Search

One of the major problems in artificial eel reproduction is identification of broodstock with high performance reproductive characteristics. The aim of this study was to study population characteristics and the reproductive potential of eels (Anguilla anguilla) located in Valle Campo valley (Comacchio, Italy). A total of 200 eels/period (spring–summer and autumn–winter) were measured to obtain an external indicator of their maturation state. Morphometric parameters were used to calculate condition factor (K), eye index (EI) and pectoral fin length index (PFLI). Silver index analyses showed the lack of silver males and of fully mature females. Most represented females were yellow females at stage II. Silver females represented 27.9% of the population. Seasonal analysis shows how temperature reduction favoured the presence of silver females versus yellow females. Statistical analysis of EI, cranial (CI), PFLI and gonadosomatic (GSI) indexes showed that significant differences were found for EI, CI, PFLI and GSI between yellow and silver eels. No significant difference was found between stage III and IV silver eels, while a significant difference for EI was found between stage I and II yellow eels and for IC at stage II with respect to all other stages. The present study defined how Valle Campo could present environmental and trophic conditions which could favour precocious development of a population of silver females with a noticeable reproductive potential, to be used in open sea release or in artificial reproduction programmes. On the contrary, the valley seems to present unfavourable conditions for both development and sexual maturation of male eels.

This study aimed to set up a method for the long-term management of Adriatic sturgeon, through the analysis of sex steroids and the genetic profiling of individuals in order to maximize the already reduced genetic variability of this species. Ten A. naccarii adults (nine of captive origin, one captured in the Ticino river and then moved into captivity) and eight subadults located in a semi-natural land-locked pond in Abbiategrasso (Milan, Italy) were analysed. Plasma testosterone differed significantly in the eight analysed subadults allowing their differentiation into two groups: the first group with an average testosterone concentration of 5.42 ± 1.31 ng/ml (probably female) and the second group with an average of 423.14 ± 75.97 ng/ml (probably male), as subsequently confirmed by artificial stripping. The plasma testosterone level was also significantly different between adult males and females (371.37 ± 43.58 vs. 95.34 ± 51.10 ng/ml), while the E2 levels showed no significant differences. Animals were genotyped on the basis of 10 microsatellite loci and their parental relationships were defined: four adults, two females and two males, generated the eight subadults. On the basis of pedigree analyses and genetic distances, 15 unrelated couples were identified for the future breeding seasons. Finally, the adult female captured in the Ticino River showed an interesting genetic profile, widely different from all of the other 17 specimens analysed, and represents a valuable source of genetic diversity.

Florfenicol (FF) is employed in fish farms to contest or prevent bacterial infections. However, this pharmaceutical may produce reactive oxygen species that may cause biochemical changes in antibiotic-treated fish. The aim of this study was to evaluate the effect of FF on Rainbow Trout Oncorhynchus mykiss treated for 10 d with 7.5 and 15 mg/kg FF followed by a withdrawal period of 5 d. Superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase, glyoxalase I and glyoxalase II, total glutathione, lactic dehydrogenase, and alkaline phosphatase were investigated in the livers of treated and untreated fish. A general impairment of antioxidant enzymes and metabolic indicators was measured in FF-treated Rainbow Trout. Onset of oxidative damage may have occurred during the antibiotic treatment as a consequence of the effect of FF toxicity at mainly the highest dose. Nevertheless, the rise in levels of total glutathione and glutathione S-transferase even after the withdrawal period may shield the antibiotic-mediated oxidative processes. Received December 22, 2015; accepted May 26, 2016.