The species of Liza tade were collected from Mawlamyine, Mon State, Myanmar during June 2018 to May 2019. The analysis of fishes was based on 1264 specimens ranging in size from 10 to 30cm and in weight from 15 to 190g. The length-weight relationship of L. tade was determined for males, females and combined sexes as W=0.016L^2.82, W=0.016L^2.84 and W=0.016L^2.83 respectively. The samples have been found to be negative allometric growth pattern (b˂3). The results indicated that the value of correlation coefficient (r) for males, females and combined sexes were as 0.972, 0.975 and 0.973, which were closer to 1 indicating that the length-weight relationship was highly correlated. The condition factor (K) was recorded as 1.088 for males, 1.140 for females and 1.114 for all individuals respectively.

Keywords Liza tade, length-weight relationship, condition factor, sex ratio

Fishes of the family Mugilidae are commonly known as “mullets” or “grey mullets”. This family includes 18 genera and 81 species.¹ Commonly found in marine and brackish waters or estuaries at 20m depth. Mullets (Mugilidae) are among the most common species from tropical and temperate marine coastal water in the world and constitute a fundamental protein resource for a number of human populations living in coastal areas.²

Tade mullet (Liza tade Forsskal 1775) is one of most important mullet species widely cultured in both brackish and freshwater mono and poly-culture fish ponds.³ Owing to its good consumer preference and market price, non-carnivorous food habit and abundant availability of seeds, tade mullet is a good candidate for poly-culture with other species including shrimp.⁴ It has a high quality flesh, superior growth, large maximum size and wide salinity and temperature tolerance power.⁵

Length-weight relationship (LWR) indicates the average weight of fish at a given length by making use of the mathematical equation to show relationship between the two.⁶ Fish can attain either isometric or allometric growth.⁷ Isometric growth indicates that both length and weight of the fish are increasing at the same rate. Allometric growth can be either positive or negative. Positive allometric implies that the fish becomes stouter or deeper-bodies as its length increases. Negative allometric implies the fish becomes slender as its length increases.

Condition factor (K) is an estimation of general well-being of fish⁸ and is based on the hypothesis or assumption that heavier fish are in better condition than the lighter ones.⁹ The condition factor of one or greater than one indicates the good condition of fish while the one less than one show bad condition.¹⁰ Condition factor can be influenced by season, sex, type of food organism consumed by fish, age of fish, amount of fat reserved, and environmental conditions.¹¹ Length-weight relationship and condition factor are important to fishery industry as they help to predict the best length and weight and time suited to harvest a particular species of fish.¹² Sex ratio and size structure constitute some of the basic information required for assessing reproductive potential and estimating stock size.¹³ The purposes of this study are to describe the length frequency distribution, to calculate length-weight relationship and condition factor of Liza tade species by observing their growth pattern between length and weight.

The samples of fishes were collected from Mawlamyine (Kyauktan) (Lat. 16º26´N, long. 97º37´N), Mon State, Myanmar. The samples were caught by cast net, gill net and small beach seine (nylon net) of various mesh sizes (2.5, 3.0 and 3.5cm) and collected from local fishermens along the study area.

Collection of samples

The specimens of L. tade were purchased monthly from landing site in Mawlamyine, during the period of June 2018 to May 2019. The samples were preserved in an ice-chest with ice cubes in the field and transported to the laboratory of Department of Marine Science, Mawlamyine University, Myanmar using for detail investigations. Total length (TL) to the nearest 0.1cm from the tip of snout to the tip of caudal fin was measured by making use of measuring board and weight (W) to the nearest 0.1g were recorded. Male and female individuals were identified after examining the gonads.

Length-weight relationship

The length weight relationship (LWR) was calculated as: W=aL^b Ricker¹⁴ and also expressed by taking the logarithms or natural logarithms transformation: LnW=Lna+bLnL (or) y=a+b*x. Where W is body wieght of fish (g), L is total length of fish (cm), a is constant/ intercept and b is isometric exponent or regression slope which usually ranges from 2 to 4. In this equation, parameters a and b were estimated by the least squares method Sparre and Venema¹⁵ after logarithmic transformation of the non-linear equation into linear form. A value ‘b’ can exhibit isometric growth, negative allometric growth or positive allometric growth pattern. The correlation coefficient ‘r’ was computed to determine the relationship between length and weight.

Condition factor

Fulton’s condition factor (K) equation was used to determine the biological changes for individual fish as: K=100*W/L³ Ricker¹⁴ where W was the average weight (g) and L was the average total length (cm) to estimate how robust, healthy or well being state of the fish.

Sex ratio

Sex ratio of species was used to determined from the ratio tends to be of 1:1 male to female in the total population by chi-square analysis as:=∑ (O-E)²/E, where O was the observed frequency of males or females and E was the expected frequency of males or females. Descriptive statistics were obtained using Excel (Microsoft Excel 2013) (Figure 1-3).

Figure 1 Map showing the study area of sample collection.

Figure 2 MapPicture of Liza tade in Mawlamyine.

Figure 3 Sketch of Liza tade.

Length frequency distribution

The length frequency distribution of L. tade, a total of 1264 samples (623 males, 641 females) was found in the present study. The total length of individuals ranged from 10-30cm and the weight ranged from 15-190g. The most dominant total length size class being 20-22cm and the second abundance total length size class was 18-20cm (Figure 4). The largest number of the species belonging to the size class 20-22cm occurred in June, July and August. In view of this observation, L. tade was dominant and peak in June, July and August that the maximum length was found to be 28-30cm in these months. The minimum total length size of 10cm and smaller samples were extremely few in June and November.

Figure 4 Total length frequency distribution of Liza tade form June 2018 to May 2019 Mawlamyine.

Length-weight relationship

The results of the length-weight relationship for L. tade species were calculated by using the equation of W=aL^b. In this study, the mean values for males were obtained to be 18.77±3.49 for length and body weight of 71.99±34.43. The mean total length of females was 18.49±3.75 and the mean weight of 72.20±36.65. The means values for combined sexes of L. tade were recorded 18.63±3.63 for length and 72.10±35.56 for body weight (Table 1). The regression statistics for length-weight relationship of species recorded the regression slopes or growth coefficients, b values of L. tade was found to be 2.82 in males, 2.84 in females and 2.83 in total respectively. The length-weight relationship was represented by the equation for L. tade species: W=0.016L^2.82, r=0.972 (in male), W=0.016L^2.84, r=0.975 (in female) and W=0.016L^2.83, r=0.973 (in combined sexes). (Table 2).

The Ln transform data of length-weight relationship was determined that the growth was positive or negative allometric for male and female, as shown in Figure 5. It was observed in the present study that the exponent b-values were also found varied from an isometric value (b=3). In general, the b-values reported for combine sexes, male and female of L. tade species ranged from 2.82-2.84. From this study, the exponent b-values of L. tade were less than 3.0.

Figure 5 Length-weight relationship of Combined sexes, Male and Female of L. tade.

Condition factor (K)

The mean K values of L. tade for the sampling period in the study area were found to be 1.08±0.037 for males, 1.14±0.031 for females and 1.11±0.024 for combined sexes respectively. The range of condition factor for Liza tade was 1.08 in males, 1.14 in females and 1.11 in total respectively. In this study, the females of L. tade had better condition factor of growth pattern than males.

Sex ratio

The monthly sex ratio of Liza tade was computed for the expected ratio of 1:1 male to female by chi-square method. During the study period, a total of 623 males and 641 females were recorded with the ratio of 1male to 1.0 female (=0.26). The present study observed that there was no significant difference in number of males and females in all months from the expected 1:1 ratio (p>0.05).

The samples of tade mullets were calculated separately for males, females and combined sexes by using the length frequency data collected from June 2018 to May 2019. Fish can exhibit different growth patterns namely isometric growth (b=3) where there is no change in body shape with increase in length, negative allometric growth (b<3) where fishes become slender with increase in length indicative of not too good environment factors and positive allometric growth (b>3) where fishes become fatter with increase in length indicative of good environmental factors such as dissolved oxygen, optimum temperature, availability and/or abundance of food.

The parameter b may vary seasonally, even daily and between habitats. Thus, the length-weight relationship in fish is affected by a number of factors including gonad maturity, sex, diet, stomach fullness, health, and preservation techniques as well as season and habitat.¹⁶ With regard to the b-value of the family Mugilidae, 3.069 in Liza aurata from the Adriatic Sea,¹⁷ 3.37-3.39 in Mugil cephalus from Parangipettai waters^,18 2.79-2.94 in Liza aurata from Homa Lagoon¹⁹ 2.951 in Liza tade from extensive brackish water farming system²⁰ 2.63058 and 2.87606 in Liza dussumieri and Valamugil seheli from Myeil waters, Taninthayi region.²¹ In the present study, the exponents b-value of the length-weight relationship (combined sexes: b=2.83; males: b=2.82 and females: b=2.84) of L. tade were estimated in Mawlamyine and showed negative allometric growth.

The results of length weight relationship of tade mullets were compared with the available literature. For L. tade, negative allometric pattern (b˂3) obtained in this study is similar to findings observed in Sunderban area²² and in extensive brackishwater farming system.²⁰ The value of exponent ‘b’ of different size of Liza tade was 2.952 and 2.834 from Sunderban area. In the present study, the b-value of this species is slightly lower than the result of Sunderban area.²² This negative allometric growth pattern could be attributed to low food items for this species in the ecosystem or reduction of their body size to escape predation or high fishing mortality or intensity and adverse effects of oil pollution on the growth.²³

The overall result of this study revealed that L. tade showed negative allometric pattern of growth with the b-values less than ideal value (3.0) which indicates that as the length of the fish increased, it become lighter, thinner or less plumpy or simply put, it shows poor growth of length and weight.²⁴ The fish did not grow symmetrically as they became thinner with increase in length.²⁵

The reason for the different result of b-value there may be ecological differences or variability such as temperature and food supply. Individuals in any fish population growing in the same areas during the growth of the individuals in different populations some differences can be observed.²⁶ If fish grow isometrically than it retains its body shape and its specific gravity will also remain unchanged during the life time, therefore, in such cases, its b-value must be equal to 3.0. Hence, this growth pattern in fish will follow the cube law. But under natural condition, most fish do not show the cube law, because they change their body shape as they grow or increase in size and become heavier in one season and lighter in the other season.²⁷

The value of coefficient of correlation (r) determined that the relationship between length and weight was significant or not which can take values ranging between -1 and +1. The value of (r) higher than 0.5 stated that length weight relationship was positively correlated.²⁸ In the present study, the correlation coefficient ‘r’ values indicated higher than 0.5 between length and weight relationships for combined sexes, males and females of L. tade. So the relation between the length and weight of tade mullets was positively correlated and highly significant. Differences in growth patterns exhibited by the different species in different environments could be due to differences in sample sizes, seasons and related environmental factors such as food availability and optimum temperature.

The condition factor of fish is a quantitative parameter of the well being state of the fish. When condition factor values are higher it means that fishes have attained a better condition and are better adapted to the environment. The variations in K values of grey mullet species might be due to the differences in the maturation of gonads, increases or decreases in feeding behavior, amounts of fats or population changes that may occurs due to the changes in food items.²⁹

In the present study, the mean condition factor estimated from the equation K=W*100/L³ was 1.08 in males, 1.14 in females and 1.11 in combined sexes for L. tade. Females of L. tade (1.14) showed the highest mean values of condition factor (K) than males, indicating that females of these mullet species at a given length were heavier than males of similar length. The highest K values recorded for L. tade was indicating that it can survive well even when environmental condition. These observations on condition factors have been influenced by a number of factors including sex, sexual activity, environmental stress, and season among others.³⁰

Sex ratio studies provide information on the proportion of male to female fish in a population and are expected to be 1:1 in nature. Any deviation from this ratio may indicate the dominance of one sex over the other.³¹ It is suited that dominance of one sex relative to the other can be due to different behaviours in the two sexes leading to an easier catch of one sex, differences in fishing methods and equipments, different fishing factors related to season and schooling in feeding and spawning ground and spatio-temporal segregation of the sexes.³² Month wise analysis of sex ratio of present study showed that the overall sex ratio of males to females was 1: 1.0 in Liza tade. Chi square analysis  of Liza tade (0.26) showed that there was no significant different at 5% probability level. Sex ratio was reported on Liza aurata¹⁹ who observed a predominance of females over males (1: 1.8) from Homa Lagoon. The sex ratio for Mugil cephalus was 1: 0.53 and this showed a statistically significant (<0.05) dominance of the males over the females for the size range.³³ However, more females than males of Liza abu in the Water of the Khozestan Province were recorded the ratio of 1: 2.7 male to female respectively. ³⁴

I am indebted to Dr. Aung Myat Kyaw Sein, Rector of Mawlamyine University, Dr. Mie Mie Sein and Dr. San San Aye, Pro-Rectors of Mawlamyine University for their permission to carry out this research work. I would like to express my gratitude to Dr. San Tha Tun, Professor and Head of Department of Marine Science, Mawlamyine University, for his valuable guidance and for providing the departmental facilities. Thanks are due to U Tint Swe, Professor (Retired), Department of Marine Science, for his guidance during this research work. Thanks are also due to all my respected teachers and colleagues for their encouragement. Finally, my infinite thanks are attributive to my beloved parents for their kind support made to reach the goal of this work.

The author declares that there is no conflicts of interest.

None.

1. Nelson JS. Fishes of the world. 4th edn. John Wiley & Sons, Inc., Hoboken, New Jersey, USA. 2006.
2. Nelson JS. Fishes of the world. John Wiley and Sons. New York. 2nd edn, 1984. 523 p.
3. Lupatsch I, Katz T, Angel DL. Assessment of the removal efficiency of fish farm effluents by grey mullets a nutritional approach. Aquaculture. 2003;34(15):1367–1377.
4. Biswas G, Ananda Raja A, De D, et al. Evaluation of production and economic returns from two brackish water polyculture systems in tide–fed ponds. Journal of Applied Ichthyology. 2012;28(1):116–122.
5. Smith MS, Swart JJ. Flathead mullet (Mugil cephalus) as potential aquaculture species in Western Cape. African Fishes and Fisheries, Diversity and Utilization, Poissons et Peches, Africans Diversite et Utilization. Coetzee L, Gon J, O Kulongoski C. editors. Graham’s town, South Africa, FISA; PARADI. 1998. 241 p.
6. Beyer JE. On length–weight relationship. Part 1. Corresponding the mean weight of a given length class. Fish bytes. 1987;5(1): 11–13.
7. Sakar UK, Khan GE, Dabas A, et al. Length–weight relationship and condition factor of selected freshwater fish species found in River Gana, Gomti and Rapti, India. J Environ Biol. 2013;34(5):951–956.
8. Oribhabo BJ, Ogbeigbu AE Udo MT. The length–weight relationship of brackish water/marine fish species assemblage in Niger Delta mangrove creek, Nigeria. Curr Res J Biol Sci. 2011;3(6):616–621.
9. Ogamba EN, Abowei JFN, Onugu A. Length–weight relationship and condition factor of selected finfish species from Odi River, Niger Delta, Nigeria. J Aquat Sci. 2014;29(1):1–12.
10. Abobi, S.M. Weight–length models and relative condition factors of nine freshwater fish species from the Yapei stretch of the White Volta, Ghana. Elixir Appl Zool. 2015;79:30427–30431.  
11. Abowei JFN. The Condition factor and Length–Weight Relationship of some Sardinella maderensis (Jenyms, 1842) from Nkoro River, Niger–Delta, Nigeria. Adv J Food Sci Technol. 2009;1(1):66–71.
12. Abobi SM, Ekau W. Length–weight relationships and condition factors of Alestes baremoze, Brycinus nurse and Schilbe intermedius from the lower reaches of White Volta River (Yapei). Ghana. Int J Fish Aquact. 2013;5(6):152–165.
13. Vazzoler AEAM. Reproduction Biology of Teleostean Fishes: Theory and Practice. Maringa, EDUEM, Brazilian Society of Ichthyology. 1996.169 p.
14. Ricker WE. Computation and interpretation of Biological Statistics of fish population. Bull Fish Res Bd Can. 1975;191:209–210.
15. Sparre P, Venema SC. Introduction to tropical fish stock assessment. Part 1. Manual. FAO Fisheries Technical Paper No. 306: 1992. 37p.
16. Erguden D, Turan C, Gurlek M. Weight–length relationships for 20 Lessepsian fish species caught by bottom trawl on the coast of Iskenderun Bay (NE Mediterranean Sea, Turkey). Journal of Applied Ichthyology, 2009;25(1);133–135.
17. Kraljevic M, Dulcic J, Pallaoro A, et al. Age and growth determination of the golden grey mullet, Liza aurata (Risso, 1810) from the Adriatic Sea by using scale readings and length frequency analysis. ACTAADRIAT. 2011;52(2):223–234.
18. Murugan S, Rahman MAU, Khan SA, et al. Growth and population dynamics of Flathead grey mullet, Mugil cephalus (Linnaeus, 1758) from Parangipettai waters (Southeast coast of India). Thalassas. 2014; 30(2):47–56.
19. Ilkyaz AT, Firat K, Saka S, et al. Age, Growth, and Sex Ratio of Golden Grey Mullet, Liza aurata (Risso, 1810) in Homa Lagoon (Izmir Bay, Aegean Sea). Turk J Zool. 2006;30:279–284.
20. Mondal A, Bhattacharyya SB, Mandal S, et al. Growth performances, feeding ecology and prey preferences of tade mullet, Liza tade (Forsskal, 1775) in extensive brackishwater farming system. International Journal of Fisheries and Aquatic Studies. 2016;4(3):436–443.
21. Nan Mya Han. Fishery Biology of Mugilidae in Myeik waters, Taninthayi Region. Unpublished Ph.D Dissertation. Department of Marine Science, University of Mawlamyine. 2014.
22. Pramanick S. Temporal variations in biological indices and feeding of threatened mullet Liza tade (Frosskal) in Sunderban Area. West Bengal University of Animal and Fishery Sciences. 2006. 131 p.
23. Law R. Fishing, selection and phenotypic evolution. ICES J Mar Sci. 2003;57(3):659–669.
24. King RP. Length weight relationships of Nigerian freshwater fishes. Naga, the ICLARM Quarterly. 1996;19(3);49–53.
25. Tesch FW. Age and growth. In: Methods for assessment of fish production in fresh water. Ricker W E. editor. Blackwell Scientific Publications. Oxford. 1971; p. 98–130.
26. Tirasin EM. Investigations of the growth parameters of fish populations (in Turkish). Tr J Zoology. 1993;17:29–82.
27. Wootton RJ. Ecology of teleost fishes. Chapman and Hall. Upper Saddle River, New Jersey, USA. 1990.
28. Omogoriola Ho, Solarin BB, Williams AB, et al. Length–weight relationships and relative condition factor (Kn) of Sciaenids, Pseudotolithus senegalensis (Valenciennes, 1833) and Pteroscion peli (Bleek, 1863), in Nigeria coastal water. Internet Journal of Food Safely. 2011;13:81–87.
29. Akombo PM, Atile JI, Adikwu IA, et al. Morphometric measurements and growth patterns of four species of the genus Synodontis (Cuvier, 1816) from Lower Benue River, Makurdi, Nigeria. Interntional journal of Fisheries and Aquaculture. 2011;3:263–270.
30. Abowei JFN. The Condition factor and Length–Weight Relationship of some Sardinella maderensis (Jenyms, 1842) from Nkoro River, Niger–Delta, Nigeria. Adv J Food Sci Technol. 2009;1(1):66–71.
31. Shamsan EF, Ansari ZA. Studies on the reproductive biology of Indian San Whiting Sillago sihama (Forsskal). Indian Journal of Marine Sciences. 2010;39(2):280–284.
32. Hakimelani M, Kamrani E, Taghavi MSA, et al. Growth parametes and mortlity rates of Liza Klunzingeri in the Iranian waters of the Persian Gulf and Oman Sea, using Length Frequency Data. Iranian Journal of Fisheries Science. 2010;9(1):87–96.  
33. Soyinka OO. Observations on the sex ratio, fecundity, egg size and gonadosomatic index of grey mullet, Mugil cephalus from High Brackish Tropical Lagoon. Journal of Fisheries and Aquatic Science. 2014;9(6):455–462.
34. Chelemal M, Jamili S, Sharifpour I. Reprductive Biology and Histological studies in Abu Mullet, Liza abu in the water of the Khozestan Province. Journal of Fisheries and Aquatic Science. 2009;4:1–11.