Catching efficiency and species selectivity of bottom longline equipped with kirbed and classical type hooks

ABSTRACT PhD THESIS CATCHING EFFICIENCY AND SPECIES SELECTIVITY OF BOTTOM LONGLİNE EQUIPPED WITH KIRBED AND CLASSICAL TYPE HOOKS Erhan AKAMCA DEPARTMENT OF FISHERIES, INSTITUTE OF NATURAL AND APPLIED SCIENCES UNIVERSITY OF ÇUKUROVA Supervisor :Prof. Dr. Abdurrahman POLAT Year: 2004, Pages: 86 Jurry :Prof. Dr. Abdurrahman POLAT :Assoc.Prof. DrNuri BAŞUSTA : Asst. Prof. Dr. Mahmut Ali GÖKÇE :Assoc.Prof. Dr. Mehmet ÇELİK :Asst. Prof. Dr. Yalçın TEPE The study was carried out in Yumurtalık Bight between August 2001 and September 2002. During the experimental fishing, total of 15600 hooks in total were used and at the end of study 390 fish belonging to 25 species and 15 families were caught. It was determined that the fish caught were dominantly belong to Sparidae (6 species and 267 individuals), Serranidae (5 species and 87 individuals) and Carangidae families (2 species and 2 individuals) both by species and also by the number of the individuals. Other individuals caught (38 individuals) were belong to 10 families and each represented by one species in each family. Catching efficiency (as number) was determined for longline used in experimental fishing. In the study, 74812, 50 g each fish were caught in total and the largest group by its weight (22128, 2 g) and the rate (30%) was sea bream. Fish amount caught by unit effort was 4,796 kg / 1000 hook when all the fish species was taken into account. Although catching efficiency of kirbed hooks was higher than that of classical type for sea bream and for some other fish, it was not significant in white sea bream, dusky grouper and white grouper. It was determined that shrimp bait was preferred by white sea bream and common cuttlefish was mostly preferred by dusky and white grouper and common cuttlefish was most preferred bait by white grouper statistically (p<0,05). Observations revealed that common cuttlefish was better at staying on hooks than shrimp. However, staying on hooks decreased with the increase of hook size. Hook size was an important factor determining the catch rate and increasing hook size reduced catch rate for all species. Depending on the increasing hook size in sea bream, mean fish length also increased. Moreover, it is determined that the mean length of the fish caught by classical type hooks was larger than that of the fish caught by kirbed type hooks. Smaller hooks in sea bream caught the individuals under landing size. Selectivity curves revealing increasing lengths related to hook size were obtained. Rise İn catching size depending on hook size was observed. It was determined that fishing size and selectivity curves varied according to hook types. It was determined that the hook types and sizes used were effective on selectivity of sea bream and classical type hooks caught larger fish than the kirbed type. Key words: Long line, hook type, bait type, hook size, selectivity. n