The body of Red mullet is long strong, and laterally slightly flat. The head is relatively short; the snout is short as well, with a steep anterior profile. The eyes are positioned near the top of the head. The mouth is small, positioned low on the head. There are two barbels under the mouth aperture. They have a sensory function and are used in searching for prey. The colour is uniformly pink, the back is darker and the belly is white. The fins are without any well-defined coloration (Tortonese, 1975; Fisher et al., 1987; Jardas, 1996; Relini et al., 1999).

Morphology data:
The number of rays in the fins is the following: D1:VII-VIII, D2: I+7-8, A: II+6-7, P: 15-17, V: I+5 (Jardas, 1996).

World:
The red mullet is distributed in the eastern Atlantic - from the North Sea and England to Senegal and in the Mediterranean.

Adriatic Sea:
It is uniformly distributed in all parts of the Adriatic (Jardas, 1996).

Habitat:
This is a benthic species, found mostly on muddy bottoms in depth range of 5 to 250 m (Relini et al., 1999). It prefers the more shallow waters of the northern and central Adriatic, i.e. depths above 100 m, while only few specimens may be caught in deeper waters (Jukić and Piccinetti, 1981).

Although the species is widely distributed, the relative index of the population abundance decreases with depth (Haidar, 1970; Jukić, 1972; Jukić and Arneri, 1984; Županović and Jardas, 1989; Jukić et al., 1999; Vrgoč, 2000).

Seasonal migration:
Spring:
During the spring, red mullet is found mostly along the eastern coast, on sandy bottoms.
Autumn:
In autumn Red mullet is found on the entire Adriatic Sea shelf (Arneri and Jukić, 1986).

Migration (inshore/offshore behaviour):
Haidar (1970) showed that in the central and northern Adriatic, there are two migration types in this species: the migration of the young fish from the coast towards the open sea and the spring migration of adult spawning fish towards channels region along the Croatian coast at depths between 50 and 85 meters. Other authors found similar inshore-offshore behaviour (Scaccini, 1947a; Županović, 1963; Jardas, 1996).

Depth:
Jukić and Piccinetti (1981) found that adult specimens did not migrate significantly during the year and migrations were limited to 100 m isobath. Županović and Jardas (1989), however, did not notice significant migrations in the Pomo/Jabuka Pit region. So, it seems that the area is primarily inhabited by adult specimens in the second year of their life (Županović, 1963). Generally, the population abundance decreases with depth (Haidar 1970; Jukić, 1972; Merker and Ninčić, 1973; Jukić, 1975; Županović and Jardas, 1989; Vrgoč, 2000).

Bottom preferences:
Regarding the type of sediment, Županović and Jardas (1989) found in the Pomo/Jabuka Pit region that the abundance of this species was higher at stations with a rugged type of sediment, which, at the same time, correlates with the shallower areas. Jukić and Piccinetti (1981) pointed out that red mullet prefer muddy and sandy bottoms, e.g. the regions with the highest availability of its food.

Size:
According to Jardas (1996), red mullet grow up to about 30 cm (about 0,5 kg). The usual total length in catches is 10 to 20 cm. On average, females have greater body length than males (Jardas, 1996). They also grow faster, which can be already noticed in the first year of their life (Haidar 1970). Therefore, almost all the bigger specimens are females (28 to 29 cm). Males do not grow more than about 20 cm (Relini et al., 1999).

Length-weight relationship:
The length-weight relationship shows that the growth of this species is isometric (Table 8) There are two different inflexion points in the length-weight relationship of females, one at 12-13 cm (corresponding to the first sexual maturity) and the other one between 16 and 17 cm. There is only one male inflexion point, between 11,5 and 12 cm and it corresponds to the length at first sexual maturity (Županović and Jardas, 1989).

Total Length (TL, cm) – weight (g) relationship.

Spawning:
According to all the authors, Red mullet spawns in the Adriatic Sea in late spring and summer (May, June, July). According to Haidar (1970), males have two types of sexual cycle: specimens smaller than 14 cm (three years according to this author) have annual sexual cycles, with the spawning phase from May to July, whereas bigger specimens have biennial sex cycle with the reproductive phase from May to December. Females always have an annual reproduction cycle and they spawn from April to May. Red mullet reach sexual maturity in the first year of life at lengths between 10 and 14 cm (Table 9). The most intensive spawning occurs at depths of 60 to 70 m. After the spawning, post larvae move towards shallower water (30-40 m) and coast (Županović and Jardas, 1989). Larvae, post larvae and juveniles up to 4-5 cm of total length are pelagic. Afterwards, individuals move towards sandy coastal areas and become demersal. They concentrate particularly near river mouths and sometimes enter rivers for several hundreds of meters (Scaccini, 1947a). Later, they start their dispersion towards sandy, muddy and gravel grounds at depths between 10 and 250 m (Relini et al., 1999). A high density of larvae was found in the Central Adriatic at 50 to 100 m depth (Guescini et al., 1983). The sex ratio is extremely variable, depending on the different zones studied. Županović (1963) demonstrated, through analysis of the literature, that in the eastern Mediterranean, including the Adriatic Sea, females predominate while an inverse situation is observed in the Western Mediterranean.

Sex Ratio:
In the Pomo/Jabuka Pit region, males are dominant at lengths up to 17 cm, while females dominate at greater lengths, most probably because of different growth rates of males and females (Županović and Jardas, 1989). This was confirmed by Vrgoč (2000) in the central and northern Adriatic, during the MEDITS expedition it was found that males were dominant in the population up to 14 to 15 cm; above 15 cm, females were dominant. In Montenegrin water the sex ratio is: M : F = 37% : 63% (Joksimovic, 2005).

Length at the first sexual maturity:

Total Length (L_m, cm) at the first sexual maturity.

Total Length and age data:

Total Length (TL, cm) and age (year) data

There are some distinct differences in the growth dynamics between males and females (see tables). Females are 1 to 2 centimetres longer than males of the same age (Županović and Jardas, 1989). The growth dynamics change also through the year Scaccini (1947b), Haidar (1970), Relini et al. (1999).

Von Bertalanffy Growth Function (VBGF).
Parameters of the Von Bertalanffy Growth Function (VBGF).

Feeding behaviour:
The red mullet is a carnivorous species. The bulk of its food is made of endo-, meso- and epi-biontic sea organisms. Jukić (1972, 1975) found that, in the central Adriatic channels, the Red mullet’s food consists of Polychaeta, Lamellibranchiata and Crustacea. The same prey was described as the dominant food of this species by Haidar (1970) and Froglia (1988). It is also observed that the larger specimens eat bigger prey (Froglia 1988). Jukić and Županović (1965) showed that, in the eastern Adriatic, the red mullet eat continuously throughout the year but more so during summer and autumn, which is probably in relation to the water temperature.
In the Adriatic, the main fish predators of juvenile and adult red mullet are Lophius piscatorius, Raja clavata, Trygon pastinaca, Galeus canis, Zeus faber and Merluccius merluccius (Haidar, 1970).

Although the red mullet is distributed in the entire Adriatic, the density of the population is not the same in terms of space as well as time. For example, Arneri and Jukić (1986) found that the biomass index between Italian and Croatian waters is about 1:4. It was also observed that the population abundance decreased with depth (Županović and Jardas, 1989).

CPUE:
In the period from 1989 to 1994, the CPUE was from 0,33 to 2,45 kg/h in the southern Adriatic and from 0,96 to 1,43 kg/h in the central and eastern Adriatic (EC XIV/298/96-EN, 1996). In the period from 2002-2004 the CPUE was 5.4 kg/h and 23.10% percentage in total catch in the open sea off Montenegrin coastal area (Joksimovic, 2005).

Biomass/Abundance Indexes:
During the MEDITS expedition (1996-1998), the average biomass index for red mullet in the central and northern Adriatic was 16,36 kg/km2. The highest population density was found in the 50 to 100 m stratum (28,81 kg/km2). The proportion of this species in the total catch of the demersal fish was 5,66% (Vrgoč, 2000). The average length value was 14,43 cm and it increased with depth.

During the “Hvar” expedition, Red mullet made about 6,27% of the catch and was the fifth species according to the proportion of catch. This proportion was 6,79% during the MEDITS expedition (ranking as fourth species in the catch).

In the summer and autumn periods, young specimens are dominant in the population. In some coastal areas of the Western Adriatic Sea, this fraction is 60-90%, with catch rates up to 100 kg/h (Froglia, 1988). (Piccinetti and Piccinetti Manfrin, 1994; Ungaro et al., 1996). Individuals older than one year were always a minor part of the catch (near 5% in autumn and 20% in spring) in the surveys performed in these seasons (Relini et al., 1999).

During a survey in open Montenegrin waters (2002-2004) the relative biomass of Mullus was 104.8 Kg/km2 (absolute biomass 242.592 kg/km2) with a total biomass of 236.61 tonnes and an estimated MSY of 37.62 (Joksimovic, 2005).

Mortality:
The red mullet mortality rates in the Adriatic are summarized in the table. They show a high exploitation level of the species.

Mortality rate coefficients for red mullet in the Adriatic.

Gear:
In the Adriatic, red mullet is almost exclusively fished with bottom trawl nets. Smaller quantities are fished with trammel-nets as well.

Fisheries statistics:
The total annual catch is about 2000 tonnes.

Mullus spp capture fishery production (Adriatic Sea*). Data: FAO-FISHSTAT (GFCM (Mediterranean and Black Sea) capture production 1970-2003 (Release date: May 2005) Regional dataset available at ftp://ftp.fao.org/fi/stat/windows/fishplus/gfcm.zip.

*According to GFCM definition of statistical sub-areas the Adriatic Sea falls within the area 2.1, thus including only the Northern and Central basins, while the Southern Adriatic basin and consequently the coast of South-eastern Italy and of Albania are included in the Ionian Sea (area 2.2). In order to have as comprehensive a picture as possible of all Adriatic Sea fishery production, Albanian data originally classified as from the Ionian Sea have been included in the Adriatic data set used. Unfortunately, this was not feasible for South-western Italy (Apulia Region).

Selectivity:
The data about the selectivity of trawl to the red mullet population are shown in table.

Selectivity of trawl towards red mullet.

* knot to knot.

 

Species	Relevant genetic results		Population biology and ecology issues
	Genetic diversity	Genetic differentiation
Mullus barbatus	Number of alleles: 12-33 (mean 22.5) Heterozigosity 60%-96% (mean 78%) HWE fitting: 80% The Adriatic samples showed high genetic diversity and respect of the HWE	Fixation indices among Adriatic samples were generally low but in some comparison they were medium-high and significant. Subtle spatial genetic heterogeneity not related to a geographic cline	The randomness of genetic differences among samples indicated that the Adriatic red mullet stock probably belongs to a single population unit. However, individuals may group into local, genetically differentiated sub-populations Correlation between geographic distance and genetic differentiation was not detected. The observed genetic fragmentation in the Adriatic stock may be generated by reproductive success, survival rates or fishing pressure.

 

Scientific name	Common name	Project framework	Sampling (Survey)	Development of genetic marker (type & number of markers)	Genetic structure (analysed samples, geographic areas)	Population units in the Adriatic shared stock	Reference associated
Mullus barbatus	Red mullet	GenPopAdr, MiPAF	√ (MEDITS 2002)	√ (microsatellites, 6 optimised loci)	√ (4; NA,MA,SA)	√ Single panmictic unit	Final report of GenPopAdr project , MiPAF Garoia et al. 2004b.

Minimum size:

Species (local or common name)	Species (scientific name)	Minimum size in cm or minimum weight in kg
ALB: It is strictly prohibited to fish and sell any aquatic species less than the minimum regulatory size as set out in Article 48.1 of Fisheries Regulations No.1 of 1997.
Barbuni	Loligo spp.	11 cm
CRO: The Order of 1998 (145/98) and amended by the Order 101/02 on the Protection of Fish and Other Marine Organisms was adopted to determine the minimum sizes of certain species of fish
Trlja od blata	-	11 cm
ITA: The self-executing rules of Reg. EC 1626/1994 establish the minimum size to protect juveniles as follows
Triglia di fango	-	11 cm
SCG: The minimum size is laid down (Table 7) as follows: (2. Decree on prohibition of capture and trade in fish juveniles, undersized fish and other marine organisms no. 10/2004)
Barbun, Trlja od blata	-	11 cm
SLO: n.a.
Bradač	-	-