The Determination of mesh size for some commercially important demersal fish species captured by deep trawl net at Babadıllimanı bright (Silifke-Mersin)

ABSTARCT PhD THESIS THE DETERMINATION OF MESH SIZE FOR SOME COMMERCIALLY IMPORTANT DEMARSAL FISH SPECIES CAPTURED BY DEEP TRAWL NET AT BABADILLIMANI BIGHT (SHJFKE-MERSIN) Caner Enver OZYTJRT DEPERTMAN OF FISHERIES INSTITUTE OF NATURAL AND APPLDZD SCTENCES UNIVERSITY OF ÇUKUROVA Supervisor : Prof. Dr. Dursun AVŞAR Year : 2003 Pages : 124 Jury : Prof. Dr. Dursun AVŞAR Prof. Dr. Ercan SARfflAN Prof. Dr. Abdurrahman POLAT Assoc. Prof. Dr. Ali İSMEN Assoc. Prof. Dr. Nuri BASUSTA This study was carried out at Babadillimani Bight in between a period of May 1999 and April 2000. Length at first maturity, spawning period and selectivity factor for 5 commercially important demersal fish species were determined. The results obtained for these species are as follows: length at first maturity for Saurida undosquamis was 12.8 cm; spawning were three times in a year which were April through May as the first with the following of September through October and November through December as the second and third respectively. Selectivity parameter (%Lso) for this species was found to be as 10.41 cm. Length at first maturity for Mullus barbatus was 10.5 cm, spawning period was between May through August, the (%L5o) value was 7.73 cm. Length at first maturity for Upeneus moluccencis was 10.4 cm, spawning period was between July through November, the (%Lso) value was 8.83 cm. Length at first maturity for Upeneus pori was 10.0 cm, spawning for this species were three times in a year which were May as the first with the following of July through August and October through December as the second and third respectively. The (%L5o) value for mis species was 9,18 cm. Length at first maturity for Spicara maerta could not be determined. However spawning period was between of February and July, and the (%L50) value was found as 7.85 cm. When the spawning periods obtained for all species taken into consideration for Eastern Mediterranean, the restriction of the fishing season should be placed between a period of April 1st through November 1st as a result of present study. When selectivity factors and length at first maturity obtained for these species were taken into consideration and evaluated all together, a suitable mesh size as an alternative could not be determined against the legal mesh size which was currently in usage as 22 mm. However, determination of the cod-end mesh size and even cod-end design for these species mat were in consideration, first, a need for very derailed selectivity studies observing the behavior of the Saurida undosquamis in the cod-end was suggested. Key Words: Deep Trawl, Cod-end Selectvity, Demersal Species, Spawning Season, Northeastern Mediterranean. II