Ali İşmen

Nematode infection in the whiting Merlangius merlangus euxinus off Turkish Coast of the Black Sea

Abstract The endoparasites of whiting, Merlangius merlangus euxinus from the Turkish Coast of the Black Sea were investigated during the years 1990–1993. Only the endoparasite, Hysterothylacium aduncum (Nematoda: Anisakidae) was recorded in all visceral organs examined. The prevalence and intensity of H. aduncum were significantly higher in the warm season (July–August) than in the colder period (January–February) (P 0.01).

Age, growth and reproduction of the common stingray, Dasyatis pastinaca from the North Aegean Sea

Abstract Age, growth and reproductive parameters of the common stingray, Dasyatis pastinaca, in the North Aegean Sea are reported. Age was estimated by counting the growth rings of thin sections of vertebral centra from 83 fish (83–114 cm total length, TL). The relationship between TL and the vertebral centrum ratio (CR) was curvilinear, therefore a quadratic model was preferred to describe between the vertebral centrum growth and body growth. The oldest common stingray were 16 years (females) and 10 years (males), which corresponded to total lengths of 114 and 83 cm, respectively. Estimates of von Bertalanffy growth parameters suggest that males attain a slightly larger asymptotic total length (L∞=188.49 cm) than females (L∞=119.96 cm) and grow more slowly (K = 0.065 year−1 and 0.086 year−1, respectively). The size at which 50% (TL50) of males and females were sexually mature at 62.5 cm TL.

REPRODUCTIVE BIOLOGY OF THE SPOTTED FLOUNDER, CITHARUS LINGUATULA (ACTINOPTERYGII: PLEURONECTIFORMES: CITHARIDAE), FROM SAROS BAY (NORTHERN AEGEAN SEA, TURKEY)

Background. Understanding the reproduction of the spotted flounder, Citharus linguatula (Linnaeus, 1758), has been considered a major step toward understanding its population dynamics, especially, in the northern Aegean Sea. So, the presently reported study aimed to study the reproductive biology of C. linguatula and provided the first data of its fecundity. Materials and methods. T his study was carried out between September 2006 and September 2008 in Saros Bay (Northern Aegean Sea, Turkey), which had been closed to trawl fishing since 2000. The gonadosomatic index, length at maturity (L50), and absolute fecundity were analysed. Results. The elevated GSI values observed, suggested the spawning period was from September to November. The length at maturity (L50) was at 15.0 cm TL for females and 14.0 TL cm for males. The relations between the absolute f ecundity and total length, total weight, and age of the spotted flounder females were estimated as Fa = 0.1878TL 3.29 , Fa = 58.515TW + 36.453, and Fa = 887.59A - 389.43, respectively. Conclusion. The identification of reproductive strategy is necessary to obtain a better understanding of its biology.

First Record of Caligus zei (Copepoda: Caligidae) on John Dory, Zeus faber in Turkish Marine Waters

The parasitic copepod, Caligus zei Norman and Scott T., 1906 was found on the John dory (Zeus faber Linnaeus, 1758) during a demersal fish stock assessment in the Sea of Marmara during April 2017. This is the first report of this copepod in Turkish marine waters. Descriptions of the male and female Caligus zei, including details of appendage structure of recovered specimens, are provided.

Length-Weight Relationships of three Fish Species in the Sea of Marmara, Turkey

Length-weight relationships (LWRs) are investigated for three fish species which sampled with a beam trawl between September 2011–July 2014 in the Sea of Marmara, Turkey: Callionymus maculatus (Rafinesque, 1810), Gaidropsarus biscayensis (Collett, 1890) and Lepidorhombus boscii (Risso, 1810). The data of length-weight relationship were found with W = 0.0042*L3.13(n = 20), TW = 0.0090*TL2.74 (n = 120) and TW = 0.0108*TL2.92 (n = 19), respectively. According to LWRs results C. maculatus showed positive allometry, G. biscayensis presented negative allometric growth and L. boscii isometric growth. The information about this issue are reported for the first time in the Sea of Marmara for such species. In this way this study is important with new results.

Catch composition of set net (fixed stake trap) fisheries in the coastal waters of Saros Bay, North Aegean Sea

Set net (fixed stake trap) fisheries are performed according to traditional methods in the coastal waters of Saros Bay, North Aegean Sea (Turkey). These fisheries systems are the gear which is passively constructed for catching fish in shallow waters with sandy–muddy substrates. We studied the fish species caught by four set nets between April and August (set net fishing season) in 2010 – 2012. In total, 37 fish species belonging to 22 families were captured from the study areas. Clupeidae (45.65%), Carangidae (16.51%) and Sparidae (13.24%) were determined as dominant families, and the total catch amount of dominant species, Sardina pilchardus (27.18%), Sardinella aurita (18.47%) and Trachurus mediterraneus (16.42%), comprised 62.07% of the total catch. Species diversity (H′log2) and evenness (J′) index values calculated for all set nets were 0 – 1.566 and 0 – 0.999, respectively. This study provides some general information about the status of set net fisheries as well as the diversity and abundance of the species caught from the set nets.

Age, growth, and reproduction of Dentex maroccanus (Actinopterygii: Perciformes: Sparidae) in the saros bay (North Aegean Sea)

In the Mediterranean, sea breams (Sparidae) are represented by 22 species belonging to 10 genera (Arculeo et al. 2003), of which 14 species are also found in the north Aegean Sea (Ismen et al. unpublished**). The Morocco dentex, Dentex maroccanus Valenciennes, 1830, is an important demersal commercial sparid species inhabiting depths ranging from 20 to 500 m and can be found throughout the Mediterranean (absent in the Adriatic), especially in the areas featuring gravel or rubble bottoms. Morocco dentex ecologically prefers deep and highersalinity waters. This species is distributed in the southern and eastern Mediterranean (Maravelias et al. 2007) and the Atlantic (Bay of Biscay to Gulf of Guinea) (Froese and Pauly 2014). The major studies on the Morocco dentex in the Mediterranean have been carried on its western basin and concerned the age, growth, feeding, reproduction, and distribution (Nguyen and Wojciechowski 1972, Mennes 1985, Lamrini and Bouymajjane 2002, Chemmam-Abdelkader et al. 2004, Maravelias et al. 2007). In the Aegean Sea (Saros Bay), a basin of the eastern-central Mediterranean, the sparids represent important components of the demersal fish stock and are generally caught by trawl, long line, and trammel nets. There is currently no information concerning the age, growth, and reproduction of this species or regarding the state of stocks in the Aegean Sea. Aspects concerning to the length–weight relation have been investigated, but these studies did not provide any population relations (Karakulak et al. 2006, Ceyhan et al. 2009). As far as we know, this is the first report that provides a comprehensive picture of population parameters (length–weight relation, age, growth, reproduction, fecundity, first maturity length) of Dentex maroccanus, with the aim of generating sufficient information to improve future stock management and sustainable fishing. ACTA ICHTHYOLOGICA ET PISCATORIA (2014) 44 (4): 295–300 DOI: 10.3750/AIP2014.44.4.03