The catches and discards of trawlers, seiners and trammel netters were stud
ied in the Algarve (southern Portugal) using observers onboard commercial f
ishing vessels. Species diversity was high, with 236 species recorded as oc
casionally, frequently or regularly discarded. Mean discard rates per trip
were 0.13, 0.20, 0.27, 0.62 and 0.70, respectively, for trammel nets, demer
sal purse seines, pelagic purse seines, fish trawls and crustacean trawls,
with high variability in terms of discard volume and discard rate, This was
especially so for se ncrs where from 0 to 100% of the total catch might be
discarded. No significant relationships were found between discard quantit
y or discard rate and characteristics of the fishing vessels sampled within
each metier (total length, TAB, hp, kW). Based on the above discard rates
and the official landings, it was estimated that in 1996, Algarve trawlers
discarded 9000-13000 tonnes (t) while seiners discarded 5500-8200 t. Discar
ding practices in these fisheries are reviewed and the reasons for discardi
ng are presented by species and metier basis. The results support the need
for more studies on the factors contributing to discarding, variability in
discard quantities and rates, the fate of discards and their importance to
the marine ecosystem, and on ways of reducing by-catch and discarding in th
ese fisheries.