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Prolonged exposure to captive conditions has led to the development of a rainbow trout ‘farmed’ pheno- type, which is different from that of wild trout. Selec- tion for desirable productive traits in hatcheries has resulted in the development of some morphological traits that are maladaptive in nature. The recent development of organic aquaculture, guided by the well-being of the fish, could potentially produce a new farmed phenotype that would be more adaptive in nature. In this study, rainbow trout reared in intensive and organic farms were compared by means of shape analysis, to detect patterns of shape variation associated with rearing environment. The results of this study highlight a significant effect of the rearing method on rainbow trout shape: organi- cally reared trout showed a higher body profile, in particular in the head and trunk regions, shorter median fins and a deeper caudal peduncle. A combined effect of density and habitat complexity could have contributed to the observed shape differences: in organic rearing systems, lower densi- ties and steady water could increase territoriality and aggressive interactions, promoting body designs more functional in rapid attacks and escapes.

One of the most common drawbacks of artificial life conditions imposed by aquaculture is the quite high presence of skeletal anomalies (SAs) in reared fish, which reduce both functional performances and marketing image ⁄ commercial value of the reared lots. Thus, skeletal malformations and their incidence are one of the most important factors affecting fish farmer s production costs, and several efforts have been due to develop appropriate tools in detecting patterns of co-variation among rearing parameters and fish quality. In this paper we explore the advantages of using Self-Organized Maps (SOMs) when dealing with the analysis of correlations between the pattern of SA presence and rearing parameters in gilthead seabream (Sparus aurata L.), that is a largely reared fish of high commercial value. SOM, which is one of the best known neural networks with unsupervised learning rules, were applied to develop a model of the occurrence of SAs, both in terms of type and quantity, in seabream lots from different rearing approaches (extensive, semi-intensive and intensive). The trained SOMs classified lots according to the variation observed in the different weights of SAs, but also allows the detection of a series of correspondence, namely between: (i) the patter of SAs occurrence and the different rearing approach currently used in seabream aquaculture; and (ii) the total SAs incidence and the variability of meristic counts, represent a completely independent dataset. Mesocosms resulted the best rearing approach to produce wild-like fish, whereas intensive rearing is characterized by the large presence of SA. Globally, results suggested that this approach is reliable to be used for estimate the distance between aquaculture products and the wild-like phenotype used as quality reference.

Summary Rainbow trout is the longest-standing intensively-reared species in Western countries, where it has been subjected by farmers to selection for productive traits for more than a century. One interesting aspect in this context is to try and understand if prolonged artificial selection has in some way altered the phenotypic plasticity of this species. In this preliminary study, we characterized meristic counts and skeletal abnormalities in two different (Italian and French) rainbow trout strains, reared during on-growing following different approaches (intensive and semi-intensive), in order to analyze whether there are any differences in the skeletal elements and if so, what. Despite the different genetic origin and rearing methodologies to which the lots analyzed were subjected, the occurrences of malformed and seriously malformed individuals were not significantly different, nor were the mean number of anomalies per specimen. The body region most affected by deformities was the caudal vertebral column in both lots, although the French lot was also characterized by an high occurrence of spinal anomalies in the haemal region. Among the meristic counts, only the number of anal and dorsal rays showed statistically different median values between the two lots.

Summary A salt water exposure trial with juvenile Adriatic sturgeon, Acipenser naccarii, (5 months old; mean (± SD) weight = 56±28 g) was initiated by direct transfer from freshwater (FW) to brackish water (BW) of medium (310 mOsm.Kg-1= 11 %o) or high salinity (640 mOsm.Kg-1= 23 %o). Survival at 6 weeks and homeostatic regulation of plasma osmolality and ion concentrations demonstrated that A. naccarii of this age and/or size class possess the ability to adapt to hyperosmotic environments. Regulation of the osmotic status of body fluids was associated with differences in the number of mitochondria-rich (MR) cells on the gill lamellae, whereby sturgeon in high salinities exhibited reduced MR cell numbers as compared with those in FW. Measurement of Na+, K+-ATPase activity in crude gill homogenates from the three groups of sturgeon revealed higher activity in sturgeon at salinities of 310 and 640 mOsm.Kg-1 relative to those in FW; significantly higher in the sturgeon at 640 mOsm.Kg-1. There were no differences in H+-ATPase activity amongst the groups, as measured on the same crude homogenates, but there was a significant increase in the ratio of Na+,K+-ATPase to H+-ATPase in the sturgeon in water at 640 mOsm.Kg-1 relative to those in FW. There was a significant negative linear correlation between gill MR cell number and Na+,K+-ATPase activity. Apparently successful adaptation to BW was also indicated by similar low levels of serum Cortisol, and similar rates of resting oxygen consumption, in all groups. Nonetheless, a growth study on triplicate groups of 40 tagged sturgeon in FW or BW at 600 mOsm.Kg-1 (20 %o) revealed that animals in BW grew less well and exhibited less efficient feed conversion. The results indicate that although sturgeon exhibit some morpho-physiological adjustments to hyperosmotic environments and are able thereby to regulate plasma ions and osmolality in BW at 310 and 640 mOsm.Kg“1, they do not grow as well in BW at 600 mOsm.Kg-1 as they do in FW and, in fact, died when disturbed by heavy activity near the tanks.

The salinity tolerance of various early life stages (prelarvae, larvae and fry) of the Adriatic sturgeon (Acipenser naccarii) was investigated using acute exposures in a 96h-LC50 test. The results were compared with a series of parallel observations on the morphological development of the osmoregulatory organs. The highest salinities tolerated by prelarave and larvae were approximately iso-osmotic with sturgeon plasma. Once, however. the organs involved in homeostatic osmoregulatory mechanisms in the adult had developed (renal-branchial-gut system), the sturgeon was able to switch from hyperosmoregulation to hypo-osmoregulation. Nevertheless, at the most advanced age tested (150 days old), water at a salinity of approximately 20 parts per thousand appeared to be the upper threshold for tolerance of acute exposure by this species.

The effects of different conditions of larval and postlarval rearing on the external morphology and morpho-anatomical characters were studied on adult specimens of Sparus aurata L. (Teleostea, Sparidae) after 15 months of common rearing in floating cages. Differences in external morphology between two samples were analysed with geometric morphometrics. Despite common rearing, significant differences in shape were found, evidence of the importance of larval and postlarval rearing conditions in determining shape features. On the same specimens, morpho-anatomical data were collected using X-rays, thus making it possible to correlate fish shape with morpho-anatomical data. Characteristic shapes were associated with particular cadres of morpho-anatomical anomalies, such as lordosis of different body regions and the bending of the same. Streamlined wild-like profiles were associated with light anomaly cadres. Fish shape is an important component affecting the market value of the species. The use of the combined approach proposed is thus recommended in the description and quantification of shape features, particularly in the context of fish quality assessment.

Summary Hatche and wild sea bass (Dicentrarchus labrax) fry were transferred from sea water to low salinities and freshwater (FW) usiny three different operational protocols: 1) direct exposure to ow salimues and FW (LC 50 test, ST 50 test); 2) quick acclimation to FW (48h); 3) slow acclimation to FW (17d). Direct exposure to freshwater led to e death of all fry. Comete survival was observed after direct transfer to salinities ≥ 9 ppt, both in wild and hatchery fry. Eatchery fry tolerate direct transfer to low salinities (LC 50=4.393 ppt) better than wild fry (LC 50 = 3.215 ppt). Slow acclimation rotocol leads to higher survival rates (nearly 90 %) than does the quick procedure. In 48h and 17d accimation trials wild fry tolerate FW better tlan hatchery fry. Hypotheses to explain observed differences in wild and hatchery tolerances to low salinities and FW are discussed.

Glass eels (Anguilla anguilla, L. 1758) caught during ascent at the mouth of the River Tiber were kept in aquaria with freshwater and full strength salinity (35 parts per thousand) for four months. Morphological features of glass eels at capture and after four months of experimental rearing are described. The structure of the gut, an important osmoregulatory organ, observed in glass eels in seawater experimental rearing suggests that they undergo an irreversible process of adaptation to freshwater, despite the fact of survival in seawater.

The development of the fin skeleton has been studied in both the wild and hatchery sea bass, Dicentrarchus labrax L., larvae, in order to identify and define morphofunctional criteria for larval quality assessments. The cartilaginous and bony skeletal elements of the larvae were studied and standard length and notochord flexure recorded. Fin anomalies were present in reared larvae, whereas they were rare or absent in specimens from the wild. These anomalies were recognizable from the very beginning of skeletal development, indicating that environmental, genetic and broodstock management factors influence even the very early stages of larval development.

Summary The thick lipped mullet, Chelon labrosus, was induced to spawn by the injection of human gonadotropin hormone. Eggs were fertilized naturally and larvae were reared at different conditions, in hatchery tanks and outdoor earthen ponds, in order to compare their growth and try to reduce production costs. Food consisted of rotifers and brine shrimp nauplii at first, then of minced fresh fish and commercial fish food. Larval survival reached maxima of 41.9 % at the age of 20 days and 33.4 % at the age of 58 days. The successful artificial reproduction of the thick lipped mullet could have potential for meeting the demands of fry for the Italian aquaculture and the mass propagation of fry could have wide applications in developing countries. Zusammenfassung Kunstliche Vermehrung and Larvenaufzucht der Dicklippigen Meerasche (Chelon labrosus) Die Dicklippige Meerasche (Chelon labrosus) wurde durch Injektion von menschlichem Gonadotropin zum Ablaicnen gebracht. Die Eier wurden naturlich befruchtet und unter verschiedenen Bedingungen in Aquarien und in Freiluftteichen aufgezogen, um Abwuchs und Produktionskosten zu vergleichen. Als Futter wurden zuerst Rotatorien und Salinekrebse, dann zerkleinerter Frischfisch und Fertigfutter verwendet. Die uberlebensrate war maximal 41.9% bei 20 Tage alten bzw. 33.4% bei 58 Tage alten Larven. Die erfolgreiche kunstliche Reproduktion von Dicklippigen Meeraschen ist vor allem im Hinblick auf die Nachfrage der italienischen Aquakultur von Bedeutung und konnte auch fur die sich entwickelnde Aquakultur in einigen Landern der dritten Welt wichtig werden. Resume Reproduction artificielle et elevage d'alevins du muge (Chelon labrosus) Le muge Chelon labrosus a ete traite avec des homones gonadotropiques humaines pour induire la ponte. Les oeufs ont ete fecondes naturellement, et les larves elevees dans des conditions differentes, a l'interieur de l'ecloserie et dans des bassins en terre, afin de comparer leur croissance et essayer de reduire les couts de production. L'alimentation comprenait rotiferes et larves d'artemia au debut, suivis de poisson frais broye et aliment sec commercial. Le taux de survie des larves a atteint des maxima de 41.9 % a 20 jours et 33.4 % a 58 jours. Ces essais de reproduction artificielle pourraient satisfaire la demande en alevin de cette espece de muge pour la pisciculture italienne, et leur sevrage a basse technologie avoir maintes applications dans l'aquaculture des Pays en Voie de Developpement.