Three longline métiers have been studied in the Algarve: 1) small hook longline for inshore (less than 30 m) "white" sea breams (Sparidae), 2) small hook longline for deeper water (40 to 60 m) "red" sea breams, and 3) deep water (500 to 700 m) semi-pelagic longline for hake Merluccius merluccius (Linnaeus, 1758). Selectivity studies were carried out with three hook sizes in the first two cases: MUSTAD brand round bent Quality 2369 hooks, numbers 15, 13, and 11, baited with a standard-sized razor-shell Ensis siliqua (Linnaeus, 1758) bait. Four hook sizes (numbers 10, 9, 7, and 5) of STELL brand, round bent, eyed hooks were used in the semi-pelagic longline selectivity study, baited with a half of a standard-sized sardine. Some factors affecting catch composition and catch rates of the small hook longlines were also evaluated: bait, gangion length, setting time, fishing ground, and depth. Species diversity was relatively high, with 40, 36 and 27 species, respectively, in the three studies. However, the catches were dominated by a limited number of species. Catch rates (number of fish per 100 hooks) were variable (<5% - >20%), with a general decrease in catch rate with increasing hook size in all the studies. In general, the catch size distributions for the different hook sizes for each species were highly overlapping, with little or no evidence of differences in size selectivity. Hooks caught a wide size-range for each species, with few or no illegal-sized fish, in most cases. Some implications of these results for the management of multi-species, multi-gear fisheries are discussed.