract

Fish samples are collected in the old days 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30 and 30 specimens are collected each day to observe life The tissue template of the fish digestive tract is coloured with hematoxylin-eosin (H & E) by histological method described by Drury & Wallington (1967) and Kiernan (1990) We conduct the specimen observation of the gastrointestinal tract tissue on a microscope (4X, 10X, 40X) to photograph to identify the

structural variation of the digestive organs such as oral cavity, esophagus, stomach, intestines

* Determination of food choice index (E)

- Sampling: Samples of plants, aquatic animals and fish are collected on days 2, 3, 4, 5, 6, 8,

10, 15, 20, 25, 30 after the layout Every day 20 units / samples are received preserved in

commercial formalin solution 10%

- Analysis of water samples:

The qualitative analysis of phytoplankton species and animals is under the document classification of Shirota (1966), Dang Ngoc Thanh et al (1980), Boltovskoy (1999)

The quantitative analysis follows method of Boyd and Tucker (1992)

- Analysis of food in the digestive tract of fish: the nutrition spectro of Channa lucius fry is

determined by the number method of Biswas (1993)

- The electivity fish food index (E): Ivlev (1961) expressed food electivity index E

(electivity Index) by formula

Where: ri: is the percentage of food found in the gut out of foods in the intestines of fish; pi: means the percentage corresponding foods found in the environment in general foods in the environment

3.2.5 Method of channa lucius neursing

3.2.5.1 Determining the time of processed food (PF) of channa lucius in stage 4-30 days

old

* The laboratory system: an experimental system consists of 12 plastic tanks with a

volume of 60 liters per tank The experiment was completely random layout with 4 treatments (Trea) converting various PF including: (Trea 1) converter of PF from the 16th day after the run; (Trea 2) converter of PF from the 13th day after the run; (Trea 3) converter of PF from the 10th day after the run and (Trea 4) converter of PF from day 7 after the run Each treatment was repeated 3 times

* Experiment Fish: Fish used to arrange experiments are from artificial breeding source

and we selected 4-day-old larvae which had spent yolk and fish with an average initial length of 0.87±0.01 cm (0.002g/unit) We randomly assigned 100 fish in each plastic tank containing 50

liters (density of 2 fish/liter) and run for 30 days

* Experiment Food: Live foods used in the experiment is moina, earthworms; Processed

E =

ri – pi (ri + pi)

food (PF) were processed between concentrated food (42.2% protein, 3.20% fat, 5.40% ash, 24.8% NFE) mixed with minced trash fish meat (81,65% protein, 2.68% fat, 5.47% ash) with the blending ratio of 1/1

- During the experimental feeding on demand, every day feeding 2 times at 7 and 16 o’clock

in the foods moina, earthworms and PF The food intake from day 1-3 was added with moina at

2-4 larvae/ml/day; 2-4-15 day with cut-chunk worms around 2-2-4g/tank/day; PF amount from 7-15 days

is around 2-4g/tank/day and PF amount from days 16-30 with 4-6 g/tank/day

- Until the replacing day, treatments have not replaced PF and the fish are fed with worms

By the time of days 7, 10, 13, 16 after the run, the worms are replaced gradually by PF presented

in Table 3.9

Table 3.9: Methods of PF gradually replacing in all treatments

3.2.5.2 30-60 day old Channa lucius Nursery with industrial pellets with different

stocking density on the tank

* Testing Systems: Experiments run from fry to fingerling on plastic tank of 60 liters (50

liters), run time is 30 days The experiment had 4 treatments run in the stocking density of 1 head/liter; 1.5 units/liter, 2 fish/liter and 2.5 fish/liter and were arranged completely randomly and each treatment was repeated 3 times

* Experiment Fish: Fish derived from semi-artificial reproduction and used concentrate

feed well Originally, fish size is 2.40 to 2.46 cm/head (wieght from 0.135 to 0.153 g/head) and the difference in the length and weight of fish initially in the treatments are not significant (P> 0.05)

* Treatment Dietary: Concentrate dietary with 42.2% protein, 3.20% fat, 5.40% ash,

24.8% NFE The amount of feed used in the experiments is 7-10% body weight and feeding 2 times a day at 7 o’clock and 16 o’clock

3.2.5.3 The track indicators

- Environmental indicators: temperature, oxygen and pH are measured 2 times a day at 7 o’clock and 14 o’clock Temperature (°C) and pH are measured by the ECO pH; dissolved oxygen

is measured by HANNA 98172 Nitrite index is determined by Griess llosvay method, colorimetric spectrophotometer is at 540 nm wavelength and it is measured 1 time/1 week at 7 pm

- Ending the experiment, we caught 30 fish in the tank randomly to determine volume, measure the length, calculate the growth rate according to DWG day (g/day), specific growth rate

- SGR (%/day), coefficient of variation in the volume of fish (CV) and compute survival rate (Survival Rate-SR),

3.3 Data processing

Data was analyzed with average value (Mean), standard deviation (Standard deviation) using Excel version 6.0 program We analyse Factor ANOVA compare compare the difference between the means of the treatments by DUNCAN test in SPSS 16.0 software

RESULTS AND DISCUSSIONS

4.1 Morphological characteristics Channa lucius

Survey results of morphological criteria of Channa lucius (from 16.3 to 40.5 cm in length,

weight 47-637 g/fish) are presented in Table 4.1

Table 4.1: Morphological criteria of Channa lucius (n= 186 samples)

deviation

Biometric index

Through observation of Channa lucius digestive organs it is shown that Channa lucius has

upper-shaped mouth and its mouth stretches and touches the vertical line drawn from the back line

of the eye and it can be flexible The teeth are pointed, strong and sharp Lower teeth and palate teeth are dog-like ones Gill rakers bones arranged in two rows on the gill arc and they turn into

many sharp thorns The esophagus of the Channa lucius connects mouth to the stomach cavity It

is a short but straight line developing horizontally, with thick walls and muscles in many folds

similar to the esophagus of seabass, Scomberidae, and Channidae (McMillan, 2007; Lagler et al., 1977) The stomach of Channa lucius has bag-shaped, short, large size and thick wall, with many

inside folds Its stomach is U-shaped like the one of some fish species, such as snakehead fish

(Nguyen Anh Tuan et al., 2004), ca leo (Phan Phuong Loan, 2006) Adult Channa lucius has 2

tubular cecum with a sealing head and the other end attached to the digestive tube junction

between the stomach and intestine, cecum number of fish like the one of Channa striata (Channa

striata) (Lagler et al., 1977, Ramel, 2009) The fish gut is straight and short Its walls are thick

and the gut length (Li) is generally shorter that the body length (L) and similar to the gut of other carnivorous fish species (Nikolsky, 1963)

4.2 Environment where Channa lucius with natural distribution

Survey result indicators of temperature, pH and dissolved oxygen (DO) of the canal level II (CL.II), canal level III (CL.III) and on-farm canals (OFC) in the localities Luong Nghia and Luong Tam communes, Long My District, Hau Giang province are presented in Table 4.2

Environment for Channa lucius breeding is the basins of CL.II, CL.III with flowing water and less

water exchange OFC Results showed that dissolved oxygen ranges from 3.43 to 5.53 mg/l, temperature ranges 28,5-30,3oC In particular, factors such as pH environment where Channa

lucius are distributed in relatively low breeding season (5.4 to 5.67) However, the above

environmental factors range in adapted areas for individual development of Channa lucius (Boyd,

1990)

Table 4.2: The factors of environment where Channa lucius are distributed naturally

Ending source

Beginning source

Ending source

Beginning source

Ending source Luong

Nghia

commune

CL.II 5.60±0.17 5.57±0.15 5.53±0.25 4.63±0.68 29.5±0.50 28.5±0.76 CL.III 5.43±0.21 5.43±0.06 5.37±0.21 4.83±0.49 29.3±0.29 29.5±0.50 OFC 5.47±0.14 5.40±0.10 5.40±0.20 3.97±0.47 30.3±0.29 29.3±0.29 Luong

Tam

commune

CL.II 5.67±0.31 5.60±0.26 5.48±0.40 3.56±0.44 29.6±0.58 29.5±0.50 CL.III 5.53±0.25 5.55±0.17 5.47±0.23 3.45±0.40 29.8±0.76 29.6±0.29 OFC 5.50±0.10 5.40±0.20 5.33±0.06 3.43±0.21 30.3±0.29 29.8±0.76

Note: CL.II (Canal level II); CL.III (Canal level III);OFC:On-farm canal

4.3 Characteristics of Channa lucius growth

Regression correlation between fish length and weight is very close by the equation W= 0.0053L3,18435, with a correlation coefficient R2 = 0.9591 (Figure 4.5); Regression correlation between the length and weight of fish is very close by the equation W=0.0044L3.2494 with index

R2=0.9157 (s=401, L from 16.3-36.0 cm, W from 49.0-550 g/fish ), the survey results on male sample (s) also showed that regression relationship between the length and the body weight by equation W=0.0047L3.2178 with index R2 = 0.9434 index (s = 494, L from 14.6 to 38.2 cm, W from 46.0 to 639 g /fish) The survey results shown in Figure 4.5 shows the growth in the size and weight of the fish is not uniform under the development stage of the fish body In early life, the fish grow faster in length than the increase in volume, and when the individual phase achieves a certain size and transitions to sexual maturity, the growth in length slowdowns and the volume growth is fast

4.4 Characteristics of Channa lucius nutrition

4.4.1 Characteristics of mature Channa lucius feeding

The results determined the rate of the gut length on the body length (RLG) of Channa lucius

are shown in Table 4.3

Table 4.3 shows RLG <1 It is base on the value of RLG to show Channa lucius belong to

violent fish group using the animals as food According to Biswas (1993), the species of fish which are going to eat animals have a ratio of gut length/body length ≤ 1

Hình 4.5: Tương quan chiều dài và khối lượng cá

W = 0,008L3,0513

R2 = 0,9979

n = 968

0 100 200 300 400 500 600 700 800

Table 4.3: The length of the intestine, the body length and RLG of Channa lucius (s = 874)

4.4.2 Nutritional spectrum of wild Channa lucius

The survey results of nutritional spectrum of wild Channa lucius (L of 16.3 to 40.5 cm, W of

49-680 g) by the volume method (Biswas 1993) shown in Figure 4.8 consist of 4 types of food and all kinds of percentages are as follows: Lowest detritus (6.3%), followed by mollusks (7.3%), worms (14.7%), crustaceans (14.8%) and accounted for the highest proportion is fish (56.9%)

The study results are also relatively similar to the Channa lucius nutrition spectrum research in

Indonesia with the ratio from fry of 70.8 to 89.0%, crustaceans of 5.81 to 16.1% (Azrita and Syandri, 2013)

4.5 Characteristics of reproductive biology of Channa lucius

4.5.1 Sexing Channa lucius

When observing many mature specimens of wild Channa lucius, we may see the males are

often dark blacker and more colorful than females But the female have more patterns on the body

than the male The color change characteristics of Channa lucius is similar to the one of female Channa punctata in the breeding season, their sides become yellow (Dehadrai et al., 1973) During the Channa lucius sexual maturity, the female often have big belly, soft dough; their genital spines

are big and blunt, round and rosy The males have small belly, and their genital spines are sharp, long and white

4.5.2 Stages (S) of development of female gonads

Based on the six-level scale of gonads of Nikolsky (1963), Channa lucius ovarian in each

stage has the following distinguishing features:

- Stage I

In this phase, the fish gonads are immature with underdeveloped ovaries It is only two white and transparent slivers The Oocytes in this stage include whole-cell and small ovum primary oocytes There are many different angles and close arrangement, big round core occupies most of the cell volume and less basophilic to capture purple blue hematoxylin, while strong basophilic cytoplasm captures pink eosin

- Stage II

In the Ovarian at this stage appear many tiny blood vessels to feed the cells and ovarian begin with pink, thin films and transparent ovaries The size of the ovary is still small and only accounts for 1/6 of the body cavity (Figure 4.11a) At this stage the fish have sexually mature

56,9 % 14.8 %

14.7 %

7.30 % 6.30 %

fishCrustaceansWormsMollusksDetritus

Figure 4.8: Nutritional spectrum (by weight) in the fish digestive tracts

coefficient of 0.25±0.01% The features of tissue cells at this stage largely contain the oocyte cytoplasm of growth period and a number of cells in the nutritional growth period The cells are rounder than the ones in the synthetic core period and they are arrange closely together (Figure 4.11b)

- Stage III

The Ovaries clearly increase in size, with straw yellow on the surface of the ovaries there are many tiny blood vessels distributed evenly across the surface Naked eye can see particles scattered eggs in the ovary (Figure 4.12a) Individuals in this stage have sexual maturity coefficient of 0.7±0.32% and 1.06 mm diameter eggs (0.98 to 1.11 mm) The features of ovarian cytology at this stage contain most of the cells in biomass growth period (Figure 4.12b)