This study investigated the effect of stocking density on growth performance, blood biochemical profiles, antioxidative capacity, and muscle quality of gibel carp (
Carassius gibelio
)
.
Gibel carps ...(initial body weight 57.04 ± 1.89 g) were reared at high stocking density (HSD, 10.85 kg m
−3
), medium stocking density (MSD, 5.06 kg m
−3
), and low stocking density (LSD, 1.47 kg m
−3
) for 60 days. The LSD group exhibited the highest growth rate, while HSD significantly inhibited fish growth. The muscular compositions of crude fat, crude ash, and moisture were significantly changed by stocking density, but crude protein content did not differ significantly. The stocking density altered the muscular texture profiles of gibel carp. Compared to either the HSD group or the MSD group, the highest levels of resilience and springiness occurred in the LSD group. Significant differences were observed in the levels of plasma glucose, alanine aminotransferase, aspartate aminotransferase, cholesterol, and creatinine among three groups. The fish exhibited the highest level of plasma cortisol as well as the lowest levels of triiodothyronine and thyroxine in the HSD group. The fish stocked in the LSD group showed the highest activities of superoxide dismutase, glutathione peroxidase, and catalase as well as the highest content of glutathione in liver. The significant highest total antioxidant capacity occurred in the fish stocked in the LSD group. The results showed that HSD resulted in chronic crowding stress, and exerted negative impact on growth performance, muscle quality, and antioxidative capacity of gibel carp.
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.
Non-native aquatic plants are amongst the major threats to freshwater biodiversity and climate change is expected to facilitate their further spread and invasiveness. To date, in Croatia, no complete ...list of non-native extant and horizon aquatic plants has been compiled nor has a risk screening been performed. To address this knowledge gap, 10 extant and 14 horizon aquatic plant species were screened for their risk of invasiveness in the Pannonian and Mediterranean regions of Croatia under current and predicted (future) climate conditions. Overall, 90% and 60% of the extant species were classified as high risk for the Pannonian and Mediterranean regions, respectively, under both climate scenarios. Of the horizon species, 42% were classified as high risk under current conditions and, under climate change, this proportion increased to 78%. The ‘top invasive’ species (i.e. scored as very high risk) under both climate conditions and for both regions were extant
Elodea nuttallii
and horizon
Lemna aequinoctialis
. The horizon
Hygrophila polysperma
was very high risk for the Mediterranean Region under current climate conditions and for both regions under projected climate conditions.
Azolla filiculoides
,
Elodea canadensis
,
Egeria densa
and
Utricularia gibba
were also classified as high risk under current climate conditions and, after accounting for climate change, they became of very high risk in both regions. Further,
Gymnocoronis spilanthoides
and
Lemna minuta
were found to pose a very high risk under climate change only for the Pannonian Region. It is anticipated that the outcomes of this study will contribute to knowledge of the invasiveness of aquatic plants in different climatic regions and enable prioritisation measures for their control/eradication.
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.
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.
Sampling was undertaken, with the same fishing gear and along the Sava River, from its source to its confluence, in September 2014 and September 2015. In total, 44 fish species were identified, of ...which 37 were native species and 7 were alien. Fish samples revealed independence in terms of both species composition and their abundance under different hydrological conditions. During flooding and high water levels in 2014, pelagic fish species were sampled in greater proportion than at lower water levels in 2015 when benthic fish species were more abundant. The flood wave in 2014 was accompanied by catch of common carp, Cyprinus carpio, a typical lower rhithron fish species in the upper course, and of tench, Tinca tinca, a typical potamon fish species of backwaters, in the main channel of the lower Sava River. One specimen of bighead goby, Ponticola kessleri, which is common in the potamon fish community, was caught during the 2015 sampling close to the boundary between the upper and middle sections of the Sava. This is the first record of Ponto-Caspian gobies in the inland waters of Slovenia. Its finding far upstream indicates a strong effect of an as yet unidentified stress along the Sava River up to the spot where the bighead goby was sampled. Finally, these results indicate that pelagic fish species are more resistant to the stressful effect of flooding than benthic species, and that the structure of fish communities is influenced/affected by flooding as a short-term stressor. The progressively increasing number of alien fish species downstream in the Sava River point to the effects of long-term human-induced stressors in the area.
Display omitted
•Farmed mirror carps were found in the trout fish zone of the Sava River•Tench, a backwater fish expelled to the main river channel by flooding•Pelagic fish species more resistant to flooding•Most upstream finding of bighead goby in the River Sava•The number of stressors on native ichthyofauna progressively increases downstream
Aquatic invasions are one of the major threats for freshwater ecosystems. However, in developing countries, knowledge of biological invasions, essential for the implementation of appropriate ...legislation, is often limited if not entirely lacking. In this regard, the identification of potentially invasive non-native species by risk screening, followed by a full risk assessment of the species ranked as higher risk, enables decision-makers to be informed about the extent of the threats posed to the recipient (risk assessment) area. In this study, 32 non-native extant and horizon fish species were screened for their risk of invasiveness under current and predicted climate conditions for the South Caucasus – a biodiversity and geopolitical hotspot that includes the countries of Armenia, Azerbaijan and Georgia. Overall, the number of very high-risk species increased from four (12.5%) under current climate conditions to 12 (37.5%) under predicted climate conditions. The highest-risk species under both conditions included the already established gibel carp
Carassius gibelio
and topmouth gudgeon
Pseudorasbora parva
, the locally translocated pikeperch
Sander lucioperca
and the horizon North African catfish
Clarias gariepinus
. Under predicted climate conditions, a very high risk of invasiveness was predicted also for the translocated three-spined stickleback
Gasterosteus aculeatus
and Eurasian perch
Perca fluviatilis
, for the already established eastern mosquitofish
Gambusia holbrooki
, ruffe
Gymnocephalus cernua
, sharpbelly
Hemiculter leucisculus
and Nile tilapia
Orechromis niloticus
, and for the horizon pumpkinseed
Lepomis gibbosus
and largemouth bass
Micropterus salmoides
. Future research on the non-native species in the South Caucasus should be conducted both country- and region-wide and should account not only for the high biodiversity, but also for the critical geopolitical situation affecting the study area.
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.
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.
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