Josipa Ferri

Growth and reproduction of Munida rutllanti (Decapoda: Anomura: Galatheidae) and impact of parasitism by Pleurocrypta sp. (Isopoda: Bopyridae) in the Adriatic Sea

Relative growth and reproductive biology of Munida rutllanti were investigated for the first time in the Adriatic Sea. A total of 93 8 individuals were analysed. Sex-ratio differed statistically from the expected 1:1. Six individuals exhibited secondary sex characteristics of both males and females. Carapace length of males ranged from 10.5 to 21.5 mm, while in females it ranged from 11.2 to 19.4 mm. Sexual dimorphism was observed in seven morphometric characters. Ovigerous females were first observed in summer and later in autumn with higher frequency. Realized fecundity showed wide variation (273 - 3250 eggs) and positive correlation between the brood and female size. An epicaridean isopod Pleurocrypta sp., parasitizing the gill chamber of both sexes was isolated and its effect on the oogenesis was studied by histological examination of host reproductive system. Growth inhibition, modification of secondary sex characteristics, as well as retardation of oogenesis and failure of oviposition, are repercussions of bopyrid infestation. Given the small prevalence ( 7 .8 5 %) of the bopyrid in the M. rutllanti Adriatic population, we assume that for the moment there is no severe effect on the host population dynamic.

The effect of artificial feed on blood biochemistry profile and liver histology of wild saddled bream, Oblada melanura (Sparidae)

Floating fish farms attract a great number of wild fish species, changing their behaviour and physiology. The saddled bream, Oblada melanura, sampled from populations aggregated around the Adriatic fish farm and from natural/control populations, were analysed for differences in eleven blood biochemistry parameters and liver histomorphology. The levels of lactate dehydrogenase (LDH), alkaline phosphatase (ALKP) and urea (URE) in cage-associated saddled bream (428.00±SD 321.56 U/L, 86.13±SD 39.87 U/L and 0.05±SD 0.16 mmol/L, respectively) were significantly lower than those observed in the control specimens (1047.06±SD 505.56 U/L, 125.75±SD 34.70 U/L and 1.99±SD 0.73 mmol/L, respectively). In contrast to that, concentrations of aspartate aminotransferase (AST) in cage-associated fish (87.63±SD 132.34 U/L) were higher than values noted for the control population (6.55±SD 5.90 U/L). URE and AST presented the main variables contributing to the discrimination between two analysed populations. One-way ANOSIM based on the blood parameters showed significant difference between saddled bream that fed around cages and those from the remote waters (R=0.697; P < 0.01). Hepatocytes of cage-associated fish contained large cytoplasmatic clear spaces indicating excessive accumulation of fat in the hepatocyte cytoplasm. All observed differences can be attributed to contrasting feeding behaviour of sampled populations but basic nutritional differences between them should be quantified in the future. Moreover, further research is necessary to detect their impact on the health status of the fish.

The age, growth and feeding habits of the European conger eel, Conger conger (L.) in the Adriatic Sea

Abstract This study determined basic biological data for the European conger eel Conger conger (L.) population in the coastal waters of the eastern Adriatic Sea. Juveniles and immature females dominated the coastal population, whereas males were relatively uncommon. The population structure determined by the study suggested spatial separation of sexes and spawning grounds in deeper waters. Both edge-type and marginal increment analyses confirmed the formation of a single growth annulus per year on the ground otoliths. The observed maximum age of the coastal conger eels was 8 years, although most of the sampled fish were 5 years old. The estimated parameters of the von Bertalanffy growth model suggested that the growth of the conger eels was relatively slow. C. conger is an opportunistic predator. Its diet was composed primarily of fishes, followed by crustaceans and cephalopods. Due to the evident site fidelity of the species, the wide prey spectrum of the conger eels (33 taxa) reflected the local benthic community structure.

A preliminary study on the age and growth of the argentine, Argentina sphyraena (Actinopterygii: Osmeriformes: Argentinidae) from the eastern Adriatic Sea

Background. Age determination is a basic step in understanding fish biology and dynamics of fish populations. The only available data on the age and growth of argentine, Argentina sphyraena Linnaeus, 1758, a noncommercially exploited species of the family Argentinidae, was published almost half a century ago. More recent reports are limited to general biological characteristics of A. sphyraena so the main goal of our study was to fill a gap by investigating age and growth of the eastern Adriatic population of this fish. Materials and methods. Samples of the argentine were collected in the eastern Adriatic Sea, during March 2011, using a bottom trawl. We analysed sagittal otolith morphology and morphometry; the age of each fish was determined from the number of growth zones on otoliths and relations between the observed otolith age and otolith morphometrics were constructed using a power model. Mean length-at-age was described using the von Bertalanffy growth model. Results. Sagittal otoliths of Argentina sphyraena displayed alternating opaque and translucent zones. The maximum observed age was 3 years for both females and males. Females that were 2+ and 3+ years old were the most numerous in the sampled population. The estimated values of the von Bertalanffy growth model parameters were: L∞ = 17.57 cm; k = 0.40 year –1; t0 = –1.39 years. The age of the argentine can be best predicted from the otolith thickness. Conclusion. The maximum lengths and ages recorded in this study confirmed that in warmer southern latitudes, Argentina sphyraena attains a smaller maximum size. It should be emphasized that the presented model described the growth of fish ages 1–3 and therefore is probably representative only for younger age groups of argentine.

Age and growth of the axillary wrasse, Symphodus mediterraneus (L.) from the eastern Adriatic Sea

Abstract The age and growth of Symphodus mediterraneus were determined by examining the sagittal otoliths of 245 specimens (81 males, 160 females and four individuals of indeterminate sex) collected in the eastern Adriatic Sea between October and December 2009. Total lengths of males and females ranged from 74 to 154 mm and from 51 to 131 mm, respectively. Polished otoliths displayed well-defined alternating opaque and translucent rings. Age was determined by two independent readers who considered one opaque and one translucent ring to represent one year’s growth. In order to determine the first annual ring we examined daily rings and concluded that the first opaque annulus roughly corresponds with the first year of life. Most of the specimens were between two and three years old, with the maximum observed age of three years for males and five years for females. The length-at-age was described by the von Bertalanffy growth curve and significant differences were found between males (L∞ = 16.09 cm, k = 0.50 and t0 = –0.83) and females (L∞ = 14.11 cm, k = 0.33 and t0 = –1.42).