Pingers as Cetacean Bycatch Mitigation Measure in Bulgarian Turbot Fishery

Bycatch (incidental catch) of small cetaceans is a major problem in a number of gillnet fisheries around
the World and harbour porpoise (Phocoena phocoena) is one of the most heavily affected species. Pingers
(acoustic deterrent devices) are recommended as mitigation measure to decrease bycatch rate. First largescale
use of pingers (Future Oceans 10 kHz and 70 kHz models) was made during standard turbot fishing
operations in Bulgarian waters of Black Sea in 2019 during spring and summer – respectively before and
after turbot fishing ban (15 April – 15 June). Four vessels have been involved with part of the nets being
without pingers – control and other parts fitted with pingers – active. A total of 105 cetaceans (Phocoena
phocoena relicta – 104 and Tursiops truncatus ponticus – 1) were recorded as bycatch in both control and
active nets in spring and summer. Bycatch rates in active and control nets have not shown significant difference
in both seasons. Significant increase in bycatch was registered in both active and control nets from
spring to summer: 3.25 to 38.76 and 1.55 to 58.58 ind.km-2.day-1, respectively.