Population dynamic and and ecotoxicology of the black bullhead (Ameiurus melas Rafinesque, 1820) in Sava Lake

Crni američki patuljasti som (Ameiurus melas Rafinesque, 1820) je najzastupljenija i najuspešnija alohtona vrsta ribe koja naseljava kopnene vode Evrope. Istraživanja koja su sprovedena u proteklih nekoliko godina ukazuju na to da je ovo dominantna invazivna vrsta i u mnogim kopnenim vodama u Srbiji. Cilj istraživanja se odnosio na ispitivanje populacionih atributa patuljastog soma u Savskom jezeru, kao i na bioakumulaciju teških metala i mikroelemenata u različitim tkivima. Terenska istraživanja vršena su u periodu od 2009. do 2012. godine. Jedinke su uzorkovane jednom mesečno, četiri dana za redom. Laboratorijska obrada prikupljenih uzoraka obuhvatila je merenje totalne dužine tela (TL) i ukupne težine tela ulovljenih primeraka. Nakon disekcije jedinki merena je težina tela bez utrobe, kao i masa jetre i gonada.Struktura populacije utvrđena je kombinovanjem dve metode – analizom starosti jedinki i analizom dužinskih frekvencija. Starost jedinki određena je takođe uz pomoć dve metode – očitavanjem naraštajnih zona otolita i Batačarija metodom. Analiza uzrasne strukture populacije pokazala je prisustvo pet uzrasnih kategorija: od 0+ do 4+. Klasa 1+ bila je najdominatnija uzrasna klasa, kako po godinama, tako i po sezonama uzorkovanja. Prosečna totalna dužina jedinki iznosila je 13,3 cm, a prosečna težina 38,26 g. Prosečna relativna težina jedinki u Savskom jezeru, u celokupnom uzorku, iznosila je 84,78 ± 1,09 g. Utvrđeno je prisustvo ukupno 8 kohorti. Na osnovu analize dužinsko-težinskih odnosa izračunate su i vrednosti faktora alometrije b koje su se kretale od 2,93 do 3,16, dok je vrednost ovog faktora u celom poduzorku iznosila 3,00. Analizom krive dužinsko-težinskog odnosa utvrđeno je da tačka infleksije ne postoji. Ribolovni napor (CPUE) je korišćen za analizu distribucije i relativne gustine jedinki, kako po staništima, tako i po godinama uzorkovanja i sezonama. Tokom 2009, 2010. i 2012. godine CPUE vrednosti varirale su od 0,4 ± 0,5 do 41,5 ± 22,1 jedinki po vrši po danu...abundant and successful non-native fish species in European freshwaters. Recent studies indicate that the black bullhead is one of the most dominant invasive fish species in Serbian waters as well. The aim of this research was to determine the population characteristics of this species in Sava Lake, as well as bioaccumulation of heavy metals and trace elements in different tissues. Fieldwork was conducted from 2009 to 2012. Black bullhead samples were collected monthly, for four days in a row. Once in the laboratory, specimens were measured for their total length (TL) and body weight (W). After dissection, the eviscerated body weight was measured, as well as liver and gonad weights. Population structure was determined by combining two methods – analyzing age and length-frequency distributions. Age was determined by combining otolith examination and Bhattacharya’s method. Age structure analysis has revealed the presence of five age classes: from 0+ to 4+. The class 1+ was the most dominant, by both year and season of sampling. The average total length was 13.3 cm and the average weight was 38.26 g. The mean value of the relative weight, across the entire sample, was 84.78 ± 1.09. The research revealed the presence of eight cohorts, in total. The length-weight allometric factor b ranged from 2.93 to 3.16, while the value of this factor, across the entire sample, was 3.00.The analysis of the length-weight relationship curve showed an absence of inflection points. Catch-per-unit-effort (CPUE) was used as an indicator of the black bullhead distribution and abundance in different habitats, years of sampling, and seasons. In 2009, 2010, and 2012, CPUE values fluctuated and ranged from 0.4 ± 0.5 to 41.5 ± 22.1 ind./net/night, while in 2011 they were low and rather uniform, ranging from 0.2 ± 0.3 to 3.4 ± 4.5 ind./net/night. CPUE values were highest in the macrophyte vegetation zone, as well as during autumn and spring..