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Discards of the beach seine fishery in the central coast of Portugal.
Get PDFThe beach seine fishery is performed regularly along the Portuguese coast in shallow water sandy areas. The catches and discards of this fishery were studied from March until November 1999, on the coast south of Lisbon. Fishing operations were monitored weekly and estimates of the weight of catches and discards per species were determined for each haul. A total of 60 fish species was identified in the catches but Scomber japonicus, Trachurus trachurus and Diplodus bellottii represented approximately 90% of the catches. For most of the species the percentage of discarded fishwas extremely high (ca. 100%). The species for which the estimates of discards were lower than 25% of the catches were Sardina pilchardus, Merluccius merluccius,\ud
Dicentrarchus labrax, Dicentrarchus punctatus, T. trachurus, several Sparidae species, Spicara maena, S. japonicus, Solea senegalensis, and Solea solea.Most of the species exhibited a marked seasonal abundance pattern that varied according to the species. Discards also varied considerably within and between seasons. The relationships between discards and total catch, species catch, mean length of fish and percentage of fish above minimum legal size were different according to species. For S. japonicus and S. pilchardus discards were negatively correlated with their catch, mean length of fish and percentage of fish\ud
above minimum legal size, while for T. trachurus significant correlations were obtained only for the last two variables
A comparative study of the species composition of discards from five fisheries from the Algarve (southern Portugal)
No full textDiscards from five of the most important fisheries (crustacean trawling, fish trawling, demersal purse seining, pelagic purse seining and trammel netting) in southern Portugal were studied and compared. A total of 236 species of all taxa were discarded, with fish and cephalopods accounting for more than 90% of the discarded biomass, except trammel nets (81%). Although there was some overlapping of species, multivariate analysis using cluster analysis for classification and multidimensional scaling (MDS) for ordination, showed that there were significant differences between the five gears in terms of species composition and biomasses discarded, with the least similarity between crustacean trawling and all other fishing operations. The differences between fisheries were probably as a result of a combination of gear selectivity and depth fished. The results suggest that discarding practices are likely to have different, yet significant impacts on the marine ecosystem, warranting further studies on the fate of discards, the factors influencing discarding and mitigation
Sardine slipping during purse-seining off northern Portugal.
No full textObservations aboard purse-seiners demonstrated that deliberate lowering of the net to allow pelagic fish to escape ("slipping") was frequent off northern Portugal during the second semester of 2001. Some slipping occurred in 25 of 30 trips observed, and the quantities slipped were significantly higher when the net was set on dense echo-sounder marks. During the 12 weeks of the study, the sampled fleet (nine vessels) landed 2196 t and deliberately released an estimated 4979 t (CV 33.6%). More than 95% of the total catch was sardine. Data provided by the skippers in the absence of shipboard observers led to considerably lower estimates of slipped quantities. The main reason for slipping was daily quota limitations, but illegal size and mixture with unmarketable bycatch were also reported. These results demonstrate the existence and potential magnitude of\ud
slipping, but indications of large seasonal and regional variations make extrapolations for the entire fishery impractical
First data on feeding ecology of Goshawk Accipiter gentilis during the breeding season in the natura 2000 site Dunas de Mira, Gândara e Gafanhas (Beira Litoral, Portugal)
Get PDFThis study describes the diet of the Goshwak Accipiter gentilis within littoral ecosystems dominated by pine trees. Samples were collected during the breeding season of 2001 in Dunas de Mira, Gândara e Gafanhas, located in the littoral centre of Portugal and recently included in the Portuguese Natura 2000 network (PTCON 055). Diet composition was assessed from the analysis of 89 pellets and 154 prey remains, collected between the 15th of April and the 25th of July of 2001. Birds represented 86.6% of the total prey items. The remaining prey items were coleoptera (6.5%), mammals (3.6%) and reptiles (3.3%). In terms of biomass birds comprised 90.9%, followed by mammals (7.3%), reptiles (1.7%) and coleoptera (0.05%). Results show that this raptor has a predominantly ornitophagous diet. Domestic pigeon Columba livia var is the most important prey in this area both in terms of frequency and biomass (42.2% and 49.9%, respectively). During the breeding season the diet of the Goshawk is largely connected to Man.\ud
Este trabalho pretendeu obter informação relativa à ecologia trófica do Açor Accipiter gentilis, de modo a tentar compreender o papel desempenhado por esta espécie de ave de rapina em ecossistemas litorais. O estudo decorreu durante a época de nidificação de 2001, na área do Sítio das "Dunas de Mira, Gândara e Gafanhas", recentemente incluÌdo na Rede Natura 2000 (PTCON 055). A composição do regime alimentar foi estudada com base em 89 regurgitaÁıes e 153 restos de presas, recolhidas entre 15 de Abril e 25 de Julho de 2001. As aves representaram 86,6% do total de presas consumidas, os coleópteros 6,5%, os mamíferos 3,6% e os répteis 3,3%. Em termos de biomassa, as aves continuam a ter um papel predominante representando 90,9% da biomassa consumida, seguidas pelos mamÌferos (7,3%), répteis (1,7%) e coleópteros (0,05%). Na área de estudo o Açor tem um comportamento alimentar predominantemente ornitófago, sendo o pombo doméstico Columba livia var a presa mais importante, tanto em termos numéricos como em biomassa (42,2% e 49,9%, respectivamente). Na base deste comportamento, estarão a elevada disponibilidade alimentar e uma maior vulnerabilidade à predação por parte desta espécie. Este regime alimentar do Açor durante o perÌodo reprodutor evidência uma clara dependÍncia desta ave de rapina em relação a uma espécie estreitamente ligada ao homem
Sardine and horse mackerel recruitment and upwelling off\ud Portugal
No full textThe results of preliminary investigations on the possible relationships between coastal\ud
upwelling variability observed with satellite remote sensing, and sardine and horse\ud
mackerel recruitment dynamics in the west coast of Portugal are presented. The\ud
analysis of a sardine-recruitment time-series for the period 1976–1998 shows that there\ud
has been a decreasing trend since 1983 (with the exceptions of 1991 and 1992), the\ud
years from 1993–1995 representing the lowest values in that time series. Horse\ud
mackerel exhibited a decrease from 1986 until 1990, and from 1992–1995, the latter\ud
representing the lowest value for the period 1986–1998. Sea surface temperature (SST)\ud
derived from satellite data were used to compute monthly SST upwelling indices along\ud
the Portuguese west coast over a period from 1987–1997. The analysis focused on\ud
seasonal and annual upwelling variability off Portugal, and its possible effects on\ud
sardine and horse mackerel recruitment to the fishery. An increasing trend in SST\ud
upwelling indices during the winter (January–March), especially between 1992 and\ud
1995 was found. The upwelling events observed off Portugal during winter months,\ud
which correspond to the spawning season for sardine and horse mackerel, had a\ud
negative impact on the recruitment of these fish species. This effect on recruitment\ud
could be due to an increase in conditions favourable to the offshore transport of larvae\ud
and consequently an increase in their mortality. Prior to 1992, when no upwelling\ud
events occurred during winter, recruitment dynamics was closely linked with the\ud
spring–summer seasonal upwelling variability off the Portuguese west coast
Sardine and horse mackerel recruitment and upwelling off Portugal
No full textThe results of preliminary investigations on the possible relationships between coastal upwelling variability observed with satellite remote sensing, and sardine and horse mackerel recruitment dynamics in the west coast of Portugal are presented. The analysis of a sardine-recruitment time-series for the period 1976–1998 shows that there has been a decreasing trend since 1983 (with the exceptions of 1991 and 1992), the years from 1993–1995 representing the lowest values in that time series. Horse mackerel exhibited a decrease from 1986 until 1990, and from 1992–1995, the latter representing the lowest value for the period 1986–1998. Sea surface temperature (SST) derived from satellite data were used to compute monthly SST upwelling indices along the Portuguese west coast over a period from 1987–1997. The analysis focused on seasonal and annual upwelling variability off Portugal, and its possible effects on sardine and horse mackerel recruitment to the fishery. An increasing trend in SST upwelling indices during the winter (January–March), especially between 1992 and 1995 was found. The upwelling events observed off Portugal during winter months, which correspond to the spawning season for sardine and horse mackerel, had a negative impact on the recruitment of these fish species. This effect on recruitment could be due to an increase in conditions favourable to the offshore transport of larvae and consequently an increase in their mortality. Prior to 1992, when no upwelling events occurred during winter, recruitment dynamics was closely linked with the spring–summer seasonal upwelling variability off the Portuguese west coast
Heavy metals in the tissues of common dolphins (Delphinus delphis) stranded on the Portuguese coast
No full textThe concentrations of Hg, Sn, Cr, Zn, Ni, Co, Cd, Mn, Fe and Cu were determined in the liver, kidney and muscle of 24 common dolphins stranded on the Portuguese coast between 1995 and 1998. Nitric acid was used to extract the metals from the tissues for analysis by inductively-coupled plasma/atomic emission spectroscopy (ICP/AES). Those metals with relatively higher concentrations included Fe, Zn and Hg, particularly in liver. Other metals including Cr, Ni and Cd tended to show much lower levels, or were even undetected (e.g. Co). Different metals seemed to show different temporal trends, although due to substantial variations of the mean concentrations for each year obtained, such temporal pattern has to be studied further. Total Hg concentration in the kidney, muscle and particularly liver, were higher in females than in males. Total Hg concentrations in all the organs increased with body length of dolphins, whilst those of Zn and Cu in muscle decreased with dolphin length. A strong correlation was found between essential metals Zn and Cu in muscle, possibly resulting from sequestration of these metals by metallothionein. In addition, significant co-associations existed between the same metal (e.g. Hg, Sn and Zn) in different organs
By-catch and discarding practices in five Algarve (southern Portugal) métiers
No full textThe catches and discards of trawlers, seiners and trammel netters were studied in the Algarve (southern Portugal) using observers onboard commercial fishing vessels. Species diversity was high, with 236 species recorded as occasionally, 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, demersal 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 seiners where from 0 to 100% of the total catch might be discarded. No significant relationships were found between discard quantity or discard rate and characteristics of the fishing vessels sampled within each métier (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. Discarding practices in these fisheries are reviewed and the reasons for discarding are presented by species and métier 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 these fisheries
Improvement of nesting conditions for Cory’s Shearwaters Calonectris diomedea in Berlenga Island (Portugal). Final project report.
No full textIn October 1999, SPEA (BirdLife in Portugal) started a project that aimed to improve nesting conditions for Cory’s Shearwaters Calonectris diomedea on the Berlengas islands, a small archipelago off mainland Portugal. Previous work showed that this breeding population (estimated at 100-120 pairs) was limited by the lack of suitable nesting sites. Three groups of volunteers built 49 artificial nests and improved 11 more in three different sites using local natural materials (mostly stones). Overall nest availability increased by 64% on these colonies. A census was also carried out (and nests mapped) estimating the population at 107-142 breeding pairs spread over 12 sites on Berlenga. A total of 68 chicks were ringed. Volunteers also received training on seabird biology, monitoring and conservation. Placards and leaflets were produced and widely distributed. In the following year (2000) 12% of the artificial nests built were occupied by breeding pairs. In one breeding site the population has increased 50 % in\ud
the first year after the project