64 research outputs found
Idegenhonos halfajok megjelenése és terjedése a Duna magyarországi szakaszán - Történeti áttekintés = Occurrence and spread of nonnative fish species in the Hungarian section of River Danube – A historical review
A total of 32 fish species have been introduced into the inland waters of Hungary, either intentionally or
accidentally. Of these, a total 24 species can be found on the Hungarian section of the River Danube, and 15
fish species of them are considered as invasive. These non‐native fish species belong to 7 families and the
origins of the species are from three continents: Asia (7), Europe (10) and North – America (7). This paper
provides a summary of data of the first record, way of introduction, mode of area expansion, impact on native
fish and estimated area of recent distribution on the Hungarian section of the River Danube. Ten of the non‐
native fish species currently occupy more than 50% of the River Danube and his tributaries and flood‐plains
territory (Ctenopharyngodon idella, Pseudorasbora parva, Carassius gibelio, Hypophthalmichtys sp., Lepomis
gibbosus, Babka gymnotrachelus Neogobius fluviatilis, Neogobius melanostomus, Ponticola kessleri,
Proterorhinus semilunaris). Some exotic fish species have only a few data about their distribution (Acipenser
baerii, Polyodon spathula, Rutilus meidingeri, Coregonus sp., Ictalurus punctatus, Ponticola syrman). This paper
is aimed to review the impacts of introduced freshwater fish in Hungarian Section of the River Danube based
on collected data. | A hazai hal‐ és halászatbiológiai kutatások összesen 32 betelepített (gazdasági vagy akvarisztikai célból),
valamint areaexpanzió útján bekerült halfajt írtak le a Magyarország vizeiből. Ezek közül napjainkra 24 faj
előfordulása igazolt a hazai Duna‐szakaszról, melyek közül 15 faj tekinthető invazívnak. Az általunk
idegenhonosnak tekintett halfajok rendszertanilag 7 családba sorolhatók, 7 Ázsiából, 10 Európából, 7 Észak‐
Amerikából származik. Jelen tanulmányunkban rendszerezni kívántuk a vonatkozó szakirodalmat,
összegyűjteni a halfajok első igazolt előfordulási adatait, meghatározni a vízrendszerbe kerülés módját, a
terjedés valószínűsíthető okait, az őshonos halfaunára gyakorolt hatásaikat és a jelenlegi elterjedésük
mértéket. Az idegenhonos fajok közül 9 a magyarországi Duna‐szakaszon és a hozzá kapcsolódó víztestek
jelentős részében gyakori (előfordulási gyakoriságuk >50%): Ctenophatyngodon idella, Pseudorasbora parva,
Carassius gibelio, Hypophthalmichtys sp., Lepomis gibbosus, Babka (Neogobius) gymnotrachelus, Neogobius
fluviatilis, Neogobius melanostomus, Ponticola (Neogobius) kessleri, Proterorhinus semilunaris. Számos fajból
csak szórványos előfordulási adatok állnak rendelkezésre (Acipenser baerii, Polyodon spathula, Rutilus
meidingeri, Coregonus sp., Ictalurus punctatus, Ponticola (Neogobius) syrman). Munkánk célja a jelenleg
igazoltan előforduló idegenhonos halfajok megjelenésének és hatásaiknak az összegzése a magyarországi
Duna‐szakaszon
Repeatability, Reproducibility, Separative Power and Subjectivity of Different Fish Morphometric Analysis Methods
We compared the repeatability, reproducibility (intra- and inter-measurer similarity), separative power and subjectivity (measurer effect on results) of four morphometric methods frequently used in ichthyological research, the "traditional" caliper-based (TRA) and truss-network (TRU) distance methods and two geometric methods that compare landmark coordinates on the body (GMB) and scales (GMS). In each case, measurements were performed three times by three measurers on the same specimen of three common cyprinid species (roach Rutilus rutilus (Linnaeus, 1758), bleak Alburnus alburnus (Linnaeus, 1758) and Prussian carp Carassius gibelio (Bloch, 1782)) collected from three closely-situated sites in the Lake Balaton catchment (Hungary) in 2014. TRA measurements were made on conserved specimens using a digital caliper, while TRU, GMB and GMS measurements were undertaken on digital images of the bodies and scales. In most cases, intra-measurer repeatability was similar. While all four methods were able to differentiate the source populations, significant differences were observed in their repeatability, reproducibility and subjectivity. GMB displayed highest overall repeatability and reproducibility and was least burdened by measurer effect. While GMS showed similar repeatability to GMB when fish scales had a characteristic shape, it showed significantly lower reproducability (compared with its repeatability) for each species than the other methods. TRU showed similar repeatability as the GMS. TRA was the least applicable method as measurements were obtained from the fish itself, resulting in poor repeatability and reproducibility. Although all four methods showed some degree of subjectivity, TRA was the only method where population-level detachment was entirely overwritten by measurer effect. Based on these results, we recommend a) avoidance of aggregating different measurer's datasets when using TRA and GMS methods; and b) use of image-based methods for morphometric surveys. Automation of the morphometric workflow would also reduce any measurer effect and eliminate measurement and data-input errors
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