Altan Lök

The effects of different cod-end design on bottom trawl selectivity in Turkish fisheries of the Aegean Sea

Abstract The effect of different cod-end designs on bottom trawl selectivity was studied using the hooped cod-end cover method. The selectivities of three different cod-ends: standard, 15% shortened lastridge rope and narrowed circumference (to 120 mesh from 150 mesh), were measured for red mullet ( Mullus barbatus L., 1758) and annular sea bream ( Diplodus annularis L., 1758) in Turkish territorial waters of the Aegean Sea in June and September 1994. Selection curves and selection parameters were calculated using a logistic model. 50% retention lengths and selection factors for red mullet were higher for the shortened lastridge rope case and narrow cod-end than the standard cod-end. There was no significant difference for annular sea bream. This can be explained by the body shape differences of the two species. The effects of different cod-end designs on the selectivity are discussed.

Turkey: A New Region for Artificial Habitats

The scientific study of artificial reefs is a comparatively new concept in Turkey, starting with the introduction of a reef at Hekim Island (Fig. 1) by the Aegean University Fisheries Faculty in 1991 and followed by the placing of a reef off Foca by Nine September University in 1993. During the 1980s small-scale reefs were deployed by diving clubs and universities, but results remain unpublished. There has also been an attempt by the Izmir Metropolis Municipality to prevent illegal trawling and to generate new fishing opportunities for sport anglers by depositing ten old trolley-bus bodies in Izmir Bay in 1989. Echo sounder studies have shown, however, that the effective height of these last structures has been reduced from 4 m to 1.5 m by sedimentation. A later project carried out by Cesme Municipality in 1995 to improve recreational fishing is too recent to have been fully evaluated. No artificial reef project in Turkey at present is being funded nationally or regionally; existing projects are all based on small-scale reefs.

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.

Mortality of Common pandora (Pagellus erythrinus Linnaeus, 1758) escaping from demersal trawl codends: Water temperature effect

Ocak-Şubat 2011 ve Eylul 2012 tarihleri arasinda toplam 24 trol cekimi yapilmistir. 800 gozlu kesimli dip trol agindan kacan kirma mercan ( Pagellus erythrinus ) bireylerini yakalamak icin ortu kullanilmistir. 40 mm kare, 44 ve 50 mm rombik gozlu trol torbalarindan kacan bireylerin olum oranlari 7 gun boyunca yapilan gozlemler ile tespit edilmistir. Ayrica su sicakliginin kirma mercan olumleri uzerine etkisi de incelenmistir. Kirma mercan’in olum oranlari dusuk bulunmustur ( 0,05 ) . Her iki mevsim icin de ag goz boyutu ve sekli istatistiksel olarak onemli bir faktor degildir (p>0,01) .

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.