Round goby
is one of the three invasive Ponto-Caspian gobies found in the Sava River basin in Croatia. It has a negative effect on the native ecosystems and is more abundant in highly polluted areas. ...The objective of this study was to determine the fluctuating asymmetry of four morphometric characters, as well as otolith width and length. Thirty individuals of
were collected and analysed at two sampling sites in the main course of the Sava (Babina Greda, Slavonski Brod) and in a modified habitat (Sava-Odra canal). The squared coefficient of asymmetry variation was used to analyse potential differences between populations. We identified variations in the asymmetry values of the analysed characters, as well as otolith width and length between sampling sites. The highest fluctuating asymmetry was observed in individuals at the Babina Greda sampling site, which could be due to high environmental stress. The results of the study show that the study of fluctuating asymmetry can be used on invasive fish species as a simple approach to identifying habitat quality.
Round goby
is one of the three invasive Ponto-Caspian gobies found in the Sava River basin in Croatia. It has a negative effect on the native ecosystems due to its high invasive potential that ...enables its rapid spread upstream in inland watercourses. The objective of this study was to determine the differences in sagittal otolith and scale shape of the frontal and established populations of
in two different habitat types. At two sampling sites in the main course of the Sava (Babina Greda, Slavonski Brod) and in a modified habitat (Sava-Odra canal), 20 individuals of
were collected and analysed. The geometric morphometric method was used together with Procrustes analysis of variance, canonical variate analysis and discriminant function analysis to analyse the otolith and scale shape. Significant differences in both otolith and scale shapes were found between settled (Babina Greda) and frontal (Slavonski Brod) populations from the main course of the Sava River. The main differences were the wider anterior part of the scales and a more pronounced open indentation on the otolith of the Babina Greda population. The settled population in the Sava-Odra canal was significantly different in otolith shape from the Babina Greda population but not from the Slavonski Brod population, suggesting that the upstream migration consisted of individuals with specific phenotype and genotype. Otoliths generally expressed greater shape variability than scales and thus may be more useful for differentiating between closely related populations on a finer scale. The results of this study suggest that the shape of otoliths and scales can be used to distinguish between closely related populations of
from different habitats but more comprehensive studies are needed due to the small number of samples.
Introduced and translocated non-native species are a major threat to biodiversity, especially in aquatic habitats. Efforts aimed at the mitigation of impacts and the implementation of preventative ...measures for the conservation of native biota must rely upon an accurate evaluation of the risks posed by non-native invasive species and are expected to be strengthened by international collaboration. In this study, 76 non-native freshwater fish species of which 48 extant (both introduced and translocated) and 28 horizon were screened for their risk of invasiveness in the neighbouring countries of Croatia and Slovenia under current and future climatic conditions. Using the Aquatic Species Invasiveness Screening Kit (AS-ISK), threshold scores for the Basic Risk Assessment (BRA) and for the combined BRA and Climate Change Assessment (BRA + CCA) allowed to distinguish with a high level of accuracy between low-, medium- and high-risk species – the latter representing ≈70% of the screened species. Brown bullhead Ameiurus nebulosus, round goby Neogobius melanostomus, topmouth gudgeon Pseudorasbora parva and Wels catfish Silurus glanis were the highest-scoring species for Croatia, and Ameiurus nebulosus, snakehead Channa argus and Pseudorasbora parva for Slovenia. There were discrepancies in medium- and high-risk rankings between Croatia and Slovenia for 12 species. Upon comparison of the BRA outcomes with those based on the Freshwater Fish Invasiveness Screening Kit (the predecessor of the AS-ISK), the risk changed for six species in Croatia and five in Slovenia. After accounting for predicted climate change conditions, the BRA + CCA risk scores increased for ≈50% of the species, with western mosquitofish Gambusia affinis, channel catfish Ictalurus punctatus and black carp Mylopharyngodon piceus achieving the highest score increment for Croatia, and round goby Neogobius melanostomus and Chinese (Amur) sleeper Perccottus glenii for Slovenia. The present outcomes will assist decision-makers in the implementation of appropriate measures for the management of extant non-native species and the potential introduction of horizon species. This is important for the regulation of pet trade and aquaculture as well as for management strategies aimed at the conservation of native biodiversity, which in the case of neighbouring countries/jurisdictions will benefit from joint efforts relying on a full risk assessment for the species classified at higher risk of invasiveness.
Introduction: The genetic diversity of brown trout in the Western Balkans has been disrupted by the introduction of non-native Atlantic phylogenetic lineages and non-native haplotypes of the Danubian ...phylogenetic lineage. The Western Balkans is characterized by the greatest phenotypic and genotypic diversity of trout populations, and a large part of the internal territory belongs to the Black Sea basin, where the Danubian Da1 haplotype is native. Artificial propagation of non-native lineages in the Western Balkans has a long history, and these populations are often the only available material for stocking rivers attractive for fishing. Material and Methods: Fifteen populations in the Danube basin of the continental Croatia were analysed. The analysis of eight microsatellite loci was performed to determine the structure of brown trout populations, as well as the degree of introgression of non-native genetic material into the native. Results and Disscusion: The results of this study showed significant genetic similarity among brown trout populations, confirming a long history of introduction with non-native genetic material. The main reason was uncontrolled stocking with inadequate material, which is available in fish farms and consists mainly of brown trout of the Atlantic phylogenetic lineage. The results of this study also indicated stocking with brown trout of the non-native haplotypes of the Danubian phylogenetic lineage. The potential breeding origin of brown trout carrying the Danubian Da2 mtDNA haplotype and ways of its introduction into rivers have yet to be investigated. For the survival of the unique gene pool of brown trout in Croatian rivers, it is of fundamental importance to know the structure of wild and farmed populations with the aim of proposing and implementing conservation measures.
Larvae of the European flat oyster (Ostrea edulis) were cryopreserved using two protocols originally developed for other bivalvian species with several modifications. Culture of the European flat ...oyster went through several setbacks due to parasitic diseases, thus, assisted reproductive technologies such as larval cryopreservation can aid in prompt restoration of lost populations and thus facilitate farming of the species. Veliger larvae were diluted in two basic extenders (0.4 M trehalose or 0.4 M sucrose) supplemented with ethylene glycol (EG), dimethyl-sulfoxide (DMSO) or propylene glycol (PG) in concentrations of 10–20% with or without the addition of polyvinylpyrrolidone (average MW-40,000; PVP-40). Larvae were loaded into 0.25-ml or 0.5-ml straws and cryopreserved in a controlled-rate freezer using two slow cooling profiles. Assessment of larval survival 20 min or 24 h post-thaw revealed that the cooling profiles and the type of extender used did not have a significant effect on survival rates. On the other hand, the type of cryoprotectant, straw volume and the time of assessment had a significant main effect on larval survival percentages (p < 0.001 in all three cases). Survival percentages of 70–80% were observed 20 min post-thaw which decreased to 40–60% at 24 h. Generally, EG and DMSO resulted in higher post-thaw larval survival than did PG when larvae were cryopreserved in 0.25-ml straws, whereas, these differences were not detected when 0.5-ml straws were employed. Results of these experiments will allow later studies on long-term survival of cryopreserved European flat oyster larvae.
•Larvae of the European flat oyster can be cryopreserved using a controlled-rate freezer•Ethylene glycol and dimethyl-sulfoxide provide good protection during cryopreservation•Post-thaw survival of larvae decreases with time\
Populacije potočne pastrve i njihova morfološka različitost u potocima Samoborsko-žumberačkog gorja još nije istraživana. Stoga je cilj ovog rada bio utvrditi kondiciju, dužinsko masene odnose, ...morfometrijske i merističke značajke između pet populacija potočne pastrve. Analizirano je ukupno 70 primjeraka potočne pastrve. Najniži Fultonov kondicijski
faktor zabilježen je na potoku Kupčina, a najviši na potoku Slapnica. Negativan alometrijski rast jedinki zabilježen je jedino na potoku Gradna. Utvrđene su značajne statističke razlike za duljinu glave, širinu i visinu usta, visinu leđne i prsne peraje, broju mekih žbica u leđnoj peraji i broju piloričkih nastavaka između lokacija. Najveća sličnost jedinki potočne pastrve na temelju morfometrijskih i merističkih značajki uočena je između populacija potoka Slapnice i Rudarske Gradne. Identificirana statistički značajna morfometrijska svojstva ukazuju na genetsku varijabilnost između analiziranih uzoraka i mogućnost da je vršeno poribljavanje s linijama pastrva iz uzgoja, osobito na potocima Slapnica i Rudarska Gradna.Daljnja istraživanja trebaju biti usmjerena na molekularne analize kako bi se utvrdila prisutnost Atlantskih linija potočne pastrve (unesenih za potrebe uzgoja) i njihove potencijalne introgresije gena u domaću Dunavsku pastrvu, kako bi se predložile odgovarajuće mjere zaštite.
The study investigates feeding habits of thermophilic species and species with subtropical affinity in the fishing catch in the Bay of Medulin (northeastern Adriatic Sea), and contributes to the ...knowledge about their presence in recently extended distributional range. In our methodology, the presence of the Seriola dumerili, Sphyraena sphyraena, Lichia amia, Coryphaena hippurus, Caranx crysos, Pomatomus saltatrix, and incidence of Trachinotus ovatus is recorded. A total of 220 specimens are captured during 2017, 2018 and 2019. A dietary assessment is performed, and the index of relative importance IRI was calculated for each prey category. Diet overlap is calculated using Schoener’s index, based on IRI. The principal diet of C. hippurus included Sardina pilchardus and Loligo vulgaris. Pomatomus saltatrix consumed species from the Sparidae family and T. ovatus crustaceans from the Mysidacea family. Different species from genus Atherina are represented important foods for L. amia, S. dumerili and S. sphyraena. Diets of significant importance for L. amia included fishes from the family Sparidae, for S. sphyraena from the Carangidae family, and S. dumerili from the Clupeidae and Muliidae families. Our analysis of diet overlap is based on IRI suggests no diet overlap between analysed fish species from Medulin Bay, and that these species utilise differing trophic niches.
At the beginning of the 20th century, the middle section of the Sava River in Croatia was unaffected by major human activities and rich in ichthyofauna. The Sava River was important for commercial ...and recreational fishing for the local population, which still remains today. However, the 1920s mining industry was established in Slovenia, which emitted carbon dust into the Sava River. At the same time, the construction of embankments to mitigate flooding started in the middle section. Furthermore, in the 1980s, the Krško nuclear power plant (NPP), and in the 2010s, the Krško hydropower plant (HPP) were built in Slovenia. These activities could have an impact on the composition of fish communities downstream from the major sources of disturbances. Therefore, the main aim of this paper were to analyze the changes in fish assemblages of the Sava River from 1978 to 2017, prior to and after the construction of Krško NPP and HPP at the Medsave site on the Sava River, 20 km downstream from the major construction operations. Collected data were divided into four sampling periods (SP): SP1, from 1978 to 1980; SP2, from 1991 to 1994; SP3, from 2001 to 2006, and SP4 from 2011 to 2017. Besides alien fish species, water quality and hydromorphological modifications were identified as significant stressors. In SP1 and SP2 limnophilic and eurytopic fish groups were predominant, and 26 different fish species were identified, but in SP3 and SP4 rheophilic fish groups become dominant, and the diversity has declined to 21 species. Threatened species blageon, Telestes souffia seems to be missing from the main course of the Sava River in last 20 years. It can be concluded that disturbances in the fish assemblage pattern have coincided with the presence of multiple stressors of human origin.
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•Variations in fish assemblages of the Sava River from 1978 to 2017 were analyzed.•Limnophilic and eurytopic types of fish group were predominant from 1978 to 1980.•Four alien fish species recorded 1978–1991, of which three remained until today.•Changes in species composition and decline in diversity has been noted after 2001.•Threatened Telestes souffia appears to be missing from the Medsave site.
Salmonids are an extensively hatchery-reared group of fishes that have been introduced worldwide mainly for their high commercial and recreational value. The Balkan Peninsula (south-eastern Europe) ...is characterised by an outstanding salmonid diversity that has become threatened by the introduction of non-native salmonids whose potential risk of invasiveness in the region remains unknown and especially so under predicted climate change conditions. In this study, 13 extant and four horizon non-native salmonid species were screened for their risk of invasiveness in the Danube and Adriatic basins of four Balkan countries. Overall, six (35%) of the screened species were ranked as carrying a high risk of invasiveness under current climate conditions, whereas under predicted conditions of global warming, this number decreased to three (17%). Under current climate conditions, the very high risk (‘top invasive’) species were rainbow trout
Oncorhynchus mykiss
and brown trout
Salmo trutta
(
sensu stricto
), whereas under predicted climate change, this was true only of
O. mykiss
. A high risk was also attributed to horizon vendace
Coregonus albula
and lake charr
Salvelinus namaycush
, and to extant Atlantic salmon
Salmo salar
and brook trout
Salvelinus fontinalis
, whose risk of invasiveness, except for
S. fontinalis
, decreased to medium. For the other eleven medium-risk species, the risk score decreased under predicted climate change, but still remained medium. The outcomes of this study reveal that global warming will influence salmonids and that only species with wider temperature tolerance, such as
O. mykiss
will likely prevail. It is anticipated that the present results may contribute to the implementation of appropriate management plans to prevent the introduction and translocation of non-native salmonids across the Balkan Peninsula. Additionally, adequate measures should be developed for aquaculture facilities to prevent escapees of non-native salmonids with a high risk of invasiveness, especially into recipient areas of high conservation value.
Brown trout is a salmonid fish with a natural range extending throughout western Eurasia and North Africa. Due to its commercial value, it has also been introduced worldwide. In continental Croatia, ...introduced trout of the Atlantic lineage hybridizes with native trout of the Danubian lineage, threatening the native genetic diversity. The geometric morphometrics approach was used in this study to analyse changes in shape between native trout, introduced trout and their hybrids, classified
a priori
by molecular phylogenetic analyses. A total of 19 landmarks and semi-landmarks were used to capture the shape of 92 trout individuals belonging to two lineages and their hybrids. Canonical variate analysis and discriminant function analysis were used to analyse and describe shape variation. A significant difference was found between the shape of the Atlantic lineage trout and both Danubian lineage trout and hybrids, with the most prominent differences in body depth, head length and eye size. No statistically significant shape differences were observed between Danubian lineage trout and the hybrids. The observed significant differences in shape could be the result of genetic diversity or trout phenotypic plasticity. Further studies are needed to clarify the origin of this variation in shape.
La truite brune est un poisson salmonidé dont l'aire de répartition naturelle s'étend à toute l'Eurasie occidentale et à l'Afrique du Nord. En raison de sa valeur commerciale, elle a également été introduite dans le monde entier. En Croatie continentale, la truite introduite de la lignée atlantique s'hybride avec la truite indigène de la lignée danubienne, menaçant la diversité génétique indigène. L'approche morphométrique géométrique a été utilisée dans cette étude pour analyser les changements de forme entre les truites indigènes, les truites introduites et leurs hybrides, classées a priori par des analyses phylogénétiques moléculaires. Un total de 19 points de repère et semi-points de repère ont été utilisés pour saisir la forme de 92 individus de truites appartenant à deux lignées et à leurs hybrides. L'analyse canonique des variables et l'analyse de la fonction discriminante ont été utilisées pour analyser et décrire la variation de forme. Une différence significative a été trouvée entre la forme de la truite de la lignée atlantique et celle de la truite de la lignée danubienne et de ses hybrides, les différences les plus importantes concernant la profondeur du corps, la longueur de la tête et la taille des yeux. Aucune différence de forme statistiquement significative n'a été observée entre les truites de la lignée danubienne et les hybrides. Les différences significatives de forme observées pourraient être le résultat de la diversité génétique ou de la plasticité phénotypique des truites. Des études supplémentaires sont nécessaires pour clarifier l'origine de cette variation de forme.
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