Length-Weight Relationship and Spawning Season of Sphyraena jello C., from Persian Gulf
Length-weight relationship and spawning season of Pickhandle
barracuda, Sphyraena jello (C.) were studied for one year in
Boushehr waters of the Persian Gulf. In the present study, 311 specimens
were collected during November 2006 to October 2007. The samples composed
of 151 (48.55%) male, 160 (51.45%) female; the sex ratio was M: F = 1:
1.06. The b value ranged between 2.77 to 2.87 for male and female fishes,
respectively. The relationship between body weight and length in total
specimens was 2.82, indicating that this species show negative allometric
growth. The peak spawning season of these fishes occur around spring,
from April to June. The lowest Gonadosomatic Index recorded in August.
The present study is the first record on length-weight relationship and
spawning season of this species in the Persian Gulf region.
The waters of the Persian Gulf are environmentally unique with an unusual faunal
assemblage (Carpenter et al., 1997). The Persian
Gulf is a semi-closed water body connected to the Oman Sea through narrow Strait
of Hormuz. The maximum width is 640 km with the average depth of 35 m (Reynolds,
1993). The Persian Gulf is in the subtropical zone lying almost entirely
between the latitudes of 24° and 30° N and longitudes of 49° to
61° 25 E. The entire water column is well mixed and lies within the
photic zone. However, primary productivity for the Persian Gulf is apparently
only in average, being higher than most the Red Sea but lower than the Arabian
Sea (Sheppard et al., 1992).
The Persian Gulf possesses various commercially important fish species. Pickhandle
barracuda, Sphyraena jello Cuvier, 1829 locally called Dewolmy is one
of the valuable commercial fishes in the south coasts of Iran and has been classified
at the top level of commercial categorization, so owing to its economic importance.
Pickhandle barracudas are migratory pelagic predators that are distributed over
continental shelves, estuaries and also in open oceans of tropical, subtropical
and warm temperate seas (Bachok et al., 2004).
The Pickhandle Barracuda (S. jello) is a long, slender schooling
fish. It is silvery with variable darker bars on the body and a deeply forked,
yellowish tail (Ramachandran et al., 2007). This
species is of importance to fisheries in many countries and is considered a
good table fish due to its excellent flesh qualities. S. jello is a commercially
important pelagic fish and is caught with different types of fishing gears such
as of trawls, long line and gill nets in coastal waters of Boushehr Province
(Hosseini et al., 2008). Barracuda (S. jello)
a trash fish of yester years is gaining importance as a potential source for
product development in recent times with a landing of about 7011 ton in 2004
(MPEDA News Letter, 2006).
Length-Weight Relationship (LWR) is of great importance in fishery assessments
(Garcia et al., 1989; Haimovici
and Velasco, 2000). Fish length-weight relationships, which describe mathematically
the correlation between fish length and weight, are useful for converting length
observations into weight estimates to provide some measure of biomass (Froese,
1998). Length and weight measurements in conjunction with age data can give
information on the stock composition, age at maturity, life span, mortality,
growth and production (Beyer, 1987; Bolger
and Connoly, 1989; King, 1996a, b;
Diaz et al., 2000). Method to estimate the length-weight
relationship was described by Biswas (1993) and King (2007).
There are only a limited number of studies on the LWR of this commercially
important fishes worldwide and there are no studies that describe length-weight
relationship and spawning season of this pelagic marine fish. Therefore,
a biological investigation on S. jello in coastal waters of Boushehr
Province was taken up. The aim of the present study was to determine the
length-weight relationship parameters and basic information on the spawning
season of S. jello from Boushehr waters (the Northeast Persian
MATERIALS AND METHODS
The fishes used for the study were collected during November 2006 to October
2007 from the Bandargah and Jofreh harbors, two important landing centers on
the Boushehr coastal. The fishing gears used in this region include gill net
and trawl. At least 20-30 specimens were randomly collected per month. The randomly
selected samples were transported in ice box to laboratory for further biological
measurement. Identification of species was made based on Smith
et al. (2003) and FAO Species identification sheets (Fischer
and Bianchi, 1984). Total length (TL) was measured from the tip of the snout
to the extended tip of the caudal fin. Body weight of individual fish was measured
to the nearest 0.01 g with an electronic balance. Then the gonads were removed
and weighed (0.001 g).
The relationship between the total length and total weight were determined
by fitting the data to a potential relationship in the form of:
where, W is the weight in grams, L the total length in centimeters, a and b
are the parameters to be estimated, with b being the coefficient of allometry
(Pauly, 1984). A logarithmic transformation was used to
make the relationship linear (Bagenal and Tesch, 1978):
For this species a regression was used to estimate the intercept (Log a) and
the regression coefficient or slope (b), using Microsoft Excel. For species
with sufficient data the LWR was determined separately for each sex in addition
to total fishes (311 specimens). Sex was determined by examination of the gonad
tissue either with eye or with the aid of a binocular (25-40x). The overall
sex ratio was assessed using Chi-square test (Zar, 1984).
Statistical analyses were performed with SPSS 11.5 software package and a significance
level of 0.05 was adopted. Gonadosomatic index (GSI %) = (gonad weight/total
body weight)x100 was calculated for each fish and all values were averaged for
each sampling date (Biswas, 1993). The gonadosomatic index
or maturity index is an indirect method for estimating spawning season of a
species (Biswas, 1993).
Based on descriptive statistics size of males ranged from 37.5 to 93.5
cm and that of females from 39.5 to 80 cm, respectively. Minimum and maximum
weights of males were between 200.15 to 2850 g, respectively and that
of females 235.10 and 2310.17 g, respectively. Mean values of length and
weight for males and females were 58.20 ± 7.79 cm, 891.26 ±
357.87 g and 58.13 ± 7.90 cm, 867.22 ± 372.47 g, respectively.
All the length data was classified into 5 cm groups and the analysis of
total length distribution frequency of all individuals is shown in Fig.
1. High abundance of this species was observed in 52.5-57.5 cm length.
The relationship between somatic weight and total length of the fish (Fig.
2a, b) were calculated separately for male and females. Significant
differences were obtained between the b exponents and 3 for isometric
growth in the sexes separately (ttest, tmale = 5.22,
tfemale= 3.98, p < 0.05), indicating negative allometric
nature of growth (b < 3) in the population. Moreover, there was a significant
difference in the b exponent between males and females (ANCOVA, F = 8.34,
p < 0.05).
||Length frequency distribution for S. jello from
Boushehr waters (the Northeast Persian Gulf)
|| Month wise sex ratio of S. jello from Boushehr
waters (the Northeast Persian Gulf)
||Length-weight relationship curves for (a) males and
(b) females of S. jello from Boushehr waters (the Northeast
||Monthly mean GSI distribution of S. jello from
Boushehr waters (the Northeast Persian Gulf) during Nov. 2006 to Oct.
Also determination and correlation coefficients show a high relationship
between these two morphometric characteristics (p < 0.05).
The sex ratio and GSI (Gonadosomatic Index) were calculated during the
study period. Table 1 shows the sex ratio observed in
different months. The results of the Chi-squire test showed that there
was no significant difference in sex ratio in all months except May and
June. Monthly fluctuations in the GSI of both males and females are shown
in Fig. 3. The highest GSI for both males and females
was observed in May, which declined gradually in the following months
up to August. From September onwards an increasing trend in GSI was observed
in males and females indicating growth of gonads. This observation also
corresponds with the gonad maturity stages. In October-November period
gonads were found to be in the early maturing stage and highest numbers
of fish with fully developed gonads were observed during April-May. This
fish is, therefore, assumed to be a spring spawner.
As shown, the GSI for both male and female remained low ( < 1.5-2)
from July to March. They increased gradually from April to May, but rapidly
to reach a peak in May (testes and ovaries). The indices then decreased,
falling to pre-spawning level by August. It could be stated that S.
jello spawns once a year in Bousher waters during the period between
April to June, with a spawning peak in May.
Due to selectivity of fishing gear, samples dont include juveniles or
very small individuals. In this context and according to Petrakis
and Stergiou (1995), the use of W-L relationship should be rigorously limited
to the size ranges applied in the estimation of the linear regression parameters.
For this reason, it is particularly difficulty to extrapolate data to fish larvae
(Pepin, 1995), juveniles (Safran,
1992) or immature stage (Bagenal, 1978).
Additionally, since samples were collected over an extended period of time,
this data is not representative of a particular season or time of the years
and for comparison purpose it should be considered only as mean annual values,
as suggested by Petrakis and Stergionu (1995). In fact,
W-L relationship isnt constant over the whole year, varying according
to factor such as food availability, feeding rate, gonad development and spawning
period. However, the parameter b is characteristic of the species and generally
doesnt vary significantly through out the year, unlike the parameter a,
which may vary daily, seasonally and or between different habitats (King,
1996b). The numerical value of b is nearly always between 2.5 and 3.5 and
is often close to 3 (Bagenal, 1978). When b = 3, the body
is increasing in all dimensions in the same proportions as it grows (Hart
and Reynolds, 2002).
In a study carried out by Al-sakaff and Essen (1999)
in Gulf of Eden, b value was 2.721 and 2.706 for male and female fishes of this
species, respectively. The observations made in the present study (b = 2.778-2.878)
also was comparable with the work of Vander-Elst (1981),
where b value was estimated to be 2.81 for this species from South African waters.
In a study by Abdurahiman et al. (2004) in Southern
coast of Karnataka state, b values obtained for male and female fishes were
3.059 and 3.170, respectively. The difference between the results of this study
and the present investigation can be attributed to difference in latitude, ecological
condition and length ranges in the studied fishes in two regions. Because firstly,
fishes mature earlier in tropical regions compared to temperate region and secondly,
the fishes studied in India belonged to lower length range and hence had higher
Sexual ratio had no significant differences in various months except May and
June; because during spawning time, females remind in spawning area more than
males (Arcand-Hoy and Benson, 1998a, b).
Bachok et al. (2004) reported a sex ratio of 0.86 in Malaysian waters.
Al-sakaff and Esseen (1999) reported a sex ratio of 1.187
for this fish in Gulf of Eden. The results obtained from these two studies and
present investigation is in agreement. Richard et al.
(1993) has stated that spawning season for this species in water of Fiji
is in summer and in the regions from the coast. Related to differences in the
GSI between reproductively active males and females, in reviewing the reproductive
biology of the S. jello it is noted that values of males are commonly
lower than those of females. Buxton (1990) pointed out
that the cost of producing sperm is thought to be less than for producing eggs.
The difference in male and female gondosomatic indices suggests that energy
invested in gamete production by male is probably less than that invested by
The present study was funded by the Department of Marine Biology, Research
Center of Persian Gulf University and the Khorramshahr University of Marine
Science and Technology (Grant No. KMSU 8234406). Authors appreciate the
comments provided by the reviewers of this study and are grateful to Mr.
Ahmad Falahati and Mr. Gholamhossean Eskandari.
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