An analysis of the effects of preferential trade policies through the estimation of quantitative models: the case of Portugal.

Doutoramento em Economia.

Age and growth of Ray's bream (Brama brama) from the south of Portugal

Age and growth of 234 Brama brama Bonnaterre (1788) (Pisces: Bramidae) caught hy semi-pelagic longline off the south coast of Portugal (Algarve) was studied using otoliths for age determination. Samples consisted of fish varying in total length from 32 to 56 cm and in weight from 332 to 2032 g. Age classes from III to XII were represented in the catches. The von Bertalanffy growth curve was fitted and the length/weight relationship was calculated. (C) 2001 Elsevier Science B.V. All rights reserved.

Age and growth, mortality and reproduction of the striped sea bream, Lithognathus mormyrus Linnaeus 1758, from the south coast of Portugal (Algarve)

The striped sea bream, Lithognathus mormyrus, used for this population dynamics study were obtained from longline catches and market sampling in the Algarve (south Portugal). The macroscopic analysis of the gonads and the gonad somatic index showed that the south Portuguese population of L. mormyrus spawns mainly between late spring and summer (June to August). The length at first maturity was similar for males and females and the value for both sexes combined was estimated to be 16.08 cm, corresponding to an age between 1 and 2 years. Fish age classes (0 to 13) were determined by reading growth rings on whole otoliths. Age determination was validated by marginal increment analysis. The estimated parameters of the von Bertalanffy growth equation were L infinity = 35.30 cm, K = 0.264 and t(0) = -0.809. Mortality rates were calculated for fish captured with longlines, and the estimated parameters were M = 0.356, Z = 0.622 and F = 0.266. From an Algarve fishery management perspective, these results suggest the need for an increase in the minimum landing size (from 15 to 17 cm), which should be beneficial for the sustainability and conservation of this species. The results also showed that fishing with longlines off the Algarve coast may allow for a sustainable use of the resource.

Age and growth, mortality, reproduction and relative yield per recruit of the bogue, Boops boops Linne, 1758 (Sparidae), from the Algarve (south of Portugal) longline fishery

Samples of Boops boops ranging from 7.4 to 30.5 cm were obtained mainly by longline, supplemented by beach seining in the Ria Formosa lagoon, and by market sampling in the Algarve (southern Portugal). The macroscopic analyses of the gonads and the gonad somatic index showed that the south coast of Portugal B. boops spawn mainly from late winter to spring, between February and May. The length at first maturity was similar for males and females and the value for both sexes combined was estimated to be 15.22 cm, corresponding to an age range of 1-3. Age was determined by reading growth bands on otoliths. Age determination was validated by marginal increment analysis. The estimated parameters were L-infinity = 28.06, K = 0.22 and t(0) = -1.42. Mortality rates were calculated for fish captured with longlines, and the estimated parameters were M = 0.33, Z = 1.04 and F = 0.71. Relative yield per recruit analysis and sensitivity analysis showed that the resource is moderately exploited. From the perspective of sustainability, these results provide support for the use of longlines as a gear that is among the least harmful for species such as the bogue.

An assessment of catches and harvest of recreational shore angling in the north of Portugal

Recreational shore angling in the Atlantic Ocean between Moledo and Aveiro (Portugal) was examined using roving creel surveys (March/September 2001). Cooperation was high (90% of 2310 anglers approached). At least 39 species of fish were caught at a rate of approximately 0.5 fish angler h(-1). An estimated 7319 kg of Dicentrarchus labrax (L.), with 45.6% below the minimum legal size, and 2040 kg of sea breams (genus Diplodus), correspond to 5.75% and 1.19% of the commercial landings in the same geographical area, respectively. The results shed light on a number of issues relevant to integrated coastal management, including temporal and spatial distribution of fishing effort, species caught, sizes of fish, catch rates, and factors influencing catches and angler satisfaction. Whilst the results suggest that the catches of sea breams and sea bass by day-time recreational shore angling in northern Portugal are small compared with commercial fishing, other recreational activities, such as boat fishing and spear-fishing, must be assessed.

Diet of the blue marlin, Makaira nigricans, off the south coast of Portugal

The blue marlin, Makaira nigricans (Istiophoridae), is a large, top predator with a worldwide distribution whose feeding ecology is still unknown in the northeast Atlantic. The stomach contents of 24 Atlantic blue marlin, caught by the Big Game fishing fleet (between 2007 and 2010) off the south coast of Portugal, were studied. All marlin fed exclusively on pelagic fish, with a total of 180 prey items recorded, belonging to 6 identified species. The most important family in the blue marlin diet was Scombridae, representing 70% of the total prey items. Among the Scombridae, the chub mackerel, Scomber colias, was the most important prey species (47.9% by weight, 51.1% by number, 58.3% by frequency of occurrence). The length of prey found in the stomachs ranged from 136 to 727 mm in length, and a significant positive correlation was found between prey and blue marlin size. Our results suggest that in this geographical area (NE Atlantic) marlin feed on a small spectrum of species, with a preference for foraging on seamounts.

Feeding habits of the two-banded sea bream (Diplodus vulgaris) and the black sea bream (Spondyliosoma gantharus) (Sparidae) from the south-west coast of Portugal

The stomach contents of Diplodus vulgaris and Spondyliosoma cantharus were: analysed using three simple methods (numeric, gravimetric and frequency of occurrence) and a composite index (I.R.I - Index of Relative Importance). To compare the species, the Schoener index was used. The diet of D. vulgaris consisted mainly of ophiuroids, polychaetes, amphipods and echinoids, while polychaetes, amphipods and hydrozoans dominated in the case of S. cantharus. There were some size-related differences in S. cantharus feeding. Diet overlap was relatively slight, with significant differences in feeding between the two species, notably in terms of greater consumption of echinoderms by D. vulgaris and hydrozoans by S. cantharus. As is the case for the majority of sea breams, D. vulgaris and S. cantharus are characterised by a diverse diet in terms of prey reflecting available prey items in their environment.

Reproductive aspects of the undulate ray, Raja undulata, from the south coast of Portugal

The maturity of the undulate ray, Raja undulata, one of the most important by-catch elasmobranch species captured in south Portugal, was studied for the first time. Females ranged in total length (TL) from 19.4 to 88.2 cm and males from 23.0 to 83.2 cm. The gonadosomatic index for females was higher during the winter, meaning that this species reproduces during this season. Females matured at significantly larger sizes and older ages than males, with 50% of the females mature at 76.2 cm TL at an age of 8.98 years while 50% maturity for males was achieved at 73.6 cm TL and 7.66 years. Females were mature at 86.3% of the maximum observed size and 69.1% of the maximum observed age while males matured at 88.5% of the maximum observed size and 63.8% of the maximum observed age, making this a very late maturing species, with important consequences in terms of fisheries management and conservation. (c) 2006 Elsevier B.V. All rights reserved.

Reproductive biology of the blackmouth catshark, Galeus melastomus (Chondrichthyes : Scyliorhinidae) off the south coast of Portugal

The reproductive biology of 1045 female (9.5-67 cm (total length(TL)) and 1007 male (9.4-64.3 cm TL) blackmouth catsharks, Galeus melastomus, was investigated. The sharks were caught off southern Portugal by bottom crustacean trawlers at depths from 209 to 754 m. The sex ratio was 1:1, and this species is sexually dimorphic with males approaching maturity at smaller size than females. Sexual segregation appears to be given for the stork within the study area. Sexual maturity was reached at a total length above 49 cm in males and above 56 cm in females. Mating and egg-deposition take place all year round, with two reproductive peaks of activity, in winter and summer. Egg capsules are, on average, 54 mm long and 21 mm wide, with a maximum of 63 x 25 mm encountered. Morphometric measurements of claspers, testes, ovaries, and oviducal glands were suitable for determining sexual maturity of blackmouth catshark.

The reproductive biology of Spondyliosoma cantharus (L.) from the SW Coast of Portugal

The study of Spondyliosoma cantharus (L.) reproduction was carried out within the framework of a project on the Fisheries resources of the south-west coast of Portugal, and was based on the analysis of the spawning season, gonad maturation, size-at-maturity, fecundity, and hermaphroditism. Spawning took place from February to April, peaking in March. Analysis of the sex ratio by size class and season showed that females were more abundant throughout the year (M/F=0.57) and in the smaller size classes. Overall size at first maturity (L-50) was 20.10 cm total length (TL), with a significant difference between males (22.41 cm, TL) and females (19.98 cm, TL). Absolute fecundity (Fa) ranged from 37,506 to 112,074 oocytes, with a mean of 61,396. A power type relationship best described the relationships between absolute fecundity and TL (Fa = 436.27TL(1.575)), and somatic weight (Fa = 2979.7SW(0.585)). The number of oocytes/g of female somatic weight ranged from 217 to 549, with a mean of 346. The reproductive strategy of this species is characterised by protogynic hermaphroditism, as indicated by the presence of individuals in transition and of testes with vestiges of preceding ovaries associated with the significant differences in the size frequency distributions of the sexes.

The reproductive biology of the two-banded sea bream (Diplodus vulgaris) from the southwest coast of Portugal

The study of the reproduction of Diplodus vulgaris (Geoff.) as part of a base-line study of the fishery resources of the southwest coast of Portugal, was based on the analysis of the spawning season, gonad maturation, size at maturity, fecundity and hermaphroditism. The spawning season is relatively long, from December to March, with peaks in January and February. No significant differences were found either in the sex ratio (M:F = 1.01) over the year or by size. The size at first maturity (L-50) for all sexes and undetermined individuals combined was 18.33 cm total length (TL), with no significant differences between males and females. The estimated L-50 is considerably greater than the minimum legal size in Portugal of 15.0 cm. Mean absolute fecundity (F-a) was 131 127 oocytes, ranging from 31 523 to 250 608. The relationship between absolute fecundity and total length (TL) (F-a = 25 398 TL-484 426) and somatic weight (SW) (F-a = 878.8SW-71 416) was of the linear type. The mean number of oocytes per gram of somatic weight was 526, ranging from 194 to 887. The reproductive strategy of this species is characterized by a rudimentary hermaphroditism with possible protandry, as evidenced by the existence of individuals in sexual transition.

Non-indigenous Japanese oyster drill Pteropurpura (Ocinebrellus) inornata (Récluz, 1851) (Gastropoda: Muricidae) on the south-west coast of Portugal

The Japanese oyster drill or rock snail Pteropurpura (Ocinebrellus) inornata (Récluz, 1851), a marine mollusc, belonging to the family Muricidae, is reported from Portugal for the first time. This non-indigenous species, most likely introduced accidentally from French oyster rearing areas into mainland Portugal, has been regularly sampled in shellfish-culture and nearby environments in Sagres, Algarve, Southwest Portugal since 2005–2008. Detailed studies are urgently needed in order to assess whether or not it has become an invasive species due to a range expansion beyond its point of initial introduction. Outputs should provide information to decision-makers to predict and limit further spread which might result in biodiversity loss and negative economical consequences in locally species-rich areas.

First record of Calcinus tubularis on the southern coast of Portugal (Crustacea: Decapoda: Anomura: Diogenidae)

Twenty-five specimens of the hermit crab Calcinus tubularis were observed during SCUBA dives for fauna and flora assessment in the shallow rocky reefs of the southern coast of Portugal between 2003 and 2008. Of the specimens observed, only one specimen used a tube gallery, while the others occupied unidentified gastropod shells with strong bio-cover. Calcinus tubularis is here recorded from the mainland Portuguese coast for the first time. This is the first record of the species in European coastal waters outside the Mediterranean Sea (excluding the Atlantic Islands) and extends the known geographical distribution of the species further north in the north-eastern Atlantic.

First record of Anachis aliceae (Mollusca: Gastropoda: Columbellidae) in the Algarve, south coast of Portugal

The marine gastropod Anachis aliceae (Pallary, 1900) is reported with certainty for the first time from the Algarve, south coast of Portugal from species-rich rocky priority biotope. Several live specimens of this species belonging to the Columbellidae family were collected and identified from by-catch samples, recovered from octopus traps set at depths between 50 and 70 m off Ponta da Piedade. Taxonomic validation of the newly recorded species is based on the comparison to other related species within the genus.