Aytaç Özgül

A preliminary study on the survival of brown comber, Serranus hepatus (Actinopterygii, Perciformes, Serranidae), escaping from the codend of a bottom trawl

Demersal trawling in Turkish Coasts is performed on the grounds where more than 50 species encounter the gear (Tosunoglu et al. 2003b). Similarly, it has been reported that trawl fisheries is generally multispecies in the Mediterranean Sea (Tudela 2004). A considerable amount of fishes such as annular seabream, (Diplodus annularis) (see Ozbilgin et al. 2005), black goby (Gobius niger), red bandfish (Cepola macrophthalma) (see Lamprakis et al. 2003) end up as discard or bycatch in the bottom trawl fishery that targets the marketable demersal species. One of the reported discard fishes captured by bottom trawls (Lamprakis et al. 2003) is brown comber, Serranus hepatus, which is a species of a minor commercial (Froese and Pauly 2009). Minimum landing size (MLS), which is designed to allow escapement of undersized fish, for this species is not specified in the Turkish Fisheries Regulations (Anonymous 2008). Discard of trawl fisheries are commonly a result of conventional diamond mesh cod-ends regarding MLS of the target species (Graham and Kynoch 2001). In Turkish waters, large amount of bycatch and discard where reported by Tosunoglu et al. (2003b) and Metin et al. (2005). According to the present legislation, minimum trawl codend mesh sizes are 40 mm for the Black Sea and 44 mm for the Aegean Sea and the Mediterranean Sea (Anonymous 2008). The fate of fish such as brown comber, in terms of unaccounted fishing mortality, is ACTA ICHTHYOLOGICA ET PISCATORIA (2010) 40 (1): 27–36 DOI: 10.3750/AIP2010.40.1.04

Two experimental fish aggregating systems (fads) in the Aegean sea: their design and application

Two steel spar buoys were constructed and moored in 50 and 100 m deep of water in the Aegean Sea to support recreational fisheries. The first FAD was deployed at coordinates 38°01´48´´N 26°58´02´´E and at a distance of 3 nautical miles from the shoreline. The other FAD was moored at 1.1 nautical miles from the shoreline at coordinates 38°03´11´´N; 26°59´01´´E. An anchor (1.2x1.2x0.8 m3) weighing approximate 2.76 metric ton, made of reinforced concrete, was used to hold a FAD weighing approximate 1.5 metric ton. Hardware and connections of FADs, ropes, mooring calculation and anchor design were made. The interaction between the forces of wave and current and FADs in those waters was investigated. In the experiment, all forces (drag force, buoyancy force etc.) acting on FADs were calculated. It is proposed that the construction of the FADs should take the following design criteria into consideration: wave and current, forces related to the FADs, deployment depth, mooring hardware and ropes. This knowledge provides an important reference for stakeholders performing projects aiming to increase the performance and service life FADs.

A new artificial reef design for octopus (Octopus vulgaris cuvier, 1797) in the Aegean sea and preliminary results

This study was carried out in the Gulf of 0zmir in the Aegean Sea between June 2006 and November 2008. The purpose was the creation of a new concept of the artificial reef for Octopus vulgaris, with a view to establishing new artificial reef sites to be used in the fisheries management of this species (MPA, NTZ or fishing areas). First, the main characteristics of natural octopus nests were recorded (entrance width, length, etc.) by divers. These characteristics were used in the construction of new octahedral artificial reef blocks. The blocks were made of reinforced concrete, in a shape like that of an inverted pyramid, with an upper surface of 100x100x25 cm3 and a lower one of 60x60 cm2. Four cylindrical holes each with two ellipsoidal openings were placed in one face and in the lateral edge of the octo-block, to serve as the entrances to the artificial nest. Each nest has a volume of 5000 cm3. Eighty octo-blocks were deployed as artificial reefs at 10 m from each other at 15 different depths at two sites by divers with the help of the winch of the R/V EGESUF. These artificial octo-reefs were censused by direct observation. Twenty-eight octopuses were sampled at the end of 25 dives. Minimum mantle length of the octopuses was 75 mm and the maximum 249 mm, with an average of 152.71 mm. The average total length was calculated to be 918.57 mm. The weight of the specimens was between 244 g and 7140 g with an average of 2335.43 g. The results showed that both sites were inhabited by octopuses coming from the artificial reefs, which used them as nests. These nests seem to have constituted special places for fisheries management and will permit the assessment of reserve areas or marine protection areas (MPA), thus opening up a new perspective for Turkish fisheries.

Comparison of fish community structure on artificial reefs deployed at different depths on turkish Aegean sea coast

Deployment depth of artificial reefs is one of the most important issue in planning stage and future success. Most of the studies aimed at determination of fish community around artificial reefs were conducted mainly 10-25m depths in Mediterranean and Aegean Sea. The goals of this study are determine and compare of fish community structure around artificial reefs which deployed 20, 30 and 40 m depths. Underwater visual census technique was used to determine fish species, number of individual and size estimation. There was no statistical difference (p>0.05) in mean fish biomass and number of individual between the depths. But mean species number was significantly greater on 20 m in comparison to 30 m and 40 m depths (p<0.05). Furthermore, calculated values of Jaccard and Bray-Curtis indexes showed low similarity (min. 3% - max. %37) between depths.