Some Biological Aspects of Largescale Tonguesole Cynoglossus arel

(Bloch and Schneider, 1801) in Iraqi Territorial Marine Waters

 

Amjed K. Resen

Department of Fisheries and Marine Resources, College of Agriculture University of Basrah, Basrah, Iraq

*Corresponding Author E-mail: amjedkrr@yahoo.com

 

Abstract:

A total of 4200 fish of large scale tongue sole Cynoglossus arel were collected from the Iraqi marine waters at the shallow tip of the Arabian Gulf during the period extended from September 2014 to July 2015 by using trawl nets. The relationship between the total length and weight was calculated according to the following equation y = 0.0064x2.8521. Regression value (b) which calculated for all species was not significantly differ from the value of 3. L∞ and K were estimated to be 38cm and 0.23, respectively. Relative ages of fish species were ranged between 1-7 years. Species value of total mortality rate (Z) was estimated to be 6.61, the value M was 1.24, thus F became 5.36. Water average annual temperature measured as 21.25 °C. Food analysis was performed according to the values of the index relative importance (IRI). Mollusca scored the highest percentage (41.3%). Food composition dominance was followed by shrimp (25 (%1 . , fish (19.2 %), crab (7.6) coming in third rank and finally digested matter which represented only (6.8 %) .

 

KEY WORDS: Fish, Cynoglossus arel, Biological Aspects, Iraqi marine waters.

 

INTRODUCTION:

The tonguefishes of family Cynoglossidae consist of approximately 77 species which are considered valid in this genus, with 27 species having been recorded from the Indo-Pacific region (Krabbenhoft and Munroe 2003; Munroe 2006; Munroe and Hashimoto 2008; Lee et al. 2009). In the Arabian Gulf, five species were recorded in this family which include largescale tonguesole Cynoglossus arel, fourlined tonguesole Cynoglossus bilineatus, hooked tonguesole Cynoglossus carpenteri, short headed tonguesole Cynoglossus kopsii, and speckled tonguesole Cynoglossus puncticeps (Gibson, 2005). These species are distributed throughout the Arabian Gulf and Sea of Oman (Yasemi et al., 2007; H. Ghaffari et al.2015). Al-Daham (1984) mentioned flatfishes from five families, including Cynoglossus arel in the Iraqi marine waters. Distinctive Characters of this species include the flat and elongate body, with dorsal and anal fins joined to caudal fin. Eyes on the left side of the body.(Mohamed, 1997; Ghaffari. et al.,2011). This relationship with the growth of the fish is important in that the knowledge of the size at which the fish increases rapidly in weight may be useful in fixing the harvesting time of the resource (Jayaprakash (2001). Researches on tongue fishes in the Persian Gulf included the identification of closely related species by means of morphometric and meristic characteristics (Yasemi et al., 2007; Kousha, et al., 2008; Ghaffari et al., 2011 and2015) and found that flatfish tend to be of different feeding groups; fish-feeders, crustacean feeders, polychaete/mollusks-feeders, thereby minimizing competition for food (Pearcy and Hancock, 1978; Steinarsson, 1979).

 

The current study focused on some biological aspects of the fish Cynoglossus arel in the Arabian Gulf because of its economic importance in the commercial fishing.

 

MATERIALS AND METHODS:

Fish samples were collected from the terretorial Iraqi marine waters at the north-west part of the Arabian Gulf (E 48˚. 45̀̀- 48˚.50̀) (N 29˚.48̀̀-29˚.45̀) (Fig. 1) during the period extended from September 2014 to July 2015 by using trawl nets. A total of 4200 fish were collected and examined. Measurements of total length (TL) and total weight (W) were taken for all fishes. The digestive tracts of 580 fish were examined for food contents.

 

 

Figure 1. Map of sampling orbicular batfish C. arel collected from the Iraqi marine waters.

 

The relationship between the total length and weight was calculated according to the following equation: W= a Lb, where X axis represented the total length, Y axis represented the other parameter. The values of K and L∞ were measured by using draft of Ford (1933). Length cohort analysis described by Jones (1984) was used to find out growth of fishes and total mortality (Z) by using L∞, extraction of relative age (t\), draw of N/∆t. Value of Z were equal to Regression Coefficient. Natural mortality (M) was calculated according to (Pauly, 1980).

 

LogM=0.006-0.279Log L∞+0.6543LogK+0.4634+LogT

T= Annul average temperature.

Fishing mortality (F) = Z-M

For feeding study, digestive tracts were removed and gave a degree of fullness (between 0 and 20) then opened in a Petri dish to count different food items. Frequency of occurrence and point methods were used to analyze food items (Hynes, 1950). Index of relative important (IRI) was calculated according to the following formula of Stergiou (1988):

IRI = Pw× F

Where Pw is weight percentage of food item and F is its frequency of occurrence.

 

RESULTS:

 

Figure 2. Length group frequency of C. arel from Iraqi marine waters.

The distribution of total length frequency for all 4200 fishes was shown in figure (2). It illustrate the existence of 22 length groups with dominant group of 14 cm (14.4% of total fish), followed by group 13 cm (10.3% of total fish). Total lengths of fishes were ranged from 9 to 30 cm and weight from 5.9 to 98.1 g. The fig. (3) indicate length-weight relationship of C. arel y = 0.0064x2.8521

 

 

Figure 3. Length-weight relationship between of C. arel (slope value 2.8521).

 

 

Figure 4. Ford and Walford draft for the relationship between lengths at time t and t+1 of C. arel.

 

Fig. (4) Show Ford and Walford draft that represented the relationship between lengths. The value of L∞ for38cm K = -lnb =0.23.

 

Table 1. Length cohort Analysis of C. arel.

L1

L2

Average

No.

t1

t2

∆t

t-

Ln(N//∆t)

9

9.9

9.45

65

1.17

1.31

0.14

1.24

29.81705

10

10.9

10.45

125

1.32

1.46

0.14

1.39

34.48796

11

11.9

11.45

276

1.48

1.63

0.15

1.555

37.46934

12

12.9

12.45

321

1.64

1.8

0.16

1.72

36.07151

13

13.9

13.45

436

1.82

1.97

0.15

1.895

40.51761

14

14.9

14.45

607

1.99

2.16

0.17

2.075

37.69723

15

15.9

15.45

389

2.18

2.35

0.17

2.265

35.07988

16

16.9

16.45

325

2.37

2.55

0.18

2.46

32.13236

17

17.9

17.45

432

2.57

2.76

0.19

2.665

31.93908

18

18.9

18.45

257

2.79

2.99

0.2

2.89

27.74538

19

19.9

19.45

206

3.01

3.22

0.21

3.115

25.37084

20

20.9

20.45

175

3.24

3.47

0.23

3.355

22.45559

21

21.9

21.45

137

3.49

3.73

0.24

3.61

20.49992

22

22.9

22.45

114

3.76

4.01

0.25

3.885

18.94479

23

23.9

23.45

104

4.04

4.31

0.27

4.175

17.20145

24

24.9

24.45

83

4.34

4.63

0.29

4.485

15.23738

25

25.9

25.45

47

4.66

4.97

0.31

4.815

12.41983

26

26.9

26.45

39

5.01

5.35

0.34

5.18

10.77518

27

27.9

27.45

28

5.38

5.76

0.38

5.57

8.768959

28

28.9

28.45

19

5.8

6.21

0.41

6.005

7.181558

29

29.9

29.45

10

6.26

6.72

0.46

6.49

5.00562

30

30.9

30.45

5

6.77

7.29

0.52

7.03

3.095073

Table (1) ) indicate age groups and numbers of fish C. arel adopted by applying Length cohort analysis to extract survival curve depending on the Value of L∞ (38) and K (0.23). Figure (5) demonstrate catch curve of fish C. arel estimating Z which shall be equal to the value of Regression Coefficient(b) after removing the minus signal which was (6.61). Water average annual temperature was (21.25 °C). The values M was (1.24), thus F became (5.36). The exhibited length groups and numbers of C. arel were exploited to apply cohort analysis technique. Seven age groups were showed containing a minimum age of I+ at lengths of 9-13 cm. The oldest age group VII encompassed fishes of 30 cm lengths (table 1).

 

 

Figure 5. Catch curve of C. arel.

 

 

Figure 6. Food analysis as demonstrated by the values of the index relative importance (IRI) of C. arel.

 

Food analysis was demonstrated according to the values of the index relative importance (IRI). Mollusca scored the highest percentage (41.3%). Food composition dominance is followed by shrimp (25(%1 ., fish (19.2 %), crab (7.6) coming in third rank and finally digested matter which represented only (6.8 %) of the diet composition as depicted in figure (6(.

 

DISCUSSION:

The temperature is one of the most important environmental factors, as it has several overlapping effects on the presence and distribution of fish (Moheseni and Stefan, 1999) and it attributed with more than 50% of the changes in the growth rates as well as the changes and control of reproduction process (Houde, 1989). The temperatures rates recorded in the current study were equal to that mentioned in many previous studies (Mohamed, 1997; Ali, 1999; Mohamed et al., 2005; Resen, 2007). Dominance were to the small lengths between 11-18 cm with special group length of 14 cm. Many of the fish are inhabiting this region because it is a fertile environment for the incubation and feeding of youngers (Ahmed and Hussain, 2000), This is consistent with many other studies in this area (Mohamed, 1997; Ghaffari et al., 2011, 2015).

 

The study of the length-weight relationship is an important vital signs from which useful information can be extracted concerning commercial fisheries, the history of the life as well as obtaining the equations which support mutual conversion between the overall height and weight (Ricker, 1975). Current results about calculated values of b of length- weight relationship did not deviate significantly from the value 3, differing from the values recorded in other studies (Mohamed, 1997; Shadi et al., 2011) The length-weight relationship may vary not only between species but even between individuals within the same sex and this is due mainly to seasonal changes in the growth, development of the gonads, the level of nutrition and the rate of deposition of fat in the body (Dooulas and Kattulas, 1984; Dulcic and Kraljevic, 1996). Different values for the L∞ were mentioned in another study in the Iraqi marine waters (Mohamed, 1997). In turn, low-lying or high values of L∞ to Lmax value were recorded in that study area because of the lack of representation for all lengths in the studied samples. The relative ages were recorded within VII age group which is consistent with Mohamed (1997) from the Iraqi marine waters north-west of the Arabian Gulf. The total mortality values Z, M and F were mentioned but there are no studies on the values of mortalities in the region.

 

Results of diet analysis using (IRI) revealed that C. ar el. was benthophagous, a bottom feeder, were diet consisted mainly of bivalves, crustaceans, shrimp and finally digested matter. It is similar to the data presented previously (Mohamed, 1997; Khalil and Ibrahim. 2016).

 

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Received on 16.07.2017       Modified on 22.10.2017

Accepted on 09.12.2017      ©A&V Publications All right reserved

Research J. Science and Tech. 2018; 10(2):115-120.

DOI: 10.5958/2349-2988.2018.00016.5