REVIEW OF THE SIZE DISTRIBUTION OF CAGED EASTERN BLUEFIN TUNA (THUNNUS THYNNUS) IN TURKISH FARMS 2014-2020

Abstract

During the 2018 stock assessment of East-Bluefin tuna it was noted substantial changes in the size distribution of caged bluefin in Turkish farms in the period 2017/2018. The size distribution of the caged fish is measured by the Stereo-camera systems when transferred from the towing vessel to the farm cages. A review of the time series of available stereoscopic measures (2014- 2020) confirmed that changes in the overall size-distribution of caged fish. Since 2017, the proportion of fish size 100-140 SFL cm increased substantially while the proportion of larger fish >200 SFL cm has reduced. Analyses with auxiliary data indicated that the fishery has concentrated in the months of June – July, while no spatial expansion of the PS fleet has been observer, however the number of fishing operations and number of PS vessels participating has increased to complete the allocated BFT catch in recent years.