Phenotypic traits of gilthead seabream Sparus aurata (Linnaeus, 1758) in wild and human-mediated environments of the eastern Adriatic Sea

Ribe, kao živi organizmi, izrazito su prilagodljive prirodnim i antropogeno uvjetovanim okolišima gdje svojstvo fenotipske plastičnosti omogućava poveznicu starih i novih sredina putem morfoloških, fizioloških prilagodbi ponašanja. Posljednjih godina zamijećeno je povećanje ulova divlje komarče na području istočnog Jadranskog mora, gdje riblji zbjegovi i priljev jedinki iz kavezno povezanih okoliša uzgajališta tuna doprinose povećanju brojnosti populacija u prirodnom staništu. Predmetnim istraživanjem vrednovane su fenotipske prilagodbe kod komarče u okolišu pod utjecajem kaveznog uzgoja tuna te fenotipska obilježja divljih i uzgojnih populacija s ciljem razvoja brzog i učinkovitog alata za raspoznavanje zbjegova u lovini. Primjenom metoda geometrijske morfometrije kvantificirana su morfološka obilježja tijela i otolita, dok je fiziološki odgovor promatran kroz trofički status i spolna obilježja protandričnih populacija. Cjelogodišnja prostorna i vremenska zastupljenost komarči oko uzgajališta tuna upućuje na važnu ulogu jadranskih uzgajališta tuna kao pogodnih staništa za divlju komarču. Taj izmijenjeni okoliš u kojem prevladava drugačija dinamika morskih struja i dostupnost plijena uvjetovao je specifičan odgovor kod komarče formirajući novi kavezno povezani morfotip. Manja i tuplja glava te vretenastije tijelo predstavljaju osnovna obilježja spomenutog morfotipa. U blizini kaveza tuna dokumentirana je promjena spola komarče pri nižim dužinskim veličinama u odnosu na prirodne populacije zbog značajne trofičke podrške koja osigurava bolji kondicijski i reproduktivni status. Promatrajući divlje i uzgojne komarče, primjenom metoda geometrijske morfometrije uspješno su klasificirane jedinke prema izvornom podrijetlu u iznosu od 99,6 % s obzirom na oblik tijela te više od 70 % u odnosu na oblik otolita. Zaokruženiji profil glave sa supraterminalnim pozicioniranim ustima te zdepast oblik tijela s tamnijom i bljeđom srebrnkasto-sivom obojenošću glavna su obilježja uzgojnih komarči, dok su divlje jedinke opisane s izduženijim tijelom i subterminalnim ustima na većem profilu glave. Prikupljene informacije primjenjive su u budućim biotehnološkim istraživanjima za potrebe prepoznavanja podrijetla ribe strojnim učenjem i dugoročno u upravljanju zbjegovima te u razvoju selekcijskih programa vrsta iz akvakulture.Fish, as living organisms, are highly adaptable to natural and human-mediated environments due to their morphological, physiological and behavioural adaptations through phenotypic plasticity. In recent years, a increase of gilthead seabream in fisheries landings has been documented in the eastern Adriatic Sea, with aquaculture escapes and spillover of seabream from tuna farm concession areas contributing to population increases in natural habitats. The aim of this research was to investigate the phenotypic adaptations of gilthead seabream in a tuna farm impacted environment and to evaluate the phenotypic characteristics of wild and farmed populations in order to develop a rapid and effective tool for detecting escapes in fisheries landings. Morphological characteristics of body and otolith shape were quantified by geometric morphometrics methods, while physiological responses were studied through trophic status and sexual characteristics of protandrous populations. The year-round spatial and temporal occurrence of seabream near tuna farms indicates that they play an important role as suitable habitat for wild seabream populations in the Adriatic Sea. This altered environment, characterised by different hydrodynamics and prey availability compared to natural habitats, has triggered a specific phenotypic response of seabream by forming a new morphotype associated with tuna farms. The smaller and blunt head and the more spindle-shaped body are the main characteristics of the mentioned morphotype. In the vicinity of tuna farms, the sex change of seabream has been documented at lower lengths compared to wild populations, due to the significant trophic support that ensures better condition and reproductive status. When observing wild and farmed seabream, geometric morphometrics methods successfully assigned 99.6% of individuals to their correct origin in terms of body shape and more than 70% in terms of otolith shape. A rounder head profile with a supraterminal positioned mouth and a stocky body shape with darker and paler silver-grey coloration are the main characteristics of farmed seabream, while wild individuals are described with an elongated body and a subterminal mouth on a larger head profile. The information collected in this research can be used in future biotechnological research to identify the origin of fish through machine learning and, in the long term, in the management of escapes and the development of selection programmes for aquaculture species