Elasmobranches and Chimaeras in Syria: Past, Present, and Future

*Adib Saad and Hasan Alkusairy*

#### **Abstract**

In this chapter, we review and discuss the cartilaginous species richness in Syrian offshore waters (Eastern Mediterranean coast) through a careful review of published taxonomic studies, historical data on species occurrence, and analysis of scientific surveys carried out over the last 10 years. The revised species produced for the Syrian coast, in this chapter, is debated in the context of current taxonomic disputes and the occurrence of species. Annual catches of each species over two consecutive years are also presented. Threats were estimated based on field surveys and observations conducted during the last three decades, particularly the results of the qualitative composition of the catch and the maturity status of individuals that were carried out during the years 2015–2018; extensively classified conservation measures have also been proposed. We listed a total of 49 species, representing 25 families and 34 genera that are currently present in Syrian marine waters. This number includes 23 species of sharks, 24 batoids (after we considered the species *Pristis pectinata* an extinct species from the Syrian marine water) and two chimaeras. In addition, the review serves as a reference for future conservation assessments of cartilaginous fishes in the region and a guide for decision-makers when promoting sustainable exploitation of fisheries resources within an ecosystem-based framework.

**Keywords:** sharks, batoids, chimaeras, Mediterranean sea, Syria

#### **1. Introduction**

Cartilaginous fishes, also called chondrichthyans, are characterized by a skeleton composed of cartilage. In addition, their skin is covered with placoid scales, which look a lot like a vertebrate tooth. This is why these animals have a rough texture to the touch. Their mouth contains many partially calcified teeth. These are not fused to the jaw, so they also have several spares. These fishes have two nostrils, a blowhole, and 5–7 gill openings. Their eyes do not have eyelids, but some of them have a light, transparent membrane, called the nictitating membrane, which performs the same function. Another main characteristic is the presence of pelvic fins in the lower part of their body, which serves as the reproductive organs of these fish. These fins, also called claspers, allow them to deposit gametes (sperm) inside the female. That is why only males have them. Cartilaginous fish are divided into three groups: A. Sharks: Most sharks are characterized by a streamlined spindle-shaped body and a well-developed caudal fin composed of two lobes, with the upper lobe longer than the lower

lobe. They have five- to seven-gill openings behind the head on each side of the body. B. Batoids (Skates, rays, sawfishes, guitarfishes): Skates and rays are characterized by their flattened shape dorsally and ventrally, as most species live sedentary on the bottom. There are five- or six-gill slits on the ventral side of the body. C. Chimaeras: They have strange shapes, and unlike other cartilaginous fish, mythical fish have one pair of gill openings covered by a skin fold.

From a taxonomic point of view, the class of cartilaginous fishes is divided into two subclasses: the subclass Elasmobranchs (sharks and batoids (rays and skate)) and the subclass Holocephali. To date, 1226 species of elasmobranches have been described (537 species of sharks belonging to 34 families, 689 species of batoids belonging to 20 families) and 56 species of Halocephali belonging to three families [1–3]. Cartilaginous fish are widely distributed in marine ecosystems, and sometimes they are also found in freshwater environments [4]. Syrian marine waters form the north-eastern part of the Levant basin in the eastern part of the Mediterranean Sea, as this basin is characterized by high salinity (39.5‰) and temperature (26°C) [5], the arrival of new species through the Suez Canal, especially of Indo-Pacific origin, has increased species richness in the eastern basin [6].

#### **Figure 1.**

*The integral Syrian coast where grovel made a survey of sharks and other marine organisms during the period 1929–1931 [7].*

#### *Elasmobranches and Chimaeras in Syria: Past, Present, and Future DOI:http://dx.doi.org/10.5772/intechopen.110408*

Before 1920, Syria's natural coast constituted the eastern coast of the Mediterranean, extending from the city of El-Arish in Egypt to the city of Iskenderun in Turkey (**Figure 1**), while currently this coast is limited to 183 km in length from the Lebanese border in the south to the Turkish border in the north [7].

The general marine fauna of the coasts of Syria can be considered as formed by the fauna of the Mediterranean, which is superimposed, in a way, an important part of the fauna of the Red Sea and the Indian Ocean. A large number of species from these last seas have found favorable biological conditions on the Syrian (including Palestinian and Lebanese) coasts (**Figure 1**). The continuous monitoring studies during the last decades confirm that the number of these forms coming through the Suez Canal grow and develop permanently over time because one or more species of Indo-Pacific origin are recorded each week in the Levantine basin in general and on the Syrian coast in particular. In addition, many species of fish of Atlantic origin are recorded in the eastern Mediterranean and the Syrian coasts. These new introductions and invasions of exotic species (whether from the Red Sea or the Atlantic Ocean) are mainly due to climate change and human activities [8, 9].

In this chapter, we revise and discuss the chondrichthyan species richness and their records. Through an accurate review of published taxonomic studies, historical data on species occurrence and analyses of scientific survey produce a revised list of species whose presence in the Syrian coast (**Figure 2**) is confirmed or highly probable and discussed on current taxonomic and occurrence disputes on the species that are instead rarer or claimed to be locally extinct.

The review serves as a reference for future conservation assessments of cartilaginous fishes in Syrian marine waters and a guide for decision-makers when promoting sustainable exploitation of fisheries resources within an ecosystem-based framework, explaining the reasons for their prolonged absence in reports.

#### **Figure 2***.*

*Map of the Mediterranean showing the study area, Syrian coast, on which the most important cities and ports are located in which the landing of fish catch every day (= two nursery areas for several species of sharks).*

#### **2. Materials and methods**

The information was collected from two main sources: 1- the reference study of previously published scientific literature and 2- field studies carried out by the authors during the last two decades. Our field studies have investigated the species diversity, abundance, longevity, sex ratio, and nursery potential of caught sharks. Samples were obtained by all fishing methods (longlines, nets, and nets) during the period 2001–2003 and 2016–2021 in Syrian waters. For scientific nomenclature, we followed the online database of the Eschmeyer's Catalog of Fish [10], which is the authoritative reference for taxonomic fish names, together with the world record of marine species (WoRMS) and Fishbase [11, 12]. Regarding the study of catch composition and species abundance level, species abundance (abundance index) was determined according to the numbers caught during the study as follows: dominant: >1000 individuals, common: 200–1000 individuals, frequent: 100–199 individuals, occasional: 10–99 and rare individuals: less than 10 individuals.

During the 3 years (2011, 2015, and 2016), daily surveys were made on species number, weight, and size structure caught by all fishing gears in the main landing of chondrichthyans on Syrian coast, the ecological indices; diversity index D, qualitative richness factor QR, and evenness factor E were used to evaluate the levels of shark diversity within the study region by all gear types [13, 14]**.**



#### *Elasmobranches and Chimaeras in Syria: Past, Present, and Future DOI:http://dx.doi.org/10.5772/intechopen.110408*

#### **Table 1.**

*The status of cartilaginous species in our field study that was carried out during the years 2015–2016; size at first maturity (mm), percentage of juvenile individuals and main catch method in the Syrian marine waters (f: Females, m: Males, TL: Total length, DW: Disc width).*

Biodiversity indicators of caught cartilaginous fish:


Juvenile individuals of the species were defined by information on size at first maturity of the Syrian marine fishes or the nearest region to Syrian coast were

extracted from peer-reviewed published sources, including 'gray' literature [13, 14]. The reproductive cycle and maturity of eight species of cartilaginous fish were studied in detail during the aforementioned period, and the results were published in scientific journals, which are listed in **Table 1**.

Possible nursery places were defined depending on individual's size of species, density of individuals, and repeat individual's appearance in the fishing area [13, 14].

#### **3. Results and discussion**

#### **3.1 Recorded species and diversity**

The study of the distribution and taxonomy of sharks in Syrian marine waters were initiated by Cruvel during the period 1927–1930 [20]. This study reported 14 species of cartilaginous fish, including six sharks, seven batoids, and one chimaera. This was followed by a short study on the assessment of demersal fish stocks during the year 1976 [21] during which it confirmed the presence of five species in addition to the previously recorded species by Gruvel [20], and then a study of the qualitative composition of cartilaginous fishes during the period 2002–2004 [22–24], and finally an extensive study on the qualitative and quantitative composition of cartilaginous fishes in Syrian marine waters [13, 14].

The number of species recorded on the Syrian coast is 49 cartilaginous species (23 sharks, 24 batoids, and two chimaera) (**Table 2**). Among them, one species of batoids (*Pristis pectinata* Latham 1794) has disappeared from the Syrian marine waters and perhaps from all the waters of the eastern part of the Mediterranean, as the last record of it in the Syrian waters is 1976 [20, 21]; this number represented about 55.1% of the cartilaginous fish in the Mediterranean Sea (what constitutes 46.9% of all shark species, 63.2% of batoids species, and 100% of chimaeras) (**Table 3**). The cartilaginous fish recorded in the Mediterranean are 89 species composed of 49 sharks, 38 batoids, and 2 chimaeras [33, 34].


#### **Table 2.**

*Synoptic table showing the number of species belonging to each systematic group of chondrichthyans. The relationship between Syrian marine waters chondrichthyans and Mediterranean is compared in terms of percentage.*





#### **Table 3.**

*List of recorded species of cartilaginous fish in Syrian marine water. The status, frequency, the first record, and first publication (N = native; AL = alien; REX = range expanding; C = common; F = frequent; R = rare; VR = very rare; EN = endangered.)*

Only two studies on biodiversity evidence for cartilaginous fish were carried out during the years 2015–2016 in Syrian marine waters [13, 14]. In these studies, the ecological indices, diversity index D, qualitative richness factor QR, and evenness factor E were used to evaluate the levels of shark diversity within the study region by all fishing methods (**Table 4**). The means of D, QR, and E through the period of study were (1.73 ± 0.21), (2.03 ± 0.40), and (0.67 ± 0.09), respectively. The seasonal variations of the three ecological indices show that, the highest mean of D values was in summer (2.41 ± 0.09), followed by spring (2.40 ± 0.05), autumn (2.37 ± 0.21), and winter (2.15 ± 0.13). Additionally, the highest mean of QR values was in spring (3.95 ± 0.13), followed by autumn (3.22 ± 0.73), summer (3.13 ± 0.44), and winter (3.13 ± 0.11), while the highest mean of E values was in summer (0.75 ± 0.03), followed by autumn (0.75 ± 0.06), spring (0.69 ± 0.03), and winter (0.68 ± 0.05). The highest values of D and QR in summer and spring are because of caught high numbers of species S and numbers of species individuals N in these seasons, which can be explained by the movements of species individuals toward coast to bear and search for feeds, while the highest value of E was in winter due to the low numbers of species S. Estimates of diversity levels in fishery studies can be useful as changes can be detected in the structure of commercially exploited populations. Diversity indices are rarely applied in chondrichthyans fisheries.


#### **Table 4.**

*Average (mean ± SD) of diversity index D, qualitative richness factor QR and evenness factor E values for a total catch of cartilaginous fish, sharks catch and batoids catch during 2015–2016 [13, 14].*

#### **3.2 Cartilaginous fish landings in 2015 and 2016**

The average of total catch amounted during 2 years to 61,912 kg. The largest amount of catch was in the month of September (**Figure 3**), as it reached in the first year 18,182 kg and in the second year 9645 kg with an average of 13,914 kg/year, followed by October with an amount of 6413 kg in the first year and in the second year 8263 kg with an average of 8138 kg, while the lowest amount of catch was in the first and second years in January 2079 kg and 2410 kg, respectively, with an average of 2244 kg. The species *Hexanchus griseus* ranked first in terms of weight in the catch, as its quantity in the first and second years amounted to 15,963 kg and 17,129 kg, with an average of 16,549 kg, followed by the species *Carcharhinus plumbeus* with 14,445 kg and 7886 kg, respectively, in the first and the second year. The average was 11,166 kg*.* The total catch of the two species of sharks, *H. griseus* and *C. plumbeus*, constituted about 40% of the total average catch in both years (2015 and 2016). The percentage of cartilaginous fish landing during 3 years 2011 [22] and 2015–2016 [13] amounted to 3.68% of the amount of marine fish caught in Syrian marine waters. The species *Centrophorus uyato* (16.8%) occupied the highest percentage of cartilaginous fish catches (in terms of number), followed by *Rhinobatus cemiculus* (10.8%) and *Squalus* sp. (9.3%). In terms of weight, *H. griseus* occupied the highest percentage (30.6%), followed by *C. plumbeus* (25.2%), then *Rhinobatus cemiculus* (8.2%) [13].

As for the average total number of individuals, it reached 11,373 individuals. The largest number of individuals of the species in the catch in the first and second years was in May with an average of 1947 individuals (**Figure 4**). This was followed by April, with an average of 1578 individuals. As for the last month in terms of the number of individuals in the catch, it was in November, with an average of 463 individuals. Dasyatis pastinaca was the most numerous species in the catch; with an average of 1949

#### **Figure 3.**

*Distribution of the total weight of cartilaginous fish caught by month from Syrian marine waters during two consecutive years (2015–2016).*

**Figure 4.**

*Distribution of the total monthly number of cartilaginous fish caught from Syrian marine waters during two consecutive years (2015–2016).*

individuals, followed by Glaucostegus cemiculus, with an average of 1652 individuals. Seasonal changes in the catch of shark species on the Syrian coast are consistent with bycatch studies of sharks in the eastern Mediterranean [35], which recorded high rates of catch in the months of April (spring) and September (autumn), due to the water temperature preferences, which force the sharks to go to the depths toward the cooler water masses, especially in the regions tropical and subtropical, at these depths sharks are less likely to be caught by longlines, reflecting lower catch rates.

The by-catch of cartilaginous fish on the Syrian coast is rarely returned to the sea, especially in the last 10 years due to the high fish prices and the general decline in the amount of fish caught (bony and cartilaginous), unlike many Mediterranean countries that exclude part of the by-catch of cartilaginous fish. Commercial fishing of target species such as *C. plumbeus* and *Mustelus spp* is seasonal and peaks in spring and summer when the species move to shallower waters. The studies [13, 14] showed regular seasonal movement toward the shore, which may be associated with the seasonal reproductive cycle. There are several species of sharks and rays of different sizes caught, but mainly the juveniles are bycatch in coastal fisheries (**Table 1**). These classes include mainly Triakids, Dasyatids, *Aetomylaeus bovinus*, and the small juveniles individuals of Carcharhinids. For deep fisheries (trawl nets and longlines) many sharks are caught: *Scyliorhinus canicula*, *Galeus melastomus*, *Squalus plainvillei, Centrophorus granulosus*, *Mustelus spp*., and some rays are common in the catches. After 2012, due to the high prices of bony fishes and reduction of fuel, all rajids and other chondrichthyans are landed to be marketed.

The data mentioned in **Table 1** indicate the seriousness and great damage to which stocks of cartilaginous fish are exposed in the Syrian marine waters, as a large percentage of the caught individuals are juvenile, sometimes reaching 100 per cent in many species (*Isurus oxyrinchus*, *Alopias superciliosus*, *Oxynotus centrina*, *Mobula mobular*,

#### *Elasmobranches and Chimaeras in Syria: Past, Present, and Future DOI:http://dx.doi.org/10.5772/intechopen.110408*

*Torpedo marmorata*, and *T. nobiliana*), and most other species have juvenile individuals above 50 per cent of the total number of individuals caught. The coastal area between Burj Islam and Ras Ibn Hani, North of Lattakia (**Figure 2**) constituted a nursery area for two species of shark, and the coastal area between Latakia and Jableh (**Figure 2**) constituted a nursery area for six species of batoids [13] the above-mentioned. Many of the ecological characteristics in the Syrian marine water are under threat with areas of potentially high cumulative threats overcoming the western and eastern basins and fewer in the southeastern region [36]. The most important causes of current and future threats for the cartilaginous species in the Syrian coast and Levantine basin are habitat loss and degradation, pollution, overexploitation, eutrophication, maritime traffic, invasive alien species, human disturbance, climate change, and bycatch. Juvenile bycatch of commercial species may harmfully affect the future stock and catch levels. Nevertheless, the bycatch of endangered species such as elasmobranchs can have troublesome ecological consequences. These groups of species are susceptible due to their specific biological characteristics [37], especially elasmobranchs that are characterized by their slow growth rate, late maturity, and low fecundity compared to bony fish. Trawling is considered responsible for a large number of elasmobranch bycatches and discards throughout the world. Trawling is prohibited in the territorial marine waters of Syria. This method is problematic and leads to juvenile catches, important discards, and negative impact on the environment. Trammel nets and gillnets are the most frequently used by small Mediterranean fisheries and there is little use of gillnets targeting sharks.

#### **4. Conclusion**

Forty-nine cartilaginous fish species include 47 Elasmobranches and two chimaera species has been recorded in the Syrian marine waters. One species (*Pristis pectinata*) that has disappeared from Syrian waters during the last three decades, it is likely that this disappearance was caused by overfishing and the destruction of the environmental habitat due to the increase of various human activities. While previously mainly bycatch, elasmobranch is now being targeted directly by commercial fishing, due to declining catches of bony fishes on the one hand and increasing consumer acceptance of cartilaginous fishes on the other. The fish catch of cartilaginous fish (Elasmobranches) represents an average of 3.68% of the total catch of Syrian marine fish during 5 years of the field study (2011–2016). Trawlers, pelagic longlines and seines appear to be the greatest threat to elasmobranch species. Sharks of the families Hexanchidae, Carcharhinidae and Scyliorhinidae and batoids of families Dasyatidae, Rajidae, Glaucostegidae, and Rhinobatidae constitute the main and commercial part of the cartilaginous fish catch on the Syrian coast. There is an important habitat for much cartilaginous fish in the Syrian marine waters, and there are sustainable communities for six species of cartilaginous fish (two sharks and four batoids). Eleven species of Elasmobranches (six sharks and five batoids) are exposed to overfishing in the Syrian marine waters. There has been a significant decline in catches in terms of both quantity and body size (total length and disc width) of individuals caught over the past 10 years [13, 14]. The coastal area between Burj Islam and Ras Ibn Hani, North of Lattakia, constituted a nursery area for two species of shark, and the coastal area between Lattakia and Jableh constituted a nursery area for six species of batoids.

### **5. Recommendations**

Capture of 11 species of cartilaginous fish should be banned, six species of sharks: *H. Perlo*, *Centrophorus uyato*, *I. oxyrinchus*, *M. mustelus*, *C. Plumbeus*, and *H. griseus*, especially during the period from the beginning of winter to the end of summer, and five species of batoids: *R. clavata*, *Dipturus oxyrinchus*, and *D. tortonesei*, *P. violacea* and *R. marginata*, especially during the spring and summer seasons, by-caught species should be released. Preventing catching of the three migratory species; two sharks: *A. superciliosus* and *Isurus oxyrinchus* and one of batoids: *Mubula mobular* taking steps to collect reliable statistics on elasmobranch landings and bycatch should be a priority for shark conservation, additionally, conducting more biological studies on species that have not been studied in Syrian marine waters.

### **Conflict of interest**

The authors declare no conflict of interest.

### **Author details**

Adib Saad1 \* and Hasan Alkusairy2

1 Al Andalus University, Tartus, Syria

2 General Commission for Fisheries Resources and Aquatic Organisms, Jablah-Lattakia, Syria

\*Address all correspondence to: adibsaad52@gmail.com; adib.saad53@au.edu.sy

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Elasmobranches and Chimaeras in Syria: Past, Present, and Future DOI:http://dx.doi.org/10.5772/intechopen.110408*

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Section 3
