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A comparision of monofilament gillnet and small hook longline selectivity in a multispecies artisanal fishery in the Algarve, southern Portugal.
No full textAs part of the ongoing studies concerned with the small-scale fisheries of the South of Portugal, experimental fishing was carried out with monofilament gillnets and small hook longlines within the same area. Sixty-two species were caught, of which 20 were common to both gears. Pronounced differences in terms of the relative importance of different species in the catches were observed. Size selection patterns also differed, with highly overlapped hook catch distributions and few species showing evidence for size selectivity. In contrast, strong selectivity was characteristic of species which tend to be wedged in gillnets. Whereas smaller stretched mesh sizes (particularly 40 and 50 mm) caught significant numbers of illegal sized fish, this was mininmal in the longlines. Some implications for management are discusse
Abundance and distribution pattern of Spanish Mackerel (Scomber japonicus) and Mackerel (Scomber scombrus) in the Portuguese continental waters (ICES DIV. IXa).
No full textSpecies and size selectivity in a Portuguese multispecies artisanal long-line fishery
No full textThe species and size selectivity of long-lines using small hooks were studied off the\ud
south coast of Portugal using ‘‘Mustad’’ brand round bent, flatted sea hooks (Quality\ud
2316 DT) numbers 15, 13, and 11 baited with razor shell clam (Ensis siliqua). Hook\ud
numbers 13 and 11 are 49 and 109% larger respectively than number 15 hooks in terms\ud
of overall size (maximum width#maximum length). A total of 39 900 hooks were\ud
fished in 45 sets and 35 species of fish and cephalopods were caught. As a group, 13\ud
species of sea breams (Sparidae) dominated the catch by numbers (58%) and weight\ud
(73%). Six species of sea breams, along with the greater weever fish (Trachinus draco)\ud
accounted for 81% of the total catch by weight, with the common or white sea bream\ud
(Diplodus sargus) being the most important (29%). Catch size distributions by hook\ud
size were, in general, highly overlapped for all species and hook size had little apparent\ud
effect on minimum size at capture. All hooks caught a wide range of sizes per species,\ud
but the catch rate (number of fish per 100 hooks) was significantly lower for the largest\ud
hook. Except for the black sea bream (Spondyliosoma cantharus), capture of illegally\ud
sized or immature fish was minimal. Small increases in average size with hook size were\ud
evident for four species: Diplodus sargus, D. vulgaris, Lithognathus mormyrus and\ud
Serranus cabrilla. No differences in size selectivity were detected for Boops boops,\ud
D. annularis, Spondyliosoma cantharus and Trachinus draco. A skew-normal model\ud
adequately described differences in size selectivity in five of six species
O Estudo de aves marinhas em Portugal
Get PDFIn this paper we review some of the most important\ud
studies of seabirds of Madeira, Azores and Portugal.\ud
There has been a considerable increase in the interest\ud
in seabirds in the last ten years, resulting in a high\ud
number of papers published in this period. A project\ud
conceming the study of Cory's Shearwater breeding\ud
in Portugal is also presented
Seasonal and interannual variability of coastal upwelling along northwest Africa and Portugal from 1981 to 1991.
No full text
Variation in measurements of Cory's shearwater between populations and sexing by discriminant analysis
No full textBiometric data were collected at three colonies of the Atlantic race of Cory's Shearwater Calonectris diomedea borealis. Significant differences were found between sexes and between study sites. For each colony, a discriminant function was derived in order to achieve external sex identification. Using three measurements, all functions correctly classified more than 95% of the birds of known sex, and the biometrical variables investigated showed no variation with age.\ud
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Marked differences in plumage and bill colour, in vocalization and in size, have led some authors to suggest that C.d. edwardsii could be considered as a distinct species. Comparison of morphological data from several colonies of Cory's Shearwater confirmed that the Cape Verde subspecies C.d. edwardsii occupies a very distinct position relative to the Atlantic and the Mediterranean (nominate C.d. diomedea) races. Birds from Mediterranean and Atlantic colonies show clinal variation in size, increasing from east to west. This morphological pattern is probably related to biological and physical conditions of the foraging areas of the different colonies
