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Growth of marbled spinefoot Siganus rivulatus Forsskål, 1775 (Teleostei: Siganidae) introduced to Antalya Bay, eastern Mediterranean Sea (Turkey)
Fisheries Research 54 (2002) 279±285
Short communication
Growth of marbled spinefoot Siganus rivulatus ForsskaÊl, 1775 (Teleostei: Siganidae) introduced to Antalya Bay, eastern Mediterranean Sea (Turkey) Murat Bilecenoglu*, Murat Kaya Faculty of Fisheries, Department of Hydrobiology, Ege University, 35100 Izmir, Turkey Received 6 December 1999; received in revised form 5 September 2000; accepted 16 October 2000
Abstract The age and growth of the marbled spinefoot, Siganus rivulatus ForsskaÊl, 1775, were determined based on specimens collected from Antalya Bay (eastern Mediterranean), during the period from October 1996 to August 1998. Total length±weight relationship was estimated as W 0:0064L3:221 for females, W 0:0079L3:135 for males. Growth parameters of the von Bertalanffy equation were computed for females and males as: L1 22:55 cm; W1 146:8 g; k 0:267 yr 1 ; t0 0:47 and L1 21:06 cm; W1 112:1 g; k 0:343 yr 1 ; t0 0:54, respectively. Age was determined by posterior body scale readings. Maximum observed age was 8 years, suggesting that the species is long-lived. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Siganus rivulatus; Lessepsian migration; Age; Growth; Eastern Mediterranean
1. Introduction The marbled spinefoot, Siganus rivulatus ForsskaÊl, 1775, is a common Lessepsian (Red Sea) immigrant ®sh species in the eastern Mediterranean Sea. It inhabits shallow waters not exceeding 60 m (BenTuvia, 1986), roaming in schools of up to 100 specimens over algae covered and rocky bottoms. As in the Indo-Paci®c region, S. rivulatus is caught in remarkable quantities by gill and trammel nets for commercial purposes in the eastern Mediterranean Sea, but not yet included in the of®cial ®shery statistics of Turkey.
*
Corresponding author. Tel.: 90-232-388-4000, ext. 1717; fax: 90-232-388-3685. E-mail address: [email protected] (M. Bilecenoglu).
In spite of the fact that S. rivulatus was the subject of intensive investigations in the context of Lessepsian migration (Tortonese, 1947; Ben-Tuvia, 1964; Por, 1978; Golani, 1998), aquaculture (Ben-Tuvia et al., 1973; Popper and Gundermann, 1975) and feeding habits (Lundberg and Lipkin, 1979; Karagitsou et al., 1986; Golani, 1993; Lundberg et al., 1999), published reports on age and growth in the eastern Mediterranean are scarce. Hussein (1986) ®rst presented data on the age of marbled spinefoot in Egypt waters, while Yeldan and Avsar (1998) determined the exploitation rate and growth in Iskenderun Bay, northeastern Mediterranean. In this paper, we provide new information on the age and growth of marbled spinefoot from Antalya Bay, eastern Mediterranean coast of Turkey. The objectives of our study were to determine the age of the species based on scale readings, ®sh lengths and
0165-7836/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 5 - 7 8 3 6 ( 0 0 ) 0 0 2 9 6 - 4
280
M. Bilecenoglu, M. Kaya / Fisheries Research 54 (2002) 279±285
weights at speci®c ages, theoretical growth parameters needed to construct age±length keys and derive length±weight and length conversions. 2. Material and methods Specimens were collected within the period from October 1996 to August 1998 by participating artisanal ®shermen from Antalya Bay (eastern Mediterranean coast of Turkey) (Fig. 1). Fish samples were generally caught by gill nets with 20 and 28 mm mesh size (knot-to-knot) from depths not exceeding 40 m. Underwater observations carried out in the region indicated that juvenile siganids occur principally in 2±10 m, so ®shing lines and a local ®shing gear (sepet) were also used to collect small-sized specimens from shallow waters. The samples obtained were measured to the nearest 0.1 cm total length (TL) and weighed to the nearest 0.1 g. The commonly used length±weight relationship W aLb was applied (Ricker, 1975), where W is the weight (g), L the total length (cm), and a and b are constants. Differences of the slopes of the length± weight regressions between sexes were detected by analysis of covariance (ANCOVA). Growth was expressed in terms of the von Bertalanffy equation: Lt L1 1 e k t t0 . The von Bertalanffy plot was
used to estimate the growth parameters (Sparre and Venema, 1992). We also used the same function for growth in weight: Wt W1 1 e k t t0 b . Age was determined by scale reading. Minute embedded scales (10±25 scales) were removed by a lancet from the posterior part of the body (below rear dorsal ®n base to lateral line) (Hussein, 1986), and cleaned in a 10% solution of NaOH. Since its spawning season ranges from June to August in the eastern Mediterranean (Zeidane and Lakkis, 1995), this period was assumed as birth date. Scales were examined under the re¯ected light of a binocular microscope magnification 10 and 20 by two independent readers for corroboration. Scales from 17 ®sh (3.3% of total) were dif®cult to interpret and therefore could not be aged. Sex in mature specimens was easily determined with naked eye, but microscopic examination was used for differentiating sex in juveniles. 3. Results 3.1. Length and weight frequency distribution The total length of all individuals n 521 ranged from 7.0 to 21.5 cm (Fig. 2) and the weight from 3.2 to 128.7 g. Mean total length and weight was greater for males than for females (Table 1), and all differences
Fig. 1. Map showing the study area.
M. Bilecenoglu, M. Kaya / Fisheries Research 54 (2002) 279±285
281
Fig. 2. Total length±frequency distribution of the marbled spinefoot.
were statistically signi®cant (t-test, p < 0:05). The bulk of samples presented distinctive peaks at 15.0± 15.9 and 17.0±17.9 cm, respectively.
Table 2 Length±weight relationship constants (a is the intercept, b the slope and r the correlation coef®cient) for each sex and sexes combined
3.2. Length±weight relationship
Females Males All fish
The length±weight relationship was calculated separately for both sexes and all ®sh (Table 2). The slopes of the length±weight regression, which differed signi®cantly between sexes (ANCOVA: F0:05 97:11; p < 0:01), indicate the allometric nature of growth. Weight increased at 3.221 (,) and 3.135 (<) power of total length in the species. Based on length±weight regressions, an average 15 cm TL male is 38.7 g, average female 39.5 g. Table 1 Range, mean (95% con®dence intervals) and standard error (S.E.), median and mode of total length (cm) and gross weight (g) for the marbled spinefoot in the eastern Mediterranean, according to sex Length (cm) ,
Weight (g) <
,
<
na 292 229 292 229 Range 7.0±21.5 7.1±20.6 3.2±128.7 3.7±101.3 Mean 15.120.32 16.090.34 45.482.84 51.822.63 S.E. 0.167 0.168 1.443 1.336 Median 15.1 16.5 41.8 51.9 Mode 17.5 17.2 50.3 51.9 a
Number of ®sh.
a
na
a
b
S.E. (b)
r
292 229 521
0.006431 0.007945 0.007137
3.221 3.135 3.179
0.1610 0.1702 0.1171
0.95 0.95 0.95
Number of species.
Since scientists may report lengths of bony ®shes using one of a variety of measurements (such as total length, standard length, or fork length), it is necessary to convert lengths for comparative purposes. In this context, we derived equations as in Table 3. Table 3 Length±length regressions for the marbled spinefoot n 295 from Antalya Bay Y a bX a Y
X
TLb TL FL FL SL SL
FLc SLd TL SL TL FL
a
a 0.1416 0.3646 0.1632 0.4785 0.2589 0.3902
(0.1974) (0.2074) (0.1804) (0.1670) (0.1690) (0.1489)
1.0842 1.2491 0.9204 1.1512 0.7986 0.8670
Values in parentheses are standard errors. Total length (cm). c Fork length (cm). d Standard length (cm). b
r2
b (0.0120) (0.0149) (0.0102) (0.0120) (0.0095) (0.0090)
0.99 0.99 0.99 0.99 0.99 0.99
282
M. Bilecenoglu, M. Kaya / Fisheries Research 54 (2002) 279±285
Table 4 Age±length key for the marbled spinefoot in Antalya Bay based on scale readings Length group (TL, cm)
Age (years) 1
Total 2
7.0±7.9 8.0±8.9 9.0±9.9 10.0±10.9 11.0±11.9 12.0±12.9 13.0±13.9 14.0±14.9 15.0±15.9 16.0±16.9 17.0±17.9 18.0±18.9 19.0±19.9 20.0±20.9 21.0±21.9
8 11 4 3
Total (n)
26
3
4
5
6
7
8
2 4 1
8 12 4 8 24 22 16 73 105 68 95 33 20 15 1
7
504
1 5 24 16 8 2
6 6 37 24 5
56
78
2 34 71 45 7
159
10 18 84 9 3
124
4 23 12 6
1 3 5
45
9
Mean TL (cm)
8.45
11.96
14.68
15.58
17.29
18.96
20.10
20.41
S.D.
1.01
1.09
0.94
0.85
0.78
0.84
0.73
0.64
Table 5 Estimates of the von Bertalanffy growth parameters L1, W1, k and t0 for females, males and sexes combined of the marbled spinefoot
Females Males All fish
L1 (cm)
W1 (g)
k (yr 1)
22.554 21.059 22.303
146.814 112.056 137.871
0.267 0.343 0.279
3.3. Age and growth Eight age classes, from 1 to 8 years, were determined by posterior body scale readings (Table 4). The marbled spinefoot can be considered as long-lived, taking into account that the oldest male was estimated to be 7 years old, the oldest female 8 years old. Modal age for all ®sh was 4 (31.55%), followed by 5 (24.60%), 3 (15.48%), 2 (11.11%), 6 (8.93%), 1 (5.16%), 7 (1.78%) and 8
t0 (years) 0.473 0.537 0.503
Table 6 Observed and calculated mean lengths (TL, cm) of the marbled spinefoot for each age group of females, males and sexes combined Age groups (years) 1
2
3
4
5
6
7
8
Females Lobserved Lcalculated
8.43 7.33
11.88 10.90
14.50 13.63
15.36 15.72
17.38 17.32
18.92 18.54
20.23 19.48
20.41 20.20
Males Lobserved Lcalculated
8.48 8.63
12.28 12.24
15.03 14.80
15.90 16.62
17.22 17.91
18.99 18.82
19.65 19.47
± ±
All fish Lobserved Lcalculated
8.45 7.65
11.96 11.22
14.68 13.92
15.58 15.96
17.29 17.51
18.96 18.68
20.10 19.56
20.41 20.23
M. Bilecenoglu, M. Kaya / Fisheries Research 54 (2002) 279±285
283
Fig. 3. The von Bertalanffy growth curve for all ®sh ®tted by length at age data.
(1.39%) age groups. The age±length key for all specimens (Table 4) revealed a considerable range in length for each age group and some overlap between adjacent age groups. An average of 2.3 age groups was presented in each 1.0 cm interval. The estimated von Bertalanffy growth constants were given in Table 5. There were no statistical differences between the observed and calculated mean lengths w2cal < w2tab ; p > 0:05 of either sex (Table 6). The growth curve ®tted by length at age data is given in Fig. 3. 4. Discussion S. rivulatus is a common commercial Red Sea species of the Levantine basin (Golani, 1993). It has quickly become one of the most abundant benthic ®shes in Mediterranean coast of Turkey since it was ®rst discovered in Iskenderun Bay in 1942 (Kosswig, 1950), followed by a rapid increase in the 1950s and the species spread further north with resultant populations in Aegean Sea (Geldiay, 1969). In the 1980s, siganids (S. rivulatus and S. luridus) together comprised 5±15% of the inshore ®sheries of Israel and Greece (Lundberg et al., 1999). Nevertheless, annual catch of siganids at the Turkish Mediterranean could not be precisely ®gured out due to absence of of®cial ®sh catch statistics at the species level. Observations carried out in the region revealed that the siganids are generally sold together with Sarpa salpa (Sparidae)
since they have similar appearances (various ®shermen, pers. comm.). According to the of®cial ®shery statistics (Anonymous, 1967±1997), total production of Turkish Mediterranean S. salpa increased gradually from an average 13.8 t (1967±1976) to 31.3 t (1977± 1986), and lately to 158.9 t (1987±1997). The marbled spinefoot, S. rivulatus, is a long-lived species; the oldest male and female were estimated to be 7 and 8 years old, respectively. Yeldan and Avsar (1998) obtained similar results from Iskenderun Bay (northeastern Mediterranean coast of Turkey), where the maximum observed life span was 7 for all ®sh. Posterior body scale readings conducted in this study have not been validated completely, however, the close agreement between our readings and those of Yeldan and Avsar (1998) provides some support for the present ®ndings. Hussein (1986) used posterior body scales to age the species collected off the Mediterranean coast of Egypt and interpreted ages up to 5. Relative information from the Red Sea coasts indicated a shorter life span for the species. Using length± frequency analysis, Hashem (1983) found the maximum age to be 6 for all individuals, while El-Gammal (1988) determined ages up to 4 for males and 5 for females based on otoliths readings. Theoretical maximal length (22.3 cm) and weight (137.8 g) seem to be realistic, since the largest specimens sampled during the surveys were 21.5 cm and 128.7 g, respectively. Concerning the Mediterranean coast of Turkey, these parameters were also in accordance with the ®ndings of Yeldan and Avsar (1998)
284
M. Bilecenoglu, M. Kaya / Fisheries Research 54 (2002) 279±285
who reported the asymptotic length and weight for S. rivulatus as L1 21:5 cm and W1 117:15 g. However, both values given above are substantially less than the 40 cm SL (50.3 cm TL, see Table 3) reported by Ben-Tuvia (1986). According to maximum recorded length values in the Mediterranean Sea, 25 cm (Tortonese, 1947), 16.5 cm (George, 1972), 16 cm (Karagitsou et al., 1986) and 23.3 cm (Gucu et al., 1994), the marbled spinefoot could hardly attain to sizes exceeding 30 cm (TL) under natural conditions. Differences noted in length may be attributed to variation in temperature (Ricker, 1975), salinity (Popper and Gundermann, 1975), and, possibly, differences in feeding habits (Golani, 1993). The growth of marbled spinefoot in Antalya Bay is allometric b 3:179 and female ®sh increase in weight at a more rapid rate than males (Table 2), similar to those inhabiting Iskenderun Bay (Yeldan and Avsar, 1998) and the Red Sea (El-Gammal, 1988). The relatively low b-values (2.8412 for females and 2.8386 for males) reported from the Red Sea (ElGammal, 1988) may indicate a lack of suitable food supply for the marbled spinefoot individuals in the region. The growth coef®cient, k 0:279, indicates slow attainment of maximum size. The estimated k-value (0.34 yr 1) for S. rivulatus from Iskenderun Bay (Yeldan and Avsar, 1998) appears to be high, because of the low asymptotic calculated length of their data. Acknowledgements We are indebted to K.B. Kunt and Dr. U. Bekoz for collecting materials and assistance during the ®eld works. References Anonymous, 1967±1997. Fisheries statistics. Publication No. 5752154. State Institute of Statistics Prime Ministry, Republic of Turkey, Ankara. Ben-Tuvia, A., 1964. Two siganid ®shes of Red Sea origin in the eastern Mediterranean. Bull. Sea Fish. Res. Station Haifa 37, 1±8. Ben-Tuvia, A., 1986. Siganidae. In: Whitehead, P.J.P., Bauchot, M.-L., Hureau, J.-C., Nielsen, J., Tortonese, E. (Eds.), Fishes of the Northeastern Atlantic and the Mediterranean UNESCO, Vol. II, pp. 964±966.
Ben-Tuvia, A., Kissil, G.Wm., Popper, D., 1973. Experiments in rearing rabbit®sh (Siganus rivulatus) in sea water. Aquaculture 1, 359±364. El-Gammal, F.I., 1988. Age, growth and mortality of the rabbit®sh Siganus rivulatus (ForsskaÊl, 1775) from the Red Sea. Bull. Inst. Oceanogr. Fish. Egypt 14 (1), 13±21. Geldiay, R., 1969. Important ®shes found in the Bay of Izmir and their possible invasions. Monographs of the Faculty Science, Ege University, No. 11, 135 pp. George, C., 1972. Notes on the breeding and movements of the rabbit®shes, Siganus rivulatus (ForsskaÊl) and S. luridus RuÈppell, in the coastal waters of the Lebanon. Estratto Dagli Annali Del Museo Civico Di Storia Naturale Di Genova, Vol. LXXIX, pp. 32±44. Golani, D., 1993. Trophic adaptation of Red Sea ®shes to the eastern Mediterranean environment Ð review and new data. Israel J. Zool. 39, 391±402. Golani, D., 1998. Distribution of Lessepsian migrant ®sh in the Mediterranean. Italian J. Zool. 65 (Suppl.), 95±99. Gucu, A.C., Bingel, F., Avsar, D., Uysal, N., 1994. Distribution and occurrence of Red Sea ®sh at the Turkish Mediterranean coast Ð northern Cilician Basin. Acta Adriatica 34 (1/2), 103±113. Hashem, M.T., 1983. Biological studies on Siganus rivulatus (Forsk.) in the Red Sea. J. Faculty Mar. Sci. 3, 119±127. Hussein, Kh.A., 1986. The use of minute embedded scales for age determination of the Mediterranean Sea siganid Siganus rivulatus ForsskaÊl. Bull. Inst. Oceanogr. Fish. Cairo 12, 187± 198. Karagitsou, E., Stergiou, K., Papaconstantinou, C., 1986. Preliminary study on the diet of Pagrus pagrus, Phycis phycis and Siganus rivulatus in the Kastellorizo waters, eastern Mediterranean, Greece. Technical Consultation of the General Fisheries Council for the Mediterranean on Stock Assessment in the Eastern Mediterranean. FAO Fisheries Report 361, pp. 125± 131. Kosswig, C., 1950. Erythraische ®sche im Mittelmeer und an der Grenze der Agais. Syllegomena Biologica, Festschrift Kleinschmidt. Akademie, Leipzig, pp. 203±212. Lundberg, B., Lipkin, Y., 1979. Natural food of the herbivorous rabbit®sh (Siganus spp.) in northern Red Sea. Botanica Marina XXII, 173±181. Lundberg, B., Payiatas, G., Argyrou, M., 1999. Notes on the diet of the Lessepsian migrant herbivorous ®shes, Siganus luridus and S. rivulatus, in Cyprus. Israel J. Zool. 45, 127±134. Popper, D., Gundermann, N., 1975. Some ecological and behavioural aspects of siganid populations in the Red Sea and Mediterranean coasts of Israel in relation to their suitability for aquaculture. Aquaculture 6, 127±141. Por, F.D., 1978. Lessepsian migration, the in¯ux of Red Sea biota into the Mediterranean by way of Suez Canal. Ecological Studies, Vol. 23. Springer, Berlin, 228 pp. Ricker, W.E., 1975. Computation and interpretation of biological statistics of ®sh populations. Bull. Fish. Res. Board Can. 191, 383. Sparre, P., Venema, S.C., 1992. Introduction to tropical ®sh stock assessment. Part I: Manual. FAO Fisheries Technical Paper No. 306, Revision I, 376 pp.
M. Bilecenoglu, M. Kaya / Fisheries Research 54 (2002) 279±285 Tortonese, E., 1947. Ricerche zoologiche nell' isola di Rodi (Mar Egeo). Pesci. Boll. Pesca Piscicul. Idrobiol 23 (2), 143± 192. Yeldan, H., Avsar, D., 1998. Kuzeydogu Akdenizdeki sokar baligi (Siganus rivulatus (ForsskaÊl, 1775)) stokundan yararlanma
285
duzeyinin belirlenmesi. XIV. Ulusal Biyoloji Kongresi, 7±10 Eylul 1998, Samsun, Cilt II, pp. 152±162. Zeidane, R., Lakkis, S., 1995. Periodes de ponte des principales especes de poissons teleostens des eaux neritiques Libanaises. Lebanese Sci. Bull. 8 (1), 27±50.
Short communication
Growth of marbled spinefoot Siganus rivulatus ForsskaÊl, 1775 (Teleostei: Siganidae) introduced to Antalya Bay, eastern Mediterranean Sea (Turkey) Murat Bilecenoglu*, Murat Kaya Faculty of Fisheries, Department of Hydrobiology, Ege University, 35100 Izmir, Turkey Received 6 December 1999; received in revised form 5 September 2000; accepted 16 October 2000
Abstract The age and growth of the marbled spinefoot, Siganus rivulatus ForsskaÊl, 1775, were determined based on specimens collected from Antalya Bay (eastern Mediterranean), during the period from October 1996 to August 1998. Total length±weight relationship was estimated as W 0:0064L3:221 for females, W 0:0079L3:135 for males. Growth parameters of the von Bertalanffy equation were computed for females and males as: L1 22:55 cm; W1 146:8 g; k 0:267 yr 1 ; t0 0:47 and L1 21:06 cm; W1 112:1 g; k 0:343 yr 1 ; t0 0:54, respectively. Age was determined by posterior body scale readings. Maximum observed age was 8 years, suggesting that the species is long-lived. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Siganus rivulatus; Lessepsian migration; Age; Growth; Eastern Mediterranean
1. Introduction The marbled spinefoot, Siganus rivulatus ForsskaÊl, 1775, is a common Lessepsian (Red Sea) immigrant ®sh species in the eastern Mediterranean Sea. It inhabits shallow waters not exceeding 60 m (BenTuvia, 1986), roaming in schools of up to 100 specimens over algae covered and rocky bottoms. As in the Indo-Paci®c region, S. rivulatus is caught in remarkable quantities by gill and trammel nets for commercial purposes in the eastern Mediterranean Sea, but not yet included in the of®cial ®shery statistics of Turkey.
*
Corresponding author. Tel.: 90-232-388-4000, ext. 1717; fax: 90-232-388-3685. E-mail address: [email protected] (M. Bilecenoglu).
In spite of the fact that S. rivulatus was the subject of intensive investigations in the context of Lessepsian migration (Tortonese, 1947; Ben-Tuvia, 1964; Por, 1978; Golani, 1998), aquaculture (Ben-Tuvia et al., 1973; Popper and Gundermann, 1975) and feeding habits (Lundberg and Lipkin, 1979; Karagitsou et al., 1986; Golani, 1993; Lundberg et al., 1999), published reports on age and growth in the eastern Mediterranean are scarce. Hussein (1986) ®rst presented data on the age of marbled spinefoot in Egypt waters, while Yeldan and Avsar (1998) determined the exploitation rate and growth in Iskenderun Bay, northeastern Mediterranean. In this paper, we provide new information on the age and growth of marbled spinefoot from Antalya Bay, eastern Mediterranean coast of Turkey. The objectives of our study were to determine the age of the species based on scale readings, ®sh lengths and
0165-7836/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 5 - 7 8 3 6 ( 0 0 ) 0 0 2 9 6 - 4
280
M. Bilecenoglu, M. Kaya / Fisheries Research 54 (2002) 279±285
weights at speci®c ages, theoretical growth parameters needed to construct age±length keys and derive length±weight and length conversions. 2. Material and methods Specimens were collected within the period from October 1996 to August 1998 by participating artisanal ®shermen from Antalya Bay (eastern Mediterranean coast of Turkey) (Fig. 1). Fish samples were generally caught by gill nets with 20 and 28 mm mesh size (knot-to-knot) from depths not exceeding 40 m. Underwater observations carried out in the region indicated that juvenile siganids occur principally in 2±10 m, so ®shing lines and a local ®shing gear (sepet) were also used to collect small-sized specimens from shallow waters. The samples obtained were measured to the nearest 0.1 cm total length (TL) and weighed to the nearest 0.1 g. The commonly used length±weight relationship W aLb was applied (Ricker, 1975), where W is the weight (g), L the total length (cm), and a and b are constants. Differences of the slopes of the length± weight regressions between sexes were detected by analysis of covariance (ANCOVA). Growth was expressed in terms of the von Bertalanffy equation: Lt L1 1 e k t t0 . The von Bertalanffy plot was
used to estimate the growth parameters (Sparre and Venema, 1992). We also used the same function for growth in weight: Wt W1 1 e k t t0 b . Age was determined by scale reading. Minute embedded scales (10±25 scales) were removed by a lancet from the posterior part of the body (below rear dorsal ®n base to lateral line) (Hussein, 1986), and cleaned in a 10% solution of NaOH. Since its spawning season ranges from June to August in the eastern Mediterranean (Zeidane and Lakkis, 1995), this period was assumed as birth date. Scales were examined under the re¯ected light of a binocular microscope magnification 10 and 20 by two independent readers for corroboration. Scales from 17 ®sh (3.3% of total) were dif®cult to interpret and therefore could not be aged. Sex in mature specimens was easily determined with naked eye, but microscopic examination was used for differentiating sex in juveniles. 3. Results 3.1. Length and weight frequency distribution The total length of all individuals n 521 ranged from 7.0 to 21.5 cm (Fig. 2) and the weight from 3.2 to 128.7 g. Mean total length and weight was greater for males than for females (Table 1), and all differences
Fig. 1. Map showing the study area.
M. Bilecenoglu, M. Kaya / Fisheries Research 54 (2002) 279±285
281
Fig. 2. Total length±frequency distribution of the marbled spinefoot.
were statistically signi®cant (t-test, p < 0:05). The bulk of samples presented distinctive peaks at 15.0± 15.9 and 17.0±17.9 cm, respectively.
Table 2 Length±weight relationship constants (a is the intercept, b the slope and r the correlation coef®cient) for each sex and sexes combined
3.2. Length±weight relationship
Females Males All fish
The length±weight relationship was calculated separately for both sexes and all ®sh (Table 2). The slopes of the length±weight regression, which differed signi®cantly between sexes (ANCOVA: F0:05 97:11; p < 0:01), indicate the allometric nature of growth. Weight increased at 3.221 (,) and 3.135 (<) power of total length in the species. Based on length±weight regressions, an average 15 cm TL male is 38.7 g, average female 39.5 g. Table 1 Range, mean (95% con®dence intervals) and standard error (S.E.), median and mode of total length (cm) and gross weight (g) for the marbled spinefoot in the eastern Mediterranean, according to sex Length (cm) ,
Weight (g) <
,
<
na 292 229 292 229 Range 7.0±21.5 7.1±20.6 3.2±128.7 3.7±101.3 Mean 15.120.32 16.090.34 45.482.84 51.822.63 S.E. 0.167 0.168 1.443 1.336 Median 15.1 16.5 41.8 51.9 Mode 17.5 17.2 50.3 51.9 a
Number of ®sh.
a
na
a
b
S.E. (b)
r
292 229 521
0.006431 0.007945 0.007137
3.221 3.135 3.179
0.1610 0.1702 0.1171
0.95 0.95 0.95
Number of species.
Since scientists may report lengths of bony ®shes using one of a variety of measurements (such as total length, standard length, or fork length), it is necessary to convert lengths for comparative purposes. In this context, we derived equations as in Table 3. Table 3 Length±length regressions for the marbled spinefoot n 295 from Antalya Bay Y a bX a Y
X
TLb TL FL FL SL SL
FLc SLd TL SL TL FL
a
a 0.1416 0.3646 0.1632 0.4785 0.2589 0.3902
(0.1974) (0.2074) (0.1804) (0.1670) (0.1690) (0.1489)
1.0842 1.2491 0.9204 1.1512 0.7986 0.8670
Values in parentheses are standard errors. Total length (cm). c Fork length (cm). d Standard length (cm). b
r2
b (0.0120) (0.0149) (0.0102) (0.0120) (0.0095) (0.0090)
0.99 0.99 0.99 0.99 0.99 0.99
282
M. Bilecenoglu, M. Kaya / Fisheries Research 54 (2002) 279±285
Table 4 Age±length key for the marbled spinefoot in Antalya Bay based on scale readings Length group (TL, cm)
Age (years) 1
Total 2
7.0±7.9 8.0±8.9 9.0±9.9 10.0±10.9 11.0±11.9 12.0±12.9 13.0±13.9 14.0±14.9 15.0±15.9 16.0±16.9 17.0±17.9 18.0±18.9 19.0±19.9 20.0±20.9 21.0±21.9
8 11 4 3
Total (n)
26
3
4
5
6
7
8
2 4 1
8 12 4 8 24 22 16 73 105 68 95 33 20 15 1
7
504
1 5 24 16 8 2
6 6 37 24 5
56
78
2 34 71 45 7
159
10 18 84 9 3
124
4 23 12 6
1 3 5
45
9
Mean TL (cm)
8.45
11.96
14.68
15.58
17.29
18.96
20.10
20.41
S.D.
1.01
1.09
0.94
0.85
0.78
0.84
0.73
0.64
Table 5 Estimates of the von Bertalanffy growth parameters L1, W1, k and t0 for females, males and sexes combined of the marbled spinefoot
Females Males All fish
L1 (cm)
W1 (g)
k (yr 1)
22.554 21.059 22.303
146.814 112.056 137.871
0.267 0.343 0.279
3.3. Age and growth Eight age classes, from 1 to 8 years, were determined by posterior body scale readings (Table 4). The marbled spinefoot can be considered as long-lived, taking into account that the oldest male was estimated to be 7 years old, the oldest female 8 years old. Modal age for all ®sh was 4 (31.55%), followed by 5 (24.60%), 3 (15.48%), 2 (11.11%), 6 (8.93%), 1 (5.16%), 7 (1.78%) and 8
t0 (years) 0.473 0.537 0.503
Table 6 Observed and calculated mean lengths (TL, cm) of the marbled spinefoot for each age group of females, males and sexes combined Age groups (years) 1
2
3
4
5
6
7
8
Females Lobserved Lcalculated
8.43 7.33
11.88 10.90
14.50 13.63
15.36 15.72
17.38 17.32
18.92 18.54
20.23 19.48
20.41 20.20
Males Lobserved Lcalculated
8.48 8.63
12.28 12.24
15.03 14.80
15.90 16.62
17.22 17.91
18.99 18.82
19.65 19.47
± ±
All fish Lobserved Lcalculated
8.45 7.65
11.96 11.22
14.68 13.92
15.58 15.96
17.29 17.51
18.96 18.68
20.10 19.56
20.41 20.23
M. Bilecenoglu, M. Kaya / Fisheries Research 54 (2002) 279±285
283
Fig. 3. The von Bertalanffy growth curve for all ®sh ®tted by length at age data.
(1.39%) age groups. The age±length key for all specimens (Table 4) revealed a considerable range in length for each age group and some overlap between adjacent age groups. An average of 2.3 age groups was presented in each 1.0 cm interval. The estimated von Bertalanffy growth constants were given in Table 5. There were no statistical differences between the observed and calculated mean lengths w2cal < w2tab ; p > 0:05 of either sex (Table 6). The growth curve ®tted by length at age data is given in Fig. 3. 4. Discussion S. rivulatus is a common commercial Red Sea species of the Levantine basin (Golani, 1993). It has quickly become one of the most abundant benthic ®shes in Mediterranean coast of Turkey since it was ®rst discovered in Iskenderun Bay in 1942 (Kosswig, 1950), followed by a rapid increase in the 1950s and the species spread further north with resultant populations in Aegean Sea (Geldiay, 1969). In the 1980s, siganids (S. rivulatus and S. luridus) together comprised 5±15% of the inshore ®sheries of Israel and Greece (Lundberg et al., 1999). Nevertheless, annual catch of siganids at the Turkish Mediterranean could not be precisely ®gured out due to absence of of®cial ®sh catch statistics at the species level. Observations carried out in the region revealed that the siganids are generally sold together with Sarpa salpa (Sparidae)
since they have similar appearances (various ®shermen, pers. comm.). According to the of®cial ®shery statistics (Anonymous, 1967±1997), total production of Turkish Mediterranean S. salpa increased gradually from an average 13.8 t (1967±1976) to 31.3 t (1977± 1986), and lately to 158.9 t (1987±1997). The marbled spinefoot, S. rivulatus, is a long-lived species; the oldest male and female were estimated to be 7 and 8 years old, respectively. Yeldan and Avsar (1998) obtained similar results from Iskenderun Bay (northeastern Mediterranean coast of Turkey), where the maximum observed life span was 7 for all ®sh. Posterior body scale readings conducted in this study have not been validated completely, however, the close agreement between our readings and those of Yeldan and Avsar (1998) provides some support for the present ®ndings. Hussein (1986) used posterior body scales to age the species collected off the Mediterranean coast of Egypt and interpreted ages up to 5. Relative information from the Red Sea coasts indicated a shorter life span for the species. Using length± frequency analysis, Hashem (1983) found the maximum age to be 6 for all individuals, while El-Gammal (1988) determined ages up to 4 for males and 5 for females based on otoliths readings. Theoretical maximal length (22.3 cm) and weight (137.8 g) seem to be realistic, since the largest specimens sampled during the surveys were 21.5 cm and 128.7 g, respectively. Concerning the Mediterranean coast of Turkey, these parameters were also in accordance with the ®ndings of Yeldan and Avsar (1998)
284
M. Bilecenoglu, M. Kaya / Fisheries Research 54 (2002) 279±285
who reported the asymptotic length and weight for S. rivulatus as L1 21:5 cm and W1 117:15 g. However, both values given above are substantially less than the 40 cm SL (50.3 cm TL, see Table 3) reported by Ben-Tuvia (1986). According to maximum recorded length values in the Mediterranean Sea, 25 cm (Tortonese, 1947), 16.5 cm (George, 1972), 16 cm (Karagitsou et al., 1986) and 23.3 cm (Gucu et al., 1994), the marbled spinefoot could hardly attain to sizes exceeding 30 cm (TL) under natural conditions. Differences noted in length may be attributed to variation in temperature (Ricker, 1975), salinity (Popper and Gundermann, 1975), and, possibly, differences in feeding habits (Golani, 1993). The growth of marbled spinefoot in Antalya Bay is allometric b 3:179 and female ®sh increase in weight at a more rapid rate than males (Table 2), similar to those inhabiting Iskenderun Bay (Yeldan and Avsar, 1998) and the Red Sea (El-Gammal, 1988). The relatively low b-values (2.8412 for females and 2.8386 for males) reported from the Red Sea (ElGammal, 1988) may indicate a lack of suitable food supply for the marbled spinefoot individuals in the region. The growth coef®cient, k 0:279, indicates slow attainment of maximum size. The estimated k-value (0.34 yr 1) for S. rivulatus from Iskenderun Bay (Yeldan and Avsar, 1998) appears to be high, because of the low asymptotic calculated length of their data. Acknowledgements We are indebted to K.B. Kunt and Dr. U. Bekoz for collecting materials and assistance during the ®eld works. References Anonymous, 1967±1997. Fisheries statistics. Publication No. 5752154. State Institute of Statistics Prime Ministry, Republic of Turkey, Ankara. Ben-Tuvia, A., 1964. Two siganid ®shes of Red Sea origin in the eastern Mediterranean. Bull. Sea Fish. Res. Station Haifa 37, 1±8. Ben-Tuvia, A., 1986. Siganidae. In: Whitehead, P.J.P., Bauchot, M.-L., Hureau, J.-C., Nielsen, J., Tortonese, E. (Eds.), Fishes of the Northeastern Atlantic and the Mediterranean UNESCO, Vol. II, pp. 964±966.
Ben-Tuvia, A., Kissil, G.Wm., Popper, D., 1973. Experiments in rearing rabbit®sh (Siganus rivulatus) in sea water. Aquaculture 1, 359±364. El-Gammal, F.I., 1988. Age, growth and mortality of the rabbit®sh Siganus rivulatus (ForsskaÊl, 1775) from the Red Sea. Bull. Inst. Oceanogr. Fish. Egypt 14 (1), 13±21. Geldiay, R., 1969. Important ®shes found in the Bay of Izmir and their possible invasions. Monographs of the Faculty Science, Ege University, No. 11, 135 pp. George, C., 1972. Notes on the breeding and movements of the rabbit®shes, Siganus rivulatus (ForsskaÊl) and S. luridus RuÈppell, in the coastal waters of the Lebanon. Estratto Dagli Annali Del Museo Civico Di Storia Naturale Di Genova, Vol. LXXIX, pp. 32±44. Golani, D., 1993. Trophic adaptation of Red Sea ®shes to the eastern Mediterranean environment Ð review and new data. Israel J. Zool. 39, 391±402. Golani, D., 1998. Distribution of Lessepsian migrant ®sh in the Mediterranean. Italian J. Zool. 65 (Suppl.), 95±99. Gucu, A.C., Bingel, F., Avsar, D., Uysal, N., 1994. Distribution and occurrence of Red Sea ®sh at the Turkish Mediterranean coast Ð northern Cilician Basin. Acta Adriatica 34 (1/2), 103±113. Hashem, M.T., 1983. Biological studies on Siganus rivulatus (Forsk.) in the Red Sea. J. Faculty Mar. Sci. 3, 119±127. Hussein, Kh.A., 1986. The use of minute embedded scales for age determination of the Mediterranean Sea siganid Siganus rivulatus ForsskaÊl. Bull. Inst. Oceanogr. Fish. Cairo 12, 187± 198. Karagitsou, E., Stergiou, K., Papaconstantinou, C., 1986. Preliminary study on the diet of Pagrus pagrus, Phycis phycis and Siganus rivulatus in the Kastellorizo waters, eastern Mediterranean, Greece. Technical Consultation of the General Fisheries Council for the Mediterranean on Stock Assessment in the Eastern Mediterranean. FAO Fisheries Report 361, pp. 125± 131. Kosswig, C., 1950. Erythraische ®sche im Mittelmeer und an der Grenze der Agais. Syllegomena Biologica, Festschrift Kleinschmidt. Akademie, Leipzig, pp. 203±212. Lundberg, B., Lipkin, Y., 1979. Natural food of the herbivorous rabbit®sh (Siganus spp.) in northern Red Sea. Botanica Marina XXII, 173±181. Lundberg, B., Payiatas, G., Argyrou, M., 1999. Notes on the diet of the Lessepsian migrant herbivorous ®shes, Siganus luridus and S. rivulatus, in Cyprus. Israel J. Zool. 45, 127±134. Popper, D., Gundermann, N., 1975. Some ecological and behavioural aspects of siganid populations in the Red Sea and Mediterranean coasts of Israel in relation to their suitability for aquaculture. Aquaculture 6, 127±141. Por, F.D., 1978. Lessepsian migration, the in¯ux of Red Sea biota into the Mediterranean by way of Suez Canal. Ecological Studies, Vol. 23. Springer, Berlin, 228 pp. Ricker, W.E., 1975. Computation and interpretation of biological statistics of ®sh populations. Bull. Fish. Res. Board Can. 191, 383. Sparre, P., Venema, S.C., 1992. Introduction to tropical ®sh stock assessment. Part I: Manual. FAO Fisheries Technical Paper No. 306, Revision I, 376 pp.
M. Bilecenoglu, M. Kaya / Fisheries Research 54 (2002) 279±285 Tortonese, E., 1947. Ricerche zoologiche nell' isola di Rodi (Mar Egeo). Pesci. Boll. Pesca Piscicul. Idrobiol 23 (2), 143± 192. Yeldan, H., Avsar, D., 1998. Kuzeydogu Akdenizdeki sokar baligi (Siganus rivulatus (ForsskaÊl, 1775)) stokundan yararlanma
285
duzeyinin belirlenmesi. XIV. Ulusal Biyoloji Kongresi, 7±10 Eylul 1998, Samsun, Cilt II, pp. 152±162. Zeidane, R., Lakkis, S., 1995. Periodes de ponte des principales especes de poissons teleostens des eaux neritiques Libanaises. Lebanese Sci. Bull. 8 (1), 27±50.