Reproduction and growth of the Red Sea goatfish Parupeneus forsskali in its new environment (Cyprus, eastern Mediterranean Sea)

INTRODUCTION

⌅

Goatfish are members of the family Mullidae and can be found worldwide in tropical, subtropical and temperate waters (Uiblein 2007Uiblein F. 2007. Goatfishes (Mullidae) as indicators in tropical and temperate coastal habitat monitoring and management. Mar. Biol. Res. 3: 275-288. https://doi.org/10.1080/17451000701687129 ). Goatfish are of great commercial and economic importance on a global scale, including the Mediterranean Sea (Whitehead et al. 1984Whitehead P.J.P., Baucho, M.L., Hurea, J-C., et al. (eds) 1984. Fishes of the North-Eastern Atlantic and the Mediterranean (Vols. 1-3). UNESCO., Nelson et al. 2016Nelson J.S., Grande T.C., Wilson M.V. 2016. Fishes of the World (5th ed.). Hoboken, New Jersey: John Wiley & Sons, 2016, 752 pp. https://doi.org/10.1002/9781119174844 ). There are six confirmed mullid species present in the Mediterranean, two of which are native (Froese and Pauly 2022Froese R., Pauly D. 2022. FishBase. World Wide Web electronic publication. www.fishbase.org, version (02/2022).): the red mullet (Mullus barbatus, Linnaeus, 1758) and the surmullet (Mullus surmuletus Linnaeus, 1758). The most recent alien goatfish species to arrive in the Mediterranean is the Red Sea goatfish (Parupeneus forsskali [Fourmanoir and Guézé, 1976]), which migrated through the Suez Canal, and was first spotted off the coast of Turkey in 2000 (Çinar et al. 2006Çinar M.E., Bilecenoglu M., Öztürk B., Can A. 2006. New records of alien species on the Levantine coast of Turkey. Aquat. Invasions1: 84-90. https://doi.org/10.3391/ai.2006.1.2.6 ).

The Red Sea goatfish is endemic to the Red Sea and the Gulf of Aden and is the most common goatfish in the area (Randall 1983Randall J.E. 1983. Red Sea Reef Fishes. Immel Publishing, 192 pp, 2004Randall J. E. 2004. Revision of the goatfish genus Parupeneus (Perciformes: Mullidae) with descriptions of two new species. Indo-Pac. Fishes 36: 1-64.), as well as one of the most exploited goatfishes in the Red Sea (Farrag et al. 2018Farrag M.M.O., Mehanna S., Ahmed Osman Y. 2018. Fisheries status of the common species of family Mullidae in the Southern Red Sea, Egypt. Egypt. J. Aquat. Biol. Fish 22: 249-265. https://doi.org/10.21608/ejabf.2018.22017 ). In its native range, it can live for up to five years (Mehanna et al. 2018Mehanna S.F., Osman A.G.M., Farrag M.M.S., Osman Y.A.A. 2018. Age and growth of three common species of goatfish exploited by artisanal fishery in Hurghada fishing area, Egypt. J. Appl. Ichthyol. 34: 917-921. https://doi.org/10.1111/jai.13590 ), reaching a total length of up to 28.5 cm (Sabrah 2015Sabrah M.M. 2015. Fisheries biology of the Red Sea goatfish Parupeneus forsskali (Fourmanoir & Guézé, 1976) from the northern Red Sea, Hurghada, Egypt. Egypt. J. Aquat. Res. 41: 111-117. https://doi.org/10.1016/j.ejar.2015.02.003 ) and a size at maturity of 16 cm (Farrag et al. 2018Farrag M.M.O., Mehanna S., Ahmed Osman Y. 2018. Fisheries status of the common species of family Mullidae in the Southern Red Sea, Egypt. Egypt. J. Aquat. Biol. Fish 22: 249-265. https://doi.org/10.21608/ejabf.2018.22017 ). The geographical range of the Red Sea goatfish has increased considerably in recent years. Since it was first spotted around Turkey in 2000, it has spread throughout the eastern Mediterranean (Evagelopoulos et al. 2020Evagelopoulos A., Nikolaou A., Michailidis N., et al. 2020. Progress of the dispersal of the alien goatfish Parupeneus forsskali (Fourmanoir & Guézé, 1976) in the Mediterranean, with preliminary information on its diet composition in Cyprus. BioInvasions Rec. 9: 209-222. https://doi.org/10.3391/bir.2020.9.2.06 ) and has been found as far west as Tunisia (Capapé et al. 2018Capapé C., Zaouali J., Ounifi-Ben Amor K., Ben Amor M.M. 2018. First record of Red Sea goatfish Parupeneus forsskali (Osteichthyes: Mullidae) from Tunisian waters (central Mediterranean Sea). Ann. Ser. Hist. 28: 107-110. http://dx.doi.org/10.19233/ASHN.2018.12 ). Its presence was first confirmed around Cyprus in 2014, when a single specimen was caught in the area of Cape Pyla (Chartosia and Michailidis 2016Chartosia N., Michailidis N. 2016. First confirmed presence of the Red Sea goatfish Parupeneus forsskali (Fourmanoir & Guézé, 1976) from Cyprus. Mar. Biodivers. Rec. 9: 33. https://doi.org/10.1186/s41200-016-0032-7 ). Since then, the species has been established around the island, possibly becoming the most abundant goatfish in shallow waters around Cyprus, and has already become commercially important (Evagelopoulos et al. 2020Evagelopoulos A., Nikolaou A., Michailidis N., et al. 2020. Progress of the dispersal of the alien goatfish Parupeneus forsskali (Fourmanoir & Guézé, 1976) in the Mediterranean, with preliminary information on its diet composition in Cyprus. BioInvasions Rec. 9: 209-222. https://doi.org/10.3391/bir.2020.9.2.06 ).

Only a few studies have been done on the biology of the Red Sea goatfish in the Mediterranean, but none of them have focused on its reproduction and spawning period, both of which are important elements for population dynamics and fisheries management (Hunter et al. 1992Hunter J.R., Macewicz B.J., Lo N.C., Kimbrell C.A. 1992. Fecundity, spawning, and maturity of female Dover sole Microstomus pacificus, with an evaluation of assumptions and precision. Fish. Bull. 90: 101-128.). In the present study, the maturity, spawning, growth and mortality of the Red Sea goatfish were examined for the first time in the Mediterranean Sea (Cyprus). The results of this study will facilitate monitoring of the population around Cyprus and help to assess the impact of its establishment on Mediterranean fisheries and on biodiversity.

MATERIALS AND METHODS

⌅

Collection of samples

⌅

Red Sea goatfish samples were collected in the first or second week of each month along the southern coast of Cyprus from November 2020 to October 2021 (12 months, n=466). They were fished by local fishers at 15 to 20 m depth using a gillnet with an 18 to 20 mm net opening and examined shortly after. An additional sampling was carried out in July 2021 using hand nets with a smaller mesh size to ensure that fish of all sizes could be examined. The samples were mostly kept and examined fresh, but some samples had to be stored in a freezer or in a 10% buffered formalin solution for later examination. Total length (TL, cm) was measured to the nearest 0.1 cm, and total weight (TW, g) and gutted weight (GW, g) were measured to the nearest 0.01 g.

Histological analysis

⌅

Determining the maturity phases of fish is done either by examining the gonads macroscopically (or visually) or by histological analysis of the gonads. When gonads are examined histologically, the maturity of oocytes in ovaries and spermatocytes in testes are used to determine the maturity phase of the gonads. The gonads were extracted and weighed to the nearest 0.001 g. The sex of the fish and the gonad maturity phases (based on size, shape, colour, stiffness and presence of blood vessels) were determined macroscopically (Brown-Peterson et al. 2011Brown-Peterson N.J., Wyanski D.M., Saborido-Rey F., et al. 2011. A standardized terminology for describing reproductive development in fishes. Mar. Coast. Fish. 3: 52-70. https://doi.org/10.1080/19425120.2011.555724 ). After weighing, the gonads were fixed and stored in 10% formalin until further examination. Ten gonad samples from each month were selected for histological analysis randomly and others were chosen because the identification of the maturity phase macroscopically was not a straightforward procedure owing to the bad condition of the gonads. For the histological analyses, about 0.5-cm-thick tissue samples were taken from the middle part of either lobe of the ovaries and testes. The samples were then dehydrated in a graded series of ethanol, embedded in paraffin wax, sectioned at 7 µm and then mounted on microscope slides and stained with haematoxylin and eosin (e.g. Longenecker et al. 2017Longenecker K., Langston R., Bolick H., et al. 2017. Rapid reproductive analysis and length-weight relations for five species of coral-reef fishes (Actinopterygii) from Papua New Guinea: Nemipterus isacanthus, Parupeneus barberinus, Kyphosus cinerascens, Ctenochaetus striatus (Perciformes), and Balistapus undulatus (Tetraodontiformes). Acta Ichthyol. Piscat. 47: 107-124. https://doi.org/10.3750/AIEP/02146 ). The sections were examined under a Zeiss Primo Star microscope, and pictures of the sections were taken with a Zeiss Axiocam ERc 5s microscope camera. The histological maturity phases were determined on the basis of oocyte and spermatocyte development (Brown-Peterson et al. 2011Brown-Peterson N.J., Wyanski D.M., Saborido-Rey F., et al. 2011. A standardized terminology for describing reproductive development in fishes. Mar. Coast. Fish. 3: 52-70. https://doi.org/10.1080/19425120.2011.555724 ).

Morphology of gonads

⌅

Ovaries and testes were divided into five clear maturity phases both macroscopically and histologically following Brown-Peterson et al. (2011)Brown-Peterson N.J., Wyanski D.M., Saborido-Rey F., et al. 2011. A standardized terminology for describing reproductive development in fishes. Mar. Coast. Fish. 3: 52-70. https://doi.org/10.1080/19425120.2011.555724 . The following five phases were determined: i) immature, where individuals never spawned (Fig. 1); ii) developing, where gonads begin to develop but they are not ready to spawn (Fig. 2); iii) spawning capable, where individuals are able to spawn in this cycle (Fig. 3); regressing, where there is cessation of spawning (Fig. 4); and regenerating, sexually mature but reproductively inactive (Fig. 5).

Fig. 1. Immature individual of P. forsskali. A, female; B, male. PG, primary growth oocytes; Sc, spermatocytes.

Fig. 2. Developing individual of P. forsskali. A, female; B, male. Vtg1, primary vitellogenic oocyte; Vtg2, secondary vitellogenic oocyte; Vtg3, tertiary vitellogenic oocyte; Sc, spermatocytes; St, spermatids; Sz, spermatozoa.

Fig. 3. Spawning capable individual of P. forsskali. A, female; B, male. GVM, germinal vesicle migration; Vtg3, tertiary vitellogenic oocyte; Sz=spermatozoa.

Fig. 4. Regressing individual of P. forsskali. A, female; B, male. POF, postovulatory follicle complex; GVBD, germinal vesicle breakdown; A, atretic oocyte; Sz, residual spermatozoa; St, spermatids.

Fig. 5. Regenerating individual of P. forsskali. A, female; B, male. PG, primary growth oocytes; CA, cortical alveolar oocytes; Sc, spermatocytes; St, spermatids; Sz, spermatozoa.

Time of spawning

⌅

The development of fish gonads in time can be described at a macroscopic level using the gonadosomatic index (GSI), which can be used to detect the onset and duration of spawning (Tsikliras et al. 2010Tsikliras A.C., Antonopoulou E., Stergiou K.I. 2010. Spawning period of Mediterranean marine fishes. Rev. Fish Biol. Fish 20: 499-538. https://doi.org/10.1007/s11160-010-9158-6 ). Monthly changes in the GSI and maturity phases were used to determine the spawning season of Red Sea goatfish. GSI was calculated using the following formula $G S I = 100 (g o n a d w e i g h t / g u t t e d w e i g h t)$ :

G S I = 100 (g o n a d w e i g h t / g u t t e d w e i g h t)

Size at first maturity

⌅

TL was used to estimate size at first sexual maturity (L_M), defined as the size at which 50% of individuals were sexually mature (Tsikliras et al. 2013Tsikliras A.C., Stergiou K.I., Froese R. 2013. Editorial note on reproductive biology of fishes. Acta Ichthyol Piscat. 43: 1-5. https://doi.org/10.3750/AIP2013.43.1.01 ) The estimation included individuals which had previously reproduced and the virgin ones that were going to reproduce in the current reproductive season for the first time. The fish were split into length classes of 0.5 cm and the proportion of the maturing individuals (P) was calculated in each length class (L). Size at first maturity (L_M) was estimated taking into account only the individuals from the spawning season (May-September), by fitting a logistic curve to the percentage of mature fish (P) per length class (L) for both sexes (Echeverria 1987Echeverria T.W. 1987. Thirty-four species of California rockfishes: Maturity and seasonality of reproduction. Fish. Bull. 85: 22.):

P = \frac{e^{(v_{1} + v_{2} L)}}{1 + e^{(v_{1} + v_{2} L)}}

and

L_{M} = - \frac{v_{1}}{v_{2}}

Length-weight relationship

⌅

The length-weight relationship (LWR) was estimated and expressed by the following equation $T W = a T L^{b}$ (Le Cren 1951Le Cren E.D. 1951. The length-weight relationship and seasonal cycle in gonad weight and condition in the perch (Perca fluviatilis). J. Anim. Ecol. 20: 201-219. https://doi.org/10.2307/1540 , Froese 2006Froese R. 2006. Cube law, condition factor and weight-length relationships: History, meta-analysis and recommendations. J. App. Ichth. 22: 241-253. https://doi.org/10.1111/j.1439-0426.2006.00805.x ):

T W = a T L^{b}

where TW is total weight, TL is total length, a (intercept) is a coefficient related to body form and b (exponent) is a coefficient indicating isometric or allometric growth (Froese 2006Froese R. 2006. Cube law, condition factor and weight-length relationships: History, meta-analysis and recommendations. J. App. Ichth. 22: 241-253. https://doi.org/10.1111/j.1439-0426.2006.00805.x ). When b=3, the growth is isometric, so the shape of the fish does not change as it grows and the condition of small and large individuals is the same. If b>3, the growth is positive allometric, so the fish increases in weight faster than in length, and if b<3 the growth is negative allometric, so the body shape becomes more elongated as the fish grows in size (Froese 2006Froese R. 2006. Cube law, condition factor and weight-length relationships: History, meta-analysis and recommendations. J. App. Ichth. 22: 241-253. https://doi.org/10.1111/j.1439-0426.2006.00805.x ).

Age and growth

⌅

Growth rate is determined by the relationship between size and age. The von Bertalanffy growth equation is likely the most commonly used growth model in fisheries biology and is used to determine growth parameters (von Bertalanffy 1938von Bertalanffy L 1938. A quantitative theory of organic growth. Human Biology 10: 181-213.):

L_{t} = L_{\infty} (1 - e^{- K (t - t_{0})})

where L_t (cm) is the fish somatic TL at time t, L_∞ (cm) is the asymptotic length, i.e. the mean length the fish would have if they were to grow indefinitely, K (y^-1) is the rate at which asymptotic length is approached, and t0 is the time when length is theoretically zero. Relative age was determined on the basis of the length-frequency distribution of the samples using Bhattacharya’s method (Bhattacharya 1967)Bhattacharya C.G. 1967. A Simple Method of Resolution of a Distribution into Gaussian Components. Biometrics 23: 115-135. https://doi.org/10.2307/2528285 , which splits a composite distribution into separate normal distributions, each representing an age group of fish. The program FISAT II (2005)FiSAT II - FAO-ICLARM stock assessment tools II: user’s guide 2005, WorldFish Center, Food and Agriculture Organization of the United Nations in English - Rev. version. was used for this analysis. The non-linear least-squares method was used to estimate the parameters of the von Bertalanffy growth function, which was fitted to the mean lengths of the age groups.

Mortality

⌅

Natural mortality (M) was estimated using Pauly’s (1980)Pauly D. 1980. On the interrelationships between natural mortality, growth parameters, and mean environmental temperature in 175 fish stocks. ICES J. Mar. Sci. 39: 175-192. https://doi.org/10.1093/icesjms/39.2.175 equation (1 $\log (M) = - 0.0066 - 0.279 \log (L_{\infty}) + 0.6543 \log (K) + 0.4634 \log (T)$ ) and the Chen and Watanabe method (2 $M (t) = \frac{K}{a_{0} + a_{1} (t - t_{M}) + {a_{2} (t - t_{M})}^{2}} w h e n t > t_{M}$ ) (Chen and Watanabe 1989Chen S., Watanabe S. 1989. Age dependence of natural mortality coefficient in fish population dynamics. Nippon Suisan Gakk 55: 205-208. https://doi.org/10.2331/suisan.55.205 ) because the latter allows the estimation of M per age class.

Then, an average M across ages was calculated as the average value of these methods (Quinn and Deriso 1999Quinn T.J. II, R.B. Deriso, 1999. Quantitative Fish Dynamics. Oxford University Press.).

\log (M) = - 0.0066 - 0.279 \log (L_{\infty}) + 0.6543 \log (K) + 0.4634 \log (T)

(1)

M (t) = \frac{K}{1 - e^{- K (t - t_{0})}} w h e n t \leq t_{M} (t_{M} = - \frac{1}{K} \log |1 - e^{K t_{0}}| + t_{0})

M (t) = \frac{K}{a_{0} + a_{1} (t - t_{M}) + {a_{2} (t - t_{M})}^{2}} w h e n t > t_{M}

(2)

Data analysis

⌅

Data analysis was done using R version 4.1.3 (R Core Team 2016R Core Team 2016. A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/ ). The Shapiro-Wilk test was used to test normality of the data, and equal variance was tested with an F-test where needed. The sex ratio between males and females was tested using a chi-squared test at a significance level of 0.05 to see if it differed from unity. Mean TL (± SD) and mean TW (± SD) were calculated and the two-sample t-test was used to test the difference in mean length between sexes. TW of males and females did not have the same variance, so Welch’s t-test was used to test the difference there.

RESULTS

⌅

Morphometric characteristics of the species

⌅

A total of 466 individuals of the Red Sea goatfish were sampled, of which 140 were females, 274 were males and 52 were unsexed (37 juveniles with non-visible gonads and 15 with either non-distinguishable or destroyed gonads). The male to female ratio of Red Sea goatfish was 1.96:1 and differed significantly from the expected ratio (1:1), since a disproportionately large proportion of males were caught (0.66, SE=0.02; chi-squared test, n=414, P<0.05).

Overall, TL ranged between 8.2 and 24.1 cm (Table 1). TL ranged from 12.1 to 26.1 cm for males (mean=19.1 cm, SD=2.48) and from 10.3 to 24.1 cm for females (mean=17.4 cm, SD=2.13). The smallest recorded individual was 8.2 cm and was unsexed, but the smallest spawning capable fish was a 10.4 cm long female. TW ranged from 16.69 to 204.22 g for males (mean=79.36 g, SD=33.52) and from 11.07 to 148.19 g for females (mean=58.90 g, SD=22.49). On average, males were heavier and bigger than females, with a significant difference in TW (t=7.26, df=383, P<0.05) and TL (t=6.52, df=412, P<0.05).

Table 1. Total length (cm) and total weight (g) of the male, female and unsexed individuals of the Red Sea goatfish collected in Cyprus waters. SD=standard deviation.

Data	Number of individuals	Total length (cm)	Mean±SD	Total weight (g)	Mean±SD
Male	272	12.1-26.1	19.0±2.48	16.69-204.22	79.06±33.52
Female	140	10.3-24.1	17.4±2.13	11.07-148.19	58.90±22.49
Unsexed	52	8.2-19.0	14.8±3.19	4.49-74.25	38.48±21.44
All	466	8.2-26.1	18.1±2.83	4.49-204.22	68.48±32.49

Spawning season

⌅

The monthly mean values of the GSI peaked in July for both males (0.747±0.109 SE) and females (4.791±0.353 SE). The GSI decreased in the autumn and reached its minimum monthly mean value in November for females (0.339±0.043 SE) and in March for males (0.072±0.012 SE). It remained low in the winter months but started to rise slowly in the spring for both sexes, and then increased rapidly from May to June (Fig. 6).

Fig. 6. Monthly mean values of the gonadosomatic index (GSI) for both males (blue line and dots) and females (red line and dots) of the Red Sea goatfish collected in Cyprus waters. Error bars indicate standard error. Numbers show the number of individuals examined.

The number of spawning capable males and females was highest in July and June for females and in August for males (Fig. 7). Males at all maturity phases were observed in August and July, whereas in November, December and January only regenerating males were present in the sample. In March all females were regenerating, and in September they were all in the regressing phase (Fig. 7).

Fig. 7. Frequency of maturity phases of the Red Sea goatfish collected in Cyprus waters in each month. Upper panel, females; lower panel, males.

Size at first sexual maturity

⌅

The smallest spawning capable female was 10.4 cm (sampled in June) and the largest immature female was 15.6 cm (sampled in July). The smallest sexually mature male was 14.3 cm (sampled in July) and the largest sexually immature male was 13.5 cm (sampled in August). The estimated size at which 50% were sexually mature was 14.2 cm for males and 11.8 cm for females (Fig. 8).

Fig. 8. Observed (dots) and estimated (line) proportion of maturing individuals at length (L, cm) of the Red Sea goatfish collected in Cyprus waters (males, solid circles; females, open rhombus). The dotted lines indicate L_M.