Càrrega parasitària de les espècies de peixos presents a la dieta del corb marí emplomallat del Mediterrani (Phalacrocorax aristotelis desmarestii)

Abstract

The Mediterranean Shag (Phalacrocorax aristotelis desmarestii) is a specie of seabird closely associated with the marine environment. It is considered an opportunistic specie, as it varies its feeding habits, spatial distribution, and timing based on the availability of prey species and their location. Although it has a variable diet, the most common prey species observed include Mediterranean sand eel (Gymnammodytes sp.), big-scale sand smelt (Atherina sp.), Balearic conger (Ariosoma balearicum), and bogue (Boops boops). This adaptability makes it widely used as an indicator of changes in marine ecosystems due to its generalist diet. In this study, the parasite load of the fish that constitute the diet of the Mediterranean Shag was examined in order to identify the transmission vectors of parasites affecting this seabird species. Morphological and, if necessary, biomolecular analysis of potential parasites present in the most common prey species in the shag's diet was conducted. A total of 207 individuals from 24 different species were analyzed. The results obtained show that H. aduncum has being the most frequent parasite, present in 60.87% of the species studied. A high prevalence of Ceratothoa parallela has being observed in the mouth of the bogue (Boops boops), and the presence of Anilocra physodes has being also detected. In the Atherinidae family, H. aduncum has being found in A. boyeri and A. hepsetus, but with a higher prevalence in A. boyeri. The grey gurnard fish (Eutrigla gurnardus) has being showed a high prevalence and average intensity of H. aduncum. Other species such as red mullet (Mullus barbatus), Mediterranean damselfish (Chromis chromis), and the four-spot megrim (Lepidorhombus boscii) also has being showed the presence of other parasites. Some species hasn’t being showed parasite infestation, possibly due to their low presence or the small number of individuals studied. Pagrus and seabream stood out with a high intensity of parasitism, as they are common fish in the Mediterranean diet. Furthermore, a significant correlation has being observed between the size and total weight of A. boyeri and the intensity of parasitism. This influence has being also observed in the weight of the group of individuals analyzed

The Mediterranean Shag (Phalacrocorax aristotelis desmarestii) is a specie of seabird closely associated with the marine environment. It is considered an opportunistic specie, as it varies its feeding habits, spatial distribution, and timing based on the availability of prey species and their location. Although it has a variable diet, the most common prey species observed include Mediterranean sand eel (Gymnammodytes sp.), big-scale sand smelt (Atherina sp.), Balearic conger (Ariosoma balearicum), and bogue (Boops boops). This adaptability makes it widely used as an indicator of changes in marine ecosystems due to its generalist diet. In this study, the parasite load of the fish that constitute the diet of the Mediterranean Shag was examined in order to identify the transmission vectors of parasites affecting this seabird species. Morphological and, if necessary, biomolecular analysis of potential parasites present in the most common prey species in the shag's diet was conducted. A total of 207 individuals from 24 different species were analyzed. The results obtained show that H. aduncum has being the most frequent parasite, present in 60.87% of the species studied. A high prevalence of Ceratothoa parallela has being observed in the mouth of the bogue (Boops boops), and the presence of Anilocra physodes has being also detected. In the Atherinidae family, H. aduncum has being found in A. boyeri and A. hepsetus, but with a higher prevalence in A. boyeri. The grey gurnard fish (Eutrigla gurnardus) has being showed a high prevalence and average intensity of H. aduncum. Other species such as red mullet (Mullus barbatus), Mediterranean damselfish (Chromis chromis), and the four-spot megrim (Lepidorhombus boscii) also has being showed the presence of other parasites. Some species hasn’t being showed parasite infestation, possibly due to their low presence or the small number of individuals studied. Pagrus and seabream stood out with a high intensity of parasitism, as they are common fish in the Mediterranean diet. Furthermore, a significant correlation has being observed between the size and total weight of A. boyeri and the intensity of parasitism. This influence has being also observed in the weight of the group of individuals analyzed