1,720,989 research outputs found
La pratica del Catch and Release per la gestione delle popolazioni ittiche nelle aree protette
No full textMonitoraggio ambientale ed ittico della popolazione di trota fario (Salmo trutta L.) nel tratto No Kill del fiume Nera in Provincia di Terni
No full textThe use of artificial spawning substrates as media to support the reproduction of Eurasian Perch in lake Piediluco
No full text
Indici di struttura ed accrescimento standard per la trota fario Salmo (trutta) trutta L. in Italia centrale
No full textLa pratica del Catch and Release per la gestione delle popolazioni ittiche nelle aree protette
No full textPopulation size structure indices and growth standards for Salmo (trutta) trutta Linnaeus, 1758 in Central Italy
No full textThe purpose of this study was to provide reference data on the growth and
population structure of brown trout Salmo (trutta) trutta Linnaeus, in Central
Italy. Standards for growth (percentiles and a standard growth model)
were developed from the von Bertalanffy growth model by using lengthat-
age data obtained from 122 sampling sites in the River Tiber basin.
Length-frequency indices provide a numeric estimation for deviations of
the population structure from a balanced population. We adapted the traditional
North American Relative Stock Density (RSD) and Proportional
Stock Density (PSD) indices to brown trout populations in Central Italy
by means of two methods. In the first method, the benchmarks of length
categories were established by using percentages applied to the largest
individual in the dataset. In the second method, asymptotic length and size
at maturity were used to define the length categories for index calculation.
Both methods were tested on length-frequency data from 263 sampling
sites in the River Tiber basin. The results showed that the PSD calculated
by the first method provided a better insight into the population structures
of brown trout.
These results provide tools that will help ichthyologists and fish managers to compare the growth and population structure of brown trout throughout Central Italy
Growth and reproduction of the goldfish Carassius auratus: a case study from Italy.
No full textThe goldfish Carassius auratus (Linnaeus, 1758) is indigenous to eastern Asia; since its introduction in the late 1990s, it has become established in Lake Trasimeno (Umbria, Italy), where it is now very abundant owing to the absence of predators, including man. This species displays a potentially invasive behaviour, owing to some ecological and biological characteristics: high tolerance of water pollution, high fecundity rate and wide-ranging diet. It exerts a negative impact on fish communities, mostly due to inter-specific competition. Biological data on Italian goldfish populations are scarce. The aim of this study was to collect data on the growth and reproductive biology of this species, in order to investigate the causes of its rapid expansion in Lake Trasimeno. Sampling was carried out monthly, from February 2003 to January 2004; the total sample comprised 3 111 specimens captured by means of electrofishing and multi-mesh nets. Results showed that the population of goldfish in Lake Trasimeno was composed mostly of females (97.4% of the total sample). Most (85%) of the females attained sexual maturity in their 2nd year, but a small percentage (7.55%) was already able to spawn in the 1st year. Fecundity varied from 286 to 219 104, averaging 46 253 eggs; the diameter of mature eggs ranged from 0.74 to 1.71 mm, with a 1.27 mm average. Average relative fecundity was 103 eggs g-1. The catching ability of the various sampling methods was compared in order to design a programme to control the density of the unwanted populations
Application of Stock Density Indices as a Tool for Broad‐Scale Population Assessment for Four Cyprinid Species in Central Italy
No full textStock-density indices are standardized methods for analyzing length-frequency data that quantify the length
structure of a fish population into length categories that are of interest to recreational anglers. We adapted North
American relative stock density (RSD) and proportional stock density (PSD) indices to four Italian endemic or native
cyprinid species by means of two methods. In accordance with the traditional approach, the benchmarks of length
categories were established according to Gabelhouse’s percentage classification and calculated on the basis of the
largest individual in the data set for each species. In the second method, asymptotic length and size at maturity were
used to define the length categories for index calculation. Both methods were tested on length-frequency data from
fish collected from sampling sites in the Tiber River basin. The results showed that the traditional approach displayed
better applicability, required less sampling effort, and provided a better insight into the length structure of the fish
populations studied
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