Untitled - CNR

Fishery and Sea ResourcesFigure 3: Longline technical parameter affecting turtle bycatch.interaction depth with longline is the upper20 m of the water column. The potentialmortality rate in bottom longlines about(40%) seems to be concentrated on juvenilesbecause bigger specimens are able todrag the main line with its weights up tothe surface, while juveniles cannot reachthe surface to breathe [13]. Finally turtlemortality seems to be correlated to the timesetting: the longer the set time, the moreturtles captured die. Loggerhead bycatch inbottom trawl probably occur during towingoperations when turtles are foraging on thebottom. Direct mortality is very low even ifa single turtle can be recaptured more thanone time. Mortality by trawling is due toforced apnoea, thus longer or faster towsare responsible of higher mortality rates.As it concerns passive nets it is realisticto consider that this fishing gear has thepotential to be more harmful than pelagiclonglines and bottom trawl. Studies ongillnets and trammel nets found that thesegears are responsible of high turtle directmortality (from 50 to 100%, Table 1).Drowning is the main reason for the sea turtlemortality since turtles get entangled innets when trying to feed on fish previouslycaptured (Table 1). To this, environmentalparameters could affect sea turtle mortality:high water temperature (such as inthe North Africa countries) associated withhigh metabolic rates, can strongly reducethe resistance to forced apnoea.4 Mitigation measuresThe identification of methods aimed at reducingor preventing sea turtle bycatch is ahigh priority for fishery managers. Themost obvious and simplest approach tosolve the bycatch problems is the reductionof the fishing effort, even if this is often nota practical or viable option for economic,1844