Depredation and Incidental Catches on Longline Fishery of Southern Mozambique - Preliminary information on ecosystem issues based on observer on-board sampling

In this report, the level of depredation on longline fishery of Sothern Mozambique and the level of impacts of fishery itself on sharks, seabirds, marine mammals and turtles were assessed. The report comes as a preliminary result of deployment of observers on board of Mozambique national longline fleet.
Results indicated that depredation was responsible for discarding of about 13% of the total target species caught in longline fishery, which is composed by swordfish, bigeye tuna and yellowfin tuna. Generally it is suspected that sharks are the main group of predators responsible for depredation in southern Mozambique longline fishery. A total of ten shark species were caught during fishing operations, including oceanic whitetip shark, blue shark and dusky shark as the main shark species. In total sharks represented 12 % of the total catch in numbers. Another charismatic species caught during fishing operations were marine turtles. On total it was observed two leatherback turtles and one green turtle giving an estimated bycatch ratio of 0.14 per 1000 hooks.
Assuming that the fishery is on initial phase and due to the temporal constriction of the observations, the findings of this report cannot be assumed as conclusive. There is a need to continue deploying observers in this fishery, which fleet is on growing, to have a better evaluation of associated ecosystem issues.