Length-weight and length-length relationships of three neritic tuna species of Sri Lankan coastal waters

Abstract

The length-weight and length-length relationships were determined for the three neritic tuna species Euthynnus affinis, Auxis thazard and Auxis rochei caught within Sri Lankan waters. Samples were collected from October 2015 to September 2017. The R 2 values for all three species were higher than 0.9 and were highly significant (p<0.001). The condition factor K, was 1.427, 1.476 and 1.361 for E. affinis, A. thazard and A. rochei respectively. The value of b in the length weight equation was shown to be 3.115, 3.431 and 3.408 for the three species indicating positive allometric growth patterns. Furthermore, the b values for the provinces studied were above 3.0 for all three species. The correlations between the total length, fork length and standard length, were also highly significant (p<0.001). The results indicate that these three species are living in a favourable environment having a healthy growth pattern along the coastal regions of Sri Lanka. 1. Introduction The length-weight relationships (LWR), length-length relationships (LLR) and Fulton's condition factor values are very useful in the management and conservation of fish resources [1]. These LWRs are useful in stock assessment models, in the estimation of biomass from length measurements, and for the comparison of the condition of fish between regions [2]. The LWRs are also important in comparing life histories of fish species [3]. The Fulton's condition factor can indicate the wellbeing of the fish, assuming that plumper fish are in a better condition [4]. LWRs have been reported for a large number of marine fish species [5, 6, 7] , freshwater fish species [8, 9] and fish species in lagoons [10, 11]. These relationships have been studied in several countries surrounding the Indian Ocean, such as India [12, 13, 14] , Pakistan [15] and Bangladesh [16, 17]. LWRs and LLRs have been studied in the past for tuna species other than neritic tunas in countries such as India [18] and Taiwan [19]. These relationships have been reported for skipjack tuna (Katsuwonus pelamis) of the South Atlantic [20] , for bigeye tuna (Thunnus obesus), yellow fin tuna (T. albacores) and albacore (T. alalunga) of the Atlantic, Indian and Eastern Pacific Oceans [21] and for bluefin tuna (T. thynnus) in the Eastern Mediterranean sea [22]. LWRs, length-length relationships and condition factors have not yet been defined for many of the commercially important marine fish species found in Sri Lankan waters. Euthynnus affinis (kawakawa), Auxis thazard (frigate tuna) and A. rochei (bullet tuna) are neritic tuna species found in the warm waters of the Indo-West Pacific [23]. They are an important group of fish species found in the coastal as well as the offshore fishery of Sri Lanka. E. affinis grows to a maximum fork length of 100 cm [24] , while A. thazard and A. rochei grow to maximum fork lengths of 65 cm [25] and 50 cm [23] respectively. The LWR and LLR data for these three species have been determined for the total catches including the coastal and offshore catches of Sri Lanka [26] , but have not yet been reported for the coastal catches reported only from the day-boats. Therefore, this study is aimed at gaining this information for the coastal catches of the three species of neritic tuna of Sri Lanka, which represent the stocks of the coastal waters surrounding the island.

Full text

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International Journal of Fisheries and Aquatic Studies 2019; 7(2): 129-133
E-ISSN: 2347-5129
P-ISSN: 2394-0506
(ICV-Poland) Impact Value: 5.62
(GIF) Impact Factor: 0.549
IJFAS 2019; 7(2): 129-133
© 2019 IJFAS
www.fisheriesjournal.com
Received: 26-01-2019
Accepted: 27-02-2019
Deishini Herath
a) Marine Biological Resources
Division, National Aquatic
Resources Research and
Development Agency, Colombo
15, Sri Lanka;
b) Department of Chemistry,
Faculty of Science, University of
Colombo, Colombo 3, Sri Lanka
Chintha Perera
Marine Biological Resources
Division, National Aquatic
Resources Research and
Development Agency, Colombo
15, Sri Lanka
Chamari Hettiarachchi
Department of Chemistry,
Faculty of Science, University of
Colombo, Cumaratunga
Munidasa Mawatha, Colombo 3,
Sri Lanka
Brian Murphy
Department of Fish & Wildlife
Conservation Virginia Tech
Blacksburg, VA 24061, USA
Correspondence
Chintha Perera
Marine Biological Resources
Division, National Aquatic
Resources Research and
Development Agency, Colombo
15, Sri Lanka
Length-weight and length-length relationships of three
neritic tuna species of Sri Lankan coastal waters
Deishini Herath, Chintha Perera, Chamari Hettiarachchi and Brian
Murphy
Abstract
The length-weight and length-length relationships were determined for the three neritic tuna species
Euthynnus affinis, Auxis thazard and Auxis rochei caught within Sri Lankan waters. Samples were
collected from October 2015 to September 2017. The R2 values for all three species were higher than 0.9
and were highly significant (p<0.001). The condition factor K, was 1.427, 1.476 and 1.361 for E. affinis,
A. thazard and A. rochei respectively. The value of b in the length weight equation was shown to be
3.115, 3.431 and 3.408 for the three species indicating positive allometric growth patterns. Furthermore,
the b values for the provinces studied were above 3.0 for all three species. The correlations between the
total length, fork length and standard length, were also highly significant (p<0.001). The results indicate
that these three species are living in a favourable environment having a healthy growth pattern along the
coastal regions of Sri Lanka.
Keywords: Euthynnus affinis, Auxis thazard, Auxis rochei, length-weight, length-length
1. Introduction
The length-weight relationships (LWR), length–length relationships (LLR) and Fulton’s
condition factor values are very useful in the management and conservation of fish resources
[1]. These LWRs are useful in stock assessment models, in the estimation of biomass from
length measurements, and for the comparison of the condition of fish between regions [2]. The
LWRs are also important in comparing life histories of fish species [3]. The Fulton’s condition
factor can indicate the wellbeing of the fish, assuming that plumper fish are in a better
condition [4]. LWRs have been reported for a large number of marine fish species [5, 6, 7],
freshwater fish species [8, 9] and fish species in lagoons [10, 11]. These relationships have been
studied in several countries surrounding the Indian Ocean, such as India [12, 13, 14], Pakistan [15]
and Bangladesh [16, 17]. LWRs and LLRs have been studied in the past for tuna species other
than neritic tunas in countries such as India [18] and Taiwan [19]. These relationships have been
reported for skipjack tuna (Katsuwonus pelamis) of the South Atlantic [20], for bigeye tuna
(Thunnus obesus), yellow fin tuna (T. albacores) and albacore (T. alalunga) of the Atlantic,
Indian and Eastern Pacific Oceans [21] and for bluefin tuna (T. thynnus) in the Eastern
Mediterranean sea [22]. LWRs, length-length relationships and condition factors have not yet
been defined for many of the commercially important marine fish species found in Sri Lankan
waters.
Euthynnus affinis (kawakawa), Auxis thazard (frigate tuna) and A. rochei (bullet tuna) are
neritic tuna species found in the warm waters of the Indo-West Pacific [23]. They are an
important group of fish species found in the coastal as well as the offshore fishery of Sri
Lanka. E. affinis grows to a maximum fork length of 100 cm [24], while A. thazard and A.
rochei grow to maximum fork lengths of 65 cm [25] and 50 cm [23] respectively. The LWR and
LLR data for these three species have been determined for the total catches including the
coastal and offshore catches of Sri Lanka [26], but have not yet been reported for the coastal
catches reported only from the day-boats. Therefore, this study is aimed at gaining this
information for the coastal catches of the three species of neritic tuna of Sri Lanka, which
represent the stocks of the coastal waters surrounding the island.

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International Journal of Fisheries and Aquatic Studies
2. Materials and Methods
A total of 488 samples of E. affinis, 408 samples A. thazard
and 196 A. rochei were collected from three provinces around
the Sri Lankan coast from October 2015 to September 2017
The samples were collected from Negombo and Beruwela in
the Western Province, Chilaw and Kalpitiya in the North
western Province and Dodanduwa, Galle and Weligama in the
Southern Province of Sri Lanka (Fig. 1). The sampling was
carried out by visiting the landing sites twice a month. The
weight to the nearest 0.1 g, total length (TL), fork length and
standard length to the nearest 0.1 cm were measured for each
fish collected. The length-weight relationship and length-
length relationships were estimated for the pooled samples
using a simple linear regression model. The length weight
relationship equation used for calculation is W=aLb [27], where
W is weight (g), L is total length (cm), a is the intercept and b
is the slope. The Fulton’s condition factor was determined
using the equation K=100W/L [3, 4]. In addition, the LW
relationships and the K factors for individual provinces were
evaluated separately.
Fig 1: Map showing the locations from which E. affinis, A. thazard and A. rochei samples were collected [Negombo and Beruwela (Western
Province), Chilaw and Kalpitiya (Northwestern Province), Dodanduwa, Galle and Weligama (Southern Province)].
3. Results and Discussion
The minimum, maximum and mean values of weights, total
length, fork length and standard length ranges for the samples
collected for the three species are given in Table 1. The b
values for the three species were 3.115, 3.431 and 3.408 for E.
affinis, A. thazard and A. rochei respectively and the
correlation coefficient R2 values ranged between 0.918 and
0.997 for the pooled samples of the three species respectively
(Table 2). The growth parameters a and b and the coefficient
of determination (R2) for the pooled samples of each species
and for the individual provinces from which samples were
collected, are given in Table 3. The b value of the LWR
equation can be used to infer the growth condition of the fish
in that environment. The b value in our study is >3.0 for
pooled values of all three species, as well as for the Western,
Northwestern and Southern Provinces separately, indicating
that their growth conditions are favourable.

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International Journal of Fisheries and Aquatic Studies
Table 1: Minimum, maximum and mean values of measurements obtained for weight and length parameters for the three species
Morphometric measurement
E. affinis
A. thazard
A. rochei
Min
Max
Mean
Min
Max
Mean
Min
Max
Mean
Weight (g)
44.5
3590.7
942.6
118.9
1430.9
619.1
76.4
424.2
276.5
Total length (cm)
16.1
63.3
38.1
21.5
44.2
33.7
22.5
30.8
27.2
Fork length (cm)
15.1
60.5
35.5
20.1
42.0
32.0
21.2
29.7
26.0
Standard length (cm)
13.9
59.3
34.9
19.4
40.7
30.8
20.5
28.5
25.1
Similar studies have been done in India for these species.
LWR has been calculated for E. affinis of Indian waters and a
and b values have been shown to be 0.0254 and 0.889
respectively [28]. In a study carried out for A. thazard, the R2
value has been 0.958 and the b value has been <3 indicating a
negative allometric growth [29].
The LWR has been determined for A. rochei in Indian waters
[30] and a and b values obtained have been 0.0076 and 3.243
respectively. The b value is very close to the value obtained in
our study for A. rochei. In a study done for A. rochei of
Turkish waters the b value has been shown to be 2.68, which
has revealed that they are having a negative allometric growth
and the R2 value has been 0.73 [31]. Comparing the results
obtained in our study show that these three species in our Sri
Lankan waters are living in good conditions and are having
healthy growth patterns.
Length-length relationships are important for comparative
growth studies in fisheries management issues [2]. The
relationships between the three length parameters of each
species were all highly significant (p<0.001) for the pooled
samples of each of the three species. The Fulton’s condition
factor (K) is >1 in the overall as well as in the individual
provinces, indicating that the condition for growth and
survival is good in all provinces studied. The K factor can
decrease if the health conditions of the fish are not good [21].
Though LLR have been determined for these three species in
Sri Lankan waters [32], this is the first attempt at determining
the LWR. Therefore, knowing the LWR for each of these
three species will help biologists to determine the weight of a
fish from length measurements taken in the field, as length
measurements are more convenient to obtain in the field.
These data will be useful in the management of these
important neritic tuna resources of Sri Lanka in the future.
Table 2: Comparison of the LWR parameters and LLR parameters of the 3 species studied.
E. affinis
A. thazard
A. rochei
Sample no. (n)
488
408
196
LWR equation
W=0.132L3.115
W=0.083L3.430
W=0.861L3.408
R2 value
0.989
0.981
0.918
b value
3.115
3.431
3.408
a value
0.132
0.083
0.861
Fulton’s condition factor (K)
1.43
1.48
1.36
FL= a + bTL
FL=-0.260 + 0.939TL R2=0.997
FL= - 0.483+0.963TL R2=0.996
FL= - 0.051+0.957TL R2 =0.968
SL=a+bTL
SL= -0.795 + 0.917TL R2=0.994
SL= - 0.582+0.929TL R2=0.988
SL = 0.584+0.900TL R2 =0.932
SL=a+bFL
SL=-0.564 + 0.977FL R2=0.997
SL= - 0.126+0.965FL R2=0.992
SL = 0.674+0.938FL R2 =0.959
Table 3: LWR parameters for E. affinis, A. thazard and A. rochei for the different Provinces
Euhynnus affinis
Auxis thazard
Auxis rochei
Overall
Western
Province
North
Western
Province
Southern
Province
Overall
Western
Province
North
Western
Province
Southern
Province
Overall
Western
Province
North
Western
Province
Southern
Province
Sample no.
(n)
489
254
137
88
388
195
129
57
178
75
20
82
LWR
equation
W=
0.130L3.
114
W=
0.138L3.087
W=
0.125L3.139
W=
0.123L3.165
W=
0.083L3.431
W=
0.089L3.388
W=
0.089L3.521
W=
0.069L3.550
W=
0.861L3.408
W=
0.879L3.308
W=
0.089L3.759
W=
0.069L3.490
R2 value
0.989
0.989
0.987
0.990
0.981
0.985
0.984
0.968
0.918
0.879
0.950
0.925
b value
3.115
3.087
3.139
3.165
3.431
3.388
3.352
3.550
3.408
3.308
3.760
3.490
a value
0.132
0.138
0.130
0.123
0.083
0.089
0.072
0.069
0.861
0.099
0.051
0.077
Fulton’s
condition
factor (K)
1.43
1.44
1.38
l1.45
1.48
1.45
1.44
1.50
1.48
1.35
1.37
1.36
4. Conclusion
Based on the results obtained in this study for the b values, R2
values and the Fulton’s condition factors, it can be concluded
that the three neritic tuna species, E. affinis, A. thazard and A.
rochei in our Sri Lankan waters are living in favourable
conditions and are having healthy growth patterns. Knowing
the LWR for each of these three species will help biologists to
determine the weight of a fish from length measurements
taken in the field. These data will be useful in the
management of these neritic tuna resources of Sri Lanka in
the future in a sustainable manner.
5. Acknowledgements
This work was funded by the National Aquatic Resources

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International Journal of Fisheries and Aquatic Studies
Research and Development Agency (NARA), Sri Lanka.
6. References
1. Ru HJ, Zhang Y, Li YF, Wu XX, Ni ZH. Length‐weight
relationships of six fishes from the Anning River, China.
Journal of Applied Ichthyology. 2018; 34:149-150.
doi:10.1111/jai.13437
2. Moutopoulos DK, Stergiou KI. Length–weight and
length–length relationships of fish species from the
Aegean Sea (Greece). Journal of Applied
Ichthyology, 2002; 18:200-203. doi:10.1046/j.1439-
0426.2002.00281.x
3. Ceyhan T, Akyol O, Erdem M. Length-Weight
Relationships of Fishes from Gökova Bay, Turkey
(Aegean Sea). Turkish Journal of Zoology. 2009; 33:69-
72.
4. Froese R. Cube law, condition factor and weight‐length
relationships: history, meta‐analysis and
recommendations. Journal of Applied Ichthyology. 2006;
22:241-253. doi:10.1111/j.1439-0426.2006.00805.x
5. Gonçalves JMS, Bentes L, Lino PG, Ribeiro J, Canário
AVM, Erzini K. Weight-length relationships for selected
fish species of the small-scale demersal fisheries of the
south and south-west coast of Portugal. Fisheries
Research. 1997; 30(3):253-256. doi:10.1016/S0165-
7836(96)00569-3
6. Filiz H, Bilge G. Length–weight relationships of 24 fish
species from the North Aegean Sea, Turkey. Journal of
Applied Ichthyology. 2004; 20:431-432. doi:
10.1111/j.1439-0426.2004.00582.x
7. Torres MA, Ramos F, Sobrino I. Length–weight
relationships of 76 fish species from the Gulf of Cadiz
(SW Spain). Fisheries Research. 2012; 127-128:171-175.
doi:10.1016/j.fishres.2012.02.001
8. Perera HACC, Rypel AL, Murphy BR, Li Z, Xia Y, Liu
J. Population characteristics of yellow catfish
(Peltobagrus fluvidraco) along the longitudinal profile of
Three Gorges Reservoir, China. Journal of Applied
Ichthyology. 2014; 29:1061-1066. doi: 10.1111/jai.12261
9. Wen ZY, Qin CJ, Xie BW, Yuan DY, Li R, Zou YC.
Length–weight relationships for two loach species,
Sinibotia superciliaris (Günther, 1892) and Sinibotia
reevesae (Chang, 1944) collected from the Tuojiang
River, China. Journal of Applied Ichthyology. 2017;
33:869-870. doi:10.1111/jai.13393
10. Karna SK. Length–weight and length–length relationship
of Thryssa purava (Hamilton, 1822), Thryssa
polybranchialis Wongratana, 1983 and Thryssa mystax
(Bloch & Schneider, 1801) from Chilika lagoon,
India. Journal of Applied Ichthyology. 2017; 33:1284-
1286. doi: https://doi.org/10.1111/jai.13503
11. Acarli D, Kara A, Bayhan B. Length–weight relations for
29 fish species from Homa Lagoon, Aegean Sea, Turkey.
Acta Ichthyologica et Piscatoria. 2014; 44:249-257. doi:
10.3750/AIP2014.44.3.09
12. Dey A, Choudhury H, Basumatary S, Bharali RC, Sarma
D. Length–weight relationships of three freshwater fish
species from the Kameng River (Brahmaputra basin) in
Arunachal Pradesh, northeast India. Journal of Applied
Ichthyology. 2018; 34:1002-1003. doi: 10.1111/jai.13635
13. Jabeen F, Choudhury H, Sarma D. Length–weight
Relationships of Barilius Bendelisis (hamilton, 1807),
Barilius Shacra (Hamilton, 1822) and Barilius Barna
(Hamilton, 1822) from Manas River in Assam. Journal of
Applied Ichthyology. 2017; 33:607-608. doi:
10.1111/jai.13269
14. Borah S, Bhattacharjya BK, Saud BJ, Yadav AK,
Debnath D, Yengkokpam S, et al. Length–weight
relationship of six indigenous fish species from Deepor
beel, a Ramsar site in Assam, India. Journal of Applied
Ichthyology. 2017; 33:655-657. doi:10.1111/jai.13348
15. Akhtar N, Khan MF. Length–weight relationships of two
Nemacheilid fish species Schistura alepidota (Mirza &
Bănărescu, 1970) and Schistura shadiwalensis (Mirza &
Nalbant, 1981) from River Swat, Pakistan. Journal of
Applied Ichthyology. 2018; 34:1073-1074. doi:
10.1111/jai.13714
16. Siddik MAB, Hanif MA, Chaklader MR. Length–weight
relationships of three fish species from the Arial Khan
River, an outlet of the river Padma, Bangladesh. Journal
of Applied Ichthyology. 2018; 34:765-767.
doi:10.1111/jai.13595
17. Islam MA, Siddik MAB, Hanif MA, Chaklader MR,
Nahar A, Ilham I. Length–weight relationships of four
small indigenous fish species from an inland artisanal
fishery, Bangladesh. Journal of Applied Ichthyology.
2017; 33:851-852. doi: https://doi.org/10.1111/jai.13374
18. Yosuva M, Jeyapragash D, Manigandan V,
Machendiranathan M, Saravanakumar A. Length-weight
relationship and relative condition factor of yellowfin
tuna (Thunnus albacares) from Parangipettai coast,
southeast coast of India. Zoology and Ecology. 2018;
28(2):94-99.
19. Hsu CC. The length–weight relationship of Albacore,
Thunnus alalunga, from the Indian Ocean. Fisheries
Research. 1999; 41(1):87-92. doi:10.1016/S0165-
7836(99)00002-8
20. Andrade HA, Campos RO. Allometry coefficient
variations of the length–weight relationship of skipjack
tuna (Katsuwonus pelamis) caught in the southwest South
Atlantic. Fisheries Research. 2002; 55:307-312.
21. Percin F, Akyol O. Length–weight and length–length
relationships of the bluefin tuna, Thunnus thynnus L., in
the Turkish part of the eastern Mediterranean Sea.
Journal of Applied Ichthyology. 2009; 25(6):782-784.
doi: 10.1111/j.1439-0426.2009.01288.x
22. Guoping Z, Liuxiong X, Yingqi Z, Xiaojie D. Length
frequency compositions and weight-length relationships
fro bigeye tuna, yellowfin tuna and albacore
(Perciformes: Scombrinae) in the Atlantic, Indian, and
the Eastern Pacific Oceans. Acta Ichthyologica Et
Piscatoria. 2008; 38(2):157-161.
23. Collette BB, Nauen CE. FAO Species Catalogue. Vol. 2.
Scombrids of the world. An annotated and illustrated
catalogue of tunas, mackerels, bonitos and related species
known to date. Rome: FAO. FAO Fisheries Synopsis.
1983; 125(2):137p.
24. Griffiths SP, Kuhnert PM, Fry GF, Manson FJ. Temporal
and size-related variation in the diet, consumption rate,
and daily ration of mackerel tuna (Euthynnus affinis) in
neritic waters of eastern Australia. ICES Journal of
Marine Science. 2009; 66(4):720-733.
doi:10.1093/icesjms/fsp065
25. Cayré P, Kothias JBA, Diouf T, Stretta JM. Biology of
tuna. In: A. Fonteneau and J. Marcille (eds.) Resources,
fishing and biology of the tropical tunas of the Eastern
Central Atlantic. FAO Fish. Tech. Pap. 292. Rome, FAO.
1993, 354 p.

~ 133 ~
International Journal of Fisheries and Aquatic Studies
26. Haputhantri SSK, Bandaranayake KHK. Analysis of
Kawakawa (Euthynnus affinis) landings in Sri Lanka and
estimation of the length-weight and length-length
relationships. 2013. Proceedings of the Third Working
Party on Neritic Tunas.
27. Le Cren ED. The length-weight relationship and seasonal
cycle in gonad weight and condition in the perch (Perca
fluviatilis). Journal of Animal Ecology. 1951; 20:201-
219. doi:10.2307/1540
28. Rohit P, Chellappan A, Abdussamad EM, Joshi KK, Said
Joya KP, Sivadas M, et al. Fishery and bionomics of the
little tuna, Euthynnus affinis (Cantor, 1849) exploited
from Indian waters. Indian Journal of Fisheries. 2012;
59(3):33-42.
29. Mudumala VK, Farejiya MK, Mali KS, Kari RR, Uikey
DE, Pradnya A, et al. Studies on Population
Characteristics of Frigate tuna, Auxis thazard
(Lacepede,1800) Occurring in the North West Coast of
India. International Journal of Life Sciences Journal.
2018; 4(2):1639-1643. doi:10.21276/ijlssr.2018.4.2.3
30. Jasmine S, Rohit P, Abdussamad EM, Said Koya, Joshi
KK, Kemparaju S, et al. Biology and fishery of the Bullet
tuna, Auxis rochei (Risso, 1810) in Indian waters. Indian
Journal Fisheries. 2013; 60(2):13-20.
31. Kahraman AE, Göktürk D, Karakulak FS. Age and
growth of bullet tuna, Auxis rochei (Risso), from the
Turkish Mediterranean coasts. African Journal of
Biotechnology. 2011; 10(15):3009-3013.
32. Bandaranayake KHK, Maldeniya R, Perera HACC. Auxis
thazard; major contributor in Sri Lankan Neritic tuna
fishery. IOTC–2015–WPNT05–18 Rev_1. 2015.
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