Culture of Seriola dumerili in a marine ecosystem: Insights from genetic and morphometric fish traits and implications of escape events

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Interakcija plivarice za ulov sitne plave ribe i njenih grabežljivaca – preliminarno istraživanje u istočnom Jadranu

Due to very good collaboration with one commercial purse seiner, using “Srdelara” and operating in fishing zone G, preliminary data concerning the interaction between small pelagic purse seine fishery and its predators were obtained. According to the notes taken by experience observer on-board in period from year 2013 to 2016, seems that tunas, dolphins and swordfish were the faithful companions of purse seiner fisherman with abundance of 68.6%, 22.0% and 9.4%, respectively. Although they were present all year round, their monthly pattern of appearance indicated that less tunas were recorded in May-June, more dolphins were noted from July to October while swordfish were mostly abundant in winter (January-March). Within the investigated period, slightly increasing trend of tuna and dolphins’ appearance was recorded, although statistically not significant. Analysing possible correlation between purse seine catches and predator’s abundances, revealed that appearance of tuna had negative impact on the catches (dispersion of schools), while realised catches in presence of dolphins were quite good so it seems that they tend to round up small pelagic fish schools.Zahvaljujući vrlo dobroj suradnji s ribarskim sektorom, točnije jednom komercijalnom plivaricom koja koristi plivaricu “Srdelaru” u ribolovnoj zoni G, su prikupljeni preliminarni podaci vezani uz interakciju ovog tipa ribolova i njegovih predatora. U razdoblju od 2013. do 2016. godine, prema podacima prikupljenim od strane iskusnog promatrača na palubi ove komercijalne plivarice, je utvrđeno da su tune, dupini i igluni najvjerniji pratioci ovog tipa ribolova te da je njihova abundancija redom bila 68,6%, 22,0% i 9,4%. Premda je uočeno da su navedeni grabežljivci prisutni tijekom cijele godine ipak je njihova pojavnost kolebala od mjeseca do mjeseca – najmanje tuna je zabilježeno u razdoblju od svibnja do lipnja, nešto više dupina je uočeno od srpnja do listopada, dok su igluni bili najbrojniji od siječnja do ožujka. Tijekom istraživanog razdoblja je utvrđeno blago povećanje broja tuna i dupina premda to povećanje nije bilo statistički značajno. Korelirajući ulove ostvarene istraživanom komercijalnom plivaricom i broja uočenih grabežljivaca, čini se da će u slučaju pojave tune ostvareni ulov biti manji s obzirom da ona rasprši ciljanu plovu sitne plave ribe, dok će relatvno dobar ulov ista plivarica ostvariti u prisutnosti dupina koji će uočenu plovu još više zbiti

Prisutnost alohtone kamenice Crassostrea gigas u Jadranskom moru

The Pacific oyster, Crassostrea gigas, was introduced into the Europe in the late 1960s for aquaculture purposes and has since spread extensively in Mediterranean waters. For the first time, screening of the four ecologically most suitable bays along the Eastern Adriatic coast was conducted to detect the possible presence of non-native oysters. Sequencing analysis of a fragment of mitochondrial 16S rRNA was examined to demonstrate the presence of the exotic species C. gigas in the natural environments of the northern and central coastal areas of the eastern Adriatic. The likely routes of invasion are discussed and the importance of monitoring the distribution of feral C. gigas populations emphasized, with a focus on the potential direct and indirect effects on the native European flat oyster, Ostrea edulis.Japanska ili pacifička kamenica, Crassostrea gigas, uvedena je u Europu kasnih 1960-ih za potrebe akvakulture i od tada se intenzivno proširila po Mediteranu. Po prvi put je izvršen pregled četiriju ekološki najprikladnijih zaljeva istočne obale Jadrana kako bi se utvrdila prisutnost alohtone kamenice. Analiza djelomičnog fragmenta mitohondrijske 16S rRNA je korištena kako bi se molekularno identificirala egzotična vrsta C. gigas u prirodnim staništima sjevernih i središnjih obalnih područja istočnog Jadrana. Mogući invazijski putevi su raspravljani kao i važnost praćenja distribucije populacija C. gigas, s naglaskom na potencijalne izravne i neizravne učinke na autohtonu europsku plosnatu kamenicu Ostrea edulis koja obitava u Jadranskom moru

Reproductive cycle of a non-native oyster, Crassostrea gigas, in the Adriatic Sea

The Pacific oyster Crassostrea gigas was introduced for the aquaculture purposes in many different parts of the world. However, the species has never been officially introduced for commercial farming in the Croatian part of the Adriatic Sea. Interestingly, in the 1970s, the Pacific oyster has been reported in the natural habitats of the Lim Bay, in northern Adriatic Sea. Although the species was recorded there, there is a lack of knowledge about its biology and ecology in this region, including a reproductive cycle. Information on the reproductive biology of non-indigenous species in new areas is crucial for prediction of their future survival and possible spread in invaded habitats. In this study, we provide the first data on the reproductive biology of the Pacific oyster in the Adriatic Sea, the northernmost part of the Mediterranean Sea. Quantitative and qualitative methods of gonad tissue analysis were conducted, and effects of environmental conditions on the gametogenesis were evaluated during two reproductive cycles. Our study confirmed that environmental conditions in the Lim Bay were favourable for the reproduction of the species. The Pacific oyster reproduced once per year and had a prolonged spawning period. Water temperature was the main factor affecting gonad development and oocyte size, while chlorophyll a concentration had an impact on the oocyte development in terms of their size.

Genetic discrimination of wild versus farmed gilthead sea bream

Farm escapees and their offspring impose a significant impact on the environment and may therefore alter the future evolutionary trajectories of wild populations. To date, there is no management plan in place in Mediterranean countries to prevent fish escapes. Here, we investigate microsatellite length variations in three candidate genes, including prolactin (PRL), growth hormone (GH), and the receptor activity modifying protein 3 gene (RAMP3), to study the genetic structure of the main fish species farmed in the Mediterranean, gilthead seabream (Sparus aurata). We also evaluate the performance of microsatellites in discriminating fish origin (wild or farmed). Results from 298 individuals, including farmed, wild adult and juvenile fish were compared with results from 19 neutral markers used in a previous study. All loci were polymorphic, selectively neutral, and had the statistical power to detect significant population differentiation. Global FST was similar to that estimated using 19 loci (0.019 and 0.023, respectively), while pairwise comparisons identified farmed populations as the main drivers of genetic divergence, with a much higher magnitude of overall genetic differentiation within farmed populations (0.076) than that estimated using the 19 neutral microsatellite loci (0.041). Bayesian structural analysis showed that the PRL, GH, and RAMP3 markers were able to distinguish farmed from wild populations, but were not able to distinguish different wild groups as 19 neutral microsatellite markers did. Farmed populations of different origins were assigned to a separate cluster with a high individual assignment score (>88%). It appears that the candidate markers are more influenced by artificial selection compared to neutral markers. Further validation of their efficiency in discriminating wild, farmed, and mixed fish origins using a more robust sample size is needed to ensure their potential use in an escaped fish monitoring programme

Anomalous colouration of a starry weever, Trachinus radiatus (Actinopterygii: Perciformes: Trachinidae), from the Adriatic Sea

The record of abnormally pigmented starry weever, Trachinus radiatus Cuvier, 1829, is described. The specimen was caught in Nature Park Lastovo archipelago, eastern Adriatic Sea, and displayed an overall lack of usual dark brown pigmentation. The skin was marked by a predominance of yellow to red pigments corresponding with a rare colour anomaly condition of xanthochromism. Due to the unusual appearance of the specimen, we used molecular methods for proper identification of the species. This seems to be the first documented record of xanthochromism in the family Trachinidae

New records of recently described Zebrus pallaoroi (Actinopterygii: Gobiiformes: Gobiidae) with notes on its morphology, ecology, and molecular identification

The family Gobiidae represents the species-richest family of fishes in the Mediterranean Sea. However, many Mediterranean gobiid species are poorly known with just one or few species records in total. Among those species, the recently described Zebrus pallaoroi Kovačić, Šanda et Vukić, 2021 has been known only from the localities in the species description: the southern Adriatic, northern Ionian, and northern and western Aegean seas. The additional specimens of this species were collected in central and northern Adriatic Sea. The identification was confirmed by morphological and genetic methods. The morphological and preserved coloration characters were compared with the data from the limited type material and the alternative preserved coloration diagnostic character was suggested. The first data on alive and freshly dead coloration are reported. The phylogenetic analysis was performed on sequenced COI, cytochrome b, and rhodopsin genes. The analyzed molecular markers placed Z. pallaoroi in a distinct clade within Zebrus–Millerigobius group. The preference of this species for the very shallow habitat is confirmed and discussed