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    Selectivity of PE and PA material codends for rose shrimp (Parapenaus longirostris) in Turkish twin rigged beam trawl fishery
    (Elsevier Science Bv, 2006) Deval, Mehmet Cengiz; Bok, Tomris; Ates, Celal; Ozbilgin, Hoseyin
    This study investigated the differences in the selective properties of 32 turn nominal polyethylene (PE) and 32, 36, 40 and 56 mm, nominal polyamide (PA) codends in beam trawl fisheries targeting rose shrimp, Parapenaeus longirostris, in the Sea of Marmara, Turkey. Data were collected in spring 2005 onboard a commercial trawler, on commercial fishing grounds. Selectivity data were collected using the covered codend method in two twin beam trawls in every haul. Using this method, four selection curves could be obtained in one haul. Selectivity parameters were calculated by fitting a logistic function using maximum likelihood. The L-50 values of 32, 36 and 40 mm PA codends were found to be 9.1, 10.2 and 12.6 cm, respectively. Due to retention of only a few specimens, realistic selectivity parameters could not be calculated for the 56 mm PA codend. Mean L-50 decreased with a change in mesh material from PA to PE. The lowest L-50 (8.0 cm) was found for the 32 mm PE material codend. This study has shown that for rose shrimp the 32 mm PA diamond mesh codend is not appropriate for the first maturity size (FMS) of 10 cm for rose shrimp in the Turkish twin rigged beam trawl fishery. In addition, the PE netting material provides a significantly lower L-50 value than the PA netting material. (c) 2006 Elsevier B.V. All rights reserved.
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    SILVER-CHEEKED TOADFISH, LAGOCEPHALUS SCELERATUS (ACTINOPTERYGII: TETRAODONTIFORMES: TETRAODONTIDAE), CAUSES A SUBSTANTIAL ECONOMIC LOSSES IN THE TURKISH MEDITERRANEAN COAST: A CALL FOR DECISION MAKERS
    (Wydawnictwo Akad Rolniczej W Szczecinie, 2015) Unal, Vahdet; Goncuoglu, Huriye; Durgun, Denizcan; Tosunoglu, Zafer; Deval, Mehmet Cengiz; Turan, Cemal
    Background. While some Lessepsian species provide economic benefits for Mediterranean fisheries, others cause economic losses. Lagocephalus sceleratus known as silver-cheeked toadfish poses a great risk to human health if consumed economic losses for fishers by damaging their fishing gears. This study aims to determine the socio-economic impact of silver-cheeked toadfish, with regards to its impact on biodiversity and socio-economic factors for small-scale fisheries. Materials and methods. Face-to-face interviews were completed with a total of 261 fishers from Izmir in the Middle Aegean region to Hatay in the Eastern Mediterranean region, to determine the problems arising from the presence of silver-cheeked toadfish species in the ecosystem and the resulting associated economic losses for a 1-year from 1 January to 30 December 2011. The elements, which should be taken into account in calculating silver-cheeked toadfish related economic losses, are related to fishing gear, labour and the associated losses in catches. However, losses associated with silver-cheeked toadfish predation were beyond the scope of this study. Results. Almost all fishers (91%) agree that silver-cheeked toadfish is a major problem, 82% believe that silver -cheeked toadfish negatively affects biodiversity, and 89% believe it lowers efficiency of their catches. Calculated silver-cheeked toadfish related losses were: 1300 TRY**. (approximate to 442 EUR) per year, per fisherman; 263 296 TRY (approximate to 89 521 EUR) per year, in total, for the interviewed fi shers (261), and 204 fi shers suffered economic losses relating to this species; which caused total losses of 6 033 577 TRY (approximate to 2 051 416 EUR) per year in total for the 4719 fi shers, which were 78% of all fi shers (6051) in the study area. Two-thirds of the study respondents think that the most effective way to battle this problem would be to try to eliminate this species from Turkish waters. Among them, 32% of the fi shers believe the most suitable gear to eliminate L. sceleratus from the marine ecosystem is the purse seine and 61% consent to fish L. sceleratus for 4 TRY each as a target species. Conclusion. To start a bounty system and a premium payment for each pufferfish caught will both help to reduce negative impact of the species on the ecosystem and provide an extra income for the fishers.