Fish stocks of the Âncora River, northern Portugal: production (original) (raw)
Related papers
Fish stocks in the Âncora River, north Portugal
Fisheries Research, 2000
In the 19 km long A Ã ncora River, divided by 20 waterfalls and dams and emptying to the Atlantic Ocean in north Portugal, ®sh were sampled for the bioenergetics study. Average monthly water temperature during the year at sites along the river course was in the range 8.5±218C. The four ®sh populations' consumption, both in energy and mass units, was lower at sites in the middle course of the river, which was isolated from upstream sites by numerous waterfalls and dams. The gross (K 1) and net (K 2) ecological ef®ciencies of brown trout, roach and nase were very low, but detritus was their dominant food item. Eel, which ate animal food only had two to three times higher growth ef®ciencies than other ®sh. High mean monthly water temperatures from May to August and the isolation effect were probably the causes of a low utilisation of consumed food for growth in the populations investigated.
Fish production in the Jarama River, Central Spain
Ecography, 1984
Fish production was estimated at three sites on the Jarama River, a smali, typical upland river in Central Spain. Population estimates were madę by the successive removal method of electrofishing. The same six species were recorded at each of the sites: Chondrostoma polylepis, Barbus barbus bocagei, Leuciscus cephalus pyraenaicus, Salmo trutta m. fario, Gobio gobio and Cobitis paludicola, with the first three species always dominant. Density, biomass, production (assuming that N o is the total number of eggs spawned), and available production were, respectively: 13502-85776 ind. ha 1 ,178.6-221.3 kg ha-1 , 221.7-583.6 kg ha-1 yr 1 ,118.1-271.9 kg ha-1 yr 1 . Production estimates based on mortality curves were 7.9-19.5% (mean: 13.7) lower than those based on estimated from the number of eggs laid. Production per unit of area was highest at the widest and deepest site. Brown trout production contributed only 2-\% of the total production for all sites.
Fisheries Management and Ecology, 2000
The distribution and abundance of many of the 23 native fish species of the Guadiana River basin in Portugal have declined markedly in the past 20 years. This is because of increased pressure to exploit the water resources of the catchment for domestic supply, agriculture and recreation, but also as a result of general habitat degradation and the introduction of exotic species. Thirteen reservoirs have already been constructed in the region and a further 25 proposals have been put forward, mainly to supply the tourist sector in the south of the country. As a result of these activities, one species of fish, Anaecypris hispanica (Steindachner), is critically endangered. The present paper examines the status of the populations of A. hispanica in the Guadiana in Portugal, assesses the impact of water resource schemes on the stocks and general biodiversity, and suggests management options for conserving and enhancing the already degraded stocks. k e y w o r d s : Anaecypris hispanica, conservation, endangered fish species, Portugal, water resources development.
One millennium of historical freshwater fish occurrence data for Portuguese rivers and streams
The insights that historical evidence of human presence and man-made documents provide are unique. For example, using historical data may be critical to adequately understand the ecological requirements of species. However, historical information about freshwater species distribution remains largely a knowledge gap. In this Data Descriptor, we present the Portuguese Historical Fish Database (PHish–DB), a compilation of 2214 records (557 at the basin scale, 184 at the sub-basin scale and 1473 at the segment scale) resulting from a survey of 194 historical documents. The database was developed using a three-scale approach that maximises the inclusion of information by allowing different degrees of spatial acuity. PHish database contains records of 25 taxonomical groups and covers a time span of one millennium, from the 11th until the 20th century. This database has already proven useful for two scientific studies, and PHish further use will contribute to correctly assess the full range of conditions tolerated by species, by establishing adequate benchmark conditions, and/or to improve existing knowledge of the species distribution limits.
Populations and production of fish in two small tributaries of the Paran� River, Paran�, Brazil
Hydrobiologia, 1995
Mean biomass (B) and production (P) of fish in two small tributaries of the Parana River (Parana, Brazil) were 61 kg ha-' and 48 kg ha 1 yr-1 in the Caracu River and 29 kg ha-1 and 26 kg ha ' yr-1 in the Agua do Rancho River, respectively. Matrix correlation analysis revealed high positive correlations of both f? and P to maximum depth and hiding places and, at a lower level of significance, to mean depth, pH and oxygen level. Lower g and P values were found in the Agua do Rancho River, whose valley has retained a more natural character, rich canopy and scarcity of macrophytes, but also lower conductivity and nitrogen and phosphate levels than those in the Caracu River .
The influence of river flow on the fish community was assessed for the Tagus estuary (Portugal), based on sampling surveys carried out between 1979 and 2002. Four estuarine areas were sampled using similar fishing gear and effort in all the years considered in this study(1978–1980;1995–1997; and 2001–2002). According to river freshwater flow values, sampling years were classified as wet (mean value of 714 m3 s–1,sd = 110 m3 s–1) or dry (mean value of 164 m3 s–1,sd = 19m3 s–1). Species richness varied between 22 and 39 according to the year, but no significant differences were related to river flow. The number of species per ecological guild was also similar in wet and dry years. Fish assemblage was dominated by marine occasional, estuarine resident and marine-estuarine opportunist species that represented near 90% of all fish species. The highest densities were represented by estuarine resident species. Fish density in dry and wet years differed significantly (mean density of 10.51 individuals 1,000 m–2 and 3.62 individuals 1,000 m–2,respectively), and the major differences were registered for estuarine resident, marine-estuarine opportunist and catadromous species. These differences probably reflected the estuarine habitat availability and also differences in fish densities in some estuarine areas under different flow conditions. The multivariate ordination analyses performed outlined both seasonal and spatial variation trends in fish distribution and abundance. The estuarine longitudinal gradient and its relationship with species distribution were less evident in dry years. Relationships between species abundance and river flow were different according to species, which is probably due to different needs in the timing and magnitude of river flow.
Population structure of fish fauna in the estuarine area of Caet� River, Bragan�a, Par�, Brazil
Acta Scientiarum Biological Sciences, 1998
This study describes the relative size and age structure of the sciaenids Macrodon ancylodon, Stellifer rastrifer and Stellifer naso, the ariid Cathorops spixii and the aspredinid Aspredo aspredo in the estuary of the Caeté River. Four bimonthly samples were collected with trawl and gill nets during August, October and December 1996 and February 1997 in three different areas: (A) main river channel, (B) bay, and (C) coastal areas. Total length and weight of 16,298 individuals of all these species were recorded. Monthly frequency distributions were plotted. Cohorts were identified by dividing the distribution into separate normal distributions; asymptotic length (L ∞) and K were estimated for these stocks by FISAT program. Biomass averages (g/m 2) were estimated using the swept area method. Average biomass of Macrodon ancylodon was 0.29g/m 2 , total length ranged from 3cm to 41cm; length frequencies identified five cohorts; L ∞ = 45.50cm and K = 0.491 year-1. For Stellifer rastrifer, average biomass was 0.31 g/m 2 ; total lengths ranged from 1 to 17cm; L ∞ = 22.5cm and K = 0.31 year-1. For Stellifer naso, average biomass was 0.03 g/m 2 ; L ∞ = 26.3cm and K = 0.321 year-1 , total lengths ranged from 2 to 25cm. For Cathorops spixii, average biomass was 0.55 g/m 2 ; L ∞ = 33.3cm and K = 0,36 year-1 ; density was much higher in the river habitats. Aspredo aspredo presented a biomass of 0.06 g/m 2 ; abundance was higher in the river; total lengths ranged from 2 to 36cm; L ∞ = 42.5cm and K = 0.35 year-1. Despite the different biological strategies of each species with respect to spatial distribution and relative abundance, they all utilize the estuarine habitat as nursery grounds in the early phases of their life cycles.
Stocks assesment, biomass and fish production in two mediterranean basins (NE Spain)
1996
In order to evaluate the success of the reintroduction of the Eurasian otter (Lutra lutra) in the Empordh wetlands ("Parc Natural dels Aiguamolls de I'Empordh"), and the Muga and Fluvih basins, density of fish, biomass and production in the Muga and Fluvia Rivers have been estimated, since fishes represent the principal prey in the otter diet. 12 study sites were selected in order to survey the main flows in both basins. Electrofishing surveys were conducted by blocking off the station with barrier nets, which was performed upon 3 successive catches. The density estimated presents a range of 1,136-1 25 ind .ha l in the Muga basin, 4,49-163 ind.ha l in the Fluvih basin and 3,76-52,2 ind.ha-l in the Empordh wetlands. Estimated biomass ranges are 0,616-277,6 &.m 2 , 8,79-351,2 g-m ', and 5,7-108 respectively. These density anfi biomass ranges are similar to other results obtained from rivers inhabited by the Eurasian otter in NE Spain.
Scientific Data, 2016
The study of freshwater fish species biodiversity and community composition is essential for understanding river systems, the effects of human activities on rivers, and the changes these animals face. Conducting this type of research requires quantitative information on fish abundance, ideally with long-term series and fish body measurements. This Data Descriptor presents a collection of 12 datasets containing a total of 146,342 occurrence records of 41 freshwater fish species sampled in 233 localities of various Iberian river basins. The datasets also contain 148,749 measurement records (length and weight) for these fish. Data were collected in different sampling campaigns (from 1992 to 2015). Eleven datasets represent large projects conducted over several years, and another combines small sampling campaigns. The Iberian Peninsula contains high fish biodiversity, with numerous endemic species threatened by various menaces, such as water extraction and invasive species. These data may support the development of large biodiversity conservation studies. Design Type observation design • species comparison design • time series design Measurement Type(s) specimens collected in one encounter Technology Type(s) observational method Factor Type(s) Sample Characteristic(s) Teleostei • Iberian Peninsula
Population structure of fish fauna in the estuarine area of Caete River, Braganca, Para, Brazil
Acta Scientiarum, 1998
This study describes the relative size and age structure of the sciaenids Macrodon ancylodon, Stellifer rastrifer and Stellifer naso, the ariid Cathorops spixii and the aspredinid Aspredo aspredo in the estuary of the Caeté River. Four bimonthly samples were collected with trawl and gill nets during August, October and December 1996 and February 1997 in three different areas: (A) main river channel, (B) bay, and (C) coastal areas. Total length and weight of 16,298 individuals of all these species were recorded. Monthly frequency distributions were plotted. Cohorts were identified by dividing the distribution into separate normal distributions; asymptotic length (L ∞) and K were estimated for these stocks by FISAT program. Biomass averages (g/m 2) were estimated using the swept area method. Average biomass of Macrodon ancylodon was 0.29g/m 2 , total length ranged from 3cm to 41cm; length frequencies identified five cohorts; L ∞ = 45.50cm and K = 0.491 year-1. For Stellifer rastrifer, average biomass was 0.31 g/m 2 ; total lengths ranged from 1 to 17cm; L ∞ = 22.5cm and K = 0.31 year-1. For Stellifer naso, average biomass was 0.03 g/m 2 ; L ∞ = 26.3cm and K = 0.321 year-1 , total lengths ranged from 2 to 25cm. For Cathorops spixii, average biomass was 0.55 g/m 2 ; L ∞ = 33.3cm and K = 0,36 year-1 ; density was much higher in the river habitats. Aspredo aspredo presented a biomass of 0.06 g/m 2 ; abundance was higher in the river; total lengths ranged from 2 to 36cm; L ∞ = 42.5cm and K = 0.35 year-1. Despite the different biological strategies of each species with respect to spatial distribution and relative abundance, they all utilize the estuarine habitat as nursery grounds in the early phases of their life cycles.