Selectividade do anzol relativamente ao Pagellus bogaraveo (goraz) e ao Helicolenus dactylopterus dactylopterus (boca negra), pescado nos Açores, TA-183, 74 p
A bottom longline selectivity experiment was conducted, in June and July of 1989, in waters of Azores Islands. These experiments aimed at estimating hook selectivity, relative to blackspot seabream Pagellus bogaraveo, (Brunnich, 1768), presently the most important species in Azores bottom longline selectivity fishery, and rockfish Helicolenus dactylopterus dactylopterus, (Delaroche, 1809), an associated species.
Hooks of 9mm., 12mm., and 18mm. were used (hook size refers to the perpendicular distance between hook point and shank, fig.5). Of several methods available in the bibliography for estimating selectivity curves, only the modified Ishida method (Manzer et al., 1965) was successfully used. For all hook sizes and for both species, the selectivity curves estimated from the size range of fish caught were of sigmoidal type, similar to the typical trawl selection curves. However, for blackspot seabream the selectivity curve may be more like a flat-topped curve. Assuming sigmoid type curves, the selectivity curves for both species and all hook sizes may be adequately defined by the lenght of first capture (lenght corrsponding to a selectivity of 50%, S50% ) and selection range (difference between the lenghts corresponding to 75% and 25% S75% - S25%).
The values of this parameters for both species and hooks used are:
- Hook of 9mm., S50%= 19cm, and S75% - S25%= 22cm. – 16cm.
- Hook of 12 mm., S50%= 26 cm, and S75% - S25%= 30cm. – 22cm.
- Hook of 18 mm., S50%= 38 cm, and S75% - S25%= 43 cm. – 33cm.
- Hook of 9 mm., S50%= 10 cm, and S75% - S25%= 11cm. – 9 cm.
- Hook of 12 mm., S50%= 14 cm, and S75% - S25%= 15 cm. – 13 cm.
- Hook of 18 mm., S50%= 21 cm, and S75% - S25%= 23 cm. – 19 cm.