Fig 1.
Longline types used by the artisanal demersal fleet.
Floated: “Piedra–Bola” configuration composed by a sequence of floats and weights. Non-floated: fishing gear typically used by small-scale vessel where only weights are attached to the mainline. The position of the time-depth recorders (TDRs) is also indicated by a red square in the floated (Float, Mid and Weight positions) and non-floated (Mid) longlines. Drawing by Toni Mulet.
Table 1.
Characteristics of the fishing gears used in demersal longliners in which the sink rates were recorded.
Fig 2.
Design of the tori line used in the trials.
Drawing by Toni Mulet.
Fig 3.
Number of bait attacks in the night setting and tori line trials (a and b). Attacks are shown per 1000 hooks set. In each trial, paired longlines were set; “Control” denotes the settings without mitigation measure. The middle line of boxes shows the median and the filled circles represent outliers.
Table 2.
Bait attacks registered by species (those most susceptible to bycatch) and mitigation measure.
Fig 4.
Total number of attacks registered at different distance intervals from the vessel stern.
Shearwaters (triangle; Scopoli’s, Balearic and Mediterranean shearwater) and gulls (square; Audouin’s and yellow-legged gulls) were considered separately. Dark refers to the control settings without tori line (No deterrent, n = 12 settings), while grey refers to experimental settings with the tori line installed (Tori line, n = 12). Dashed line denotes the limit of the area covered by the streamers.
Table 3.
Fish catches registered for those mitigation measures that involved a change in the longline configuration and fishing practices.
Table 4.
Time and sink rate to 10-m depth and 10-m access window by longline configuration.
Fig 5.
Sink rates of the baited hooks in the first 10 meters depth.
The values (mean + CI 95%) came from the hooks located at (1) different positions inside of the float-weight sequence (Float = near to the float, Mid = between the float and the weight, Weight = near to the weight) and (2) longline sections (initial, middle and final). The hook sink rates were collected in the same vessel and from gear with a “Piedra–Bola” configuration (Floated 1). Numbers inside bars denote the sample sizes.
Fig 6.
Sink-rate comparison of the longlines set with or without additional weights.
The values (mean ± CI 95%) were registered in the control (n = 13) and experimental longlines with an added weight above hooks of 10 g (n = 14) and 20 g (n = 10). Data were collected from hooks located in the middle section of the longline and near to the floats.